Evolution of Critical Shear Stress in the Seabed of an Urbanized Estuary and Natural Estuary after the Passage of Hurricane Ian

Evolution of Critical Shear Stress in the Seabed of an Urbanized Estuary and Natural Estuary after the Passage of Hurricane Ian | 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 Evolution of Critical Shear Stress in the Seabed of an Urbanized Estuary and Natural Estuary after the Passage of Hurricane Ian David Fugate This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5938586/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Jun, 2025 Read the published version in Geo-Marine Letters → Version 1 posted 10 You are reading this latest preprint version Abstract Sediment transport and mixing in estuaries impact a number of ecosystem services, including the flux of nutrients and the mediation of turbidity of the water column, which in turn affects the health of seagrasses and other benthic primary producers. A key factor to predicting the direction and strength of sediment transport is the critical shear stress required to erode sediment from the bed. But the erodibility of fine sediments is poorly constrained because of the complicated interactions between grainsize, consolidation, and biological factors. This study assessed the evolution of critical shear stress and erodibility of the seabed in southwest Florida, USA after the intense disturbance of Hurricane Ian. We also compared how the evolution of the bed differed in a location that has had extensive development with a nearby but undeveloped bay with no anthropogenic development. Erodibility and critical shear stress were measured with Gust-type erosional chambers. Profiles of 7 Be and Xradiographs were used to determine the extent of new sediment deposition and bioturbation. Hydrodynamics were measured with an acoustic doppler current profiler. Hurricane Ian initially eroded the seabed down to a consolidated layer with high critical shear stress (1-1.5 Pa) and low erodibility at both sites. In the subsequent months, new sediments were deposited and rapid bioadvection of the top 6 cm ensued. The shear stress was reduced (~0.25 Pa) and erodibility increased by the end of the study. Recovery was more rapid in the undeveloped site because the hydrodynamics were more energetic. Both sites returned to stability within one year of the passage of the storm. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Sediment transport and mixing in estuaries impact the flux of nutrients and sediment associated contaminants horizontally within the aquatic system and vertically within the seabed. Additionally, the transport of sediment affects the turbidity of the water column, which in turn affects the health of seagrasses and other benthic primary producers. Sediment transport also determines the morphology of the seabed, which can change rapidly during storm conditions. A key factor to predicting the direction and strength of sediment transport is the critical shear stress required to erode sediment from the bed. But the erodibility of fine sediments is poorly constrained because of the complicated interactions between grainsize, consolidation, and biological factors (Xie et al., 2021). Because of these complexities it has not been possible to predict erodibility without site specific measurements (Wiberg, 2013). The goal of this project was to assess the evolution of critical shear stress and erodibility of the seabed in southwest Florida after the intense disturbance of Hurricane Ian. The critical shear stress and erodibility of the seabed depends not only upon the size of the sediment, but the opposing effects of algal mat and bacterial biofilm production versus bioturbation and bioadvection. We also compared how the evolution of the bed differed in a location that has had extensive development with a nearby but undeveloped bay with no anthropogenic development. Hurricane Ian struck southwest Florida as a Category 4 storm on September 28, 2022. Storm surge reached nearly 4 m near the coast and maximum sustained winds between 80 and 100 mph in the city of Naples (Fig. 1). Ian was a slow-moving storm, and the combination of storm surge and wind speed occurred during high tide causing extensive destruction and death. Turbidity in Estero Bay, Fl, a natural preserve near the sites for this study in Naples, was measured during the storm and showed extremely high levels of sediment resuspension. Additionally, salinity gradients were greatly increased, which set up the potential for stronger gravitational circulation to import sediment into the estuary. These conditions were likely to have strongly disturbed the pre-existing seabed and to have produced significant deposition. It was hypothesized that critical shear stresses were greatly decreased and the potential for transport of sediment and sediment affiliated contaminants was greatly increased just after the passage of the storm. This is a special concern as storm surges from hurricanes are known to increase heavy metal concentrations in the seabed (Han et al., 2022; Personna et al., 2015). Mixed coarse and fine grain sediments often develop biological films and mats that increase the critical shear stress necessary to resuspend and transport the sediments (e.g. Chen et al., 2017). In contrast, bioturbation and bioadvection by benthic fauna can disaggregate the sediment and break up biological films and mats, resulting in decreased shear stress and more easily transported sediments(e.g. Porter et al., 2020; Widdows & Brinsley, 2002). We hypothesized that the passage of the storm created a major disturbance to the sediment bed and broke up any algal mats or biofilms that may have stabilized the bed. Subsequently sediment could be easily resuspended to scavenge pollutants and enhance transport. This study quantified the timing and evolution of the critical shear stress and erodibility of the seabed as well as assessed the degree of bioturbation. We also examined how the seabed evolution differs between two nearby sites in southwest Florida, Naples Bay and Dollar Bay (Fig. 1) Naples Bay is heavily urbanized with extensive seawall construction bordering the Bay and associated finger canals. Dollar Bay is nearby but has no anthropogenic development. Previous work by Dellapenna et al. (2013) suggested that in the undeveloped region of Dollar Bay, the trapping of fine sediments in the mangrove fringe reduced the fine sediment fraction in the open bay. In contrast, Naples Bay with greatly reduced natural mangrove fringe was found to have more mobile fine sediment in the open Bay. We hypothesized that the difference in sediment size fractions affected the evolution of the critical bed shear stress in the two sites. Physical Setting and Sampling Description The developed site was located at latitude 26.10226° N, longitude 81.79831° W in lower Naples Bay and was surrounded by residential development (Fig. 1). Salinity in this location is usually near ocean salinity values (Taylor Engineering, Inc., 2005) except during the rainy season when lower salinity episodically appears. The site is microtidal with mixed-semidiurnal tides. The undeveloped site was located at latitude 26.09224° N, longitude 81.78543° W in nearby Dollar Bay, about 1.8 km away from the Naples Bay site. With close access to the Gulf of Mexico, salinity, tidal frequency and tidal range are similar to the ocean and the Naples Bay site. The two sites were visited seasonally starting in spring 2023 through winter 2024. At each site and sampling event three cores were obtained for erodibility analysis, Xradiographs, and radioisotope counting, for a total of nine cores. Because of the necessity of analyzing erodibility as soon as possible after taking each core, and the fact that it takes about 4 hours to process each core, sample times of the two sites were lagged one to two weeks. The sampling dates for each site and season were as follows: Spring 2023 March 29, 2023, Dollar Bay April 7, 2023, Naples Bay Summer 2023 July 5, 2023, Dollar Bay July 12, 2023, Naples Bay Fall 2023 Nov 2, 2023, Naples Bay Nov 14, 2023, Dollar Bay Winter 2024 Mar 2, 2023, Dollar Bay Mar 9, 2023, Naples Bay Methods Critical Shear Stress and Erodibility Critical shear stress and erodibility was measured with a Gust-type erosion chamber comprising a housing with a rotating shear plate, removable lid, and water input and output connections. It uses a rotating disk with central suction to apply a nearly uniform shear stress on the surface of a ten-centimeter diameter core. The rotating head fits directly onto the core tube and a uniform shear stress can be applied across the sediment surface by controlling both the rotation rate of the shear plate, and the rate at which water is pumped through the device. Water and entrained sediment are pumped from the chamber through a turbidity meter and into sampling bottles to measure the eroded mass. The applied shear stress was increased in seven steps beginning with 0.01 Pa for thirty minutes of flushing, followed by a typical series of 0.05, 0.10, 0.20, 0.30, 0.45, and 0.60 Pa for twenty minutes each (e.g. Dickhudt et al., 2009 ; Fugate et al., 2021 ; Wiberg et al., 2013 ). Maintaining the in-situ salinity at the time of coring is important to prevent laboratory induced changes in flocculation, so water collected from the site was used to replenish the water that was pumped out for analysis. The effluent was filtered through preweighed glass microfiber 0.7 µm filters, dried for four or more days and reweighed to determine the eroded mass at each step. Three replicate 50–80 cm long and 10 cm diameter acrylic cores of sediment were taken in seasonally from spring 2023 to winter 2024 at each of the two sites. Cores were retrieved by hand in 1-1.5 m water depth. Analysis was on the same day or day after the cores were retrieved to reduce the potential effects of consolidation. The erodibility and critical shear stress are determined by solving the Sanford and Maa ( 2001 ) formulation for Type 1 erosion: $$\:E=M{[{\tau\:}_{b}-{\tau\:}_{c}\left(z\right)]}^{n}$$ 1 where E is the erosion rate in mass per area per time, M is an empirical constant called the mass transfer rate, τ b is the applied bottom shear stress, τ c is the critical shear stress for erosion, z is depth, and n is an empirical constant. Type 1 erosion is characterized by an increasing critical shear stress with depth. However, type 2 erosion, in which the critical shear stress does not increase with depth is also covered by this