Water pH as a driver of bryophyte species distribution in Moss Balls of Lake Kussharo, Japan

Water pH as a driver of bryophyte species distribution in Moss Balls of Lake Kussharo, Japan | 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 Water pH as a driver of bryophyte species distribution in Moss Balls of Lake Kussharo, Japan Arisa Kanetou, Yuki Yoshida, Tomoko Yoshikawa, Hiroshi Kanda, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8748825/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Lake Kussharo is the largest caldera lake in Japan and serves as the habitat for "Marigoke" (moss balls), which was designated as a natural monument of Teshikaga Town on July 11, 1969. Recently, a decline has been observed in both Marigoke and its constituent plant species. This study aimed to clarify the impact of the pH of lake water on Marigoke and its constituent plants. Historically, the constituent species were Drepanocladus fluitans var. kutcharokensis and Jungermannia exsertifolia Steph. However, current observations indicate that Fontinalis antipyretica Hedw. is dominant in neutral environments, while Drepanocladus fluitans (Hedw.) Warnst. prevails in acidic environments. Furthermore, this study revealed the existence of two distinct types of Marigoke in Lake Kussharo, each composed of different species depending on the pH of the environment. The growth process of Marigoke is governed by a complex interplay of multiple factors, including water quality, presence or absence spring water, geology, sediment, topography, and flow characteristics. The formation of Marigoke requires specific environmental conditions, including physical factors, and its occurrence is restricted to extremely limited areas. Lake Kussharo Marigoke Fontinalis antipyretica Hedw. Drepanocladus fluitans (Hedw.) Warnst. pH spring water Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Akan-Mashu National Park in Hokkaido consists of three calderas, and Lake Kussharo, located within the Kussharo Caldera, is the largest caldera lake in Japan (Ministry of the Environment, Akan-Mashu National Park Management Office 2020 ). Lake Kussharo is a habitat for Marigoke (moss balls), which was designated as a natural monument of Teshikaga Town on July 11, 1969 (Teshikaga Town, Hokkaido 2025). Marigoke are consisted of lake-bottom mosses that are detached by strong wave action and become entangled with fragments of aquatic plants and debris during the rotation process, eventually forming a spherical shape (Baba and Iwatsuki 1973 ). Marigoke has also been reported in Gennarbyviken in southern Finland (Luther 1979 ) and Lake Parillar in southern Chile (Frahm 2001) but is extremely rare on a global scale. In Lake Kussharo, species such as Drepanocladus fluitans var. kutcharokensis Kanda and Jungermannia exsertifolia Steph. have been previously reported as the constituent plants of Marigoke (Iwatsuki et al. 1983 ). Marigoke are frequently observed along the eastern shores of Lake Kussharo, such as in Wakoto and Nibushi (Iwatsuki et al. 1983 ). Sato et al. ( 2023 ) conducted research on the eastern shore of Lake Kussharo. However, since the survey conducted in 2003 (Sato et al. 2023 ), no detailed assessment of its current status has been conducted. This study aimed to clarify how the pH of the lake water in Lake Kussharo affects the distribution of Marigoke and its constituent plant species. Methods Lake Kussharo, is located in the eastern part of Hokkaido (Fig. 1 ). According to meteorological data from Teshikaga Town (2010–2020), the average temperature is 5.6°C, the annual precipitation is 1,091 mm, and the maximum snow depth is 118 cm (Japan Meteorological Agency 2025 ). The Kushiro River, which is the only outflow river of Lake Kussharo, forms the Kushiro Marsh, Japan’s largest wetland registered under the Ramsar Convention (Kikuchi 2017 ). Lake Kussharo is a caldera lake formed within the Kussharo Caldera (Teshikaga Town History Compilation Committee 2005 ). It is the premier vast freshwater lake in Hokkaido, spanning approximately 12.5 km from north to south and 7.2 km from east to west, with a shoreline of 57 km and a surface area of 79.3 km² (Teshikaga Town History Compilation Committee 2005 ). The surface elevation of the lake is 121 m, with a maximum depth of 117.5 m and an average depth of 28.4 m (Teshikaga Town History Compilation Committee 2005 ). In Lake Kussharo, there was a period when the lake water became strongly acidified due to iron and aluminum sulfates derived from hot spring wastewater from the Kawayu Onsen (Yukawa). Surveys conducted between 1929 and 1968 showed pH values ranging from 3.3–5.5 (Hashimoto 1989 ). Subsequently, neutralization has progressed since the 1980s, with pH levels exceeding 7.0 in 2004 (Tanaka 2004 ). First, we surveyed locations where Marigoke had been