Species Composition and New Records of Epiphytic Diatoms on Seagrass Zostera marina from Qingdao Bay, China

Abstract

Epiphytes significantly contribute to the overall primary productivity of seagrass beds. Among them, diatoms are the most diverse and important component of the epiphytic community in seagrass beds. However, studies on this group of diatoms are still limited in China. In this research, we investigated the epiphytic diatoms on Zostera marina Linnaeus from Qingdao Bay on the western coast of the Yellow Sea. A total of 112 taxa belonging to 31 families and 57 genera were morphologically identified, of which 16 taxa were newly recorded in China. Each taxon was illustrated with corresponding light micrographs. The most common genera were Navicula Bory with 12 taxa, Amphora (Ehrenberg) Kützing with 10 taxa, and Nitzschia Hassall with 10 taxa. Notably, species of Cocconeis Ehrenberg were ubiquitous and found in every sample. Based on our observations, the sediment is proposed as a likely source of these epiphytic communities. None of the newly recorded diatoms had been previously reported as epiphytes on seagrasses. Our results improve the understanding of species diversity and distribution of seagrass epiphytic diatoms along the coasts of China.

1. Introduction

Seagrass, the only angiosperm that completes its life cycle in seawater on the globe, is a unique marine flowering plant that generates annual crops of leaves from its perennial rhizomes buried in the sediment [1]. Currently, a total of 74 seagrass species are globally recognized, belonging to 13 genera and 6 families [2]. They are widespread in shallow coastal waters, forming extensive multispecific or monospecific beds [3,4]. Seagrass beds are one of the three typical offshore marine ecosystems, playing an important role in carbon sequestration, water purification, sediment stabilization, nutrients cycling and coastal protection [5,6,7]. They can serve as nursery grounds for many invertebrate and small vertebrate organisms, such as copepods, amphipods, shrimp, crabs, gastropods and small fishes [8].

Despite occupying merely 0.2% of the world ocean area, seagrass beds are the most productive ecosystems on earth [9]. Recent studies suggested that epiphytic algae contribute more productivity than the seagrass itself [9,10,11]. Epiphytic diatoms, which can utilize all available surfaces for attachment, have been shown to account for 71–83% of benthic net community production within seagrass bed ecosystems [8,12,13]. As a result, over recent decades, diatoms living on seagrasses have been documented in many regions worldwide. The reported species diversity of seagrass epiphytic diatoms vary greatly, ranging from 10 to 235 taxa [9,14]. Meanwhile, new diatom species have been continuously described from seagrasses, such as Cocconeis thalassiana Romero & López-Fuerte, Nagumoea serrata Majewska & Van de Vijver and Gomphonemopsis nana Lang Li, Yuhang Li & Junxiang Lai [15,16,17].

Depending on their growth forms, epiphytic diatoms are commonly divided into three types: adnate species (e.g., Cocconeis Ehrenberg), erect species (e.g., Licmophora Agardh, Tabularia (Kützing) Williams & Round, Gomphonemopsis Medlin, Fragilaria Lyngbye, Grammatophora Ehrenberg) and motile species (e.g., Navicula Bory, Pleurosigma Smith) [18]. Additionally, some planktonic diatoms (e.g., Chaetoceros Ehrenberg) that loosely attach to the substrata may also be regarded as temporary residents of the epiphytic community [11]. The colonization of epiphytes on seagrasses proceeds in a sequence: 1. formation of a basal crust by pioneer diatoms, i.e., Cocconeis spp.; 2. settlement by coralline algae; 3. development of a complex diatom community, including some erect and motile species [18,19,20]. The composition of epiphytic diatoms associated with seagrasses can be influenced by both biotic factors (morphology and lifespan of seagrasses, herbivory action) and abiotic factors (temperature, salinity, depth, current, nutrients and light availability) [11,21]. However, due to limited research and highly dynamic shallow coastal environment, the main drivers structuring the diatom community are still unclear [7].

In China’s coastal waters, the area of seagrass beds is 26,495.69 ha. There are 16 species of seagrasses from nine genera in total [22]. However, knowledge on the diversity of seagrass epiphytic diatoms is also very limited in China. Gao et al. (2010) [14] reported ten diatom species and ten macroalgal species growing on Z. marina Linnaeus in Sanggou Bay, Yellow Sea. In an annual survey, Li (2016) [23] identified a total of 61 epiphytic diatom species on Halophila ovalis (Brown) Hooker from Liusha Bay, South China Sea. Therefore, in order to improve our understanding of the epiphytic diatom diversity of seagrass in China, the present study investigated the species composition and taxonomic information of diatoms living on Z. marina in Qingdao Bay, China.

2. Materials and Methods

Samplings were conducted in the intertidal zone of Qingdao Bay (36°3′33.45″ N, 120°18′56.26″ E), the Yellow Sea on 11 October 2022 (autumn) and 10 January 2023 (winter). Qingdao Bay is an open gulf located in the southern part of Qingdao City, within the northern temperate monsoon zone. It features a natural eelgrass (Z. marina) bed near the Zhaniqao pier, which is situated in a flat sandy-muddy beach area. The bay has an average water depth of approximately 3.50 m, and exhibits a semidiurnal tidal pattern with an average range of 2.78 m [24]. The Zhanqiao pier is a very famous tourist attraction in Qingdao, characterized by considerable daily foot traffic. Due to the construction of sewage and stormwater drains on the eastern side of Zhanqiao Pier in the early 1990s, the coastal seawater here has suffered from severe eutrophication [25].