formulation when n is found to be equal to one. The analysis is performed using Matlab code that was originally developed by Patrick Dickhudt and then modified by subsequent users (e.g. Fugate et al., 2021 ). The Gust chamber analysis allows measurement of change in critical shear stress at a very high resolution, often on the order of millimeters. Because of the very fine depth scale, which would be difficult to measure, the amount of eroded mass from each core provides a proxy for depth so that it is possible to visualize the vertical changes in critical shear stress over a very small depth range. Radioisotopes Three 4-inch diameter aluminum cores were taken at each site and each sampling event. The cores were split open and sectioned into 1-cm depth samples down to 7 cm. The samples were sent to Texas A&M University for further processing by Tim Dellapenna’s laboratory team. The sediment samples were dried in an oven at 50–60°C, and then ground with a SPEX SamplePrep 8000M mixer/mill. About 8.0 g of sediment was packed in a volume of 5 mL in the counting tube. The sample was allowed to be counted for 24 hours with a SAGe well detector with a 120cc-16 mm well (Mirion, USA). Activity concentrations of 7 Be were measured by gamma counting the 477.6 keV line and activity of 210 Pb was measured by gamma counting at 46.5 keV. The decays per minute to counts per minute ratio is obtained by previous calibration. Activities were decay corrected but grainsizes were found to be similar at both sites and all depths, so corrections for grainsize were not made. Grainsize Grainsize results were available from two sources. The first source was sediment samples from three cores at each site that were used to measure radioisotope activity during fall 2023 and winter 2024. They provided profiles of the grainsize every centimeter down to seven centimeters. These samples were analyzed with a Malvern Mastersizer 2000G. The second source was from surface (top cm) grabs that were wet sieved during the first (spring 2023) and last (winter 2024) sampling events. Sieve sizes for the spring 2023 sample were 125 µm -250 µm, 250 µm -500 µm, 500 µm – 1000 µm, 1000 µm – 2000 µm, and > 2000 µm. Sieve sizes for the winter 2024 sample were 63 µm -125 µm, 125 µm – 250 µm, 250 µm -500 µm, 500 µm – 600 µm, 600 µm – 2000 µm 2000 µm – 4000 µm, and > 4000 µm. Though these sieve sizes were not all the same for the two seasons, the dominant grain sizes appeared in the size ranges that were the same for both seasons, i.e. the 125 µm − 250 µm, and 250 µm – 500 µm ranges. Current Measurements Current velocities were measured at each site for about two weeks during the fall 2023 sampling event with a Nortek 2000 kHz Aquadopp HR profiler. The instruments were deployed upward looking with a cell size of 50 mm and blanking distance of 104 mm. Bursts of 4800 measurements were made at a sampling rate of 8 Hz at intervals of 30 minutes. Xradiographs Sediment cores were taken with 4 in diameter polycarbonate tubes and packed with floral foam before sending to Texas A&M University for X-raying by Tim Dellapenna’s laboratory team using a MinXray TR8020. Results Critical Shear Stress and Erodibility Profiles of critical shear stress by eroded mass (a proxy for depth in sediment) are variable for all cores from both the Dollar Bay site and the Naples Bay site (Fig. 2 ). Initial critical shear stress values show little variation, most appear between 0.05 and 0.1 Pa for both sites. To better examine differences, these profiles were fit to a power law (Dickhudt et al., 2009 ): $$\:{\tau\:}_{c}=a{m}^{b}+{\tau\:}_{c0}$$ 2 where τ c is the critical shear stress for erosion, m is the cumulated eroded mass, τ c0 is the initial surface critical shear stress for erosion, and a and b are fitted parameters. One core from Dollar Bay in winter 2024 and one core from Naples Bay in fall 2023 proved to have poor fits of the erosion equation (equation #1) during the Gust analyses, and these cores are removed from the analysis. Comparisons of the fitted critical shear stress after a fixed amount (0.05 kg m − 2 ) of mass has been eroded produce more discernable patterns than the raw analyses. The median fit critical shear stress near the surface at 0.05 kg m − 2 was higher during spring 2023 at both sites (Fig. 3 ), although ANOVA results showed marginal significance (p = 0.10) for differences in critical shear stress by season at the Dollar Bay site and no significant difference at the Naples site (p = 0.52). Predicted critical shear stress near the surface was 1.6 Pa in spring 2023 at Dollar Bay and fell to around 0.2 - 0.3 Pa for the other seasons. Predicted critical shear stress near the surface was 0.9 Pa in spring 2023 at Dollar Bay and ranged from 0.3 - 0.8 Pa for the other seasons. Figure 3 Predicted critical shear stress after 0.05 kg m -2 have been eroded from a) Dollar Bay site and b) Naples Bay site. Excludes one core with poor fit from each site. Red line shows median, edges of box are 25th and 75th percentiles, whiskers extend to maximum and minimum values. The erodibility of the sediment for each core can also be quantified by the cumulative amount of mass eroded at the end of the 0.45 Pa step in the erosion chamber (e.g. Dickhudt et al., 2009 ; Fugate et al., 2021 ; Wiberg et al., 2013 ). The temporal pattern of median eroded mass better shows the evolution of the seabed and is consistent with the pattern of critical shear stress at both sites (Fig. 4 ). Right after the hurricane, the median eroded sediment was lower at both sites, reflecting the higher critical shear stress and consolidated bed. The amount of eroded mass at the end of the 0.45 Pa step increased significantly and by nine months after the passage of the hurricane remained about the same (2-way ANOVA, p=0.009). Sediment from Dollar Bay was consistently more erodible than that from Naples Bay (2-way ANOVA, p=0.002). Eroded mass at Dollar Bay rapidly rose from 0.06 kg m -2 in spring 2023 to 0.12 kg m -2 in summer 2023 and leveled off to around 0.17 kg m -2 in fall 2023 and winter 2024. In Naples Bay the eroded mass was around 0.04 kg m -2 in spring 2023 and rose only slightly to 0.04 kg m-2 in fall 2023. The erodibility then rose rapidly to 0.11 kg m -2 in fall 2023 and was only slightly lower (0.09 kg m -2 ) in winter 2024. These results suggest that during the hurricane, the bed was eroded to a consolidated layer that had a high critical shear stress and low erodibility. As time passed more unconsolidated sediments were deposited, or bioturbation increased the erodibility, or both. Grainsize Grainsize results were available from two sources. Profiles of grainsize determined by the Malvern were available for fall 2023 and winter 2024 at both sites. Surface sample grabs from the top centimeter of sediment that was wet-sieved were available for the first (spring 2023) and last (winter 2024) deployments at each site. Profiles of the mean of median diameters measured by the Malvern from the three cores at each site and season show that there was not much vertical variation or difference between the two sites and two seasons (Figs. 5ab). The fall 2023 results indicate that the Naples Bay sediment may have been somewhat coarser, but not statistically so at each depth. Dollar Bay sediments had median diameters between 25 µm and 50 µm along the vertical profile. Median diameters of Naples Bay sediments ranged from 50 µm to 150 µm, with the coarser end of the range in the top 4 cm. There was a localized increase in median grain size to about 150 µm at the Naples Bay site in the 3–4 cm depth samples. The winter 2024 grainsize distributions were more similar between sites and vertically than the fall cores and suggested a slight fining of sediments at Naples Bay between 1 and 4 cm depth. Median diameters ranged between 25 µm to 50 µm between both sites and depth in the sediment, except for the surface which had median grain sizes 675 µm or larger at both sites. The main difference between the fall 2023 and winter 2024 grainsizes was this much larger median diameter at the surface layer during the winter 2024 at both sites. This may be attributed to an increase in bivalve populations creating shell hash at the surface at both sites. Because of the general similarities in grainsize both between seasons and with depth, the 7 Be activities were not normalized by grainsize. Surface grab samples from the sites showed little variation in grainsize through the course of the study (Figs. 5cd). However, the results indicate that there was more shell hash at Dollar Bay than Naples Bay at the beginning and end of the study. The dominant peak in grain size frequency appeared at both sites in the 250–500 µm range in spring 2023 and in the 125–250 µm range in winter 2024, indicating a slight fining of the particles over the course of the study. This is consistent with the change in Naples Bay sediment sizes from the core samples but is not reflected in the Dollar Bay sediment sizes from the core samples. A general fining of the sediment would be consistent with deposition of new fine sediment that is mixed down into the sediment from bioadvection. The surface grab sample increase in shell hash in Dollar Bay compared to Naples Bay during both seasons suggests that Dollar Bay was more biologically dynamic and had a larger bivalve population than Naples Bay. Radioisotopes No significant 7 Be was found in the top 3 cm of any of the three cores at either of the two sites in the spring 2023 sampling event, so no more radioisotope analyses were performed for the lower depths. This finding suggests that recently deposited sediments were eroded by the hurricane and there was no new deposition. By summer 2023, 7 Be was found in Dollar Bay and distributed throughout the top 6 cm. Mean decay rates in Dollar Bay ranged from 0-0.05 Bq kg − 1 . Naples Bay had very low levels of 7 Be in summer 2023 (maximum mean of 0.005 Bq kg − 1 at 5.5 cm depth) but more in fall 2023 and winter 2024 which ranged from 0-0.025 Bq kg − 1 . The highly variable profiles at both sites suggest that once 7 Be was deposited at the bed surface it was rapidly bioadvected throughout the top 7 cm in Dollar Bay and the top 6 cm in Naples Bay. Total inventories better show the evolution of the bed (Fig. 6 ). Dollar Bay accumulated new sediment more rapidly after scouring by the hurricane than Naples Bay, but both reached peak inventories in fall 2023 when rainfall was higher. Activity rates dropped at both sites during the dry season of winter 2024. Dollar