previously reported (Iwatsuki et al. 1983 ; Sato et al. 2023 ). We found Marigoke only in northeastern part of the Lake and we selected study sites A-D along the shore (Fig. 1 ). To assess the distribution of lake-bottom vegetation, aerial photographs of the lake bed were taken using a drone (Mavic 2 Pro, DJI, Fig. 2 ). Specifically, at Sites C and D, lake-bottom plants were collected using a boat. Additionally, Marigoke and other plant materials washed ashore at Sites B, C, and D were also collected. The identification for bryophytes followed Iwatsuki ( 2001 ). In addition pH of the Lake water were also measured at each site (LAQUAtwin-pH-11B; HORIBA). Some submerged bryophytes are known to inhabit in areas with spring water (Kadono 2020 ). Springs have been confirmed in Lake Kussharo and spring discharge points were identified by utilizing the temperature difference between the spring water and the lake water. The surveys using an unmanned aerial vehicle (UAV; Mavic 3 Thermal, DJI) equipped with an infrared (IR) camera were conducted to cover the northeastern shore, during a period when the spring water temperature was lower than the lake water temperature. The total distance of the surveyed area was 4.65 km. Results Constituent plants of Marigoke and Lake-bottom vegetation The Marigoke-constituent plants and pH levels at each site are listed in Table 1. At site A, Marigoke-constituent plants were not found. At Site B, Fontinalis antipyretica Hedw. was identified. At Site C, both Drepanocladus fluitans (Hedw.) Warnst. and F. antipyretica were found. At Site D, only D. fluitans was confirmed. pH measurement At Sites A–C, the pH levels ranged from 6.8 to 7.7, showing no significant variation. In contrast, Site D exhibited acidic conditions, with pH values between 3.4 and 4.6. Around Site D, pH levels were lower to the north, where Yukawa liver mouth is located, reaching a minimum of 2.9, and higher to the south, reaching a maximum of 6.2 (Fig. 2 , Fig. 3 ). Spring water The shoreline segments where water temperatures were lower than the surrounding lake water totaled 2.87 km within the surveyed distance of 4.65 km (Fig. 4 ). Regarding the bottom substrate, Site A consisted predominantly of gravel, although some areas contained sandy mud and pebbles. At Site B, although some gravelly areas were observed, the substrate was mostly composed of sandy mud and pebbles. Sites C and D were characterized by sandy mud and pebbles. Groundwater discharge (springs) was observed at all study sites. Discussion Past reports confirmed Drepanocladus fluitans var. kutcharokensis Kanda and Jungermannia exsertifolia . as the constituent plants of Marigoke in Lake Kussharo (Iwatsuki et al. 1983 ). However, in this study, Fontinalis antipyretica and D. fluitans were identified as constituent species. One of the factors contributing to this change is the difference in pH. At Sites A–C, where the pH was in the neutral range (6.0–7.0), F. antipyretica was found to grow, and Marigoke was composed of this species. In contrast, Site D was an acidic environment with a pH of 3.0–4.0, where communities of D. fluitans and Marigoke composed of this species were confirmed. These results suggest that two types of Marigoke, consisting of different species depending on the pH of the environment, exist in Lake Kussharo. Presence of spring water, geology, bottom sediment, and topography may influence the differences in constituent species and formation of Marigoke. While spring water was confirmed at Sites A–C, Site D received an inflow of both spring and hot spring water. Regarding the geology, Site A is located on basaltic and andesitic outer crater rim, whereas Sites B–D consist of alluvial deposits (Teshikaga Town History Compilation Committee 2005 , Fig. 5 ). The topography of Site A characterized by a steeper slope, where the water depth reached 20 m at a short distance from the shore compared to the other sites (Fig. 1 ). Therefore, even if Marigoke is formed, it may be less likely to wash ashore because of the steep topography, and the lack of light reaching the bottom in deeper water may make the environment unsuitable for moss growth. At Sites B and C, the depth was shallow for a long distance from the shore, Marigoke washes ashore more easily, and the presence of spring water creates an ideal environment for the growth of F. antipyretica . Similarly, Site D was shallow and suitable for Marigoke formation. The coexistence of spring and hot spring water at this site creates a favorable environment for D. fluitans , resulting in a different moss species compared to the other sites. We found that the habitat of Marigoke is shaped by a complex interplay of multiple factors, including water quality, presence of spring water, geology, bottom sediments, topography, and flow characteristics. Protection of spring water, such as avoiding bank constructions, would contribute to conservation of Marigoke. Statements & Declarations Funding This research was conducted with funding from the Teshikaga Town Board of Education (Joint Research Project Concerning the Survey of Marigoke Vegetation at Lake Kussharo, a Cultural Property of Teshikaga Town). Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Yuki Yoshida, Tomoko Yoshikawa, Hiroshi Kanda and Yoshi Minami. The first draft of the manuscript was written by Arisa Kanetou and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Example statements The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. References Baba Y, Iwatsuki Z (1973) Notes on moss balls of Lake Inawashiro. Miscellanea Bryologica et Lichenologica 6:117–119. (In Japanese) Frahm Jan-Pether (2001) Aquatic mossballs of Blindia inundata in Patagonia. The Bryologist 104: 502―503. https://doi.org/10.1639/0007-2745(2001)104[0503:NMOBII]2.0.CO;2. Hashimoto S (1989) Environmental Disruption by Waste Water from a Hot Spring—II: Effects of Waste Water Pollution of the “Kawayu-Onsen” on Fish in the “Kusirogawa-River Systems”. Scientific Reports of the Hokkaido Salmon Hatchery 43:39–51. https://salmon.fra.affrc.go.jp/kankobutu/srhsh/data/srhsh332.pdf . (In Japanese with English abstract) Iwatsuki Z. (2001) Mosses and Liverworts of Japan . Heibonsha, Tokyo. Iwatsuki Z, Takita K, Glime J. M (1983) Moss balls of Lake Kussharo. Hokkaido. Miscellanea Bryologica et Lichenologica 9:199–201. (In Japanese) Japan Meteorological Agency. Historical Weather Data. https://www.data.jma.go.jp/stats/etrn/index.php. Accessed 5 December 2025. (In Japanese) Kadono Y (2020) Present status of alien aquatic plants in spring-fed waters in Japan. Japanese Journal of Conservation Ecology 25: 265–277. https://doi.org/10.18960/hozen.2004. (In Japanese with English abstract) Kikuchi Y (2017) Kushiro-shitsugen: Passions of the local community surrounding the first Ramsar site in Japan. Wetland Research 7:53–57. https://doi.org/10.24785/wetlandresearch.WR007009. (In Japanese) Luther H (1979) Aquatic moss balls in southern Finland. Annales Botanici Fennici 16:163―172. https://www.jstor.org/stable/23725152. Ministry of the Environment, Akan-Mashu National Park Management Office (2020) Akan-Mashu National Park Trail Guide . (In Japanese) https://hokkaido.env.go.jp/kushiro/content/900144902.pdf. Accessed 30 December 2025. (In Japanese) Sato H, Hachiya M, Hosokawa O (2023) A Record of Moss balls Growth in Lake Kussharo, Akan-Mashu National Park in Hokkaido. Memoirs of the Kushiro City Museum 41:5–10. https://www.city.kushiro.lg.jp/_res/projects/default_project/_page_/001/011/507/bulletin41_sato_et_al.pdf. (In Japanese) Tanaka A (2004) Investigating the causes of the natural neutralization of Lake Kussharo. NIES News , 23. National Institute for Environmental Studies. https://www.nies.go.jp/kanko/news/23/23-4/23-4-03.html . Accessed 2 January 2024. (In Japanese) Teshikaga Town History Compilation Committee (2005) History of Teshikaga Town . Teshikaga Town Office. (In Japanese) Teshikaga Town, Hokkaido (2025) Cultural Properties. https://www.town.teshikaga.hokkaido.jp/kurashi/soshikiichiran/kyoikuiinkai_shakaikyoikuka/2/2/658.html. Accessed 12 October 2025. Table Table 1. Main constituent bryyophyte of Marigoke (Moss balls) Site Species Site A Site B Site C Site D MB DR MB DR MB DR MB DR Drepanocladus fluitans (Hedw.) Warnst. ○ ○ ○ ○ Fontinalis antipyretica Hedw. ○ ○ ○ ○ pH 7.7 7.5 7.2 4.2 MB and DR indicate moss balls and drift, respectively. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 01 Mar, 2026 Reviewers invited by journal 08 Feb, 2026 Editor invited by journal 06 Feb, 2026 Editor assigned by journal 06 Feb, 2026 First submitted to journal 04 Feb, 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. 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-8748825","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":587672982,"identity":"4dcda199-ffa9-4ac9-b520-bd754c5b3a14","order_by":0,"name":"Arisa Kanetou","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABN0lEQVRIiWNgGAWjYHACNoaPf2zk2NgbMKUSsKnnAWphnNmQZszHc4ARqMmAOC3MvA2HE+dJJGBqwQrs+Q8/e8C7g5mxTfL588c8DH/kdduPX/zMU8Mgz9/A8OwBNlsk0swNJM+wMbNJ5xg28zAYGG47k1MszXOMwXDGAYZ0bJbySDCYSRiw8bABtTCCtDBuO5CTIJ3DxsC4gYEhTQKbFv7j3yQS2CR42CSPPwRpsd92/k3y75x/DPY4tTDkmEkcbDOQYJNgADsscduN9GPSuW0MiTi13Mgpk2w4kwB0W47hzDkGxsnbbrxhs/7bJ5E84zB2v7D3H98m/afif/389uMPPrypkLPddj798c0Z32xs+9t70rCFGBoAm8oDIoFOYuZJI6wDajPMbPZjxGoZBaNgFIyCYQ0AqQVfxF3rLgMAAAAASUVORK5CYII=","orcid":"https://orcid.org/0009-0001-7387-154X","institution":"Tamagawa University College of Agriculture Graduate School of Agriculture: Tamagawa Daigaku Nogakubu Daigakuin Nogaku Kenkyuka","correspondingAuthor":true,"prefix":"","firstName":"Arisa","middleName":"","lastName":"Kanetou","suffix":""},{"id":587672983,"identity":"c4037dbf-924a-4795-ad30-ed8308667826","order_by":1,"name":"Yuki