All samples were collected at low tide. During each sampling time, three replicates of Z. marina leaves associated with epiphytic diatoms were randomly obtained by cutting with scissors in situ. The eelgrass leaves were immediately stored in separate Ziploc bags and transported to the laboratory in a cooler box. Simultaneously, water temperature and salinity were measured with a thermometer (Wuqiang Guanghua Instrument Factory, Hengshui, China) and a RHS-10ATC refractometer (Xiamen Mingxin Instrument, Xiamen, China), respectively. In the laboratory, leaf samples were gently rinsed three times with filtered seawater for removal of sediments and free microalgae. To isolate epiphytes on the leaves, the samples were cut into 1–2 cm long fragments and ultrasonicated at 300 W in filtered seawater for 25 s [17]. Following fixation with 5% formaldehyde, the removed epiphytes were settled for 24 h and concentrated to about 100 mL. Afterwards, they were oxidized with HCl (36–38%) in boiling water for 20 min to clean the diatom frustules [17]. The materials were then washed with distilled water, dried onto coverslips and mounted on glass slides with Mountmedia (Wako Pure Chemical Industries, Ltd., Osaka, Japan). Slides were inspected under a Zeiss Imager Z2 light microscope (Carl Zeiss Microscopy GmbH, Göttingen, Germany) equipped with differential interference contrast (DIC) and a Axiocam 512 color digital camera (Carl Zeiss Microscopy GmbH, Göttingen, Germany).

In the present study, diatoms were identified based on their valve morphology, primarily with reference to Witkowski et al. (2000) and Chin et al. (1982, 1991) [26,27,28]. All taxa are listed according to the classification of Guiry (2024) [29].

3. Results

The thorough inspection of epiphytes on the eelgrass leaves yielded 112 diatom taxa, belonging to 19 orders, 31 families, and 57 genera (Table 1; Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6 and Figure 7). At the class level, 88% (99 taxa) were Bacillariophyceae, 8% (9) were Mediophyceae, and 4% (4) were Coscinodiscophyceae. The families best represented were Naviculaceae (19), Bacillariaceae (17), Catenulaceae (11), and Cocconeidaceae (8). Meanwhile, the dominant genera in terms of the number of taxa were Navicula Bory (12), Amphora (Ehrenberg) Kützing (10), Nitzschia Hassall (10), Cocconeis Ehrenberg (5), Halamphora (Cleve) Mereschkowsky (5), and Licmophora Agardh (4). These accounted for 41% of the total taxa recorded in this study. In contrast, for 40 genera only a single taxon was observed, representing 36% of all the records collected. Additionally, 16 taxa could not be identified to the species level, such as Plagiogrammopsis sp., Delphineis sp., Achnanthes sp., and Navicula sp. 2. Overall, 16 taxa were new recordings for the coasts of China: Cyclotella litoralis Lange & Syvertsen, Ellerbeckia sol (Ehrenberg) Crawford & Sims, Pierrecomperia catenuloides Sabbe, Vyverman & Ribero, Plagiogrammopsis crawfordii Witkowski, Lange-Bertalot & Metzeltin, Achnanthes fimbriata (Grunow) Ross, Monoalveoneis convexa (Giffen) Yurchak, Gogorev, Kezlya & Kulikovskiy, Parlibellus delognei (Van Heurck) Cox, Navicula arenaria var. rostellata Lange-Bertalot, Navicula eidrigiana Carter, Navicula flebilis Cholnoky, Donkinia carinata (Donkin) Ralfs, Amphora abludens Simonsen, Amphora americana Wachnicka & Gaiser, Amphora eximia Carter, Amphora proteoides f. varians Proshkina-Lavrenko, and Nitzschia aequorea Hustedt. Moreover, it should be noted that 36 taxa of epiphytic diatoms were recorded exclusively in autumn, 43 taxa found exclusively in winter, and 33 taxa were observed in both seasons (Table 1). From autumn to winter, the average water temperature decreased from 24.1 °C to 10.5 °C, whereas the salinity increased slightly from 30.3 psu to 30.7 psu.

Following is the checklist of epiphytic diatoms on Z. marina sampled from Qingdao Bay on 11 October 2022 and 10 January 2023, in which taxa denoted by an asterisk (*) are new records for China.

Table 1. Systematic list of epiphytic diatom taxa living on the seagrass Zostera marina sampled from Qingdao Bay, China. + = presence, * = new records for China.

