Presence of epiphytic algae, Vertebrata lanosa, positively impacts host algae, Ascophyllum nodosum, by reducing desiccation rates.

Presence of epiphytic algae, Vertebrata lanosa, positively impacts host algae, Ascophyllum nodosum, by reducing desiccation rates. | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Presence of epiphytic algae, Vertebrata lanosa, positively impacts host algae, Ascophyllum nodosum, by reducing desiccation rates. Gemma DeCarolis, Kenyon Moore, Kathryn Michele Anderson This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9162511/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract This study explicitly aims to understand the potential positive effects of the intertidal red algal epiphyte Vertebrata lanosa on its brown algal host Ascophyllum nodosum via reductions in desiccation and herbivory rates. To determine the effect of this epiphyte on the desiccation rates of its host, desiccation rates of both the host and epiphyte were measured when allowed to dry in contact with or in isolation from each other in high and low light conditions. To test if V. lanosa might reduce herbivore pressure on A. nodosum by providing an alternative and preferred food source, the feeding rates of two common herbivorous snail congeners ( Littorina littorea and L. obtusata ) on both algae were measured when offered each alga simultaneously or in isolation. Specimens used were collected from Bailey Island, Maine, USA (43.721249, -70.001740) in July 2024 and May 2025. The preferences and consumption rates of our herbivores were fixed regardless of whether they had a choice of which algae to eat, indicating that this epiphyte does not benefit its host by altering the behavior of these dominant herbivore species. However, the epiphyte significantly reduced the hosts’ rate of water loss but only in low light conditions. As most intertidal Fucoid algae photosynthesize fastest at low to intermediate levels of desiccation, the presence of V. lanosa is likely to allow A. nodosum to have greater photosynthetic rates for longer, during periods of emersion, allowing for greater overall growth. Epiphytes algae desiccation intertidal emersion Figures Figure 1 Figure 2 Figure 3 Introduction The rocky intertidal is a uniquely stressful and variable environment which forces intertidal organisms to evolve to fill a variety of hyper specific niches (Truchot and Duhamel-Jouve 1980 ). During periods in which organisms are exposed to the air such as low tide, the lack of water surrounding an organism causes water loss from the organism itself in a process known as desiccation. Desiccation directly impacts metabolic processes at both organismal and cellular levels, changing the balance of ions within intracellular and extracellular tissue. Ecologically, there is precedence that desiccation is one of the driving stressors to organisms who live within the intertidal (Lubchenco 1980 ). However, emersion, or the general time organisms spend outside of water, is also important for organismal function (Yu et al. 2013 ). For algae within the intertidal, emersion is a necessary part of optimizing photosynthesis, allowing for increased photosynthetic productivity as compared to when the alga is submerged (Dring and Brown 1982 ). Photosynthesis reaches a maximum when 20% to 30% of initial water content is lost in Fucus spp., then decreases as the algae dries out further (Dring and Brown 1982 ). Previous research has postulated that this increase in photosynthetic efficiency could be due to a lack of water absorbing light before reaching the algae or due to physiological changes within algae upon initial emersion (Wu et al. 2021 ; Dring and Brown 1982 ). Further, the rate of supply of CO 2 is lower to algae underwater than in air because of the approximately 10 4 times lower diffusion coefficient (Madsen and Maberly 1990 ). Therefore, as emersed plants have higher access to air via desiccation, photosynthesis increases. As cited by Dring and Brown ( 1982 ), a thin film of water over freshly emersed algae might initially inhibit carbon dioxide diffusion from the air, but as desiccation increases higher CO 2 diffusion occurs leading to greater levels of photosynthesis. Abiotic stressors are not the only stressors which intertidal algae have to deal with to survive. Instead it has long been understood that the interplay between the abiotic environment and species interactions shape species distributions in the intertidal (Wethey 1983 ). Epiphytes are photosynthesizers which anchor themselves on to other photosynthesizers instead of directly to the substrate. Algal epiphytes are generally thought to cause negative or neutral effects for the host algal species. In a study by Kraberg and Norton ( 2007 ), it was found that A. nodosum individuals with greater epiphyte coverage show decreased reproductive output compared to individuals without its epiphyte, V. lanosa , even accounting for variations in size. Epiphytes on intertidal algae can also change the level of hydrodynamic forces exerted on the host fronds; a higher epiphytic load causes increased drag on the host species making the likelihood of dislodgement greater if the epiphytes do not dislodge from the host before the host dislodges from the substrate (Anderson and Martone 2014 ). Epiphytes grow on the exterior of the host, often directly blocking light that the host would otherwise have received (Fong et al. 2000 ). However, the negative impacts of epiphyte shading may be species specific, especially depending on morphology. For example, Anderson ( 2012 ) argues the host of the epiphyte Soranthera ulvoidea , a brown, semi-translucent, sac-like alga, will be less impacted by shading than hosts with a more opaque epiphyte. Excessive epiphytes can compete with hosts for nutrients, increasing stress on the host and potentially leading to mortality (Nelson 2017 ). Finally, the direct transfer of nutrients has been noted between seagrass and their algal epiphytes, wherein an epiphytic alga directly takes nutrients from the host seagrass (Harlin 1973 ). However, this has not been observed in algae-algae host-epiphyte relationships. While less research has been done on the topic, there may be ways in which having an epiphyte benefits a host alga. For example, Anderson ( 2012 ) found that amphipods preferred grazing epiphyte S. ulvoidea over its red algal host Odonthalia floccosa. Additionally, these amphipods ate more host tissue in the absence of the epiphyte, indicating a switch in their diet dependent on epiphyte presence. Similarly, both gammarid amphipods and the gastropod, Littorina scutulata preferentially consume the epiphytes living on the host red alga Rhodomela (D’Antonio 1985 ). Isopods appear to prefer the epiphytic Pilayella littoralis and Ceramium nodulosum than their host, A. nodosum (Pavia et al. 1999 ). Thus, because of their high palatability, the presence of an epiphyte might reduce the herbivory rates experienced by the host via providing a better alternative food source. Additionally, while high population densities have been found to reduce the water loss of algae during heatwaves (Harris et al. 2025 ), the presence of epiphytes on both marine vascular plants and macroalgae has specifically been found to reduce the effects of desiccation on the host species. Algal epiphytes have been shown to reduce desiccation of seagrasses in estuarine habitats during warm, sunny weather at low tide trapping water between blades (Penhale and Smith 1977 ; Richardson 1980 ). Additionally, O. floccosa desiccates significantly more quickly in the absence of its water holding epiphyte S. ulvoidea (Anderson 2012 ). Further, Mycosphaerella ascophylli , a mycobiont of A. nodosum , has a role in protecting A. nodosum zygotes from desiccation through the hyphal structure of the mycobiont (Garbary and London 1995 ). This demonstrates that hosts are not always negatively impacted by epiphytes. Instead, epiphytes may retain larger amounts of thallus water and decrease the rate of desiccation on surrounding algae. One of the most common host-epiphyte relationships in the temperate rocky intertidal is between the epiphyte V. lanosa and its host A. nodosum . A. nodosum is a brown alga commonly found in the northern Atlantic Ocean. It is a foundational species for the mid-intertidal environment, playing a key role in carbon cycling, community composition and community richness (Pereira et al. 2020 ; Phillippi et al. 2014 ). A. nodosum is also an economically relevant species as it is used in fertilizer and animal feed across the north Atlantic region (Shukla et al. 2019 ; Chwastowska-Siwiecka and Micinski 2023). However, A. nodosum is also specifically at risk due to climate change, as researchers have seen a decrease in population densities associated with temperature increases towards the southern end of its distribution (Keser et al. 2005 ). V. lanosa is a red alga that grows exclusively as an epiphyte on A. nodosum . V. lanosa is typically more abundant on A. nodosum individuals living in the lower intertidal (Levin and Mathieson 1991 ). V. lanosa tends to colonize A. nodosum through surface irregularities which have accumulated over A. nodosum’s lifetime (Longtin and Scrosati 2009 ). Research looking at the relationship between these two species has found that V. lanosa does not appear to take nutrients from its host but instead uses A. nodosum exclusively as a substrate for attachment (Harlin and Craigie 1975 ). As previously noted, reproductive output of A. nodosum is negatively impacted by an increase in epiphytes, including V. lanosa (Kraberg and Norton 2007 ). This is likely because V. lanosa establishes primarily on the lateral pits of A. nodosum at the location of its receptacles, therefore directly interfering with reproduction (Lobban and Baxter 1983 ). While this is clearly a large negative impact, there may be other mechanisms through which a host alga might be positively or neutrally impacted by the presence of an epiphyte such as changes in hydrodynamic forces (Anderson and Martone 2014 ), herbivory (D’Antonio 1985 ; Pavia et al. 1999 ; Anderson 2012 ), and desiccation (Anderson 2012 ; Kraberg and Norton 2007 ; Dring and Brown 1982 ). While many herbivores are present in the intertidal environment, the periwinkles L. obtusata and L. littorea are two of the most common meso herbivores in the north Atlantic rocky intertidal (Jackson 2008; Soleto et al. 2020). While both herbivores are abundant within the same intertidal zone as A. nodosum and V. lanosa , L. obtusata is generally thought of as a Fucoid specialist eating primarily A. nodosum and other Fucoid algae from the Fucus genus commonly found in the same area (Soleto et al. 2020). L. obtusata has further been documented to induce anti-herbivore defenses in both A. nodosum and F. vesiculosus (Toth and Pavia 2000 ; Long et al. 2007 ). This is so even given multiple reports of L. obtusata preferentially grazing on non-Fucoid algae when given the opportunity (Watson and Norton 1987 ; Bracken and Low 2012 ). By contrast, L. littorea is more often thought of as a generalist herbivore that avoids A. nodosum and other Fucoids (Imrie et al. 1990 ). However, there are reports of L. littorea grazing on and even inducing antiherbivore defenses in the Fucoid F. vesiculosus (Emiline et al. 2021). In this research, we aim to see if the epiphyte V. lanosa has any positive impacts on A. nodosum with regards to slowing desiccation rates and reducing herbivory. Based on previous research showing that epiphytes slow the rate of desiccation, we predicted that V. lanosa will decrease the desiccation rate of A. nodosum . Additionally, we hypothesized that desiccation rates will be greater with more intense sunlight and thus V. lanosa will benefit A. nodosum the most under high light conditions. In this way having an epiphyte may be particularly beneficial in the harshest of intertidal conditions. For the herbivory portion of our study, we hypothesized that because L. obtusata is a Fucoid specialist it would only consume A. nodosum and would consume the same amount of A. nodosum regardless of whether or not the epiphyte was around. However, we