Yoshida","email":"","orcid":"","institution":"Tamagawa University College of Agriculture Graduate School of Agriculture: Tamagawa Daigaku Nogakubu Daigakuin Nogaku Kenkyuka","correspondingAuthor":false,"prefix":"","firstName":"Yuki","middleName":"","lastName":"Yoshida","suffix":""},{"id":587672984,"identity":"a79770db-abd5-4aaa-8f7f-8ff9c3f42b8c","order_by":2,"name":"Tomoko Yoshikawa","email":"","orcid":"","institution":"Tamagawa University College of Agriculture Graduate School of Agriculture: Tamagawa Daigaku Nogakubu Daigakuin Nogaku Kenkyuka","correspondingAuthor":false,"prefix":"","firstName":"Tomoko","middleName":"","lastName":"Yoshikawa","suffix":""},{"id":587672985,"identity":"3c4de43d-a594-45a0-817e-f2d459248d01","order_by":3,"name":"Hiroshi Kanda","email":"","orcid":"","institution":"National Institute of Polar Research Division for Research and Education: Kokuritsu Kyokuchi Kenkyujo Kenkyu Kyoikukei","correspondingAuthor":false,"prefix":"","firstName":"Hiroshi","middleName":"","lastName":"Kanda","suffix":""},{"id":587672986,"identity":"c85cf848-9a6d-400a-8ca7-8b784f8cdc47","order_by":4,"name":"Yoshi Minami","email":"","orcid":"","institution":"Tamagawa University College of Agriculture Graduate School of Agriculture: Tamagawa Daigaku Nogakubu Daigakuin Nogaku Kenkyuka","correspondingAuthor":false,"prefix":"","firstName":"Yoshi","middleName":"","lastName":"Minami","suffix":""}],"badges":[],"createdAt":"2026-01-31 10:13:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8748825/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8748825/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102746944,"identity":"aee1df56-3e37-4049-8919-51a469216571","added_by":"auto","created_at":"2026-02-16 09:03:03","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":398202,"visible":true,"origin":"","legend":"\u003cp\u003eTopography around Lake Kussharo and the survey locations. Near Site D, there is the Yukawa River, where hot spring water flows into the lake. This figure was modified from the Geospatial Information Authority of Japan (2025).\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8748825/v1/ca270dfd58b7a78b9a70469f.jpeg"},{"id":102565874,"identity":"0a0921af-c236-470b-ad6f-38f55d1cc8dd","added_by":"auto","created_at":"2026-02-13 05:46:08","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":346680,"visible":true,"origin":"","legend":"\u003cp\u003eAerial photographs of Site D. A is an aerial photograph modified from the Geospatial Information Authority of Japan (2025). B: Photograph taken using UAV.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8748825/v1/4ffb10c2239ed9a45ba907b3.jpeg"},{"id":102565870,"identity":"6ba511e6-f7b9-48e8-9526-9a9b041611c5","added_by":"auto","created_at":"2026-02-13 05:46:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":402690,"visible":true,"origin":"","legend":"\u003cp\u003epH range map of Site D. The range map have been modified from the Geospatial Information Authority of Japan (2025).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8748825/v1/e332ab2b8d51625913e7821c.png"},{"id":102565872,"identity":"acadb696-e4d5-4904-934c-77b89d19b541","added_by":"auto","created_at":"2026-02-13 05:46:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":297929,"visible":true,"origin":"","legend":"\u003cp\u003eSpring Water and Sediment at Points A-D\u003c/p\u003e\n\u003cp\u003eThis is a map of the eastern shore of Lake Kussharo. Black lines indicate spring water, yellow indicates gravel, and red indicates sandy silt and small gravel. This figure was modified from the Geospatial Information Authority of Japan (2025).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8748825/v1/7f8f8ff0d7257f3b967afcf3.png"},{"id":102746953,"identity":"dc73840b-2c23-49ce-87dc-5abced1b959c","added_by":"auto","created_at":"2026-02-16 09:03:08","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":556609,"visible":true,"origin":"","legend":"\u003cp\u003eGeological map of the area around Sites A–D. Geological map of Lake Kussharo. The symbols \"a\" and \"KC\u003csub\u003e1\u003c/sub\u003e\" indicate alluvium and the outer crater rim of the Kussharo Volcano, respectively. Both panels were partially modified from the \u003cem\u003eHistory of Teshikaga Town\u003c/em\u003e (2005).