	Season	Autumn	Winter
Taxon
Division Heterokontophyta Moestrup, Andersen & Guiry
Class Mediophyceae Medlin & Kaczmarska
Order Thalassiosirales Glezer & Makarova
Family Thalassiosiraceae Lebour
Genus Cymatotheca Hendey
Cymatotheca minima Voigt (Figure 1D)		+	+
Genus Tryblioptychus Hendey
Tryblioptychus cocconeiformis (Grunow) Hendey (Figure 1E)		+	+
Order Stephanodiscales Nikolaev & Harwood
Family Stephanodiscaceae Makarova
Genus Cyclotella (Kützing) Brébisson
Cyclotella litoralis Lange & Syvertsen * (Figure 1A)			+
Order Anaulales Round & Crawford
Family Anaulaceae (Schütt) Lemmermann
Genus Eunotogramma Weisse
Eunotogramma debile Grunow (Figure 1I)		+	+
Order Cymatosirales Round & Crawford
Family Cymatosiraceae Hasle, von Stosch & Syvertsen
Genus Cymatosira Grunow
Cymatosira gibberula Cheng & Gao (Figure 1J)			+
Genus Pierrecomperia Sabbe, Vyverman & Ribero
Pierrecomperia catenuloides Sabbe, Vyverman & Ribero * (Figure 1H)			+
Genus Plagiogrammopsis Hasle, Stosch & Syvertsen
Plagiogrammopsis crawfordii Witkowski, Lange-Bertalot & Metzeltin * (Figure 1K)		+	+
Plagiogrammopsis mediaequata Gardner & Crawford (Figure 1L)			+
Plagiogrammopsis sp. (Figure 1M)			+
Class Coscinodiscophyceae Round & Crawford
Order Melosirales Crawford
Family Hyalodiscaceae Crawford
Genus Podosira Ehrenberg
Podosira stelligera (Bailey) Mann (Figure 1C)			+
Order Paraliales Crawford
Family Paraliaceae Crawford
Genus Paralia Heiberg
Paralia sulcata (Ehrenberg) Cleve (Figure 1F)		+
Family Radialiplicataceae Gleser & Moisseeva
Genus Ellerbeckia Crawford
Ellerbeckia sol (Ehrenberg) Crawford & Sims * (Figure 1B)		+
Order Aulacoseirales Crawford
Family Aulacoseiraceae Crawford
Genus Aulacoseira Thwaites
Aulacoseira granulata var. angustissima (Müller) Simonsen (Figure 1G)		+
Class Bacillariophyceae Haeckel
Order Fragilariales Silva
Family Staurosiraceae Medlin
Genus Staurosirella Wiliams & Round
Staurosirella martyi (Héribaud) Morales & Manoylov (Figure 1N)		+
Genus Nanofrustulum Round, Hallsteinsen & Paasche
Nanofrustulum sopotense (Witkowski & Lange-Bertalot) Morales, Wetzel & Ector (Figure 1O)		+
Order Licmophorales Round
Family Ulnariaceae Cox
Genus Tabularia (Kützing) Williams & Round
Tabularia fasciculata (Agardh) Williams & Round (Figure 2C)		+
Tabularia parva (Kützing) Williams & Round (Figure 2B)		+	+
Genus Trachysphenia Petit
Trachysphenia australis Petit (Figure 2A)			+
Family Licmophoraceae Kützing
Genus Licmophora Agardh
Licmophora californica Grunow (Figure 2D,D’)		+	+
Licmophora ehrenbergii (Kützing) Grunow (Figure 2F)			+
Licmophora flabellata (Greville) Agardh (Figure 2G)			+
Licmophora paradoxa (Lyngbye) Agardh (Figure 2E)		+	+
Order Rhaphoneidales Round
Family Rhaphoneidaceae Forti
Genus Rhaphoneis Ehrenberg
Rhaphoneis rhomboides Hendey (Figure 2I)			+
Genus Delphineis Andrews
Delphineis australis (Petit) Watanabe, Tanaka, Reid, Kumada & Nagumo (Figure 2J)		+	+
Delphineis minutissima (Hustedt) Simonsen (Figure 2L)			+
Delphineis sp. (Figure 2K)		+	+
Genus Neodelphineis Takano
Neodelphineis silenda (Hohn & Hellerman) Desianti & Potapova (Figure 2M)		+
Order Rhabdonematales Round & Crawford
Family Grammatophoraceae Lobban & Ashworth
Genus Grammatophora Ehrenberg
Grammatophora marina (Lyngbye) Kützing (Figure 3C)		+
Grammatophora oceanica Ehrenberg (Figure 3A)		+
Grammatophora undulata Ehrenberg (Figure 3B)		+
Genus Hyalosira Kützing
Hyalosira delicatula Kützing (Figure 2H)			+
Order Lyrellales Mann
Family Lyrellaceae Mann
Genus Moreneis Park, Koh & Witkowski
Moreneis coreana Park, Koh & Witkowski (Figure 4D)			+
Order Mastogloiales Mann
Family Mastogloiaceae Mereschkowsky
Genus Tetramphora Mereschkowsky
Tetramphora lineolata (Ehrenberg) Mereschkowsky (Figure 6M)			+
Order Cymbellales Mann
Family Rhoicospheniaceae Chen & Zhu
Genus Rhoicosphenia Grunow
Rhoicosphenia genuflexa (Kützing) Medlin (Figure 3F,F’)		+	+
Genus Gomphonemopsis Medlin
Gomphonemopsis exigua (Kützing) Medlin (Figure 3Q)		+	+
Gomphonemopsis nana Li, Li & Lai (Figure 3R)		+
Order Achnanthales Silva
Family Achnanthaceae Kützing
Genus Achnanthes Bory
Achnanthes fimbriata (Grunow) Ross * (Figure 3D)		+
Achnanthes sp. (Figure 3E)		+
Family Cocconeidaceae Kützing
Genus Cocconeis Ehrenberg
Cocconeis costata Gregory (Figure 3H)			+
Cocconeis notata Petit (Figure 3I)		+
Cocconeis scutellum Ehrenberg (Figure 3M,M’)		+	+
Cocconeis sp. 1 (Figure 3K,K’)			+
Cocconeis sp. 2 (Figure 3L,L’)		+
Genus Monoalveoneis Yurchak, Gogorev, Kezlya & Kulikovskiy
Monoalveoneis convexa (Giffen) Yurchak, Gogorev, Kezlya & Kulikovskiy * (Figure 3J,J’)			+
Genus Cocconeiopsis Witkowski, Lange-Bertalot & Metzeltin
Cocconeiopsis kantsiensis (Giffen) Witkowski, Lange-Bertalot & Metzeltin (Figure 3P)		+
Genus Anorthoneis Grunow