Bay also had consistently higher total activity rates than Naples Bay, suggesting higher deposition rates. These data are consistent with the erodibility analyses that suggested that Dollar Bay received sediment deposits by the summer, while Naples Bay did not have much sediment deposition until fall. The overall higher erodibility of Dollar Bay is also consistent with the 7 Be inventory pattern of more deposition of fine sediments at Dollar Bay. The differences in the summer values also suggest that rainfall was not the main determinant of 7 Be variation, since the rainfall would have been the same for the two geographically close stations. Lead-210 isotope activity was available for the summer, fall, and winter seasons. Variable profiles of activity support the presence of bioadvection in the sediment, with peaks in activity all at 3.5 cm or below. Peak mean 210 PB activity ranged from 0.14 to 0.16 Bq kg -1 at Dollar Bay and from 0.07 to 0.11 Bq kg -1 at Naples Bay. The total inventory of 210 Pb remained relatively constant from summer 2023 to winter 2024 at both sites. Dollar Bay inventories were consistently about to 0.7e -3 Bq cm -2 higher than Naples Bay. Current Velocities Current velocities at Dollar Bay were much stronger than those at Naples Bay and exhibited a more recognizable tidal pattern (Fig. 7 ). The ADCP at Naples Bay failed after 6.5 days, so currents are compared only for the times when measurements were available from both sites. Horizontal velocities at 0.33 m above the bottom in Dollar Bay ranged from − 0.16 m s − 1 to 0.16 m s − 1 (flood is positive). Horizontal velocities at 0.33 m above the bottom in Naples Bay only ranged from − 0.04 m s − 1 to 0.07 m s − 1 . These differences in current velocities were likely responsible for most of the differences observed in the evolution of the respective beds at each site. The Naples Bay site is in an enclosed basin with little circulation compared to Dollar Bay which has access to Gulf at both ends and stronger potential for sediment transport. Xradiographs Xradiographs shed little light on the evolution of the seabed. All xradiographs showed similar characteristics of a mottled fine grained matrix embedded with bivalves. There was no apparent change in the appearance across time or between the sites. However, while not apparent from the xradiographs, both large and small burrows and bioturbating organisms such as Alpheidae spp . (snapping shrimp) and Cerithium aratum (gastropods) were observed in the polycarbonate cores used for the Gust analysis starting in summer 2023 at Dollar Bay (Fig. 15), but not in the previous spring. Discussion and Conclusions The results from the data did not support the hypothesis that the hurricane deposited large amounts of unconsolidated sediment. Instead of depositing sediment, the hurricane scoured the seabed at both sites to a more consolidated layer. Critical shear stress was higher just after passage of the hurricane and erodibility was lower. Wang et al. ( 2000 ) also found that during episodic wind events erosion occurred down to a more consolidated bed below a thin layer of loosely consolidated material, leaving a seabed with higher critical shear stress and lower erodibility. Defne et al. ( 2019 ) found that Hurricane Sandy eroded sediment from shallow and shoal areas and redeposited over the adjacent low lying land in a back barrier estuary in New Jersey, USA. This is the likely scenario that occurred at the sites in Naples Bay and Dollar Bay after the passage of Hurricane Ian. By summer 2023, the undeveloped site, Dollar Bay, had recent sediment deposits as shown by 7 Be counts. These deposits were more easily erodible and in the next two seasons as more sediment was deposited the bed became more erodible. Additionally, the hurricane likely dampened bioturbation along with the scouring. By summer 2023 bioturbating organisms were recruited to the area as evidenced by 7 Be profiles exhibiting bioadvection, and by visual inspection of cores. The sediment bed at the developed site, Naples Bay, lagged in recovery compared to Dollar Bay because of the enclosed basin and resultant minimal flow dynamics there. The weaker hydrodynamics of the Naples Bay site is also likely responsible for the smaller grainsize found there by Dellapenna et al. ( 2013 ) compared to the Dollar Bay site. Prediction of sediment transport after storms using numerical models must first establish the condition of the seabed after the storm. We found that scouring by the storm left a seabed with a consolidated surface critical shear stress between 1.0 and 1.5 Pa at Naples Bay and Dollar Bay, respectively. After deposition of fine sediment, the critical shear stresses dropped to around 0.25 Pa at both sites. These values are somewhat higher than critical shear stresses determined in other estuaries. In San Jacinto, TX, Saleh and Strom (2012) found critical shear stresses of 0.14 Pa and 0.06 Pa in sediments with median diameters slightly lower (93 µm and 42 µm, respectively) than those in this study. Widdows et al. ( 2006 ) found a critical shear stress of 0.12 Pa after consolidation of emplaced fine sediments (> 72% silt) in Essex, UK estuary. Deposition at the Naples Bay site was lagged about 3 months because of the lower energy environment and reduced sediment availability. Both sites were recolonized by bioadvectors within 9 to 12 months of the hurricane, with the Naples Bay site again lagged one season behind the Dollar Bay site. The presence or absence of mangroves had less of an effect on sediment transport than the level of hydrodynamic energy at the two sites. Thrush et al. ( 2003 ) found a complete recovery of macrofauna after sediment deposition in 2 out of 6 sites within 212 days. Local hydrodynamics were also fundamental to determining the rates of recovery, with those living in more energetic environments recovering more rapidly. Though the disturbance in Thrush et al.’s study was sediment deposition rather than sediment erosion, the key findings were similar to this study with respect to the importance of hydrodynamics and the timing of recovery. Forsberg et al. (2018) found opposite results from this study after storms in a Danish lagoon. They concluded that the erosion of submerged aquatic vegetation during storms decreased the critical shear stress and increased the erodibility of the seabed. Despite the intensity of Hurricane Ian, the seabed at the two study sites appeared to have stabilized and recovered within a year of passage of the storm. The results of this project and comparisons with other studies confirm the variable responses of different estuaries to storms and that site specific measurements need to be made to predict critical shear stress. The results also suggest that resources may be better spent on repair of infrastructure and buildings after a destructive storm rather than restoration of the natural environment, which has proved to be resilient at these two sites. Declarations Funding was provided by the National Science Foundation under Grant Number 2306741. The author has no competing interests to declare that are relevant to the content of this article. Author Contribution David Fugate wholly contributed to the conception of the work, the acquisition of funding and data, analysis, and interpretation of the data and wrote the manuscript. Acknowledgement The author would like to thank Captain Brandon Galindo and my students that helped in the field and laboratory, Laura Dunn, Braden Wood, Elizabeth Dahedl, Nyx Schuler, and Kaitlyn Beynon. The author is also deeply grateful to Tim Dellapenna and his laboratory staff at Texas A&M University, Galveston for performing radioisotope counting and Xradiographs. This work was supported by the National Science Foundation under Grant Number 2306741. Data Availability Data Management PlanFollowing is the plan for managing the scientific data generated as a result of the proposedresearch.1. Types of data, samples, physical collections, software, curriculum materials, and othermaterials to be produced in the course of the project.This project will produce data from three primary sources, Gust erosion experiments, X-radiographs of cores, and 7Be core profiles. Gust data obtained include:• Log sheets manually prepared during the experiment that document the start and end times of each shear stress step and the sample bottles used to collect effluent.• Log sheets generated by the Gust system that include the date time signature, the elapsed time, the NTUs from the turbidimeter and the RPMs of the Gust plate.• Total suspended sediment concentrations from the effluent bottles.Xradiograph data will include:• Digital images of each core7Be data will include:• Data sheets denoting the core #, site, date time, core interval, and 7Be concentration2. Standards to be used for data and metadata format and content.Data generated from the Gust experiments will be formatted in comma delimited text files. The reason for using text files rather than the more generally used netCDF format is that the commonly used software to analyze Gust experiment data is written in Matlab which reads the input data in the form of these text input files.The digital images from the core Xradiographs will be stored in .jpeg format.Data from the 7Be profiles will be stored in text format.3. Policies for access and sharing including provisions for appropriate protection of privacy,confidentiality, security, intellectual property, or other rights or requirements.Data collected under the project will be made available to the public with as few restrictionsas possible. The data will be submitted to the Marine Geoscience Data System. All data products will be made publicly accessible within two (2) years of collection and maintained for a minimum of three (3) years after the end of the project, in accordance with NSF and OCE Division policies.4. Policies and provisions for re-use, re-distribution, and the production of derivatives.Data generated from this project will be archived at the Marine Geoscience Data System by September 2026 References Chen, X., Zhang, C., Paterson, D., Thompson, C., Townend, I., Gong, Z., Zhou, Z., & Feng, Q. (2017). Hindered erosion: The biological mediation of noncohesive sediment behavior. Water Resources Research , 53 (6), 4787–4801. Defne, Z., Ganju, N. K., & Moriarty, J. M. (2019). Hydrodynamic and morphologic response of a back‐barrier estuary to an extratropical storm. Journal of Geophysical Research: Oceans , 124 (11), 