hypothesized that L. littorea would consume both species of algae, but when given the choice would show a preference for V. lanosa. In this way, A. nodosum would benefit from having V. lanosa as an epiphyte as it reduces the herbivory rates the host alga experiences from more generalist herbivores. Methods Desiccation Assay A. nodosum individuals with V. lanosa epiphytes were collected from the mid intertidal zone of the Giant Stairs, Bailey Island (43.721249, -70.001740) on July 17, 2024. Individuals selected were 81.38 ± 3.18 cm in length, masses of 29.35 ± 2.81 g, and 5.51 ± 0.30 years old (based on air bladder counts); all with 44.05 ± 4.81 g of V. lanosa epiphytes (all measurements presented as means ± SE). Algae were placed into a seawater table at 12°C and a salinity of 30–35% (Instant Ocean salt mix) at Bates College, Lewiston Maine, within 3 h of collection. All algae were tested within 5 days of their collection. During the desiccation trials, we placed algae on opaque plastic trays on the roof of the Carnegie Science building at Bates College, Lewiston Maine. We placed half the algae within a greenhouse on the roof and the other half directly on the external roof of the building. Because the walls of the greenhouse are made of a semi-translucent glass, the algae in the greenhouse only received diffuse and indirect sunlight, our low light level. By contrast the algae placed directly on the roof were exposed to direct sunlight, our high light level. We weighed all the algae once every 15 minutes or so for two hours to monitor loss of water mass, and we kept track of exactly how much time had passed between each weighing. Prior to desiccation assay, V. lanosa was removed from all A. nodosum thalli. However, half of the A. nodosum individuals had their epiphytes placed back on top of them after every weighing, while the other half were kept separate from their epiphytes. The host and epiphytes were weighed separately throughout the desiccation assay regardless of whether or not they were in physical contact with each other. In this way, we were able to measure the desiccation rates of each species when in contact with the other species (i.e. V. lanosa on A. nodosum ) or not. After exposure on the roof, completely dehydrated weight was measured by dehydrating host fronds in a drying oven at 65°C for 48 hours. We measured a series of environmental parameters during this trial in order to make sure there weren’t confounding environmental variables. We used a multifunctional windmeter with built in temperature and humidity meters to measure temperature and humidity every 15 minutes during the desiccation trials both in and outside the green house (BTMETER wind speed meter anemometer BT-8806WM-APP). Wind speed was also collected every 15 minutes, but only outside. Light levels were collected via a LI-205A light meter every 15 minutes both in and outside the greenhouse (LI-COR, Lincoln, NE, USA). Herbivory Assay For this assay, L. littorea individuals with an average length of 22.36 ± 0.30 mm, and L. obtusata with an average length of 12.71 ± 0.07 mm were collected from the low to mid intertidal zone of the Giant Stairs, Bailey Island on May 9, 2025 (all measurements presented as means ± SE). The snails were transported in a cooler with 11°C seawater to keep them at a stable temperature. In the laboratory, six of each snail species were haphazardly placed in small mesh cages within recirculating sea tables similar to the ones used to house algae prior to the desiccation assay. A. nodosum individuals with significant V. lanosa present on the thallus were haphazardly collected from the mid intertidal zone of the Giant Stairs, Bailey Island (on May 11, 2025). A single A. nodosum individual was placed in each of the ten seawater tables as the snails, but not inside a mesh cage. All snails were starved for two days prior to the start of the feeding experiment. On May 12, 2025, the algae was taken out of seawater tanks. Six apical tips, weighing 0.2-0.5g, were cut from each A. nodosum individual and blotted with paper towels until no water was visible on the paper towels to measure the wet mass. Each apical tip was weighed using the OHAUS Explorer scale. Six clumps of V. lanosa , weighing 0.2-0.5g, were taken from each A. nodosum individual and blotted in the same method before weighing. We placed the A. nodosum and V. lanosa cuttings into cages. Three cages held just A. nodosum tips with one of three herbivore treatments: (1) two L. obtusata ; (2) two L. littorea ; or (3) a no herbivore control containing just the algae. Three other cages contained V. lanosa clumps. To consider the impacts of herbivore choice, a final three cages held the cuttings of both algae simultaneously. The cages holding the V. lanosa and those holding both algae simultaneously were assigned one of the same three herbivore treatments. Each of the ten sea tables then received nine cages, one from each treatment combination. All of the algal clippings in a single sea table were taken from a single A. nodosum and the V. lanosa epiphytes growing on it. After nine days, we weighed the algae again using the same technique and scale. After the algae were reweighed the change in mass of each piece was scaled to account for mass changes in the controls using the formula T i (C f /C i ) – T f , from Sotka et al., where T i and T f represent the initial and final masses, respectively, of tissue subject to grazing and C i and C f represent, respectively the initial and final masses of the control tissue (2002). Data Analysis To standardize the desiccation rates by the size of the algae we divided all masses recorded during the trial by its dry weight. We then ran a regression analysis looking at the effect of time on the weight of the algae for each A. nodosum . We did the same for the V. lanosa that had been growing on each A. nodosum . We used the resulting slope from the line of best fit as the desiccation rate measured in proportion of mass lost per minute. In this way, we had desiccation rates for each A. nodosum and its epiphytic V. lanosa . We ran linear models on the desiccation rates of each of the two algae looking at the primary and interactive effects of light intensity and proximity (whether the epiphytic V. lanosa had been placed back on its host V. lanosa or been kept separate). We used linear models to see if there was a significant difference in abiotic conditions in and out of the green house for temperature, humidity, and light. We used a one factor t-test to see if the wind speed outside the green house was significantly different from zero, the wind speed in the green house. Herbivory data was analyzed in a single three-way linear mixed-effects model using the lmer() function in the lmerTest package (Kuznetsova et al. 2017 ). Snail species, algal species, and whether the snails were offered each alga simultaneously or individually were all used as fixed effects. Because our replicates were blocked according to tank, tank was used as a random variable. All data was analyzed using R Statistical Software (v 4.5.2; R Core Team 2025 ). Results Our t-tests confirmed that there were no significant differences in the humidity or temperature inside versus outside the greenhouse (Table 1 ). Similarly, wind speed outside the greenhouse was not significantly different from zero, the presumed wind speed inside the greenhouse. There was, however, a significant difference in the light conditions inside and outside the greenhouse. On average, there was 8.7x the amount of light outside the greenhouse as inside the greenhouse (Table 1 ). Table 1 Summary of environmental parameters means (standard error) with t-test results. We used a two-sample t-test to compare each parameter inside to outside of the greenhouse for wind speed. We used a one-sample t-test to test if the wind speed outside was significantly different than zero. Significant results indicated in bold. Parameter Outside Inside df F p Humidity 27.8 (1.5) 28.2 (0.9) 1,43 0.033 0.86 Light 1304 (99) 150 (18) 1,46 121.54 < 0.0001 Temperature 35.34 (0.67) 36.21 (0.78) 1,43 8.56 0.40 Wind Speed 1.95 (1.18) - - - 0.12 We found significant main and interactive effects of light intensity and epiphyte presence on the desiccation rate of A. nodosum (Fig. 1 ; Table 2 ). Desiccation rates of A. nodosum were significantly slower, by 52% on average, when the algae were in the low light of the green house and in contact with V. lanosa . However, A. nodosum that was in low light and not in contact with any epiphytes evaporated at the same rate as the A. nodosum in high light both in contact and not in contact with V. lanosa. Table 2 ANOVA table showing the impact of epiphyte presence, light intensity, and their interaction on the desiccation rates of A. nodosum . Significant factors and their p-values indicated in bold. Parameter Df Sum sq Mean Sq F p Epiphyte Presence 1 1.74 1.74 7.76 0.008 Light Intensity 1 4.95 4.95 22.09 < 0.0001 Interaction 1 1.43 1.43 6.30 0.015 Residuals 40 8.97 0.22 We found a significant main effect of light intensity and host presence on the desiccation rates of V. lanosa , but no interactive effects (Fig. 2 ; Table 3 ). V. lanosa desiccated more quickly when in high light and when in contact with A. nodosum . These effects were additive, meaning that V. lanosa desiccated fastest in high light in the presence of its host alga and slowest in low light and when isolated from its host alga. Table 3 ANOVA table showing the impact of host presence, light intensity, and their interaction on the desiccation rates of V. lanosa . Significant factors and their p-values indicated in bold. Parameter Df Sum sq Mean Sq F p Host Presence 1 9.64 9.64 4.64 0.037 Light Intensity 1 58.63 58.63 28.36 < 0.0001 Interaction 1 1.15 1.15 0.55 0.46 Residuals 40 83.00 2.08 There were no significant main effects of algal species, snail species, or whether the snails were presented with a choice or not (Fig. 3 , Table 4 ). There was a significant interactive effect between algal species and snail species whereby L. littorea preferentially grazed on V. lanosa and L. obtusata preferentially grazed on A. nodosum regardless of whether the algae were presented simultaneously or in isolation. There were no other two-way interactions and no three-way interaction between algal species, snail species, or whether the snails were presented with a choice or not. Table 4 ANOVA table showing how algal consumption was impacted by algal species, snail (herbivore) species, or whether the snails were presented with a choice or not. Significant factors and their p-values indicated in bold. Parameter Df Sum sq Mean Sq F p Algal Species 1,63 0.0037 0.0037 3.13 0.08 Snail Species 1,63 0.0001 0.0001 0.06 0.80 Isolation Condition 1,63 0.0006 0.0006 0.47 0.59 Algal sp x Snail sp 1,63 0.0310 0.0310 25.89 < 0.0001 Algal sp x Isolation Con 1,63 < 0.0001 < 0.0001 0.02 0.88 Snail sp x Isolation Con 1,63 < 0.0001 < 0.0001 < 0.01 0.98 Three-Way Interaction 1,63 0.0003 0.0003 0.24 0.62 Discussion We found that desiccation rates of A. nodosum are lowered by the presence of V. lanosa in low light conditions. This is the first research looking at the impacts of V. lanosa on the desiccation of A. nodosum , a dominant species in the North Atlantic rocky intertidal environment. This effect may be key in understanding the host-epiphyte relationship between the two macroalgae. Previous studies found that epiphytes protect hosts from desiccation in both seagrass and macroalgal communities (Penhale and Smith 1977 , Anderson 2012 ). Reducing desiccation rates of algae has been shown to be beneficial for photosynthesis up to a certain threshold in Fucoid algal species. Dring and Brown ( 1982 ) found that for genus Fucus , confamilials of A. nodosum , a slight amount of desiccation leads to an increase in photosynthesis rates. In their research, photosynthesis reached a maximum value when 20% to 30% of the initial tissue water content had been lost. However, as the thallus dried out further, photosynthesis decreased, reaching zero before full desiccation had occurred. In a different study, Fucus spiralis exhibited similar trends with maximum photosynthesis