Anorthoneis excentrica (Donkin) Grunow (Figure 3G)			+
Family Achnanthidiaceae Mann
Genus Achnanthidium Kützing
Achnanthidium glyphos Riaux-Gobin, Compère & Witkowski (Figure 3O)		+
Genus Pseudoplanothidium Tseplik, Glushchenko, Genkal, Maltsev & Kulikovskiy
Pseudoplanothidium delicatulum (Kützing) Tseplik, Glushchenko, Genkal, Maltsev & Kulikovskiy (Figure 3N)		+	+
Order Naviculales Bessey
Family Berkeleyaceae Mann
Genus Parlibellus Cox
Parlibellus delognei (Van Heurck) Cox * (Figure 4B)			+
Parlibellus rhombicus (Gregory) Cox (Figure 4A)			+
Genus Berkeleya Greville
Berkeleya rutilans (Trentepohl ex Roth) Grunow (Figure 4E)		+	+
Family Scoliotropidaceae Mereschkowsky
Genus Biremis Mann & Cox
Biremis ambigua (Cleve) Mann (Figure 4C)			+
Family Sellaphoraceae Mereschkowsky
Genus Fallacia Stickle & Mann
Fallacia forcipata (Greville) Stickle & Mann (Figure 4F)		+	+
Family Naviculales incertae sedis
Genus Pseudofallacia Liu, Kociolek & Wang
Pseudofallacia tenera (Hustedt) Liu, Kociolek & Wang (Figure 4G)		+	+
Genus Fogedia Witkowski, Lange-Bertalot, Metzeltin & Bafana
Fogedia lyra Park, Khim, Koh & Witkowski (Figure 5E)		+
Family Diploneidaceae Mann
Genus Diploneis (Ehrenberg) Cleve
Diploneis aestuarii Hustedt (Figure 5A)		+	+
Family Naviculaceae Kützing
Genus Navicula Bory
Navicula arenaria var. rostellata Lange-Bertalot * (Figure 4I)		+
Navicula digitoradiata (Gregory) Ralfs (Figure 4L)			+
Navicula eidrigiana Carter * (Figure 4O)		+
Navicula flanatica Grunow (Figure 4P)		+
Navicula flebilis Cholnoky * (Figure 4N)			+
Navicula gregaria Donkin (Figure 5D)			+
Navicula pavillardii Hustedt (Figure 4M)			+
Navicula perminuta Grunow (Figure 5B)		+	+
Navicula platyventris Meister (Figure 5C)		+
Navicula salinicola Hustedt (Figure 4K)			+
Navicula sp. 1 (Figure 4H)			+
Navicula sp. 2 (Figure 4J)			+
Genus Trachyneis Cleve
Trachyneis aspera (Ehrenberg) Cleve (Figure 5F)		+
Genus Seminavis Mann
Seminavis exigua Chen, Zhuo & Gao (Figure 6L)		+	+
Seminavis robusta Danielidis & Mann (Figure 6K)		+	+
Genus Caloneis Cleve
Caloneis brevis var. distoma (Grunow) Cleve (Figure 5G)			+
Genus Gyrosigma Hassall
Gyrosigma cf. tenuissimum (Smith) Griffith & Henfrey (Figure 5I)		+
Gyrosigma sp. 1 (Figure 5J)		+	+
Gyrosigma sp. 2 (Figure 5K)		+
Family Amphipleuraceae Grunow
Genus Halamphora (Cleve) Mereschkowsky
Halamphora aponina (Kützing) Levkov (Figure 6P)		+	+
Halamphora coffeiformis (Agardh) Levkov (Figure 6O)		+	+
Halamphora tenerrima (Aleem & Hustedt) Levkov (Figure 6S)		+
Halamphora sp. 1 (Figure 6Q)		+
Halamphora sp. 2 (Figure 6R)			+
Family Pleurosigmataceae Mereschowsky
Genus Pleurosigma Smith
Pleurosigma stuxbergii Cleve & Grunow (Figure 5H)			+
Genus Donkinia Ralfs
Donkinia carinata (Donkin) Ralfs * (Figure 5L)		+	+
Order Thalassiophysales Mann
Family Catenulaceae Mereschkowsky
Genus Catenula Mereschkowsky
Catenula adhaerens (Mereschkowsky) Mereschkowsky (Figure 6A)		+	+
Genus Amphora (Ehrenberg) Kützing
Amphora abludens Simonsen * (Figure 6G)		+	+
Amphora americana Wachnicka & Gaiser * (Figure 6H)		+
Amphora cf. marina Smith (Figure 6C)		+
Amphora eximia Carter * (Figure 6B)		+
Amphora holsaticoides Nagumo & Kobayasi (Figure 6N)			+
Amphora incrassata Giffen (Figure 6D)		+
Amphora laevissima Gregory (Figure 6I)			+
Amphora proteoides f. varians Proshkina-Lavrenko * (Figure 6J)		+
Amphora sp. 1 (Figure 6E)			+
Amphora sp. 2 (Figure 6F)			+
Order Bacillariales Hendey
Family Bacillariaceae Ehrenberg
Genus Bacillaria Gmelin
Bacillaria socialis (Gregory) Ralfs (Figure 7S)		+	+
Genus Psammodictyon Mann
Psammodictyon constrictum (Gregory) Mann (Figure 7O)		+	+
Genus Tryblionella Smith
Tryblionella apiculata Gregory (Figure 7N)			+
Tryblionella hungarica (Grunow) Frenguelli (Figure 7M)			+
Genus Cymbellonitzschia Hustedt
Cymbellonitzschia szulczewskii Witkowski, Lange-Bertalot & Metzeltin (Figure 7P)		+
Genus Nitzschia Hassall
Nitzschia aequorea Hustedt * (Figure 7G)			+
Nitzschia amabilis Suzuki (Figure 7I)			+
Nitzschia bicapitata Cleve (Figure 7F)			+
Nitzschia capitellata Hustedt (Figure 7B)			+
Nitzschia cf. sicula (Castracane) Hustedt (Figure 7E)			+
Nitzschia frustulum (Kützing) Grunow (Figure 7H)		+	+
Nitzschia hybrida Grunow (Figure 7D)		+	+
Nitzschia palea (Kützing) Smith (Figure 7C)			+
Nitzschia reversa Smith (Figure 7A)		+
Nitzschia valdestriata Aleem & Hustedt (Figure 7J)		+	+
Genus Homoeocladia Agardh
Homoeocladia distans (Gregory) Kuntze (Figure 7R)		+	+
Homoeocladia volvendirostrata (Ashworth, Dᶏbek & Witkowski) Lobban & Ashworth (Figure 7Q)		+
Order Surirellales Mann
Family Entomoneidaceae Reimer
Genus Entomoneis Ehrenberg
Entomoneis paludosa (Smith) Reimer (Figure 7K)		+
Family Surirellaceae Kützing
Genus Campylodiscus (Ehrenberg) Kützing
Campylodiscus neofastuosus Ruck & Nakov (Figure 7L)		+	+