\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8748825/v1/3e752f49672dfbe701a13af1.jpeg"},{"id":102750755,"identity":"3406e3ae-1566-4ca8-b54f-779b687c8d8c","added_by":"auto","created_at":"2026-02-16 09:21:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2254794,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8748825/v1/ab598b52-bc45-4dad-8061-32c8bfc15de5.pdf"}],"financialInterests":"","formattedTitle":"Water pH as a driver of bryophyte species distribution in Moss Balls of Lake Kussharo, Japan","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAkan-Mashu National Park in Hokkaido consists of three calderas, and Lake Kussharo, located within the Kussharo Caldera, is the largest caldera lake in Japan (Ministry of the Environment, Akan-Mashu National Park Management Office \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Lake Kussharo is a habitat for Marigoke (moss balls), which was designated as a natural monument of Teshikaga Town on July 11, 1969 (Teshikaga Town, Hokkaido 2025). Marigoke are consisted of lake-bottom mosses that are detached by strong wave action and become entangled with fragments of aquatic plants and debris during the rotation process, eventually forming a spherical shape (Baba and Iwatsuki \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1973\u003c/span\u003e). Marigoke has also been reported in Gennarbyviken in southern Finland (Luther \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1979\u003c/span\u003e) and Lake Parillar in southern Chile (Frahm 2001) but is extremely rare on a global scale. In Lake Kussharo, species such as \u003cem\u003eDrepanocladus fluitans\u003c/em\u003e var. \u003cem\u003ekutcharokensis\u003c/em\u003e Kanda and \u003cem\u003eJungermannia exsertifolia\u003c/em\u003e Steph. have been previously reported as the constituent plants of Marigoke (Iwatsuki et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). Marigoke are frequently observed along the eastern shores of Lake Kussharo, such as in Wakoto and Nibushi (Iwatsuki et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). Sato et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) conducted research on the eastern shore of Lake Kussharo. However, since the survey conducted in 2003 (Sato et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), no detailed assessment of its current status has been conducted. This study aimed to clarify how the pH of the lake water in Lake Kussharo affects the distribution of Marigoke and its constituent plant species.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003eLake Kussharo, is located in the eastern part of Hokkaido (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). According to meteorological data from Teshikaga Town (2010–2020), the average temperature is 5.6°C, the annual precipitation is 1,091 mm, and the maximum snow depth is 118 cm (Japan Meteorological Agency \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The Kushiro River, which is the only outflow river of Lake Kussharo, forms the Kushiro Marsh, Japan’s largest wetland registered under the Ramsar Convention (Kikuchi \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Lake Kussharo is a caldera lake formed within the Kussharo Caldera (Teshikaga Town History Compilation Committee \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). It is the premier vast freshwater lake in Hokkaido, spanning approximately 12.5 km from north to south and 7.2 km from east to west, with a shoreline of 57 km and a surface area of 79.3 km² (Teshikaga Town History Compilation Committee \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). The surface elevation of the lake is 121 m, with a maximum depth of 117.5 m and an average depth of 28.4 m (Teshikaga Town History Compilation Committee \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). In Lake Kussharo, there was a period when the lake water became strongly acidified due to iron and aluminum sulfates derived from hot spring wastewater from the Kawayu Onsen (Yukawa). Surveys conducted between 1929 and 1968 showed pH values ranging from 3.3–5.5 (Hashimoto \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Subsequently, neutralization has progressed since the 1980s, with pH levels exceeding 7.0 in 2004 (Tanaka \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFirst, we surveyed locations where Marigoke had been previously reported (Iwatsuki et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; Sato et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). We found Marigoke only in northeastern part of the Lake and we selected study sites A-D along the shore (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). To assess the distribution of lake-bottom vegetation, aerial photographs of the lake bed were taken using a drone (Mavic 2 Pro, DJI, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Specifically, at Sites C and D, lake-bottom plants were collected using a boat. Additionally, Marigoke and other plant materials washed ashore at Sites B, C, and D were also collected. The identification for bryophytes followed Iwatsuki (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). In addition pH of the Lake water were also measured at each site (LAQUAtwin-pH-11B; HORIBA).