rates at tissue water contents of 96% to 92%, but as water content decreased, net photosynthesis declined linearly. Photosynthesis then reached zero at a water content of around 15% (Madsen and Maberly 1990 ). Thus, reducing desiccation rates may serve an important role in maintaining high photosynthesis rates for longer during periods of emersion in the intertidal zone. By slowing desiccation rates, V. lanosa may extend the amount of time its host’s water content remains high enough for it to photosynthesize. V. lanosa is desiccated significantly quicker when A. nodosum was present regardless of light conditions, indicating that A. nodosum takes water from the thallus of V. lanosa . According to our measurements V. lanosa’ s thallus weighs five to twenty times its dry mass when first emersed. By contrast, A. nodosum only weighs two to four times its dry mass directly following emersion. This difference in water content may explain how this epiphyte slows the desiccation rates of its host. We suspect that V. lanosa ’s ability to hold proportionally more water than A. nodosum is probably due to its fine filamentous texture. As reviewed by Kain and Norton ( 1990 ), V. lanosa loses water slower than its congener V. fucoides . This difference may be explained by morphology. V. lanosa has a fine polysiphonous thalli with a high degree of branching leading to the formation of dense tufts, while V. fucoides has less branching and is more elongated (reviewed in Kain and Norton 1990 ). Similarly, the morphology of A. nodosum may explain its lower water retention capabilities. A. nodosum has a thick, leathery, branched, and straplike thallus that may be less efficient at holding water than finely branched species. Both species desiccated faster in high light than they did in low light conditions. In high light conditions, V. lanosa was not effective in protecting A. nodosum from desiccation, as A. nodosum desiccated at the same rate regardless of epiphyte presence in high light. This occurred despite apparent water transfer from V. lanosa to A. nodosum , as V. lanosa always desiccated faster in the presence of the host than in isolation. This means that higher levels of light irradiance cause evaporative water loss in A. nodosum that were too extreme to be mitigated by its epiphytic alga. Thus, any benefit that A. nodosum receives from V. lanosa in terms of staving off desiccation is likely to be limited to moderate weather conditions. The high levels of light at 1304 ± 383 umol/m2/s (± s) were around 8.7 times greater than the low light conditions at 150 ± 70 umol/m2/s (± s). These light levels overlap with previously recorded levels in the rocky intertidal. Lamote and Lamoine (2012) measured light levels of 800 to 2200 umol/m2/s during “sunny-calm” conditions and levels of 200 to 300 umol/m2/s during “cloudy-calm” conditions. These researchers also recorded higher evaporation rates under high light conditions than under lower light conditions in the confamilial Fucus disticus (Lamote and Lamoine 2012). While we were able to observe a positive effect of V. lanosa on its host alga in terms of slowing desiccation rates, we noted that the presence of V. lanosa did not alter the feeding patterns of L. littorea or L. obtusata . Each species had a preference for A. nodosum or V. lanosa respectively, regardless of being allowed a choice or not. Previous research has found that many herbivores preferentially graze on epiphytic algae over host algae. Amphipods have been shown to graze preferentially on the brown algal epiphyte S. ulvoidea over its red algal host O. floccosa (Anderson 2012 ). While L. obtusata has long been regarded as Fucoid specialist (Soleto et al. 2020), Bracken and Low ( 2012 ) found that when offered multiple species simultaneously, L obtusata consumed less of the F. vesiculosus and A. nodosum offered than the red and green algae offered. While their study did not include V. lanosa as one of the potential foods, we were surprised that in our study this same herbivore chose A. nodosum , one its less preferred foods, over V. lanosa . By contrast we were less surprised that L. littorea did not consume much A. nodosum even when it was the only food option as it has been previously shown to avoid A. nodosum consumption (Watson and Norton 1985 ). Due to strong and consistent herbivore preference, it does not appear that the presence of epiphytic V. lanosa would reduce consumption rates of A. nodosum by these two dominant intertidal herbivores. It is important to note that while our results are robust, there are factors that exist in the field that may augment the impact V. lanosa has on the desiccation rates of A. nodosum such as the size and population density of A. nodosum . Stengel and Dring ( 1997 ) found that A. nodosum branches with larger bladders remained on the top of the algal canopy. These branches with larger bladders thereby protect the smaller bladdered branches from desiccation and extreme temperatures. Additionally, the morphology of A. nodosum may also shift across tidal height. Relatively broad, flat axes are typical of plants on the upper shore and may have allowed closer packing during emersion providing greater self-shading and desiccation protection (Stengel and Dring 1997 ). Since our experiment only analyzed the effects of desiccation on single strands of A. nodosum , the effects of V. lanosa in mediating desiccation may have been enhanced compared to their effects in the field, where A. nodosum may be better able to self-shade. Further, because we only looked at a subset of A. nodosum strands from each individual separate from a densely packed population, our study may not fully replicate the experience of the entire individual in the field. Desiccation of V. lanosa may also be affected by its position on A. nodosum fronds. Longtin and Scrosati ( 2009 ) found that desiccation was greater in A. nodosum in the distal segments compared to the basal and middle segments. V. lanosa is typically found at higher density in the middle segments of A. nodosum fronds, which are less affected by desiccation (Longtin and Scrosati 2009 ). It is unclear whether the desiccation has been slowed additionally by the presence of V. lanosa , as in our study, or if self-shading within the canopy of A. nodosum is also concentrated within the middle segments. As such, the position of V. lanosa on its host may help to limit its own water loss. Future studies should look at the photosynthetic rate and growth effects of V. lanosa on A. nodosum . While decreasing desiccation rates increases the amount of time the host algae would have to photosynthesize (Dring and Brown 1982 ; Madsen and Maberly 1990 ), there might be other ways the epiphyte reduces photosynthesis. Epiphyte cover has been shown to reduce light reaching A. nosodum fronds by up to 40% (Kraberg and Norton 2007 ). Like most photosynthesizers, initial increases in light intensity increase the growth of A. nodosum (Sheader and Moss 1975 ). The question then becomes, is the impact of shading on photosynthetic yield offset by the benefits of slower desiccation rates? Alternatively, It is possible that the shading by V. lanosa is an additional benefit of its presence. When algae are exposed to high levels of light irradiance, oxidative free radicals are released and can cause cellular damage (Kennedy et al. 2020 ). Epiphytes have been shown to protect hosts from desiccation and UV radiation in seagrass communities (Penhale and Smith 1977 ). Here, V. lanosa could aid A. nodosum from both water loss and the harmful solar radiation. Anthropogenic climate change can alter interspecific interactions and produce unexpected changes in species distribution and structure. This is particularly relevant for the intertidal zone as these organisms already live near their thermal tolerance limits and may experience daily stressful conditions. As temperature has increased the upper intertidal distribution of many species have decreased, but the upper distributional limits of interacting species do not always shift at the same (Harley 2011 ). By reducing desiccation stress, V. lanosa may slow changes in A. nodosum intertidal distribution. Conclusion This study found that V. lanosa epiphytes may mediate desiccation of their host, A. nodosum under mild light conditions. Additionally, A. nodosum appears to take water from the thallus of V. lanosa , likely due to the differences in morphology between the species. V. lanosa serves as an epiphyte and has been shown to decrease reproductive output and block light from reaching its host A. nodosum . However, V. lanosa may help prevent desiccation of its host during mild light conditions, potentially revealing a semi-mutualistic relationship between the two algae. This is the first study to demonstrate desiccation benefits conferred on A. nodosum by V. lanosa. This study also found that V. lanosa does not prevent herbivory of Littorina sp. on A. nodosum which conflicts with the theory of V. lanosa as a mutualistic herbivory protector of A. nodosum. Further examination of how desiccation affects epiphytic relationships between algal species in the rocky intertidal zone may help reveal key adaptations to climate change and increases solar radiation. Declarations Funding Research expenses and G. DeCarolis’s spring 2025 salary were funded through the Bates Faculty Development Fund. G. DeCarolis’s summer 2024 stipend came from Bates College’s STEM Faculty-Student Summer Grant. K. Moore’s stipend was funded through Bates College’s Summer Research Fellowship. All three funding programs were provided through the Dean of the Faculty's office at Bates College. Author information Authors and Affiliations Department of Biology, Bates College, Lewiston, ME 04240, USA. Gemma DeCarolis, Kenyon Moore, Kathryn M Anderson Department of Biology, The Graduate Center, The City University of New York, 10016, U.S.A Kenyon Moore (current) Division of Integrative and Marine Sciences, University of Maine at Machias, Machias, ME 04654, USA Kathryn M Anderson (current) Contributions Project conceptualization, development of methodology, and writing of the original draft was led by G. DeCarolis and K. Moore with assistance from K. Anderson. The investigation was conducted by G. DeCarolis and K. Moore. Formal analysis was done by K. Anderson with assistance from G. DeCarolis. Data visualisation, data curation, supervision, project administration, funding acquisition, and resource provisioning done by K. Anderson. All authors were actively involved in the revision and editing of the manuscript. Corresponding author Kathryn M. Anderson: [email protected] Ethics declarations Conflict of interest The authors have no relevant financial or non-financial interests to disclose. Ethical approval This research met institutional, national, and international ethical standards. Acknowledgements We would like to thank Viuro Nkemngong for his help in the lab and field. We would also like to thank Sonya Locke for her continued support with equipment, filing for reimbursement, and general knowledge about resources within the Biology Department at Bates. We would also like to thank Zoom, snacks, and our pets, without which this paper would have never been written. Data availability Data and code used for data analysis will be made available upon request to the corresponding author. References Anderson L (2012) Costs and benefits of intertidal algal epiphytism. Master’s thesis, University of British Columbia Anderson LM, Martone PT (2014) Biomechanical consequences of epiphytism in intertidal macroalgae. 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Ecol 88:1232–1240. https://doi.org/10.1890/06-1585 Longtin CM, Scrosati RA (2009) Role of surface wounds and brown algal epiphytes in the colonization of Ascophyllum nodosum (phaeophyceae) fronds by Vertebrata lanosa (rhodophyta). J Phycol 45:535–539. https://doi.org/10.1111/j.1529-8817.2009.00672.x Lubchenco J (1980) Algal zonation in the New England rocky intertidal community: an experimental analysis. Ecol 61:333–344. https://doi.org/10.2307/1935192 Madsen TV, Maberly SC (1990) A comparison of air and water as environments for photosynthesis by the intertidal alga Fucus Spiralis (phaeophyta). J Phycol 26:24–30. https://doi.org/10.1111/j.0022-3646.1990.00024.x Nelson WG (2017) Development of an epiphyte indicator of nutrient enrichment: threshold values for seagrass epiphyte load. Ecol Indic 74:343–356. https://doi.org/10.1016/j.ecolind.2016.11.035 Pavia H, Toth GB (2000) Inducible chemical resistance to herbivory in the brown seaweed Ascophyllum nodosum . 