Table 1. Systematic list of epiphytic diatom taxa living on the seagrass Zostera marina sampled from Qingdao Bay, China. + = presence, * = new records for China.

	Season	Autumn	Winter
Taxon
Division Heterokontophyta Moestrup, Andersen & Guiry
Class Mediophyceae Medlin & Kaczmarska
Order Thalassiosirales Glezer & Makarova
Family Thalassiosiraceae Lebour
Genus Cymatotheca Hendey
Cymatotheca minima Voigt (Figure 1D)		+	+
Genus Tryblioptychus Hendey
Tryblioptychus cocconeiformis (Grunow) Hendey (Figure 1E)		+	+
Order Stephanodiscales Nikolaev & Harwood
Family Stephanodiscaceae Makarova
Genus Cyclotella (Kützing) Brébisson
Cyclotella litoralis Lange & Syvertsen * (Figure 1A)			+
Order Anaulales Round & Crawford
Family Anaulaceae (Schütt) Lemmermann
Genus Eunotogramma Weisse
Eunotogramma debile Grunow (Figure 1I)		+	+
Order Cymatosirales Round & Crawford
Family Cymatosiraceae Hasle, von Stosch & Syvertsen
Genus Cymatosira Grunow
Cymatosira gibberula Cheng & Gao (Figure 1J)			+
Genus Pierrecomperia Sabbe, Vyverman & Ribero
Pierrecomperia catenuloides Sabbe, Vyverman & Ribero * (Figure 1H)			+
Genus Plagiogrammopsis Hasle, Stosch & Syvertsen
Plagiogrammopsis crawfordii Witkowski, Lange-Bertalot & Metzeltin * (Figure 1K)		+	+
Plagiogrammopsis mediaequata Gardner & Crawford (Figure 1L)			+
Plagiogrammopsis sp. (Figure 1M)			+
Class Coscinodiscophyceae Round & Crawford
Order Melosirales Crawford
Family Hyalodiscaceae Crawford
Genus Podosira Ehrenberg
Podosira stelligera (Bailey) Mann (Figure 1C)			+
Order Paraliales Crawford
Family Paraliaceae Crawford
Genus Paralia Heiberg
Paralia sulcata (Ehrenberg) Cleve (Figure 1F)		+
Family Radialiplicataceae Gleser & Moisseeva
Genus Ellerbeckia Crawford
Ellerbeckia sol (Ehrenberg) Crawford & Sims * (Figure 1B)		+
Order Aulacoseirales Crawford
Family Aulacoseiraceae Crawford
Genus Aulacoseira Thwaites
Aulacoseira granulata var. angustissima (Müller) Simonsen (Figure 1G)		+
Class Bacillariophyceae Haeckel
Order Fragilariales Silva
Family Staurosiraceae Medlin
Genus Staurosirella Wiliams & Round
Staurosirella martyi (Héribaud) Morales & Manoylov (Figure 1N)		+
Genus Nanofrustulum Round, Hallsteinsen & Paasche
Nanofrustulum sopotense (Witkowski & Lange-Bertalot) Morales, Wetzel & Ector (Figure 1O)		+
Order Licmophorales Round
Family Ulnariaceae Cox
Genus Tabularia (Kützing) Williams & Round
Tabularia fasciculata (Agardh) Williams & Round (Figure 2C)		+
Tabularia parva (Kützing) Williams & Round (Figure 2B)		+	+
Genus Trachysphenia Petit
Trachysphenia australis Petit (Figure 2A)			+
Family Licmophoraceae Kützing
Genus Licmophora Agardh
Licmophora californica Grunow (Figure 2D,D’)		+	+
Licmophora ehrenbergii (Kützing) Grunow (Figure 2F)			+
Licmophora flabellata (Greville) Agardh (Figure 2G)			+
Licmophora paradoxa (Lyngbye) Agardh (Figure 2E)		+	+
Order Rhaphoneidales Round
Family Rhaphoneidaceae Forti
Genus Rhaphoneis Ehrenberg
Rhaphoneis rhomboides Hendey (Figure 2I)			+
Genus Delphineis Andrews
Delphineis australis (Petit) Watanabe, Tanaka, Reid, Kumada & Nagumo (Figure 2J)		+	+
Delphineis minutissima (Hustedt) Simonsen (Figure 2L)			+
Delphineis sp. (Figure 2K)		+	+
Genus Neodelphineis Takano
Neodelphineis silenda (Hohn & Hellerman) Desianti & Potapova (Figure 2M)		+