7700–7717. Dellapenna, T. M., Fielder, B., Noll, C. J. I., & Savarese, M. (2013). Geological responses to urbanization of the Naples Bay Estuarine System, southwester Florida, USA. Estuaries and Coasts . https://doi.org/10.1007/s12237-013-9704-2 Dickhudt, P. J., Friedrichs, C. T., Schaffner, L. C., & Sanford, L. P. (2009). Spatial and temporal variation in cohesive sediment erodibility in the York River estuary, eastern USA: a biologically influenced equilibrium modified by seasonal deposition. Marine Geology , 267 , 128–140. Fugate, D. C., Thomas, S., & Scinto, L. J. (2021). Particle dynamics in stormwater treatment areas. Ecological Engineering , 160 , 106131. Han, I., Whitworth, K. W., Christensen, B., Afshar, M., Han, H. A., Rammah, A., Oluwadairo, T., & Symanski, E. (2022). Heavy metal pollution of soils and risk assessment in Houston, Texas following Hurricane Harvey. Environmental Pollution , 296 , 118717. Personna, Y. R., Geng, X., Saleh, F., Shu, Z., Jackson, N., Weinstein, M. P., & Boufadel, M. C. (2015). Monitoring changes in salinity and metal concentrations in New Jersey (USA) coastal ecosystems Post-Hurricane Sandy. Environmental Earth Sciences , 73 , 1169–1177. Porter, E. T., Johnson, B. J., & Sanford, L. P. (2020). Effects of hard clam (Mercenaria mercenaria) density and bottom shear stress on cohesive sediment erodibility and implications for benthic-pelagic coupling . Salehi, M., & Strom, K. (2012). Measurement of critical shear stress for mud mixtures in the San Jacinto estuary under different wave and current combinations. Continental Shelf Research , 47 , 78–92. Sanford, L. P., & Maa, J. P. (2001). A unified erosion formulation for fine sediments. Marine Geology , 179 , 9–23. Taylor Engineering, Inc. (2005). Evaluation of Naples Bay Water Quality and Hydrologic Data . South Florida Water Management District. Thrush, S. F., Hewitt, J. E., Norkko, A., Cummings, V. J., & Funnell, G. A. (2003). Macrobenthic recovery processes following catastrophic sedimentation on estuarine sandflats. Ecological Applications , 13 (5), 1433–1455. Wang, Y., Bohlen, W. F., & O’donnell, J. (2000). Storm enhanced bottom shear stress and associated sediment entrainment in a moderate energetic estuary. Journal of Oceanography , 56 , 311–317. Wiberg, P. L., Law, B. A., Wheatcroft, R. A., Milligan, T. G., & Hill, P. S. (2013). Seasonal variations in erodibility and sediment transport potential in a mesotidal channel-flat complex, Willapa Bay, WA. Hydrodynamics and Sedimentation on Mesotidal Sand- and Mudflats , 60 , S185–S197. https://doi.org/10.1016/j.csr.2012.07.021 Widdows, J., & Brinsley, M. (2002). Impact of biotic and abiotic processes on sediment dynamics and the consequences to the structure and functioning of the intertidal zone. Structuring Factors of Shallow Marine Coastal Communities, Part I , 48 (2), 143–156. https://doi.org/10.1016/S1385-1101(02)00148-X Widdows, J., Brinsley, M., Pope, N., Staff, F., Bolam, S., & Somerfield, P. (2006). Changes in biota and sediment erodability following the placement of fine dredged material on upper intertidal shores of estuaries. Marine Ecology Progress Series , 319 , 27–41. Xie, W., Wang, X., Guo, L., He, Q., Dou, S., & Yu, X. (2021). Impacts of a storm on the erosion process of a tidal wetland in the Yellow River Delta. Catena , 205 , 105461. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 06 Jun, 2025 Read the published version in Geo-Marine Letters → Version 1 posted Editorial decision: Revision requested 22 Mar, 2025 Reviews received at journal 28 Feb, 2025 Reviews received at journal 18 Feb, 2025 Reviewers agreed at journal 06 Feb, 2025 Reviewers agreed at journal 06 Feb, 2025 Reviewers agreed at journal 06 Feb, 2025 Reviewers invited by journal 06 Feb, 2025 Editor assigned by journal 06 Feb, 2025 Submission checks completed at journal 06 Feb, 2025 First submitted to journal 31 Jan, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-5938586","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":412464662,"identity":"24545efe-9f30-41d8-91a5-1f2a290fce58","order_by":0,"name":"David Fugate","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYDCCwwfAlBx7A5hmJkLLsQQgkcBgzHOAVC2JPURr4TvGY/zi5w+b9B7+xc8kGCqsExsIaZE8xmNm2ZOQltsj8cxMguFMOmEtBvd7zAx4Eg7n7pc4wybB2HaYCC1AWwz/JPxP5wFr+UecFuPHPAkHEnj4e4BaGojQInmMrYxZJi3ZsEeCzdgi4Vi6MUEtfMeYN398Y2Mnz8N/+OGNDzXWsgS1AAGbBJiSSADFD3GA+QOY4j9ApPpRMApGwSgYcQAAvEs+nTvhYMoAAAAASUVORK5CYII=","orcid":"","institution":"Florida Gulf Coast University","correspondingAuthor":true,"prefix":"","firstName":"David","middleName":"","lastName":"Fugate","suffix":""}],"badges":[],"createdAt":"2025-01-31 19:53:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5938586/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5938586/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00367-025-00812-w","type":"published","date":"2025-06-06T15:57:46+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":75742229,"identity":"a86ab9ef-683d-4720-9fea-1a88b53d19d1","added_by":"auto","created_at":"2025-02-07 16:54:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":117003,"visible":true,"origin":"","legend":"\u003cp\u003eColor codes show maximum winds during Hurricane Ian from September 27 to 30, 2022. (NOAA, NWS, Sources: Esri, TomTom, Garmin, FAO, NOAA, USGS, © OpenStreetMap contributors, and the GIS User Community)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/996755a2a203858757604fa4.png"},{"id":75742230,"identity":"d53f725f-da5d-43b2-86f3-9d11408b73be","added_by":"auto","created_at":"2025-02-07 16:54:20","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":48681,"visible":true,"origin":"","legend":"\u003cp\u003eProfiles of critical shear stress (τ\u003csub\u003ec\u003c/sub\u003e) by eroded mass, a proxy for depth as measured by the Gust chamber analyses, for all cores from a) Dollar Bay and b) Naples Bay.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/a36d767b8bc57987eddfb436.png"},{"id":75742465,"identity":"aad5dda3-b70d-42f3-ac95-490e9a1a023d","added_by":"auto","created_at":"2025-02-07 17:02:20","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":18531,"visible":true,"origin":"","legend":"\u003cp\u003ePredicted critical shear stress after 0.05 kg m\u003csup\u003e-2\u003c/sup\u003e have been eroded from a) Dollar Bay site and b) Naples Bay site. Excludes one core with poor fit from each site. Red line shows median, edges of box are 25th and 75th percentiles, whiskers extend to maximum and minimum values.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/9947569d7d50e8ed9f2c1dbb.png"},{"id":75743081,"identity":"a1c1bc32-97c1-4517-a62e-8e886a7ffa21","added_by":"auto","created_at":"2025-02-07 17:10:20","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":24347,"visible":true,"origin":"","legend":"\u003cp\u003eTime series of mean eroded mass after the 0.45 Pa applied stress step from the Gust chamber analyses. Error bars show one standard error of mean above and below.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/669800570831950e3b60e59e.png"},{"id":75742245,"identity":"eb7a19fd-1081-4599-9b89-27e7e32abdd7","added_by":"auto","created_at":"2025-02-07 16:54:20","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":87073,"visible":true,"origin":"","legend":"\u003cp\u003eMean of median diameter measured using a Malvern size detector for 3 cores at each site from a) fall 2023 and b) winter 2024. Error bars show one standard error of mean above and below mean. Size distributions from wet sieving grab samples from the top c\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/f6c6e758c2f0a5935ba80dca.png"},{"id":75742234,"identity":"07b9e789-cbda-4bb3-9afd-dc60d7eb85d5","added_by":"auto","created_at":"2025-02-07 16:54:20","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":18362,"visible":true,"origin":"","legend":"\u003cp\u003eTotal inventories of \u003csup\u003e7\u003c/sup\u003eBe activity by season. Error bars show one standard error of mean above and below.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/5beb4e06b328500bb4e9ffca.png"},{"id":75742239,"identity":"61502ba1-b06c-447c-b5d5-4409e5174cd6","added_by":"auto","created_at":"2025-02-07 16:54:20","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":53715,"visible":true,"origin":"","legend":"\u003cp\u003eWater velocity at 0.33 m above the bottom. Flood is positive.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/964ea7cadf74992108ad4505.png"},{"id":84242604,"identity":"35bcf783-5f3b-4f56-a006-7eab413471e3","added_by":"auto","created_at":"2025-06-09 16:10:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":787980,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5938586/v1/df4f1631-70fa-417c-a0bf-12522804bbd5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evolution of Critical Shear Stress in the Seabed of an Urbanized Estuary and Natural Estuary after the Passage of Hurricane Ian","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSediment transport and mixing in estuaries impact the flux of nutrients and sediment associated contaminants horizontally within the aquatic system and vertically within the seabed. Additionally, the transport of sediment affects the turbidity of the water column, which in turn affects the health of seagrasses and other benthic primary producers. Sediment transport also determines the morphology of the seabed, which can change rapidly during storm conditions. A key factor to predicting the direction and strength of sediment transport is the critical shear stress required to erode sediment from the bed. But the erodibility of fine sediments is poorly constrained because of the complicated interactions between grainsize, consolidation, and biological factors\u0026nbsp;(Xie et al., 2021). Because of these complexities it has not been possible to predict erodibility without site specific measurements (Wiberg, 2013).\u003c/p\u003e\n\u003cp\u003eThe goal of this project was to assess the evolution of critical shear stress and erodibility of the seabed in southwest Florida after the intense disturbance of Hurricane Ian. The critical shear stress and erodibility of the seabed depends not only upon the size of the sediment, but the opposing effects of algal mat and bacterial biofilm production versus bioturbation and bioadvection. We also compared how the evolution of the bed differed in a location that has had extensive development with a nearby but undeveloped bay with no anthropogenic development.