\u003c/p\u003e\u003cp\u003eSome submerged bryophytes are known to inhabit in areas with spring water (Kadono \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Springs have been confirmed in Lake Kussharo and spring discharge points were identified by utilizing the temperature difference between the spring water and the lake water. The surveys using an unmanned aerial vehicle (UAV; Mavic 3 Thermal, DJI) equipped with an infrared (IR) camera were conducted to cover the northeastern shore, during a period when the spring water temperature was lower than the lake water temperature. The total distance of the surveyed area was 4.65 km.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eConstituent plants of Marigoke and Lake-bottom vegetation\u003c/p\u003e \u003cp\u003eThe Marigoke-constituent plants and pH levels at each site are listed in Table\u0026nbsp;1. At site A, Marigoke-constituent plants were not found. At Site B, \u003cem\u003eFontinalis antipyretica\u003c/em\u003e Hedw. was identified. At Site C, both \u003cem\u003eDrepanocladus fluitans\u003c/em\u003e (Hedw.) Warnst. and \u003cem\u003eF. antipyretica\u003c/em\u003e were found. At Site D, only \u003cem\u003eD. fluitans\u003c/em\u003e was confirmed.\u003c/p\u003e \u003cp\u003epH measurement\u003c/p\u003e \u003cp\u003eAt Sites A\u0026ndash;C, the pH levels ranged from 6.8 to 7.7, showing no significant variation. In contrast, Site D exhibited acidic conditions, with pH values between 3.4 and 4.6. Around Site D, pH levels were lower to the north, where Yukawa liver mouth is located, reaching a minimum of 2.9, and higher to the south, reaching a maximum of 6.2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSpring water\u003c/p\u003e \u003cp\u003eThe shoreline segments where water temperatures were lower than the surrounding lake water totaled 2.87 km within the surveyed distance of 4.65 km (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Regarding the bottom substrate, Site A consisted predominantly of gravel, although some areas contained sandy mud and pebbles. At Site B, although some gravelly areas were observed, the substrate was mostly composed of sandy mud and pebbles. Sites C and D were characterized by sandy mud and pebbles. Groundwater discharge (springs) was observed at all study sites.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003ePast reports confirmed \u003cem\u003eDrepanocladus fluitans\u003c/em\u003e var. \u003cem\u003ekutcharokensis\u003c/em\u003e Kanda and \u003cem\u003eJungermannia exsertifolia\u003c/em\u003e. as the constituent plants of Marigoke in Lake Kussharo (Iwatsuki et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). However, in this study, \u003cem\u003eFontinalis antipyretica\u003c/em\u003e and \u003cem\u003eD. fluitans\u003c/em\u003e were identified as constituent species. One of the factors contributing to this change is the difference in pH. At Sites A\u0026ndash;C, where the pH was in the neutral range (6.0\u0026ndash;7.0), \u003cem\u003eF. antipyretica\u003c/em\u003e was found to grow, and Marigoke was composed of this species. In contrast, Site D was an acidic environment with a pH of 3.0\u0026ndash;4.0, where communities of \u003cem\u003eD. fluitans\u003c/em\u003e and Marigoke composed of this species were confirmed. These results suggest that two types of Marigoke, consisting of different species depending on the pH of the environment, exist in Lake Kussharo. Presence of spring water, geology, bottom sediment, and topography may influence the differences in constituent species and formation of Marigoke. While spring water was confirmed at Sites A\u0026ndash;C, Site D received an inflow of both spring and hot spring water.\u003c/p\u003e \u003cp\u003eRegarding the geology, Site A is located on basaltic and andesitic outer crater rim, whereas Sites B\u0026ndash;D consist of alluvial deposits (Teshikaga Town History Compilation Committee \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The topography of Site A characterized by a steeper slope, where the water depth reached 20 m at a short distance from the shore compared to the other sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Therefore, even if Marigoke is formed, it may be less likely to wash ashore because of the steep topography, and the lack of light reaching the bottom in deeper water may make the environment unsuitable for moss growth. At Sites B and C, the depth was shallow for a long distance from the shore, Marigoke washes ashore more easily, and the presence of spring water creates an ideal environment for the growth of \u003cem\u003eF. antipyretica\u003c/em\u003e. Similarly, Site D was shallow and suitable for Marigoke formation. The coexistence of spring and hot spring water at this site creates a favorable environment for \u003cem\u003eD. fluitans\u003c/em\u003e, resulting in a different moss species compared to the other sites.