Order Rhabdonematales Round & Crawford
Family Grammatophoraceae Lobban & Ashworth
Genus Grammatophora Ehrenberg
Grammatophora marina (Lyngbye) Kützing (Figure 3C)		+
Grammatophora oceanica Ehrenberg (Figure 3A)		+
Grammatophora undulata Ehrenberg (Figure 3B)		+
Genus Hyalosira Kützing
Hyalosira delicatula Kützing (Figure 2H)			+
Order Lyrellales Mann
Family Lyrellaceae Mann
Genus Moreneis Park, Koh & Witkowski
Moreneis coreana Park, Koh & Witkowski (Figure 4D)			+
Order Mastogloiales Mann
Family Mastogloiaceae Mereschkowsky
Genus Tetramphora Mereschkowsky
Tetramphora lineolata (Ehrenberg) Mereschkowsky (Figure 6M)			+
Order Cymbellales Mann
Family Rhoicospheniaceae Chen & Zhu
Genus Rhoicosphenia Grunow
Rhoicosphenia genuflexa (Kützing) Medlin (Figure 3F,F’)		+	+
Genus Gomphonemopsis Medlin
Gomphonemopsis exigua (Kützing) Medlin (Figure 3Q)		+	+
Gomphonemopsis nana Li, Li & Lai (Figure 3R)		+
Order Achnanthales Silva
Family Achnanthaceae Kützing
Genus Achnanthes Bory
Achnanthes fimbriata (Grunow) Ross * (Figure 3D)		+
Achnanthes sp. (Figure 3E)		+
Family Cocconeidaceae Kützing
Genus Cocconeis Ehrenberg
Cocconeis costata Gregory (Figure 3H)			+
Cocconeis notata Petit (Figure 3I)		+
Cocconeis scutellum Ehrenberg (Figure 3M,M’)		+	+
Cocconeis sp. 1 (Figure 3K,K’)			+
Cocconeis sp. 2 (Figure 3L,L’)		+
Genus Monoalveoneis Yurchak, Gogorev, Kezlya & Kulikovskiy
Monoalveoneis convexa (Giffen) Yurchak, Gogorev, Kezlya & Kulikovskiy * (Figure 3J,J’)			+
Genus Cocconeiopsis Witkowski, Lange-Bertalot & Metzeltin
Cocconeiopsis kantsiensis (Giffen) Witkowski, Lange-Bertalot & Metzeltin (Figure 3P)		+
Genus Anorthoneis Grunow
Anorthoneis excentrica (Donkin) Grunow (Figure 3G)			+
Family Achnanthidiaceae Mann
Genus Achnanthidium Kützing
Achnanthidium glyphos Riaux-Gobin, Compère & Witkowski (Figure 3O)		+
Genus Pseudoplanothidium Tseplik, Glushchenko, Genkal, Maltsev & Kulikovskiy
Pseudoplanothidium delicatulum (Kützing) Tseplik, Glushchenko, Genkal, Maltsev & Kulikovskiy (Figure 3N)		+	+
Order Naviculales Bessey
Family Berkeleyaceae Mann
Genus Parlibellus Cox
Parlibellus delognei (Van Heurck) Cox * (Figure 4B)			+
Parlibellus rhombicus (Gregory) Cox (Figure 4A)			+
Genus Berkeleya Greville
Berkeleya rutilans (Trentepohl ex Roth) Grunow (Figure 4E)		+	+
Family Scoliotropidaceae Mereschkowsky
Genus Biremis Mann & Cox
Biremis ambigua (Cleve) Mann (Figure 4C)			+
Family Sellaphoraceae Mereschkowsky
Genus Fallacia Stickle & Mann
Fallacia forcipata (Greville) Stickle & Mann (Figure 4F)		+	+
Family Naviculales incertae sedis
Genus Pseudofallacia Liu, Kociolek & Wang
Pseudofallacia tenera (Hustedt) Liu, Kociolek & Wang (Figure 4G)		+	+
Genus Fogedia Witkowski, Lange-Bertalot, Metzeltin & Bafana
Fogedia lyra Park, Khim, Koh & Witkowski (Figure 5E)		+
Family Diploneidaceae Mann
Genus Diploneis (Ehrenberg) Cleve
Diploneis aestuarii Hustedt (Figure 5A)		+	+
Family Naviculaceae Kützing
Genus Navicula Bory
Navicula arenaria var. rostellata Lange-Bertalot * (Figure 4I)		+
Navicula digitoradiata (Gregory) Ralfs (Figure 4L)			+
Navicula eidrigiana Carter * (Figure 4O)		+
Navicula flanatica Grunow (Figure 4P)		+
Navicula flebilis Cholnoky * (Figure 4N)			+