\u003c/p\u003e\n\u003cp\u003eHurricane Ian struck southwest Florida as a Category 4 storm on September 28, 2022. Storm surge reached nearly 4 m near the coast and maximum sustained winds between 80 and 100 mph in the city of Naples (Fig. 1). Ian was a slow-moving storm, and the combination of storm surge and wind speed occurred during high tide causing extensive destruction and death. Turbidity in Estero Bay, Fl, a natural preserve near the sites for this study in Naples, was measured during the storm and showed extremely high levels of sediment resuspension. Additionally, salinity gradients were greatly increased, which set up the potential for stronger gravitational circulation to import sediment into the estuary. These conditions were likely to have strongly disturbed the pre-existing seabed and to have produced significant deposition. It was hypothesized that critical shear stresses were greatly decreased and the potential for transport of sediment and sediment affiliated contaminants was greatly increased just after the passage of the storm. This is a special concern as storm surges from hurricanes are known to increase heavy metal concentrations in the seabed (Han et al., 2022; Personna et al., 2015).\u003c/p\u003e\n\u003cp\u003eMixed coarse and fine grain sediments often develop biological films and mats that increase the critical shear stress necessary to resuspend and transport the sediments (e.g. Chen et al., 2017). In contrast, bioturbation and bioadvection by benthic fauna can disaggregate the sediment and break up biological films and mats, resulting in decreased shear stress and more easily transported sediments(e.g. Porter et al., 2020; \u0026nbsp;Widdows \u0026amp; Brinsley, 2002). We hypothesized that the passage of the storm created a major disturbance to the sediment bed and broke up any algal mats or biofilms that may have stabilized the bed. Subsequently sediment could be easily resuspended to scavenge pollutants and enhance transport. This study quantified the timing and evolution of the critical shear stress and erodibility of the seabed as well as assessed the degree of bioturbation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe also examined how the seabed evolution differs between two nearby sites in southwest Florida, Naples Bay and Dollar Bay (Fig. 1) Naples Bay is heavily urbanized with extensive seawall construction bordering the Bay and associated finger canals. Dollar Bay is nearby but has no anthropogenic development. \u0026nbsp;Previous work by Dellapenna et al. (2013) suggested that in the undeveloped region of Dollar Bay, the trapping of fine sediments in the mangrove fringe reduced the fine sediment fraction in the open bay. In contrast, Naples Bay with greatly reduced natural mangrove fringe was found to have more mobile fine sediment in the open Bay. We hypothesized that the difference in sediment size fractions affected the evolution of the critical bed shear stress in the two sites.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePhysical Setting and Sampling Description\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe developed site was located at latitude 26.10226\u0026deg; N, longitude 81.79831\u0026deg; W in lower Naples Bay and was surrounded by residential development (Fig. 1). Salinity in this location is usually near ocean salinity values (Taylor Engineering, Inc., 2005) except during the rainy season when lower salinity episodically appears. The site is microtidal with mixed-semidiurnal tides. The undeveloped site was located at latitude 26.09224\u0026deg; N, longitude 81.78543\u0026deg; W in nearby Dollar Bay, about 1.8 km away from the Naples Bay site. With close access to the Gulf of Mexico, salinity, tidal frequency and tidal range are similar to the ocean and the Naples Bay site.\u003c/p\u003e\n\u003cp\u003eThe two sites were visited seasonally starting in spring 2023 through winter 2024. At each site and sampling event three cores were obtained for erodibility analysis, Xradiographs, and radioisotope counting, for a total of nine cores. Because of the necessity of analyzing erodibility as soon as possible after taking each core, and the fact that it takes about 4 hours to process each core, sample times of the two sites were lagged one to two weeks. The sampling dates for each site and season were as follows:\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSpring 2023\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eMarch 29, 2023, Dollar Bay\u003c/p\u003e\n\u003cp\u003eApril 7, 2023, Naples Bay\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSummer 2023\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eJuly 5, 2023, Dollar Bay\u003c/p\u003e\n\u003cp\u003eJuly 12, 2023, Naples Bay\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFall 2023\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eNov 2, 2023, Naples Bay\u003c/p\u003e\n\u003cp\u003eNov 14, 2023, Dollar Bay\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eWinter 2024\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eMar 2, 2023, Dollar Bay\u003c/p\u003e\n\u003cp\u003eMar 9, 2023, Naples Bay\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCritical Shear Stress and Erodibility\u003c/h2\u003e \u003cp\u003eCritical shear stress and erodibility was measured with a Gust-type erosion chamber comprising a housing with a rotating shear plate, removable lid, and water input and output connections. It uses a rotating disk with central suction to apply a nearly uniform shear stress on the surface of a ten-centimeter diameter core. The rotating head fits directly onto the core tube and a uniform shear stress can be applied across the sediment surface by controlling both the rotation rate of the shear plate, and the rate at which water is pumped through the device. Water and entrained sediment are pumped from the chamber through a turbidity meter and into sampling bottles to measure the eroded mass.\u003c/p\u003e \u003cp\u003eThe applied shear stress was increased in seven steps beginning with 0.01 Pa for thirty minutes of flushing, followed by a typical series of 0.05, 0.10, 0.20, 0.30, 0.45, and 0.60 Pa for twenty minutes each (e.g. Dickhudt et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Fugate et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wiberg et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Maintaining the in-situ salinity at the time of coring is important to prevent laboratory induced changes in flocculation, so water collected from the site was used to replenish the water that was pumped out for analysis. The effluent was filtered through preweighed glass microfiber 0.7 \u0026micro;m filters, dried for four or more days and reweighed to determine the eroded mass at each step.\u003c/p\u003e \u003cp\u003eThree replicate 50\u0026ndash;80 cm long and 10 cm diameter acrylic cores of sediment were taken in seasonally from spring 2023 to winter 2024 at each of the two sites. Cores were retrieved by hand in 1-1.5 m water depth. Analysis was on the same day or day after the cores were retrieved to reduce the potential effects of consolidation.\u003c/p\u003e \u003cp\u003eThe erodibility and critical shear stress are determined by solving the Sanford and Maa (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) formulation for Type 1 erosion:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:E=M{[{\\tau\\:}_{b}-{\\tau\\:}_{c}\\left(z\\right)]}^{n}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere E is the erosion rate in mass per area per time, M is an empirical constant called the mass transfer rate, τ\u003csub\u003eb\u003c/sub\u003e is the applied bottom shear stress, τ\u003csub\u003ec\u003c/sub\u003e is the critical shear stress for erosion, z is depth, and n is an empirical constant. Type 1 erosion is characterized by an increasing critical shear stress with depth. However, type 2 erosion, in which the critical shear stress does not increase with depth is also covered by this formulation when n is found to be equal to one. The analysis is performed using Matlab code that was originally developed by Patrick Dickhudt and then modified by subsequent users (e.g. Fugate et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The Gust chamber analysis allows measurement of change in critical shear stress at a very high resolution, often on the order of millimeters. Because of the very fine depth scale, which would be difficult to measure, the amount of eroded mass from each core provides a proxy for depth so that it is possible to visualize the vertical changes in critical shear stress over a very small depth range.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eRadioisotopes\u003c/h3\u003e\n\u003cp\u003eThree 4-inch diameter aluminum cores were taken at each site and each sampling event. The cores were split open and sectioned into 1-cm depth samples down to 7 cm. The samples were sent to Texas A\u0026amp;M University for further processing by Tim Dellapenna\u0026rsquo;s laboratory team. The sediment samples were dried in an oven at 50\u0026ndash;60\u0026deg;C, and then ground with a SPEX SamplePrep 8000M mixer/mill. About 8.0 g of sediment was packed in a volume of 5 mL in the counting tube. The sample was allowed to be counted for 24 hours with a SAGe well detector with a 120cc-16 mm well (Mirion, USA). Activity concentrations of \u003csup\u003e7\u003c/sup\u003eBe were measured by gamma counting the 477.6 keV line and activity of \u003csup\u003e210\u003c/sup\u003ePb was measured by gamma counting at 46.5 keV. The decays per minute to counts per minute ratio is obtained by previous calibration. Activities were decay corrected but grainsizes were found to be similar at both sites and all depths, so corrections for grainsize were not made.\u003c/p\u003e\n\u003ch3\u003eGrainsize\u003c/h3\u003e\n\u003cp\u003eGrainsize results were available from two sources. The first source was sediment samples from three cores at each site that were used to measure radioisotope activity during fall 2023 and winter 2024. They provided profiles of the grainsize every centimeter down to seven centimeters. These samples were analyzed with a Malvern Mastersizer 2000G. The second source was from surface (top cm) grabs that were wet sieved during the first (spring 2023) and last (winter 2024) sampling events. Sieve sizes for the spring 2023 sample were 125 \u0026micro;m -250 \u0026micro;m, 250 \u0026micro;m -500 \u0026micro;m, 500 \u0026micro;m \u0026ndash; 1000 \u0026micro;m, 1000 \u0026micro;m \u0026ndash; 2000 \u0026micro;m, and \u0026gt;\u0026thinsp;2000 \u0026micro;m. Sieve sizes for the winter 2024 sample were 63 \u0026micro;m -125 \u0026micro;m, 125 \u0026micro;m \u0026ndash; 250 \u0026micro;m, 250 \u0026micro;m -500 \u0026micro;m, 500 \u0026micro;m \u0026ndash; 600 \u0026micro;m, 600 \u0026micro;m \u0026ndash; 2000 \u0026micro;m 2000 \u0026micro;m \u0026ndash; 4000 \u0026micro;m, and \u0026gt;\u0026thinsp;4000 \u0026micro;m. Though these sieve sizes were not all the same for the two seasons, the dominant grain sizes appeared in the size ranges that were the same for both seasons, i.e. the 125 \u0026micro;m \u0026minus;\u0026thinsp;250 \u0026micro;m, and 250 \u0026micro;m \u0026ndash; 500 \u0026micro;m ranges.