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JEMBE 369:79–86. https://doi.org/10.1016/j.jembe.2008.09.019 Phillippi A, Tran K, Perna A (2014) Does intertidal canopy removal of Ascophyllum nodosum alter the community structure beneath? JEMBE 461:53–60. https://doi.org/10.1016/j.jembe.2014.07.018 R Core Team (2025) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.r-project.org/ Richardson FD (1980) Ecology of Ruppia Maritima L. in New Hampshire (USA) tidal marshes. Rhodora 82:403–439 Sheader A, Moss B (1975) Effects of light and temperature on germination and growth of Ascophyllum nodosum (L.) Le Jol. Estuar Coast Mar Sci 3:125–132. https://doi.org/10.1016/0302-3524(75)90015-8 Shukla PS, Mantin EG, Adil M, Bajpai S, Critchley AT, Prithiviraj B (2019) Ascophyllum nodosum -based biostimulants: sustainable applications in agriculture for the stimulation of plant growth, stress tolerance, and disease management. Front Plant Sci. https://doi.org/10.3389/fpls.2019.00655 Sotelo G, Duvetorp M, Costa D, Panova M, Johannesson K, Faria R (2020) Phylogeographic history of flat periwinkles, Littorina fabalis and L. obtusata . BMC Evol Biol 20:23. https://doi.org/10.1186/s12862-019-1561-6 Sotka EE, Taylor RB, Hay ME (2002) Tissue-specific induction of resistance to herbivores in a brown seaweed: the importance of direct grazing versus waterborne signals from grazed neighbors. JEMBE 277:1–12. https://doi.org/10.1016/S0022-0981(02)00128-4 Stengel D, Dring M (1997) Morphology and in situ growth rates of plants of Ascophyllum nodosum (Phaeophyta) from different shore levels and responses of plants to vertical transplantation. Eur J Phycol 32:193–202. https://doi.org/10.1080/09670269710001737129 Truchot J-P, Duhamel-Jouve A (1980) Oxygen and carbon dioxide in the marine intertidal environment: diurnal and tidal changes in rockpools. Respir Physiol 39:241–254. https://doi.org/10.1016/0034-5687(80)90056-0 Wang D, Yu X, Xu K, Bi G, Cao M, Zelzion E, Fu C, Sun P, Liu Y, Kong F, Du G, Tang X, Yang R, Wang J, Tang L, Wang L, Zhao Y, Ge Y, Zhuang Y, Mo Z, Chen Y, Gao T, Guan X, Chen R, Qu W, Sun B, Bhattacharya D, Mao Y (2020) Pyropia yezoensis genome reveals diverse mechanisms of carbon acquisition in the intertidal environment. Nat Commun 11:4028. https://doi.org/10.1038/s41467-020-17689-1 Watson DC, Norton TA (1985) Dietary preferences of the common periwinkle, Littorina littorea (L). JEMBE 88:193–211. https://doi.org/10.1016/0022-0981(85)90230-8 Watson DC, Norton TA (1987) The habitat and feeding preferences of Littorina obtusata (L.) and L. mariae sacchi et rastelli. JEMBE 112:61–72. https://doi.org/10.1016/S0022-0981(87)80015-1 Wethey DS (1983) Geographic limits and local zonation: the barnacles Semibalanus ( Balanus ) and Chthamalus in New England. Biol Bull 165:330–341. https://doi.org/10.2307/1541373 Wu X, Pan J, Ren W, Yang J, Luo L (2021) The effects of water depth on the growth of two submerged macrophytes in an in situ experiment. J Freshw Ecol 36:271–284. https://doi.org/10.1080/02705060.2021.1969294 Yu YQ, Zhang QS, Tang YZ, Li XM, Liu HL, Li LX (2013) Diurnal changes of photosynthetic quantum yield in the intertidal macroalga Sargassum thunbergii under simulated tidal emersion conditions. J Sea Res 80:50–57. https://doi.org/10.1016/j.seares.2013.02.008 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 07 Apr, 2026 Reviewers invited by journal 07 Apr, 2026 Editor assigned by journal 02 Apr, 2026 First submitted to journal 24 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9162511","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":618605993,"identity":"d3b8db3b-1d04-4cfb-b073-0d2d8417372e","order_by":0,"name":"Gemma DeCarolis","email":"","orcid":"","institution":"Bates College","correspondingAuthor":false,"prefix":"","firstName":"Gemma","middleName":"","lastName":"DeCarolis","suffix":""},{"id":618605994,"identity":"fc4e232b-733c-4f69-aaf0-f433c16e88c0","order_by":1,"name":"Kenyon Moore","email":"","orcid":"","institution":"CUNY-Graduate Center ZGM: CUNY Graduate Center","correspondingAuthor":false,"prefix":"","firstName":"Kenyon","middleName":"","lastName":"Moore","suffix":""},{"id":618605995,"identity":"1ef14388-c57f-4d1e-82dd-e5aa3e64cad3","order_by":2,"name":"Kathryn Michele Anderson","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFklEQVRIiWNgGAWjYBACCQYGNhjbAEzyA/EBMOsALi3MaFokG0jWYgBXiUOLZPv5Y48r2+4w8M9u3vi44o9NnvG1ww8PF1QwyPHdSMCqRZonmd3wbNszBok7x4qBjLRis9tpBodnnGEwlsShRY4hmU2yse0wA8ONHDPJxobDidtuJxgc5m1jSNyASwv/Y4gW+Rs55j8b/hxO3Dw7/cNh3n8M9bi0SEtAbTEA2sLYwHY4cYN0DtCWBoYEAxxaJGc8NpNsOHeYx/BGWjFQb1rijNs5BYd5jkkYzjzzAKsWifOJzyQbyg7Lyd1I3vix4Y9NYv/s9M2feWps5PmOY7cFDBjZGHgwzMKtHAz+EJAfBaNgFIyCkQ0AYm5lzFdMqe0AAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-8107-4594","institution":"University of Maine at Machias","correspondingAuthor":true,"prefix":"","firstName":"Kathryn","middleName":"Michele","lastName":"Anderson","suffix":""}],"badges":[],"createdAt":"2026-03-18 19:12:04","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9162511/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9162511/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106793738,"identity":"a7970ec5-2bb3-40cd-bd7d-3a395286e606","added_by":"auto","created_at":"2026-04-13 13:43:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":63374,"visible":true,"origin":"","legend":"\u003cp\u003eProportional mass of \u003cem\u003eA. nodosum\u003c/em\u003e over time according to light conditions and presence of the epiphyte, \u003cem\u003eV. lanosa\u003c/em\u003e. Dashed red lines and exes indicate algae was in the presence of the epiphyte, \u003cem\u003eV. lanosa\u003c/em\u003e. Solid blue lines and empty circles indicate that alga was isolated from the epiphyte \u003cem\u003eV. lanosa\u003c/em\u003e. Each exe and circle is a single measurement as each alga was measured once every 15 minutes during the two-hour experiment. Thin lines represent the line of best fit for each replicate alga, while thick lines represent the line of best for all replicates of a treatment.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-9162511/v1/700e3ef33c1b80fdaf1922a0.png"},{"id":106960613,"identity":"0fe17ce7-8eb3-48fc-9cf2-9f0f2762ecbf","added_by":"auto","created_at":"2026-04-15 09:22:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":56806,"visible":true,"origin":"","legend":"\u003cp\u003eProportional mass of \u003cem\u003eV. lanosa \u003c/em\u003eover time according to light conditions and presence of its host\u003cem\u003eA. nodosum\u003c/em\u003e. Dashed red lines and exes indicate algae was in the presence of its host\u003cem\u003e A. nodosum\u003c/em\u003e. Solid blue lines and empty circles indicate that alga was isolated from its host\u003cem\u003e A. nodosum\u003c/em\u003e. Each exe and circle is a single measurement where each alga was measured once every 15 minutes during the two-hour experiment. Thin lines represent the line of best fit for each replicate alga, while thick lines represent the line of best for all replicates of a treatment.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-9162511/v1/92487483469748d7b577b77f.png"},{"id":106793745,"identity":"c35d1915-39c5-4619-8bd7-782d10c6d459","added_by":"auto","created_at":"2026-04-13 13:43:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":13023,"visible":true,"origin":"","legend":"\u003cp\u003eMass of algae, \u003cem\u003eA. nodosum\u003c/em\u003e and \u003cem\u003eV. lanosa,\u003c/em\u003e when consumed by herbivorous snails \u003cem\u003eL. littorea \u003c/em\u003eand\u003cem\u003e L. obtusata\u003c/em\u003e. Blue and open dots indicate that the snails were not given a choice between the two species of algae, while red and exes indicate that the snails were presented with both simultaneously (i.e. given a choice). Boxes show interquartile range (IQR), solid circles indicate values more than 1.5x the IQR, while whiskers indicate the bounds of all other values. Open circles and exes show individual data points for all measurements.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-9162511/v1/f4136f41feaeb8ff0b61728c.png"},{"id":106964536,"identity":"cf9abea2-d1a0-4e84-938c-21fae067f7ce","added_by":"auto","created_at":"2026-04-15 09:50:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":824576,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9162511/v1/0cd1a5bf-23ec-46ff-9594-ab284e3249e9.pdf"}],"financialInterests":"","formattedTitle":"Presence of epiphytic algae, Vertebrata lanosa, positively impacts host algae, Ascophyllum nodosum, by reducing desiccation rates.","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe rocky intertidal is a uniquely stressful and variable environment which forces intertidal organisms to evolve to fill a variety of hyper specific niches (Truchot and Duhamel-Jouve \u003cspan class=\"CitationRef\"\u003e1980\u003c/span\u003e). During periods in which organisms are exposed to the air such as low tide, the lack of water surrounding an organism causes water loss from the organism itself in a process known as desiccation. Desiccation directly impacts metabolic processes at both organismal and cellular levels, changing the balance of ions within intracellular and extracellular tissue. Ecologically, there is precedence that desiccation is one of the driving stressors to organisms who live within the intertidal (Lubchenco \u003cspan class=\"CitationRef\"\u003e1980\u003c/span\u003e). However, emersion, or the general time organisms spend outside of water, is also important for organismal function (Yu et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e). For algae within the intertidal, emersion is a necessary part of optimizing photosynthesis, allowing for increased photosynthetic productivity as compared to when the alga is submerged (Dring and Brown \u003cspan class=\"CitationRef\"\u003e1982\u003c/span\u003e). Photosynthesis reaches a maximum when 20% to 30% of initial water content is lost in \u003cem\u003eFucus\u003c/em\u003e spp., then decreases as the algae dries out further (Dring and Brown \u003cspan class=\"CitationRef\"\u003e1982\u003c/span\u003e). Previous research has postulated that this increase in photosynthetic efficiency could be due to a lack of water absorbing light before reaching the algae or due to physiological changes within algae upon initial emersion (Wu et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e; Dring and Brown \u003cspan class=\"CitationRef\"\u003e1982\u003c/span\u003e). Further, the rate of supply of CO\u003csub\u003e2\u003c/sub\u003e is lower to algae underwater than in air because of the approximately 10\u003csup\u003e4\u003c/sup\u003e times lower diffusion coefficient (Madsen and Maberly \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e). Therefore, as emersed plants have higher access to air via desiccation, photosynthesis increases. As cited by Dring and Brown (\u003cspan class=\"CitationRef\"\u003e1982\u003c/span\u003e), a thin film of water over freshly emersed algae might initially inhibit carbon dioxide diffusion from the air, but as desiccation increases higher CO\u003csub\u003e2\u003c/sub\u003e diffusion occurs leading to greater levels of photosynthesis.