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe found that the habitat of Marigoke is shaped by a complex interplay of multiple factors, including water quality, presence of spring water, geology, bottom sediments, topography, and flow characteristics. Protection of spring water, such as avoiding bank constructions, would contribute to conservation of Marigoke.\u003c/p\u003e"},{"header":"Statements \u0026 Declarations","content":"\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research was conducted with funding from the Teshikaga Town Board of Education (Joint Research Project Concerning the Survey of Marigoke Vegetation at Lake Kussharo, a Cultural Property of Teshikaga Town).\u003c/p\u003e\n\u003cp\u003eCompeting Interests\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Yuki Yoshida, Tomoko Yoshikawa, Hiroshi Kanda and Yoshi Minami. The first draft of the manuscript was written by Arisa Kanetou and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eExample statements\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBaba Y, Iwatsuki Z (1973) Notes on moss balls of Lake Inawashiro. \u003cem\u003eMiscellanea Bryologica et Lichenologica\u003c/em\u003e 6:117\u0026ndash;119. (In Japanese)\u003c/li\u003e\n \u003cli\u003eFrahm Jan-Pether (2001) Aquatic mossballs of Blindia inundata in Patagonia. The Bryologist 104: 502―503. https://doi.org/10.1639/0007-2745(2001)104[0503:NMOBII]2.0.CO;2.\u003c/li\u003e\n \u003cli\u003eHashimoto S (1989) Environmental Disruption by Waste Water from a Hot Spring\u0026mdash;II: Effects of Waste Water Pollution of the \u0026ldquo;Kawayu-Onsen\u0026rdquo; on Fish in the \u0026ldquo;Kusirogawa-River Systems\u0026rdquo;. \u003cem\u003eScientific Reports of the Hokkaido Salmon Hatchery\u003c/em\u003e 43:39\u0026ndash;51. https://salmon.fra.affrc.go.jp/kankobutu/srhsh/data/srhsh332.pdf . (In Japanese with English abstract)\u003c/li\u003e\n \u003cli\u003eIwatsuki Z. (2001) \u003cem\u003eMosses and Liverworts of Japan\u003c/em\u003e. Heibonsha, Tokyo.\u003c/li\u003e\n \u003cli\u003eIwatsuki Z, Takita K, Glime J. M (1983) Moss balls of Lake Kussharo. Hokkaido. \u003cem\u003eMiscellanea Bryologica et Lichenologica\u003c/em\u003e 9:199\u0026ndash;201. (In Japanese)\u003c/li\u003e\n \u003cli\u003eJapan Meteorological Agency. Historical Weather Data. https://www.data.jma.go.jp/stats/etrn/index.php. Accessed 5 December 2025. (In Japanese)\u003c/li\u003e\n \u003cli\u003eKadono Y (2020) Present status of alien aquatic plants in spring-fed waters in Japan. \u003cem\u003eJapanese Journal of Conservation Ecology\u003c/em\u003e 25: 265\u0026ndash;277. https://doi.org/10.18960/hozen.2004. (In Japanese with English abstract)\u003c/li\u003e\n \u003cli\u003eKikuchi Y (2017) Kushiro-shitsugen: Passions of the local community surrounding the first Ramsar site in Japan. \u003cem\u003eWetland Research\u003c/em\u003e 7:53\u0026ndash;57. https://doi.org/10.24785/wetlandresearch.WR007009. (In Japanese)\u003c/li\u003e\n \u003cli\u003eLuther H (1979) Aquatic moss balls in southern Finland. Annales Botanici Fennici 16:163―172. https://www.jstor.org/stable/23725152.\u003c/li\u003e\n \u003cli\u003eMinistry of the Environment, Akan-Mashu National Park Management Office (2020) \u003cem\u003eAkan-Mashu National Park Trail Guide\u003c/em\u003e. (In Japanese) https://hokkaido.env.go.jp/kushiro/content/900144902.pdf. Accessed 30 December 2025. (In Japanese)\u003c/li\u003e\n \u003cli\u003eSato H, Hachiya M, Hosokawa O (2023) A Record of Moss balls Growth in Lake Kussharo, Akan-Mashu National Park in Hokkaido. \u003cem\u003eMemoirs of the Kushiro City Museum\u0026nbsp;\u003c/em\u003e41:5\u0026ndash;10. https://www.city.kushiro.lg.jp/_res/projects/default_project/_page_/001/011/507/bulletin41_sato_et_al.pdf. (In Japanese)\u003c/li\u003e\n \u003cli\u003eTanaka A (2004) Investigating the causes of the natural neutralization of Lake Kussharo. \u003cem\u003eNIES News\u003c/em\u003e, 23. National Institute for Environmental Studies. https://www.nies.go.jp/kanko/news/23/23-4/23-4-03.html . Accessed 2 January 2024. (In Japanese)\u003c/li\u003e\n \u003cli\u003eTeshikaga Town History Compilation Committee (2005) \u003cem\u003eHistory of Teshikaga Town\u003c/em\u003e. Teshikaga Town Office. (In Japanese)\u003c/li\u003e\n \u003cli\u003eTeshikaga Town, Hokkaido (2025) Cultural Properties. https://www.town.teshikaga.hokkaido.jp/kurashi/soshikiichiran/kyoikuiinkai_shakaikyoikuka/2/2/658.html. Accessed 12 October 2025.