Navicula gregaria Donkin (Figure 5D)			+
Navicula pavillardii Hustedt (Figure 4M)			+
Navicula perminuta Grunow (Figure 5B)		+	+
Navicula platyventris Meister (Figure 5C)		+
Navicula salinicola Hustedt (Figure 4K)			+
Navicula sp. 1 (Figure 4H)			+
Navicula sp. 2 (Figure 4J)			+
Genus Trachyneis Cleve
Trachyneis aspera (Ehrenberg) Cleve (Figure 5F)		+
Genus Seminavis Mann
Seminavis exigua Chen, Zhuo & Gao (Figure 6L)		+	+
Seminavis robusta Danielidis & Mann (Figure 6K)		+	+
Genus Caloneis Cleve
Caloneis brevis var. distoma (Grunow) Cleve (Figure 5G)			+
Genus Gyrosigma Hassall
Gyrosigma cf. tenuissimum (Smith) Griffith & Henfrey (Figure 5I)		+
Gyrosigma sp. 1 (Figure 5J)		+	+
Gyrosigma sp. 2 (Figure 5K)		+
Family Amphipleuraceae Grunow
Genus Halamphora (Cleve) Mereschkowsky
Halamphora aponina (Kützing) Levkov (Figure 6P)		+	+
Halamphora coffeiformis (Agardh) Levkov (Figure 6O)		+	+
Halamphora tenerrima (Aleem & Hustedt) Levkov (Figure 6S)		+
Halamphora sp. 1 (Figure 6Q)		+
Halamphora sp. 2 (Figure 6R)			+
Family Pleurosigmataceae Mereschowsky
Genus Pleurosigma Smith
Pleurosigma stuxbergii Cleve & Grunow (Figure 5H)			+
Genus Donkinia Ralfs
Donkinia carinata (Donkin) Ralfs * (Figure 5L)		+	+
Order Thalassiophysales Mann
Family Catenulaceae Mereschkowsky
Genus Catenula Mereschkowsky
Catenula adhaerens (Mereschkowsky) Mereschkowsky (Figure 6A)		+	+
Genus Amphora (Ehrenberg) Kützing
Amphora abludens Simonsen * (Figure 6G)		+	+
Amphora americana Wachnicka & Gaiser * (Figure 6H)		+
Amphora cf. marina Smith (Figure 6C)		+
Amphora eximia Carter * (Figure 6B)		+
Amphora holsaticoides Nagumo & Kobayasi (Figure 6N)			+
Amphora incrassata Giffen (Figure 6D)		+
Amphora laevissima Gregory (Figure 6I)			+
Amphora proteoides f. varians Proshkina-Lavrenko * (Figure 6J)		+
Amphora sp. 1 (Figure 6E)			+
Amphora sp. 2 (Figure 6F)			+
Order Bacillariales Hendey
Family Bacillariaceae Ehrenberg
Genus Bacillaria Gmelin
Bacillaria socialis (Gregory) Ralfs (Figure 7S)		+	+
Genus Psammodictyon Mann
Psammodictyon constrictum (Gregory) Mann (Figure 7O)		+	+
Genus Tryblionella Smith
Tryblionella apiculata Gregory (Figure 7N)			+
Tryblionella hungarica (Grunow) Frenguelli (Figure 7M)			+
Genus Cymbellonitzschia Hustedt
Cymbellonitzschia szulczewskii Witkowski, Lange-Bertalot & Metzeltin (Figure 7P)		+
Genus Nitzschia Hassall
Nitzschia aequorea Hustedt * (Figure 7G)			+
Nitzschia amabilis Suzuki (Figure 7I)			+
Nitzschia bicapitata Cleve (Figure 7F)			+
Nitzschia capitellata Hustedt (Figure 7B)			+
Nitzschia cf. sicula (Castracane) Hustedt (Figure 7E)			+
Nitzschia frustulum (Kützing) Grunow (Figure 7H)		+	+
Nitzschia hybrida Grunow (Figure 7D)		+	+
Nitzschia palea (Kützing) Smith (Figure 7C)			+
Nitzschia reversa Smith (Figure 7A)		+
Nitzschia valdestriata Aleem & Hustedt (Figure 7J)		+	+
Genus Homoeocladia Agardh
Homoeocladia distans (Gregory) Kuntze (Figure 7R)		+	+
Homoeocladia volvendirostrata (Ashworth, Dᶏbek & Witkowski) Lobban & Ashworth (Figure 7Q)		+
Order Surirellales Mann
Family Entomoneidaceae Reimer
Genus Entomoneis Ehrenberg
Entomoneis paludosa (Smith) Reimer (Figure 7K)		+
Family Surirellaceae Kützing
Genus Campylodiscus (Ehrenberg) Kützing
Campylodiscus neofastuosus Ruck & Nakov (Figure 7L)		+	+