\u003c/p\u003e \u003cp\u003eAbiotic stressors are not the only stressors which intertidal algae have to deal with to survive. Instead it has long been understood that the interplay between the abiotic environment and species interactions shape species distributions in the intertidal (Wethey \u003cspan class=\"CitationRef\"\u003e1983\u003c/span\u003e). Epiphytes are photosynthesizers which anchor themselves on to other photosynthesizers instead of directly to the substrate. Algal epiphytes are generally thought to cause negative or neutral effects for the host algal species. In a study by Kraberg and Norton (\u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e), it was found that \u003cem\u003eA. nodosum\u003c/em\u003e individuals with greater epiphyte coverage show decreased reproductive output compared to individuals without its epiphyte, \u003cem\u003eV. lanosa\u003c/em\u003e, even accounting for variations in size. Epiphytes on intertidal algae can also change the level of hydrodynamic forces exerted on the host fronds; a higher epiphytic load causes increased drag on the host species making the likelihood of dislodgement greater if the epiphytes do not dislodge from the host before the host dislodges from the substrate (Anderson and Martone \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). Epiphytes grow on the exterior of the host, often directly blocking light that the host would otherwise have received (Fong et al. \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e). However, the negative impacts of epiphyte shading may be species specific, especially depending on morphology. For example, Anderson (\u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e) argues the host of the epiphyte \u003cem\u003eSoranthera ulvoidea\u003c/em\u003e, a brown, semi-translucent, sac-like alga, will be less impacted by shading than hosts with a more opaque epiphyte. Excessive epiphytes can compete with hosts for nutrients, increasing stress on the host and potentially leading to mortality (Nelson \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). Finally, the direct transfer of nutrients has been noted between seagrass and their algal epiphytes, wherein an epiphytic alga directly takes nutrients from the host seagrass (Harlin \u003cspan class=\"CitationRef\"\u003e1973\u003c/span\u003e). However, this has not been observed in algae-algae host-epiphyte relationships.\u003c/p\u003e \u003cp\u003eWhile less research has been done on the topic, there may be ways in which having an epiphyte benefits a host alga. For example, Anderson (\u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e) found that amphipods preferred grazing epiphyte \u003cem\u003eS. ulvoidea\u003c/em\u003e over its red algal host \u003cem\u003eOdonthalia floccosa.\u003c/em\u003e Additionally, these amphipods ate more host tissue in the absence of the epiphyte, indicating a switch in their diet dependent on epiphyte presence. Similarly, both gammarid amphipods and the gastropod, \u003cem\u003eLittorina scutulata\u003c/em\u003e preferentially consume the epiphytes living on the host red alga \u003cem\u003eRhodomela\u003c/em\u003e (D’Antonio \u003cspan class=\"CitationRef\"\u003e1985\u003c/span\u003e). Isopods appear to prefer the epiphytic \u003cem\u003ePilayella littoralis\u003c/em\u003e and \u003cem\u003eCeramium nodulosum\u003c/em\u003e than their host, \u003cem\u003eA. nodosum\u003c/em\u003e (Pavia et al. \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e). Thus, because of their high palatability, the presence of an epiphyte might reduce the herbivory rates experienced by the host via providing a better alternative food source.\u003c/p\u003e \u003cp\u003eAdditionally, while high population densities have been found to reduce the water loss of algae during heatwaves (Harris et al. \u003cspan class=\"CitationRef\"\u003e2025\u003c/span\u003e), the presence of epiphytes on both marine vascular plants and macroalgae has specifically been found to reduce the effects of desiccation on the host species. Algal epiphytes have been shown to reduce desiccation of seagrasses in estuarine habitats during warm, sunny weather at low tide trapping water between blades (Penhale and Smith \u003cspan class=\"CitationRef\"\u003e1977\u003c/span\u003e; Richardson \u003cspan class=\"CitationRef\"\u003e1980\u003c/span\u003e). Additionally, \u003cem\u003eO. floccosa\u003c/em\u003e desiccates significantly more quickly in the absence of its water holding epiphyte \u003cem\u003eS. ulvoidea\u003c/em\u003e (Anderson \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). Further, \u003cem\u003eMycosphaerella ascophylli\u003c/em\u003e, a mycobiont of \u003cem\u003eA. nodosum\u003c/em\u003e, has a role in protecting \u003cem\u003eA. nodosum\u003c/em\u003e zygotes from desiccation through the hyphal structure of the mycobiont (Garbary and London \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e). This demonstrates that hosts are not always negatively impacted by epiphytes. Instead, epiphytes may retain larger amounts of thallus water and decrease the rate of desiccation on surrounding algae.\u003c/p\u003e \u003cp\u003eOne of the most common host-epiphyte relationships in the temperate rocky intertidal is between the epiphyte \u003cem\u003eV. lanosa\u003c/em\u003e and its host \u003cem\u003eA. nodosum\u003c/em\u003e. \u003cem\u003eA. nodosum\u003c/em\u003e is a brown alga commonly found in the northern Atlantic Ocean. It is a foundational species for the mid-intertidal environment, playing a key role in carbon cycling, community composition and community richness (Pereira et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Phillippi et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). \u003cem\u003eA. nodosum\u003c/em\u003e is also an economically relevant species as it is used in fertilizer and animal feed across the north Atlantic region (Shukla et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e; Chwastowska-Siwiecka and Micinski 2023). However, \u003cem\u003eA. nodosum\u003c/em\u003e is also specifically at risk due to climate change, as researchers have seen a decrease in population densities associated with temperature increases towards the southern end of its distribution (Keser et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cem\u003eV. lanosa\u003c/em\u003e is a red alga that grows exclusively as an epiphyte on \u003cem\u003eA. nodosum\u003c/em\u003e. \u003cem\u003eV. lanosa\u003c/em\u003e is typically more abundant on \u003cem\u003eA. nodosum\u003c/em\u003e individuals living in the lower intertidal (Levin and Mathieson \u003cspan class=\"CitationRef\"\u003e1991\u003c/span\u003e). \u003cem\u003eV. lanosa\u003c/em\u003e tends to colonize \u003cem\u003eA. nodosum\u003c/em\u003e through surface irregularities which have accumulated over \u003cem\u003eA. nodosum’s\u003c/em\u003e lifetime (Longtin and Scrosati \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e). Research looking at the relationship between these two species has found that \u003cem\u003eV. lanosa\u003c/em\u003e does not appear to take nutrients from its host but instead uses \u003cem\u003eA. nodosum\u003c/em\u003e exclusively as a substrate for attachment (Harlin and Craigie \u003cspan class=\"CitationRef\"\u003e1975\u003c/span\u003e). As previously noted, reproductive output of \u003cem\u003eA. nodosum\u003c/em\u003e is negatively impacted by an increase in epiphytes, including \u003cem\u003eV. lanosa\u003c/em\u003e (Kraberg and Norton \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e). This is likely because \u003cem\u003eV. lanosa\u003c/em\u003e establishes primarily on the lateral pits of \u003cem\u003eA. nodosum\u003c/em\u003e at the location of its receptacles, therefore directly interfering with reproduction (Lobban and Baxter \u003cspan class=\"CitationRef\"\u003e1983\u003c/span\u003e). While this is clearly a large negative impact, there may be other mechanisms through which a host alga might be positively or neutrally impacted by the presence of an epiphyte such as changes in hydrodynamic forces (Anderson and Martone \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e), herbivory (D’Antonio \u003cspan class=\"CitationRef\"\u003e1985\u003c/span\u003e; Pavia et al. \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e; Anderson \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e), and desiccation (Anderson \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; Kraberg and Norton \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e; Dring and Brown \u003cspan class=\"CitationRef\"\u003e1982\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWhile many herbivores are present in the intertidal environment, the periwinkles \u003cem\u003eL. obtusata\u003c/em\u003e and \u003cem\u003eL. littorea\u003c/em\u003e are two of the most common meso herbivores in the north Atlantic rocky intertidal (Jackson 2008; Soleto et al. 2020). While both herbivores are abundant within the same intertidal zone as \u003cem\u003eA. nodosum\u003c/em\u003e and \u003cem\u003eV. lanosa\u003c/em\u003e, \u003cem\u003eL. obtusata\u003c/em\u003e is generally thought of as a Fucoid specialist eating primarily \u003cem\u003eA. nodosum\u003c/em\u003e and other Fucoid algae from the \u003cem\u003eFucus\u003c/em\u003e genus commonly found in the same area (Soleto et al. 2020). \u003cem\u003eL. obtusata\u003c/em\u003e has further been documented to induce anti-herbivore defenses in both \u003cem\u003eA. nodosum\u003c/em\u003e and \u003cem\u003eF. vesiculosus\u003c/em\u003e (Toth and Pavia \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e; Long et al. \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e). This is so even given multiple reports of \u003cem\u003eL. obtusata\u003c/em\u003e preferentially grazing on non-Fucoid algae when given the opportunity (Watson and Norton \u003cspan class=\"CitationRef\"\u003e1987\u003c/span\u003e; Bracken and Low \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). By contrast, \u003cem\u003eL. littorea\u003c/em\u003e is more often thought of as a generalist herbivore that avoids \u003cem\u003eA. nodosum\u003c/em\u003e and other Fucoids (Imrie et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e). However, there are reports of \u003cem\u003eL. littorea\u003c/em\u003e grazing on and even inducing antiherbivore defenses in the Fucoid \u003cem\u003eF. vesiculosus\u003c/em\u003e (Emiline et al. 2021).\u003c/p\u003e \u003cp\u003eIn this research, we aim to see if the epiphyte \u003cem\u003eV. lanosa\u003c/em\u003e has any positive impacts on \u003cem\u003eA. nodosum\u003c/em\u003e with regards to slowing desiccation rates and reducing herbivory. Based on previous research showing that epiphytes slow the rate of desiccation, we predicted that \u003cem\u003eV. lanosa\u003c/em\u003e will decrease the desiccation rate of \u003cem\u003eA. nodosum\u003c/em\u003e. Additionally, we hypothesized that desiccation rates will be greater with more intense sunlight and thus \u003cem\u003eV. lanosa\u003c/em\u003e will benefit \u003cem\u003eA. nodosum\u003c/em\u003e the most under high light conditions. In this way having an epiphyte may be particularly beneficial in the harshest of intertidal conditions. For the herbivory portion of our study, we hypothesized that because \u003cem\u003eL. obtusata\u003c/em\u003e is a Fucoid specialist it would only consume \u003cem\u003eA. nodosum\u003c/em\u003e and would consume the same amount of \u003cem\u003eA. nodosum\u003c/em\u003e regardless of whether or not the epiphyte was around. However, we hypothesized that \u003cem\u003eL. littorea\u003c/em\u003e would consume both species of algae, but when given the choice would show a preference for \u003cem\u003eV. lanosa.\u003c/em\u003e In this way, \u003cem\u003eA. nodosum\u003c/em\u003e would benefit from having \u003cem\u003eV. lanosa\u003c/em\u003e as an epiphyte as it reduces the herbivory rates the host alga experiences from more generalist herbivores.\u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003eDesiccation Assay\u003c/p\u003e\u003cp\u003e \u003cem\u003eA. nodosum\u003c/em\u003e individuals with \u003cem\u003eV. lanosa\u003c/em\u003e epiphytes were collected from the mid intertidal zone of the Giant Stairs, Bailey Island (43.721249, -70.001740) on July 17, 2024. Individuals selected were 81.38 ± 3.18 cm in length, masses of 29.35 ± 2.81 g, and 5.51 ± 0.30 years old (based on air bladder counts); all with 44.05 ± 4.81 g of \u003cem\u003eV. lanosa\u003c/em\u003e epiphytes (all measurements presented as means ± SE). Algae were placed into a seawater table at 12°C and a salinity of 30–35% (Instant Ocean salt mix) at Bates College, Lewiston Maine, within 3 h of collection. All algae were tested within 5 days of their collection.