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1. Main constituent bryyophyte of Marigoke (Moss balls)\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"501\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"11\" style=\"width: 359px;\"\u003e\n \u003cp\u003eSite\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 115px;\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 75px;\"\u003e\n \u003cp\u003eSite A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSite B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSite C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSite D\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eMB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eDR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eMB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eDR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eMB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eDR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eMB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eDR\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u003cem\u003eDrepanocladus fluitans\u003c/em\u003e (Hedw.) Warnst.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 115px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u003cem\u003eFontinalis antipyretica\u003c/em\u003e Hedw.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e○\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 75px;\"\u003e\n \u003cp\u003e7.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 76px;\"\u003e\n \u003cp\u003e7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 76px;\"\u003e\n \u003cp\u003e7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 76px;\"\u003e\n \u003cp\u003e4.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;MB and DR indicate moss balls and drift, respectively.\u003c/p\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"wetlands","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wela","sideBox":"Learn more about [Wetlands](https://www.springer.com/journal/13157)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/wela/default.aspx","title":"Wetlands","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Lake Kussharo, Marigoke, Fontinalis antipyretica Hedw., Drepanocladus fluitans (Hedw.) Warnst., pH, spring water","lastPublishedDoi":"10.21203/rs.3.rs-8748825/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8748825/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLake Kussharo is the largest caldera lake in Japan and serves as the habitat for \"Marigoke\" (moss balls), which was designated as a natural monument of Teshikaga Town on July 11, 1969. Recently, a decline has been observed in both Marigoke and its constituent plant species. This study aimed to clarify the impact of the pH of lake water on Marigoke and its constituent plants. Historically, the constituent species were \u003cem\u003eDrepanocladus fluitans\u003c/em\u003e var. \u003cem\u003ekutcharokensis\u003c/em\u003e and \u003cem\u003eJungermannia exsertifolia\u003c/em\u003e Steph. However, current observations indicate that \u003cem\u003eFontinalis antipyretica\u003c/em\u003e Hedw. is dominant in neutral environments, while \u003cem\u003eDrepanocladus fluitans\u003c/em\u003e (Hedw.) Warnst. prevails in acidic environments. Furthermore, this study revealed the existence of two distinct types of Marigoke in Lake Kussharo, each composed of different species depending on the pH of the environment. The growth process of Marigoke is governed by a complex interplay of multiple factors, including water quality, presence or absence spring water, geology, sediment, topography, and flow characteristics. The formation of Marigoke requires specific environmental conditions, including physical factors, and its occurrence is restricted to extremely limited areas.\u003c/p\u003e","manuscriptTitle":"Water pH as a driver of bryophyte species distribution in Moss Balls of Lake Kussharo, Japan","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-13 05:46:04","doi":"10.21203/rs.3.rs-8748825/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-03-01T14:39:33+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-08T10:15:22+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Wetlands","date":"2026-02-06T19:30:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-06T12:50:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Wetlands","date":"2026-02-05T01:39:23+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"wetlands","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wela","sideBox":"Learn more about [Wetlands](https://www.springer.com/journal/13157)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/wela/default.aspx","title":"Wetlands","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"d841b47a-0418-4167-bf13-4f46289862bf","owner":[],"postedDate":"February 13th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-13T05:46:04+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-13 05:46:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8748825","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8748825","identity":"rs-8748825","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}