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eCurrent Measurements\u003c/h2\u003e \u003cp\u003eCurrent velocities were measured at each site for about two weeks during the fall 2023 sampling event with a Nortek 2000 kHz Aquadopp HR profiler. The instruments were deployed upward looking with a cell size of 50 mm and blanking distance of 104 mm. Bursts of 4800 measurements were made at a sampling rate of 8 Hz at intervals of 30 minutes.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eXradiographs\u003c/h2\u003e \u003cp\u003eSediment cores were taken with 4 in diameter polycarbonate tubes and packed with floral foam before sending to Texas A\u0026amp;M University for X-raying by Tim Dellapenna\u0026rsquo;s laboratory team using a MinXray TR8020.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eCritical Shear Stress and Erodibility\u003c/h2\u003e \u003cp\u003eProfiles of critical shear stress by eroded mass (a proxy for depth in sediment) are variable for all cores from both the Dollar Bay site and the Naples Bay site (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Initial critical shear stress values show little variation, most appear between 0.05 and 0.1 Pa for both sites. To better examine differences, these profiles were fit to a power law (Dickhudt et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2009\u003c/span\u003e):\u003c/p\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{\\tau\\:}_{c}=a{m}^{b}+{\\tau\\:}_{c0}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003ewhere τ\u003csub\u003ec\u003c/sub\u003e is the critical shear stress for erosion, m is the cumulated eroded mass, τ\u003csub\u003ec0\u003c/sub\u003e is the initial surface critical shear stress for erosion, and a and b are fitted parameters. One core from Dollar Bay in winter 2024 and one core from Naples Bay in fall 2023 proved to have poor fits of the erosion equation (equation #1) during the Gust analyses, and these cores are removed from the analysis. Comparisons of the fitted critical shear stress after a fixed amount (0.05 kg m\u003csup\u003e− 2\u003c/sup\u003e) of mass has been eroded produce more discernable patterns than the raw analyses. The median fit critical shear stress near the surface at 0.05 kg m\u003csup\u003e− 2\u003c/sup\u003e was higher during spring 2023 at both sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e3\u003c/span\u003e), although ANOVA results showed marginal significance (p = 0.10) for differences in critical shear stress by season at the Dollar Bay site and no significant difference at the Naples site (p = 0.52). Predicted critical shear stress near the surface was 1.6 Pa in spring 2023 at Dollar Bay and fell to\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e around 0.2 - 0.3 Pa for the other seasons. Predicted critical shear stress near the surface was 0.9 Pa in spring 2023 at Dollar Bay and ranged from 0.3 - 0.8 Pa for the other seasons.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e3\u003c/span\u003e \u003cem\u003ePredicted critical shear stress after 0.05 kg m\u003c/em\u003e\u003csup\u003e\u003cem\u003e-2\u003c/em\u003e\u003c/sup\u003e \u003cem\u003ehave been eroded from a) Dollar Bay site and b) Naples Bay site. Excludes one core with poor fit from each site. Red line shows median, edges of box are 25th and 75th percentiles, whiskers extend to maximum and minimum values.\u003c/em\u003e\u003c/p\u003e \u003cp\u003eThe erodibility of the sediment for each core can also be quantified by the cumulative amount of mass eroded at the end of the 0.45 Pa step in the erosion chamber (e.g. Dickhudt et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Fugate et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wiberg et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The temporal pattern of median eroded mass better shows the evolution of the seabed and is consistent with the pattern of critical shear stress at both sites (Fig. \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Right after the hurricane, the median eroded sediment was lower at both sites, reflecting the higher critical shear stress and consolidated bed. The amount of eroded mass at the end of the 0.45 Pa step increased significantly and by nine months after the passage of the hurricane remained about the same (2-way ANOVA, p=0.009). Sediment from Dollar Bay was consistently more erodible than that from Naples Bay (2-way ANOVA, p=0.002). Eroded mass at Dollar Bay rapidly rose from 0.06 kg m\u003csup\u003e-2\u003c/sup\u003e in spring 2023 to 0.12 kg m\u003csup\u003e-2\u003c/sup\u003e in summer 2023 and leveled off to around 0.17 kg m\u003csup\u003e-2\u003c/sup\u003e in fall 2023 and winter 2024. In Naples Bay the eroded mass was around 0.04 kg m\u003csup\u003e-2\u003c/sup\u003e in spring 2023 and rose only slightly to 0.04 kg m-2 in fall 2023. The erodibility then rose rapidly to 0.11 kg m\u003csup\u003e-2\u003c/sup\u003e in fall 2023 and was only slightly lower (0.09 kg m\u003csup\u003e-2\u003c/sup\u003e) in winter 2024. These results suggest that during the hurricane, the bed was eroded to a consolidated layer that had a high critical shear stress and low erodibility. As time passed more unconsolidated sediments were deposited, or bioturbation increased the erodibility, or both.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eGrainsize\u003c/em\u003e \u003c/p\u003e \u003cp\u003eGrainsize results were available from two sources. Profiles of grainsize determined by the Malvern were available for fall 2023 and winter 2024 at both sites. Surface sample grabs from the top centimeter of sediment that was wet-sieved were available for the first (spring 2023) and last (winter 2024) deployments at each site.\u003c/p\u003e \u003cp\u003eProfiles of the mean of median diameters measured by the Malvern from the three cores at each site and season show that there was not much vertical variation or difference between the two sites and two seasons (Figs.\u0026nbsp;5ab). The fall 2023 results indicate that the Naples Bay sediment may have been somewhat coarser, but not statistically so at each depth. Dollar Bay sediments had median diameters between 25 µm and 50 µm along the vertical profile. Median diameters of Naples Bay sediments ranged from 50 µm to 150 µm, with the coarser end of the range in the top 4 cm. There was a localized increase in median grain size to about 150 µm at the Naples Bay site in the 3–4 cm depth samples. The winter 2024 grainsize distributions were more similar between sites and vertically than the fall cores and suggested a slight fining of sediments at Naples Bay between 1 and 4 cm depth. Median diameters ranged between 25 µm to 50 µm between both sites and depth in the sediment, except for the surface which had median grain sizes 675 µm or larger at both sites. The main difference between the fall 2023 and winter 2024 grainsizes was this much larger median diameter at the surface layer during the winter 2024 at both sites. This may be attributed to an increase in bivalve populations creating shell hash at the surface at both sites. Because of the general similarities in grainsize both between seasons and with depth, the \u003csup\u003e7\u003c/sup\u003eBe activities were not normalized by grainsize.\u003c/p\u003e \u003cp\u003eSurface grab samples from the sites showed little variation in grainsize through the course of the study (Figs.\u0026nbsp;5cd). However, the results indicate that there was more shell hash at Dollar Bay than Naples Bay at the beginning and end of the study. The dominant peak in grain size frequency appeared at both sites in the 250–500 µm range in spring 2023 and in the 125–250 µm range in winter 2024, indicating a slight fining of the particles over the course of the study. This is consistent with the change in Naples Bay sediment sizes from the core samples but is not reflected in the Dollar Bay sediment sizes from the core samples. A general fining of the sediment would be consistent with deposition of new fine sediment that is mixed down into the sediment from bioadvection. The surface grab sample increase in shell hash in Dollar Bay compared to Naples Bay during both seasons suggests that Dollar Bay was more biologically dynamic and had a larger bivalve population than Naples Bay.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eRadioisotopes\u003c/h2\u003e \u003cp\u003eNo significant \u003csup\u003e7\u003c/sup\u003eBe was found in the top 3 cm of any of the three cores at either of the two sites in the spring 2023 sampling event, so no more radioisotope analyses were performed for the lower depths. This finding suggests that recently deposited sediments were eroded by the hurricane and there was no new deposition. By summer 2023, \u003csup\u003e7\u003c/sup\u003eBe was found in Dollar Bay and distributed throughout the top 6 cm. Mean decay rates in Dollar Bay ranged from 0-0.05 Bq kg\u003csup\u003e− 1\u003c/sup\u003e. Naples Bay had very low levels of \u003csup\u003e7\u003c/sup\u003eBe in summer 2023 (maximum mean of 0.005 Bq kg\u003csup\u003e− 1\u003c/sup\u003e at 5.5 cm depth) but more in fall 2023 and winter 2024 which ranged from 0-0.025 Bq kg\u003csup\u003e− 1\u003c/sup\u003e. The highly variable profiles at both sites suggest that once \u003csup\u003e7\u003c/sup\u003eBe was deposited at the bed surface it was rapidly bioadvected throughout the top 7 cm in Dollar Bay and the top 6 cm in Naples Bay.