\u003c/p\u003e\u003cp\u003eDuring the desiccation trials, we placed algae on opaque plastic trays on the roof of the Carnegie Science building at Bates College, Lewiston Maine. We placed half the algae within a greenhouse on the roof and the other half directly on the external roof of the building. Because the walls of the greenhouse are made of a semi-translucent glass, the algae in the greenhouse only received diffuse and indirect sunlight, our low light level. By contrast the algae placed directly on the roof were exposed to direct sunlight, our high light level.\u003c/p\u003e\u003cp\u003eWe weighed all the algae once every 15 minutes or so for two hours to monitor loss of water mass, and we kept track of exactly how much time had passed between each weighing. Prior to desiccation assay, \u003cem\u003eV. lanosa\u003c/em\u003e was removed from all \u003cem\u003eA. nodosum\u003c/em\u003e thalli. However, half of the \u003cem\u003eA. nodosum\u003c/em\u003e individuals had their epiphytes placed back on top of them after every weighing, while the other half were kept separate from their epiphytes. The host and epiphytes were weighed separately throughout the desiccation assay regardless of whether or not they were in physical contact with each other. In this way, we were able to measure the desiccation rates of each species when in contact with the other species (i.e. \u003cem\u003eV. lanosa\u003c/em\u003e on \u003cem\u003eA. nodosum\u003c/em\u003e) or not. After exposure on the roof, completely dehydrated weight was measured by dehydrating host fronds in a drying oven at 65°C for 48 hours.\u003c/p\u003e\u003cp\u003eWe measured a series of environmental parameters during this trial in order to make sure there weren’t confounding environmental variables. We used a multifunctional windmeter with built in temperature and humidity meters to measure temperature and humidity every 15 minutes during the desiccation trials both in and outside the green house (BTMETER wind speed meter anemometer BT-8806WM-APP). Wind speed was also collected every 15 minutes, but only outside. Light levels were collected via a LI-205A light meter every 15 minutes both in and outside the greenhouse (LI-COR, Lincoln, NE, USA).\u003c/p\u003e\u003cp\u003eHerbivory Assay\u003c/p\u003e\u003cp\u003eFor this assay, \u003cem\u003eL. littorea\u003c/em\u003e individuals with an average length of 22.36 ± 0.30 mm, and \u003cem\u003eL. obtusata\u003c/em\u003e with an average length of 12.71 ± 0.07 mm were collected from the low to mid intertidal zone of the Giant Stairs, Bailey Island on May 9, 2025 (all measurements presented as means ± SE). The snails were transported in a cooler with 11°C seawater to keep them at a stable temperature. In the laboratory, six of each snail species were haphazardly placed in small mesh cages within recirculating sea tables similar to the ones used to house algae prior to the desiccation assay. \u003cem\u003eA. nodosum\u003c/em\u003e individuals with significant \u003cem\u003eV. lanosa\u003c/em\u003e present on the thallus were haphazardly collected from the mid intertidal zone of the Giant Stairs, Bailey Island (on May 11, 2025). A single \u003cem\u003eA. nodosum\u003c/em\u003e individual was placed in each of the ten seawater tables as the snails, but not inside a mesh cage. All snails were starved for two days prior to the start of the feeding experiment.\u003c/p\u003e\u003cp\u003eOn May 12, 2025, the algae was taken out of seawater tanks. Six apical tips, weighing 0.2-0.5g, were cut from each \u003cem\u003eA. nodosum\u003c/em\u003e individual and blotted with paper towels until no water was visible on the paper towels to measure the wet mass. Each apical tip was weighed using the OHAUS Explorer scale. Six clumps of \u003cem\u003eV. lanosa\u003c/em\u003e, weighing 0.2-0.5g, were taken from each \u003cem\u003eA. nodosum\u003c/em\u003e individual and blotted in the same method before weighing. We placed the \u003cem\u003eA. nodosum\u003c/em\u003e and \u003cem\u003eV. lanosa\u003c/em\u003e cuttings into cages. Three cages held just \u003cem\u003eA. nodosum\u003c/em\u003e tips with one of three herbivore treatments: (1) two \u003cem\u003eL. obtusata\u003c/em\u003e; (2) two \u003cem\u003eL. littorea\u003c/em\u003e; or (3) a no herbivore control containing just the algae. Three other cages contained \u003cem\u003eV. lanosa\u003c/em\u003e clumps. To consider the impacts of herbivore choice, a final three cages held the cuttings of both algae simultaneously. The cages holding the \u003cem\u003eV. lanosa\u003c/em\u003e and those holding both algae simultaneously were assigned one of the same three herbivore treatments. Each of the ten sea tables then received nine cages, one from each treatment combination. All of the algal clippings in a single sea table were taken from a single \u003cem\u003eA. nodosum\u003c/em\u003e and the \u003cem\u003eV. lanosa\u003c/em\u003e epiphytes growing on it.\u003c/p\u003e\u003cp\u003eAfter nine days, we weighed the algae again using the same technique and scale. After the algae were reweighed the change in mass of each piece was scaled to account for mass changes in the controls using the formula T\u003csub\u003ei\u003c/sub\u003e(C\u003csub\u003ef\u003c/sub\u003e/C\u003csub\u003ei\u003c/sub\u003e) – T\u003csub\u003ef\u003c/sub\u003e, from Sotka et al., where T\u003csub\u003ei\u003c/sub\u003e and T\u003csub\u003ef\u003c/sub\u003e represent the initial and final masses, respectively, of tissue subject to grazing and C\u003csub\u003ei\u003c/sub\u003e and C\u003csub\u003ef\u003c/sub\u003e represent, respectively the initial and final masses of the control tissue (2002).\u003c/p\u003e\u003ch2\u003eData Analysis\u003c/h2\u003e\u003cp\u003eTo standardize the desiccation rates by the size of the algae we divided all masses recorded during the trial by its dry weight. We then ran a regression analysis looking at the effect of time on the weight of the algae for each \u003cem\u003eA. nodosum\u003c/em\u003e. We did the same for the \u003cem\u003eV. lanosa\u003c/em\u003e that had been growing on each \u003cem\u003eA. nodosum\u003c/em\u003e. We used the resulting slope from the line of best fit as the desiccation rate measured in proportion of mass lost per minute. In this way, we had desiccation rates for each \u003cem\u003eA. nodosum\u003c/em\u003e and its epiphytic \u003cem\u003eV. lanosa\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eWe ran linear models on the desiccation rates of each of the two algae looking at the primary and interactive effects of light intensity and proximity (whether the epiphytic \u003cem\u003eV. lanosa\u003c/em\u003e had been placed back on its host \u003cem\u003eV. lanosa\u003c/em\u003e or been kept separate).\u003c/p\u003e\u003cp\u003eWe used linear models to see if there was a significant difference in abiotic conditions in and out of the green house for temperature, humidity, and light. We used a one factor t-test to see if the wind speed outside the green house was significantly different from zero, the wind speed in the green house.\u003c/p\u003e\u003cp\u003eHerbivory data was analyzed in a single three-way linear mixed-effects model using the lmer() function in the lmerTest package (Kuznetsova et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). Snail species, algal species, and whether the snails were offered each alga simultaneously or individually were all used as fixed effects. Because our replicates were blocked according to tank, tank was used as a random variable. All data was analyzed using R Statistical Software (v 4.5.2; R Core Team \u003cspan class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eOur t-tests confirmed that there were no significant differences in the humidity or temperature inside versus outside the greenhouse (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Similarly, wind speed outside the greenhouse was not significantly different from zero, the presumed wind speed inside the greenhouse. There was, however, a significant difference in the light conditions inside and outside the greenhouse. On average, there was 8.7x the amount of light outside the greenhouse as inside the greenhouse (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of environmental parameters means (standard error) with t-test results. We used a two-sample t-test to compare each parameter inside to outside of the greenhouse for wind speed. We used a one-sample t-test to test if the wind speed outside was significantly different than zero. Significant results indicated in bold.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOutside\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInside\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003edf\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHumidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.8 (1.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28.2 (0.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1,43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.033\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLight\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1304 (99)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e150 (18)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e1,46\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e121.54\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTemperature\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35.34 (0.67)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e36.21 (0.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1,43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWind Speed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.95 (1.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWe found significant main and interactive effects of light intensity and epiphyte presence on the desiccation rate of \u003cem\u003eA. nodosum\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Desiccation rates of \u003cem\u003eA. nodosum\u003c/em\u003e were significantly slower, by 52% on average, when the algae were in the low light of the green house and in contact with \u003cem\u003eV. lanosa\u003c/em\u003e. However, \u003cem\u003eA. nodosum\u003c/em\u003e that was in low light and not in contact with any epiphytes evaporated at the same rate as the \u003cem\u003eA. nodosum\u003c/em\u003e in high light both in contact and not in contact with \u003cem\u003eV. lanosa.\u003c/em\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eANOVA table showing the impact of epiphyte presence, light intensity, and their interaction on the desiccation rates of \u003cem\u003eA. nodosum\u003c/em\u003e. Significant factors and their p-values indicated in bold.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDf\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSum sq\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMean Sq\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEpiphyte Presence\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.008\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLight Intensity\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eInteraction\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.015\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResiduals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWe found a significant main effect of light intensity and host presence on the desiccation rates of \u003cem\u003eV. lanosa\u003c/em\u003e, but no interactive effects (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). \u003cem\u003eV. lanosa\u003c/em\u003e desiccated more quickly when in high light and when in contact with \u003cem\u003eA. nodosum\u003c/em\u003e. These effects were additive, meaning that \u003cem\u003eV. lanosa\u003c/em\u003e desiccated fastest in high light in the presence of its host alga and slowest in low light and when isolated from its host alga.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eANOVA table showing the impact of host presence, light intensity, and their interaction on the desiccation rates of \u003cem\u003eV. lanosa\u003c/em\u003e. Significant factors and their p-values indicated in bold.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDf\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSum sq\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMean Sq\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHost Presence\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.037\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLight Intensity\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e58.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e58.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInteraction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResiduals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e83.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThere were no significant main effects of algal species, snail species, or whether the snails were presented with a choice or not (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). There was a significant interactive effect between algal species and snail species whereby \u003cem\u003eL. littorea\u003c/em\u003e preferentially grazed on \u003cem\u003eV. lanosa\u003c/em\u003e and \u003cem\u003eL. obtusata\u003c/em\u003e preferentially grazed on \u003cem\u003eA. nodosum\u003c/em\u003e regardless of whether the algae were presented simultaneously or in isolation. There were no other two-way interactions and no three-way interaction between algal species, snail species, or whether the snails were presented with a choice or not.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eANOVA table showing how algal consumption was impacted by algal species, snail (herbivore) species, or whether the snails were presented with a choice or not. Significant factors and their p-values indicated in bold.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDf\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSum sq\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMean Sq\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlgal Species\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0037\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0037\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSnail Species\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIsolation Condition\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAlgal sp x Snail sp\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0310\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0310\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e25.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlgal sp x Isolation Con\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSnail sp x Isolation Con\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.98\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThree-Way Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1,63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe found that desiccation rates of \u003cem\u003eA. nodosum\u003c/em\u003e are lowered by the presence of \u003cem\u003eV. lanosa\u003c/em\u003e in low light conditions. This is the first research looking at the impacts of \u003cem\u003eV. lanosa\u003c/em\u003e on the desiccation of \u003cem\u003eA. nodosum\u003c/em\u003e, a dominant species in the North Atlantic rocky intertidal environment. This effect may be key in understanding the host-epiphyte relationship between the two macroalgae. Previous studies found that epiphytes protect hosts from desiccation in both seagrass and macroalgal communities (Penhale and Smith \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1977\u003c/span\u003e, Anderson \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Reducing desiccation rates of algae has been shown to be beneficial for photosynthesis up to a certain threshold in Fucoid algal species. Dring and Brown (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1982\u003c/span\u003e) found that for genus \u003cem\u003eFucus\u003c/em\u003e, confamilials of \u003cem\u003eA. nodosum\u003c/em\u003e, a slight amount of desiccation leads to an increase in photosynthesis rates. In their research, photosynthesis reached a maximum value when 20% to 30% of the initial tissue water content had been lost. However, as the thallus dried out further, photosynthesis decreased, reaching zero before full desiccation had occurred. In a different study, \u003cem\u003eFucus spiralis\u003c/em\u003e exhibited similar trends with maximum photosynthesis rates at tissue water contents of 96% to 92%, but as water content decreased, net photosynthesis declined linearly. Photosynthesis then reached zero at a water content of around 15% (Madsen and Maberly \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). Thus, reducing desiccation rates may serve an important role in maintaining high photosynthesis rates for longer during periods of emersion in the intertidal zone. By slowing desiccation rates, \u003cem\u003eV. lanosa\u003c/em\u003e may extend the amount of time its host\u0026rsquo;s water content remains high enough for it to photosynthesize.\u003c/p\u003e \u003cp\u003e \u003cem\u003eV. lanosa\u003c/em\u003e is desiccated significantly quicker when \u003cem\u003eA. nodosum\u003c/em\u003e was present regardless of light conditions, indicating that \u003cem\u003eA. nodosum\u003c/em\u003e takes water from the thallus of \u003cem\u003eV. lanosa\u003c/em\u003e. According to our measurements \u003cem\u003eV. lanosa\u0026rsquo;\u003c/em\u003es thallus weighs five to twenty times its dry mass when first emersed. By contrast, \u003cem\u003eA. nodosum\u003c/em\u003e only weighs two to four times its dry mass directly following emersion. This difference in water content may explain how this epiphyte slows the desiccation rates of its host. We suspect that \u003cem\u003eV. lanosa\u003c/em\u003e\u0026rsquo;s ability to hold proportionally more water than \u003cem\u003eA. nodosum\u003c/em\u003e is probably due to its fine filamentous texture. As reviewed by Kain and Norton (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), \u003cem\u003eV. lanosa\u003c/em\u003e loses water slower than its congener \u003cem\u003eV. fucoides\u003c/em\u003e. This difference may be explained by morphology. \u003cem\u003eV. lanosa\u003c/em\u003e has a fine polysiphonous thalli with a high degree of branching leading to the formation of dense tufts, while \u003cem\u003eV. fucoides\u003c/em\u003e has less branching and is more elongated (reviewed in Kain and Norton \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). Similarly, the morphology of \u003cem\u003eA. nodosum\u003c/em\u003e may explain its lower water retention capabilities. \u003cem\u003eA. nodosum\u003c/em\u003e has a thick, leathery, branched, and straplike thallus that may be less efficient at holding water than finely branched species.\u003c/p\u003e \u003cp\u003eBoth species desiccated faster in high light than they did in low light conditions. In high light conditions, \u003cem\u003eV. lanosa\u003c/em\u003e was not effective in protecting \u003cem\u003eA. nodosum\u003c/em\u003e from desiccation, as \u003cem\u003eA. nodosum\u003c/em\u003e desiccated at the same rate regardless of epiphyte presence in high light. This occurred despite apparent water transfer from \u003cem\u003eV. lanosa\u003c/em\u003e to \u003cem\u003eA. nodosum\u003c/em\u003e, as \u003cem\u003eV. lanosa\u003c/em\u003e always desiccated faster in the presence of the host than in isolation. This means that higher levels of light irradiance cause evaporative water loss in \u003cem\u003eA. nodosum\u003c/em\u003e that were too extreme to be mitigated by its epiphytic alga. Thus, any benefit that \u003cem\u003eA. nodosum\u003c/em\u003e receives from \u003cem\u003eV. lanosa\u003c/em\u003e in terms of staving off desiccation is likely to be limited to moderate weather conditions.\u003c/p\u003e \u003cp\u003eThe high levels of light at 1304\u0026thinsp;\u0026plusmn;\u0026thinsp;383 umol/m2/s (\u0026plusmn;\u0026thinsp;s) were around 8.7 times greater than the low light conditions at 150\u0026thinsp;\u0026plusmn;\u0026thinsp;70 umol/m2/s (\u0026plusmn;\u0026thinsp;s). These light levels overlap with previously recorded levels in the rocky intertidal. Lamote and Lamoine (2012) measured light levels of 800 to 2200 umol/m2/s during \u0026ldquo;sunny-calm\u0026rdquo; conditions and levels of 200 to 300 umol/m2/s during \u0026ldquo;cloudy-calm\u0026rdquo; conditions. These researchers also recorded higher evaporation rates under high light conditions than under lower light conditions in the confamilial \u003cem\u003eFucus disticus\u003c/em\u003e (Lamote and Lamoine 2012).\u003c/p\u003e \u003cp\u003eWhile we were able to observe a positive effect of \u003cem\u003eV. lanosa\u003c/em\u003e on its host alga in terms of slowing desiccation rates, we noted that the presence of \u003cem\u003eV. lanosa\u003c/em\u003e did not alter the feeding patterns of \u003cem\u003eL. littorea\u003c/em\u003e or \u003cem\u003eL. obtusata\u003c/em\u003e. Each species had a preference for \u003cem\u003eA. nodosum\u003c/em\u003e or \u003cem\u003eV. lanosa\u003c/em\u003e respectively, regardless of being allowed a choice or not. Previous research has found that many herbivores preferentially graze on epiphytic algae over host algae. Amphipods have been shown to graze preferentially on the brown algal epiphyte \u003cem\u003eS. ulvoidea\u003c/em\u003e over its red algal host \u003cem\u003eO. floccosa\u003c/em\u003e (Anderson \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). While \u003cem\u003eL. obtusata\u003c/em\u003e has long been regarded as Fucoid specialist (Soleto et al. 2020), Bracken and Low (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) found that when offered multiple species simultaneously, \u003cem\u003eL obtusata\u003c/em\u003e consumed less of the \u003cem\u003eF. vesiculosus\u003c/em\u003e and \u003cem\u003eA. nodosum\u003c/em\u003e offered than the red and green algae offered. While their study did not include \u003cem\u003eV. lanosa\u003c/em\u003e as one of the potential foods, we were surprised that in our study this same herbivore chose \u003cem\u003eA. nodosum\u003c/em\u003e, one its less preferred foods, over \u003cem\u003eV. lanosa\u003c/em\u003e. By contrast we were less surprised that \u003cem\u003eL. littorea\u003c/em\u003e did not consume much \u003cem\u003eA. nodosum\u003c/em\u003e even when it was the only food option as it has been previously shown to avoid \u003cem\u003eA. nodosum\u003c/em\u003e consumption (Watson and Norton \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1985\u003c/span\u003e). Due to strong and consistent herbivore preference, it does not appear that the presence of epiphytic \u003cem\u003eV. lanosa\u003c/em\u003e would reduce consumption rates of \u003cem\u003eA. nodosum\u003c/em\u003e by these two dominant intertidal herbivores.\u003c/p\u003e \u003cp\u003eIt is important to note that while our results are robust, there are factors that exist in the field that may augment the impact \u003cem\u003eV. lanosa\u003c/em\u003e has on the desiccation rates of \u003cem\u003eA. nodosum\u003c/em\u003e such as the size and population density of \u003cem\u003eA. nodosum\u003c/em\u003e. Stengel and Dring (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) found that \u003cem\u003eA. nodosum\u003c/em\u003e branches with larger bladders remained on the top of the algal canopy. These branches with larger bladders thereby protect the smaller bladdered branches from desiccation and extreme temperatures. Additionally, the morphology of \u003cem\u003eA. nodosum\u003c/em\u003e may also shift across tidal height. Relatively broad, flat axes are typical of plants on the upper shore and may have allowed closer packing during emersion providing greater self-shading and desiccation protection (Stengel and Dring \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). Since our experiment only analyzed the effects of desiccation on single strands of \u003cem\u003eA. nodosum\u003c/em\u003e, the effects of \u003cem\u003eV. lanosa\u003c/em\u003e in mediating desiccation may have been enhanced compared to their effects in the field, where \u003cem\u003eA. nodosum\u003c/em\u003e may be better able to self-shade. Further, because we only looked at a subset of \u003cem\u003eA. nodosum\u003c/em\u003e strands from each individual separate from a densely packed population, our study may not fully replicate the experience of the entire individual in the field.