\u003c/p\u003e \u003cp\u003eTotal inventories better show the evolution of the bed (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Dollar Bay accumulated new sediment more rapidly after scouring by the hurricane than Naples Bay, but both reached peak inventories in fall 2023 when rainfall was higher. Activity rates dropped at both sites during the dry season of winter 2024. Dollar Bay also had consistently higher total activity rates than Naples Bay, suggesting higher deposition rates. These data are consistent with the erodibility analyses that suggested that Dollar Bay received sediment deposits by the summer, while Naples Bay did not have much sediment deposition until fall. The overall higher erodibility of Dollar Bay is also consistent with the \u003csup\u003e7\u003c/sup\u003eBe inventory pattern of more deposition of fine sediments at Dollar Bay. The differences in the summer values also suggest that rainfall was not the main determinant of \u003csup\u003e7\u003c/sup\u003eBe variation, since the rainfall would have been the same for the two geographically close stations.\u003c/p\u003e \u003cp\u003e Lead-210 isotope activity was available for the summer, fall, and winter seasons. Variable profiles of activity support the presence of bioadvection in the sediment, with peaks in activity all at 3.5 cm or below. Peak mean \u003csup\u003e210\u003c/sup\u003ePB activity ranged from 0.14 to 0.16 Bq kg\u003csup\u003e-1\u003c/sup\u003e at Dollar Bay and from 0.07 to 0.11 Bq kg\u003csup\u003e-1\u003c/sup\u003e at Naples Bay. The total inventory of \u003csup\u003e210\u003c/sup\u003ePb remained relatively constant from summer 2023 to winter 2024 at both sites. Dollar Bay inventories were consistently about to 0.7e -3 Bq cm\u003csup\u003e-2\u003c/sup\u003e higher than Naples Bay.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eCurrent Velocities\u003c/h2\u003e \u003cp\u003eCurrent velocities at Dollar Bay were much stronger than those at Naples Bay and exhibited a more recognizable tidal pattern (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The ADCP at Naples Bay failed after 6.5 days, so currents are compared only for the times when measurements were available from both sites. Horizontal velocities at 0.33 m above the bottom in Dollar Bay ranged from − 0.16 m s\u003csup\u003e− 1\u003c/sup\u003e to 0.16 m s\u003csup\u003e− 1\u003c/sup\u003e (flood is positive). Horizontal velocities at 0.33 m above the bottom in Naples Bay only ranged from − 0.04 m s\u003csup\u003e− 1\u003c/sup\u003e to 0.07 m s\u003csup\u003e− 1\u003c/sup\u003e. These differences in current velocities were likely responsible for most of the differences observed in the evolution of the respective beds at each site. The Naples Bay site is in an enclosed basin with little circulation compared to Dollar Bay which has access to Gulf at both ends and stronger potential for sediment transport.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eXradiographs\u003c/h2\u003e \u003cp\u003eXradiographs shed little light on the evolution of the seabed. All xradiographs showed similar characteristics of a mottled fine grained matrix embedded with bivalves. There was no apparent change in the appearance across time or between the sites. However, while not apparent from the xradiographs, both large and small burrows and bioturbating organisms such as \u003cem\u003eAlpheidae spp\u003c/em\u003e. (snapping shrimp) and \u003cem\u003eCerithium aratum\u003c/em\u003e (gastropods) were observed in the polycarbonate cores used for the Gust analysis starting in summer 2023 at Dollar Bay (Fig.\u0026nbsp;15), but not in the previous spring.\u003c/p\u003e \u003c/div\u003e "},{"header":"Discussion and Conclusions","content":"\u003cp\u003eThe results from the data did not support the hypothesis that the hurricane deposited large amounts of unconsolidated sediment. Instead of depositing sediment, the hurricane scoured the seabed at both sites to a more consolidated layer. Critical shear stress was higher just after passage of the hurricane and erodibility was lower. Wang et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2000\u003c/span\u003e) also found that during episodic wind events erosion occurred down to a more consolidated bed below a thin layer of loosely consolidated material, leaving a seabed with higher critical shear stress and lower erodibility. Defne et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) found that Hurricane Sandy eroded sediment from shallow and shoal areas and redeposited over the adjacent low lying land in a back barrier estuary in New Jersey, USA. This is the likely scenario that occurred at the sites in Naples Bay and Dollar Bay after the passage of Hurricane Ian.\u003c/p\u003e\u003cp\u003eBy summer 2023, the undeveloped site, Dollar Bay, had recent sediment deposits as shown by \u003csup\u003e7\u003c/sup\u003eBe counts. These deposits were more easily erodible and in the next two seasons as more sediment was deposited the bed became more erodible. Additionally, the hurricane likely dampened bioturbation along with the scouring. By summer 2023 bioturbating organisms were recruited to the area as evidenced by \u003csup\u003e7\u003c/sup\u003eBe profiles exhibiting bioadvection, and by visual inspection of cores. The sediment bed at the developed site, Naples Bay, lagged in recovery compared to Dollar Bay because of the enclosed basin and resultant minimal flow dynamics there. The weaker hydrodynamics of the Naples Bay site is also likely responsible for the smaller grainsize found there by Dellapenna et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) compared to the Dollar Bay site.\u003c/p\u003e\u003cp\u003ePrediction of sediment transport after storms using numerical models must first establish the condition of the seabed after the storm. We found that scouring by the storm left a seabed with a consolidated surface critical shear stress between 1.0 and 1.5 Pa at Naples Bay and Dollar Bay, respectively. After deposition of fine sediment, the critical shear stresses dropped to around 0.25 Pa at both sites. These values are somewhat higher than critical shear stresses determined in other estuaries. In San Jacinto, TX, Saleh and Strom (2012) found critical shear stresses of 0.14 Pa and 0.06 Pa in sediments with median diameters slightly lower (93 µm and 42 µm, respectively) than those in this study. Widdows et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) found a critical shear stress of 0.12 Pa after consolidation of emplaced fine sediments (\u0026gt; 72% silt) in Essex, UK estuary.\u003c/p\u003e\u003cp\u003eDeposition at the Naples Bay site was lagged about 3 months because of the lower energy environment and reduced sediment availability. Both sites were recolonized by bioadvectors within 9 to 12 months of the hurricane, with the Naples Bay site again lagged one season behind the Dollar Bay site. The presence or absence of mangroves had less of an effect on sediment transport than the level of hydrodynamic energy at the two sites. Thrush et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) found a complete recovery of macrofauna after sediment deposition in 2 out of 6 sites within 212 days. Local hydrodynamics were also fundamental to determining the rates of recovery, with those living in more energetic environments recovering more rapidly. Though the disturbance in Thrush et al.’s study was sediment deposition rather than sediment erosion, the key findings were similar to this study with respect to the importance of hydrodynamics and the timing of recovery. Forsberg et al. (2018) found opposite results from this study after storms in a Danish lagoon. They concluded that the erosion of submerged aquatic vegetation during storms decreased the critical shear stress and increased the erodibility of the seabed.\u003c/p\u003e\u003cp\u003eDespite the intensity of Hurricane Ian, the seabed at the two study sites appeared to have stabilized and recovered within a year of passage of the storm. The results of this project and comparisons with other studies confirm the variable responses of different estuaries to storms and that site specific measurements need to be made to predict critical shear stress. The results also suggest that resources may be better spent on repair of infrastructure and buildings after a destructive storm rather than restoration of the natural environment, which has proved to be resilient at these two sites.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eFunding was provided by the National Science Foundation under Grant Number 2306741. The author has no competing interests to declare that are relevant to the content of this article.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eDavid Fugate wholly contributed to the conception of the work, the acquisition of funding and data, analysis, and interpretation of the data and wrote the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe author would like to thank Captain Brandon Galindo and my students that helped in the field and laboratory, Laura Dunn, Braden Wood, Elizabeth Dahedl, Nyx Schuler, and Kaitlyn Beynon. The author is also deeply grateful to Tim Dellapenna and his laboratory staff at Texas A\u0026amp;M University, Galveston for performing radioisotope counting and Xradiographs. This work was supported by the National Science Foundation under Grant Number 2306741.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData Management PlanFollowing is the plan for managing the scientific data generated as a result of the proposedresearch.1. Types of data, samples, physical collections, software, curriculum materials, and othermaterials to be produced in the course of the project.This project will produce data from three primary sources, Gust erosion experiments, X-radiographs of cores, and 7Be core profiles. Gust data obtained include:\u0026bull; Log sheets manually prepared during the experiment that document the start and end times of each shear stress step and the sample bottles used to collect effluent.\u0026bull; Log sheets generated by the Gust system that include the date time signature, the elapsed time, the NTUs from the turbidimeter and the RPMs of the Gust plate.