\u003c/p\u003e \u003cp\u003eDesiccation of \u003cem\u003eV. lanosa\u003c/em\u003e may also be affected by its position on \u003cem\u003eA. nodosum\u003c/em\u003e fronds. Longtin and Scrosati (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) found that desiccation was greater in \u003cem\u003eA. nodosum\u003c/em\u003e in the distal segments compared to the basal and middle segments. \u003cem\u003eV. lanosa\u003c/em\u003e is typically found at higher density in the middle segments of \u003cem\u003eA. nodosum\u003c/em\u003e fronds, which are less affected by desiccation (Longtin and Scrosati \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). It is unclear whether the desiccation has been slowed additionally by the presence of \u003cem\u003eV. lanosa\u003c/em\u003e, as in our study, or if self-shading within the canopy of \u003cem\u003eA. nodosum\u003c/em\u003e is also concentrated within the middle segments. As such, the position of \u003cem\u003eV.\u003c/em\u003e lanosa on its host may help to limit its own water loss.\u003c/p\u003e \u003cp\u003eFuture studies should look at the photosynthetic rate and growth effects of \u003cem\u003eV. lanosa\u003c/em\u003e on \u003cem\u003eA. nodosum\u003c/em\u003e. While decreasing desiccation rates increases the amount of time the host algae would have to photosynthesize (Dring and Brown \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Madsen and Maberly \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), there might be other ways the epiphyte reduces photosynthesis. Epiphyte cover has been shown to reduce light reaching \u003cem\u003eA. nosodum\u003c/em\u003e fronds by up to 40% (Kraberg and Norton \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Like most photosynthesizers, initial increases in light intensity increase the growth of \u003cem\u003eA. nodosum\u003c/em\u003e (Sheader and Moss \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1975\u003c/span\u003e). The question then becomes, is the impact of shading on photosynthetic yield offset by the benefits of slower desiccation rates? Alternatively, It is possible that the shading by \u003cem\u003eV. lanosa\u003c/em\u003e is an additional benefit of its presence. When algae are exposed to high levels of light irradiance, oxidative free radicals are released and can cause cellular damage (Kennedy et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Epiphytes have been shown to protect hosts from desiccation and UV radiation in seagrass communities (Penhale and Smith \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1977\u003c/span\u003e). Here, \u003cem\u003eV. lanosa\u003c/em\u003e could aid \u003cem\u003eA. nodosum\u003c/em\u003e from both water loss and the harmful solar radiation.\u003c/p\u003e \u003cp\u003eAnthropogenic climate change can alter interspecific interactions and produce unexpected changes in species distribution and structure. This is particularly relevant for the intertidal zone as these organisms already live near their thermal tolerance limits and may experience daily stressful conditions. As temperature has increased the upper intertidal distribution of many species have decreased, but the upper distributional limits of interacting species do not always shift at the same (Harley \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). By reducing desiccation stress, \u003cem\u003eV. lanosa\u003c/em\u003e may slow changes in \u003cem\u003eA. nodosum\u003c/em\u003e intertidal distribution.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study found that \u003cem\u003eV. lanosa\u003c/em\u003e epiphytes may mediate desiccation of their host, \u003cem\u003eA. nodosum\u003c/em\u003e under mild light conditions. Additionally, \u003cem\u003eA. nodosum\u003c/em\u003e appears to take water from the thallus of \u003cem\u003eV. lanosa\u003c/em\u003e, likely due to the differences in morphology between the species. \u003cem\u003eV. lanosa\u003c/em\u003e serves as an epiphyte and has been shown to decrease reproductive output and block light from reaching its host \u003cem\u003eA. nodosum\u003c/em\u003e. However, \u003cem\u003eV. lanosa\u003c/em\u003e may help prevent desiccation of its host during mild light conditions, potentially revealing a semi-mutualistic relationship between the two algae. This is the first study to demonstrate desiccation benefits conferred on \u003cem\u003eA. nodosum\u003c/em\u003e by \u003cem\u003eV. lanosa.\u003c/em\u003e This study also found that \u003cem\u003eV. lanosa\u003c/em\u003e does not prevent herbivory of \u003cem\u003eLittorina sp.\u003c/em\u003e on \u003cem\u003eA. nodosum\u003c/em\u003e which conflicts with the theory of \u003cem\u003eV. lanosa\u003c/em\u003e as a mutualistic herbivory protector of \u003cem\u003eA. nodosum.\u003c/em\u003e Further examination of how desiccation affects epiphytic relationships between algal species in the rocky intertidal zone may help reveal key adaptations to climate change and increases solar radiation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eResearch expenses and G. DeCarolis\u0026rsquo;s spring 2025 salary were funded through the Bates Faculty Development Fund. G. DeCarolis\u0026rsquo;s summer 2024 stipend came from Bates College\u0026rsquo;s STEM Faculty-Student Summer Grant. K. Moore\u0026rsquo;s stipend was funded through Bates College\u0026rsquo;s Summer Research Fellowship. All three funding programs were provided through the Dean of the Faculty's office at Bates College.\u003c/p\u003e \u003cp\u003eAuthor information\u003c/p\u003e \u003cp\u003eAuthors and Affiliations\u003c/p\u003e \u003cp\u003eDepartment of Biology, Bates College, Lewiston, ME 04240, USA.\u003c/p\u003e \u003cp\u003eGemma DeCarolis, Kenyon Moore, Kathryn M Anderson\u003c/p\u003e \u003cp\u003eDepartment of Biology, The Graduate Center, The City University of New York, 10016, U.S.A\u003c/p\u003e \u003cp\u003eKenyon Moore (current)\u003c/p\u003e \u003cp\u003eDivision of Integrative and Marine Sciences, University of Maine at Machias, Machias, ME 04654, USA\u003c/p\u003e \u003cp\u003eKathryn M Anderson (current)\u003c/p\u003e \u003cp\u003eContributions\u003c/p\u003e \u003cp\u003eProject conceptualization, development of methodology, and writing of the original draft was led by G. DeCarolis and K. Moore with assistance from K. Anderson. The investigation was conducted by G. DeCarolis and K. Moore. Formal analysis was done by K. Anderson with assistance from G. DeCarolis. Data visualisation, data curation, supervision, project administration, funding acquisition, and resource provisioning done by K. Anderson. All authors were actively involved in the revision and editing of the manuscript.\u003c/p\u003e \u003cp\u003eCorresponding author\u003c/p\u003e \u003cp\u003eKathryn M. Anderson: [email protected]\u003c/p\u003e \u003cp\u003eEthics declarations\u003c/p\u003e \u003cp\u003eConflict of interest\u003c/p\u003e \u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e \u003cp\u003eEthical approval\u003c/p\u003e \u003cp\u003eThis research met institutional, national, and international ethical standards.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eWe would like to thank Viuro Nkemngong for his help in the lab and field. We would also like to thank Sonya Locke for her continued support with equipment, filing for reimbursement, and general knowledge about resources within the Biology Department at Bates. We would also like to thank Zoom, snacks, and our pets, without which this paper would have never been written.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eData and code used for data analysis will be made available upon request to the corresponding author.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnderson L (2012) Costs and benefits of intertidal algal epiphytism. Master\u0026rsquo;s thesis, University of British Columbia\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnderson LM, Martone PT (2014) Biomechanical consequences of epiphytism in intertidal macroalgae. 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J Sea Res 80:50\u0026ndash;57. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.seares.2013.02.008\u003c/span\u003e\u003cspan address=\"10.1016/j.seares.2013.02.008\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"marine-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mabi","sideBox":"Learn more about [Marine Biology](https://www.springer.com/journal/227)","snPcode":"227","submissionUrl":"https://submission.nature.com/new-submission/227/3","title":"Marine Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Epiphytes, algae, desiccation, intertidal, emersion","lastPublishedDoi":"10.21203/rs.3.rs-9162511/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9162511/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study explicitly aims to understand the potential positive effects of the intertidal red algal epiphyte \u003cem\u003eVertebrata lanosa\u003c/em\u003e on its brown algal host \u003cem\u003eAscophyllum nodosum\u003c/em\u003e via reductions in desiccation and herbivory rates. To determine the effect of this epiphyte on the desiccation rates of its host, desiccation rates of both the host and epiphyte were measured when allowed to dry in contact with or in isolation from each other in high and low light conditions. To test if \u003cem\u003eV. lanosa\u003c/em\u003e might reduce herbivore pressure on \u003cem\u003eA. nodosum\u003c/em\u003e by providing an alternative and preferred food source, the feeding rates of two common herbivorous snail congeners (\u003cem\u003eLittorina littorea\u003c/em\u003e and \u003cem\u003eL. obtusata\u003c/em\u003e) on both algae were measured when offered each alga simultaneously or in isolation. Specimens used were collected from Bailey Island, Maine, USA (43.721249, -70.001740) in July 2024 and May 2025. The preferences and consumption rates of our herbivores were fixed regardless of whether they had a choice of which algae to eat, indicating that this epiphyte does not benefit its host by altering the behavior of these dominant herbivore species. However, the epiphyte significantly reduced the hosts\u0026rsquo; rate of water loss but only in low light conditions. As most intertidal Fucoid algae photosynthesize fastest at low to intermediate levels of desiccation, the presence of \u003cem\u003eV. lanosa\u003c/em\u003e is likely to allow \u003cem\u003eA. nodosum\u003c/em\u003e to have greater photosynthetic rates for longer, during periods of emersion, allowing for greater overall growth.\u003c/p\u003e","manuscriptTitle":"Presence of epiphytic algae, Vertebrata lanosa, positively impacts host algae, Ascophyllum nodosum, by reducing desiccation rates.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-13 13:42:58","doi":"10.21203/rs.3.rs-9162511/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-04-07T17:22:45+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-07T04:51:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-02T11:23:06+00:00","index":"","fulltext":""},{"type":"submitted","content":"Marine Biology","date":"2026-03-24T13:33:01+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"marine-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mabi","sideBox":"Learn more about [Marine Biology](https://www.springer.com/journal/227)","snPcode":"227","submissionUrl":"https://submission.nature.com/new-submission/227/3","title":"Marine Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e0522eb0-405a-40ac-a2fe-059ab9337537","owner":[],"postedDate":"April 13th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Acceptable after minor revision","date":"2026-04-30T20:06:35+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-01T00:07:53+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-13 13:42:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9162511","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9162511","identity":"rs-9162511","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}