\u0026bull; Total suspended sediment concentrations from the effluent bottles.Xradiograph data will include:\u0026bull; Digital images of each core7Be data will include:\u0026bull; Data sheets denoting the core #, site, date time, core interval, and 7Be concentration2. Standards to be used for data and metadata format and content.Data generated from the Gust experiments will be formatted in comma delimited text files. The reason for using text files rather than the more generally used netCDF format is that the commonly used software to analyze Gust experiment data is written in Matlab which reads the input data in the form of these text input files.The digital images from the core Xradiographs will be stored in .jpeg format.Data from the 7Be profiles will be stored in text format.3. Policies for access and sharing including provisions for appropriate protection of privacy,confidentiality, security, intellectual property, or other rights or requirements.Data collected under the project will be made available to the public with as few restrictionsas possible. The data will be submitted to the Marine Geoscience Data System. All data products will be made publicly accessible within two (2) years of collection and maintained for a minimum of three (3) years after the end of the project, in accordance with NSF and OCE Division policies.4. Policies and provisions for re-use, re-distribution, and the production of derivatives.Data generated from this project will be archived at the Marine Geoscience Data System by September 2026\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eChen, X., Zhang, C., Paterson, D., Thompson, C., Townend, I., Gong, Z., Zhou, Z., \u0026amp; Feng, Q. (2017). Hindered erosion: The biological mediation of noncohesive sediment behavior. \u003cem\u003eWater Resources Research\u003c/em\u003e, \u003cem\u003e53\u003c/em\u003e(6), 4787\u0026ndash;4801.\u003c/li\u003e\n\u003cli\u003eDefne, Z., Ganju, N. K., \u0026amp; Moriarty, J. M. (2019). Hydrodynamic and morphologic response of a back‐barrier estuary to an extratropical storm. \u003cem\u003eJournal of Geophysical Research: Oceans\u003c/em\u003e, \u003cem\u003e124\u003c/em\u003e(11), 7700\u0026ndash;7717.\u003c/li\u003e\n\u003cli\u003eDellapenna, T. M., Fielder, B., Noll, C. J. I., \u0026amp; Savarese, M. (2013). Geological responses to urbanization of the Naples Bay Estuarine System, southwester Florida, USA. \u003cem\u003eEstuaries and Coasts\u003c/em\u003e. https://doi.org/10.1007/s12237-013-9704-2\u003c/li\u003e\n\u003cli\u003eDickhudt, P. J., Friedrichs, C. T., Schaffner, L. C., \u0026amp; Sanford, L. P. (2009). Spatial and temporal variation in cohesive sediment erodibility in the York River estuary, eastern USA: a biologically influenced equilibrium modified by seasonal deposition. \u003cem\u003eMarine Geology\u003c/em\u003e, \u003cem\u003e267\u003c/em\u003e, 128\u0026ndash;140.\u003c/li\u003e\n\u003cli\u003eFugate, D. C., Thomas, S., \u0026amp; Scinto, L. J. (2021). Particle dynamics in stormwater treatment areas. \u003cem\u003eEcological Engineering\u003c/em\u003e, \u003cem\u003e160\u003c/em\u003e, 106131.\u003c/li\u003e\n\u003cli\u003eHan, I., Whitworth, K. W., Christensen, B., Afshar, M., Han, H. A., Rammah, A., Oluwadairo, T., \u0026amp; Symanski, E. (2022). Heavy metal pollution of soils and risk assessment in Houston, Texas following Hurricane Harvey. \u003cem\u003eEnvironmental Pollution\u003c/em\u003e, \u003cem\u003e296\u003c/em\u003e, 118717.\u003c/li\u003e\n\u003cli\u003ePersonna, Y. R., Geng, X., Saleh, F., Shu, Z., Jackson, N., Weinstein, M. P., \u0026amp; Boufadel, M. C. (2015). Monitoring changes in salinity and metal concentrations in New Jersey (USA) coastal ecosystems Post-Hurricane Sandy. \u003cem\u003eEnvironmental Earth Sciences\u003c/em\u003e, \u003cem\u003e73\u003c/em\u003e, 1169\u0026ndash;1177.\u003c/li\u003e\n\u003cli\u003ePorter, E. T., Johnson, B. J., \u0026amp; Sanford, L. P. (2020). \u003cem\u003eEffects of hard clam (Mercenaria mercenaria) density and bottom shear stress on cohesive sediment erodibility and implications for benthic-pelagic coupling\u003c/em\u003e.\u003c/li\u003e\n\u003cli\u003eSalehi, M., \u0026amp; Strom, K. (2012). Measurement of critical shear stress for mud mixtures in the San Jacinto estuary under different wave and current combinations. \u003cem\u003eContinental Shelf Research\u003c/em\u003e, \u003cem\u003e47\u003c/em\u003e, 78\u0026ndash;92.\u003c/li\u003e\n\u003cli\u003eSanford, L. P., \u0026amp; Maa, J. P. (2001). A unified erosion formulation for fine sediments. \u003cem\u003eMarine Geology\u003c/em\u003e, \u003cem\u003e179\u003c/em\u003e, 9\u0026ndash;23.\u003c/li\u003e\n\u003cli\u003eTaylor Engineering, Inc. (2005). \u003cem\u003eEvaluation of Naples Bay Water Quality and Hydrologic Data\u003c/em\u003e. South Florida Water Management District.\u003c/li\u003e\n\u003cli\u003eThrush, S. F., Hewitt, J. E., Norkko, A., Cummings, V. J., \u0026amp; Funnell, G. A. (2003). Macrobenthic recovery processes following catastrophic sedimentation on estuarine sandflats. \u003cem\u003eEcological Applications\u003c/em\u003e, \u003cem\u003e13\u003c/em\u003e(5), 1433\u0026ndash;1455.\u003c/li\u003e\n\u003cli\u003eWang, Y., Bohlen, W. F., \u0026amp; O\u0026rsquo;donnell, J. (2000). Storm enhanced bottom shear stress and associated sediment entrainment in a moderate energetic estuary. \u003cem\u003eJournal of Oceanography\u003c/em\u003e, \u003cem\u003e56\u003c/em\u003e, 311\u0026ndash;317.\u003c/li\u003e\n\u003cli\u003eWiberg, P. L., Law, B. A., Wheatcroft, R. A., Milligan, T. G., \u0026amp; Hill, P. S. (2013). Seasonal variations in erodibility and sediment transport potential in a mesotidal channel-flat complex, Willapa Bay, WA. \u003cem\u003eHydrodynamics and Sedimentation on Mesotidal Sand- and Mudflats\u003c/em\u003e, \u003cem\u003e60\u003c/em\u003e, S185\u0026ndash;S197. https://doi.org/10.1016/j.csr.2012.07.021\u003c/li\u003e\n\u003cli\u003eWiddows, J., \u0026amp; Brinsley, M. (2002). Impact of biotic and abiotic processes on sediment dynamics and the consequences to the structure and functioning of the intertidal zone. \u003cem\u003eStructuring Factors of Shallow Marine Coastal Communities, Part I\u003c/em\u003e, \u003cem\u003e48\u003c/em\u003e(2), 143\u0026ndash;156. https://doi.org/10.1016/S1385-1101(02)00148-X\u003c/li\u003e\n\u003cli\u003eWiddows, J., Brinsley, M., Pope, N., Staff, F., Bolam, S., \u0026amp; Somerfield, P. (2006). Changes in biota and sediment erodability following the placement of fine dredged material on upper intertidal shores of estuaries. \u003cem\u003eMarine Ecology Progress Series\u003c/em\u003e, \u003cem\u003e319\u003c/em\u003e, 27\u0026ndash;41.\u003c/li\u003e\n\u003cli\u003eXie, W., Wang, X., Guo, L., He, Q., Dou, S., \u0026amp; Yu, X. (2021). Impacts of a storm on the erosion process of a tidal wetland in the Yellow River Delta. \u003cem\u003eCatena\u003c/em\u003e, \u003cem\u003e205\u003c/em\u003e, 105461.\u003c/li\u003e\n\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":"geo-marine-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gmle","sideBox":"Learn more about [Geo-Marine Letters](http://link.springer.com/journal/367)","snPcode":"367","submissionUrl":"https://submission.nature.com/new-submission/367/3","title":"Geo-Marine Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5938586/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5938586/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSediment transport and mixing in estuaries impact a number of ecosystem services, including the flux of nutrients and the mediation of turbidity of the water column, which in turn affects the health of seagrasses and other benthic primary producers. A key factor to predicting the direction and strength of sediment transport is the critical shear stress required to erode sediment from the bed. But the erodibility of fine sediments is poorly constrained because of the complicated interactions between grainsize, consolidation, and biological factors. This study assessed the evolution of critical shear stress and erodibility of the seabed in southwest Florida, USA after the intense disturbance of Hurricane Ian. We also compared how the evolution of the bed differed in a location that has had extensive development with a nearby but undeveloped bay with no anthropogenic development. Erodibility and critical shear stress were measured with Gust-type erosional chambers. Profiles of \u003csup\u003e7\u003c/sup\u003eBe and Xradiographs were used to determine the extent of new sediment deposition and bioturbation. Hydrodynamics were measured with an acoustic doppler current profiler. Hurricane Ian initially eroded the seabed down to a consolidated layer with high critical shear stress (1-1.5 Pa) and low erodibility at both sites. In the subsequent months, new sediments were deposited and rapid bioadvection of the top 6 cm ensued. The shear stress was reduced (~0.25 Pa) and erodibility increased by the end of the study. Recovery was more rapid in the undeveloped site because the hydrodynamics were more energetic. Both sites returned to stability within one year of the passage of the storm.\u003c/p\u003e","manuscriptTitle":"Evolution of Critical Shear Stress in the Seabed of an Urbanized Estuary and Natural Estuary after the Passage of Hurricane Ian","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-07 16:54:15","doi":"10.21203/rs.3.rs-5938586/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-22T13:43:16+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-28T05:02:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-18T15:24:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"58645869138936891882859585762124880052","date":"2025-02-07T03:20:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"308875116610945886343239221279267505591","date":"2025-02-06T14:29:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"333955512269289671643724431777761390869","date":"2025-02-06T13:05:13+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-02-06T12:47:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-02-06T12:40:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-02-06T06:19:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Geo-Marine Letters","date":"2025-01-31T19:39:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"geo-marine-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gmle","sideBox":"Learn more about [Geo-Marine Letters](http://link.springer.com/journal/367)","snPcode":"367","submissionUrl":"https://submission.nature.com/new-submission/367/3","title":"Geo-Marine Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ea43de9d-9a40-4f55-af61-d5ce3c89ce7d","owner":[],"postedDate":"February 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-06-09T16:03:54+00:00","versionOfRecord":{"articleIdentity":"rs-5938586","link":"https://doi.org/10.1007/s00367-025-00812-w","journal":{"identity":"geo-marine-letters","isVorOnly":false,"title":"Geo-Marine Letters"},"publishedOn":"2025-06-06 15:57:46","publishedOnDateReadable":"June 6th, 2025"},"versionCreatedAt":"2025-02-07 16:54:15","video":"","vorDoi":"10.1007/s00367-025-00812-w","vorDoiUrl":"https://doi.org/10.1007/s00367-025-00812-w","workflowStages":[]},"version":"v1","identity":"rs-5938586","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5938586","identity":"rs-5938586","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}