Figure 1. (A) Cyclotella litoralis; (B) Ellerbeckia sol; (C) Podosira stelligera; (D) Cymatotheca minima; (E) Tryblioptychus cocconeiformis; (F) Paralia sulcata; (G) Aulacoseira granulata var. angustissima; (H) Pierrecomperia catenuloides; (I) Eunotogramma debile; (J) Cymatosira gibberula; (K) Plagiogrammopsis crawfordii; (L) Plagiogrammopsis mediaequata; (M) Plagiogrammopsis sp.; (N) Staurosirella martyi; (O) Nanofrustulum sopotense. Scale bar = 10 μm.

Figure 1. (A) Cyclotella litoralis; (B) Ellerbeckia sol; (C) Podosira stelligera; (D) Cymatotheca minima; (E) Tryblioptychus cocconeiformis; (F) Paralia sulcata; (G) Aulacoseira granulata var. angustissima; (H) Pierrecomperia catenuloides; (I) Eunotogramma debile; (J) Cymatosira gibberula; (K) Plagiogrammopsis crawfordii; (L) Plagiogrammopsis mediaequata; (M) Plagiogrammopsis sp.; (N) Staurosirella martyi; (O) Nanofrustulum sopotense. Scale bar = 10 μm.

Figure 2. (A) Trachysphenia australis; (B) Tabularia parva; (C) Tabularia fasciculata; (D,D′) Licmophora californica; (E) Licmophora paradoxa; (F) Licmophora ehrenbergii; (G) Licmophora flabellata; (H) Hyalosira delicatula; (I) Rhaphoneis rhomboides; (J) Delphineis australis; (K) Delphineis sp.; (L) Delphineis minutissima; (M) Neodelphineis silenda. Scale bar = 10 μm.

Figure 2. (A) Trachysphenia australis; (B) Tabularia parva; (C) Tabularia fasciculata; (D,D′) Licmophora californica; (E) Licmophora paradoxa; (F) Licmophora ehrenbergii; (G) Licmophora flabellata; (H) Hyalosira delicatula; (I) Rhaphoneis rhomboides; (J) Delphineis australis; (K) Delphineis sp.; (L) Delphineis minutissima; (M) Neodelphineis silenda. Scale bar = 10 μm.

Figure 3. (A) Grammatophora oceanica; (B) Grammatophora undulata; (C) Grammatophora marina; (D) Achnanthes fimbriata; (E) Achnanthes sp.; (F,F′) Rhoicosphenia genuflexa; (G) Anorthoneis excentrica; (H) Cocconeis costata; (I) Cocconeis notata; (J,J′) Monoalveoneis convexa; (K,K′) Cocconeis sp. 1; (L,L′) Cocconeis sp. 2; (M,M′) Cocconeis scutellum; (N) Pseudoplanothidium delicatulum; (O) Achnanthidium glyphos; (P) Cocconeiopsis kantsiensis; (Q) Gomphonemopsis exigua; (R) Gomphonemopsis nana. Scale bar = 10 μm.

Figure 3. (A) Grammatophora oceanica; (B) Grammatophora undulata; (C) Grammatophora marina; (D) Achnanthes fimbriata; (E) Achnanthes sp.; (F,F′) Rhoicosphenia genuflexa; (G) Anorthoneis excentrica; (H) Cocconeis costata; (I) Cocconeis notata; (J,J′) Monoalveoneis convexa; (K,K′) Cocconeis sp. 1; (L,L′) Cocconeis sp. 2; (M,M′) Cocconeis scutellum; (N) Pseudoplanothidium delicatulum; (O) Achnanthidium glyphos; (P) Cocconeiopsis kantsiensis; (Q) Gomphonemopsis exigua; (R) Gomphonemopsis nana. Scale bar = 10 μm.

Figure 4. (A) Parlibellus rhombicus; (B) Parlibellus delognei; (C) Biremis ambigua; (D) Moreneis coreana; (E) Berkeleya rutilans; (F) Fallacia forcipata; (G) Pseudofallacia tenera; (H) Navicula sp. 1; (I) Navicula arenaria var. rostellata; (J) Navicula sp. 2; (K) Navicula salinicola; (L) Navicula digitoradiata; (M) Navicula pavillardii; (N) Navicula flebilis; (O) Navicula eidrigiana; (P) Navicula flanatica. Scale bar = 10 μm.

Figure 4. (A) Parlibellus rhombicus; (B) Parlibellus delognei; (C) Biremis ambigua; (D) Moreneis coreana; (E) Berkeleya rutilans; (F) Fallacia forcipata; (G) Pseudofallacia tenera; (H) Navicula sp. 1; (I) Navicula arenaria var. rostellata; (J) Navicula sp. 2; (K) Navicula salinicola; (L) Navicula digitoradiata; (M) Navicula pavillardii; (N) Navicula flebilis; (O) Navicula eidrigiana; (P) Navicula flanatica. Scale bar = 10 μm.

Figure 5. (A) Diploneis aestuarii; (B) Navicula perminuta; (C) Navicula platyventris; (D) Navicula gregaria; (E) Fogedia lyra; (F) Trachyneis aspera; (G) Caloneis brevis var. distoma; (H) Pleurosigma stuxbergii; (I) Gyrosigma cf. tenuissimum; (J) Gyrosigma sp. 1; (K) Gyrosigma sp. 2; (L) Donkinia carinata. Scale bar = 10 μm.

Figure 5. (A) Diploneis aestuarii; (B) Navicula perminuta; (C) Navicula platyventris; (D) Navicula gregaria; (E) Fogedia lyra; (F) Trachyneis aspera; (G) Caloneis brevis var. distoma; (H) Pleurosigma stuxbergii; (I) Gyrosigma cf. tenuissimum; (J) Gyrosigma sp. 1; (K) Gyrosigma sp. 2; (L) Donkinia carinata. Scale bar = 10 μm.

Figure 6. (A) Catenula adhaerens; (B) Amphora eximia; (C) Amphora cf. marina; (D) Amphora incrassata; (E) Amphora sp. 1; (F) Amphora sp. 2; (G) Amphora abludens; (H) Amphora americana; (I) Amphora laevissima; (J) Amphora proteoides f. varians; (K) Seminavis robusta; (L) Seminavis exigua; (M) Tetramphora lineolata; (N) Amphora holsaticoides; (O) Halamphora coffeiformis; (P) Halamphora aponina; (Q) Halamphora sp. 1; (R) Halamphora sp. 2; (S) Halamphora tenerrima. Scale bar = 10 μm.

Figure 6. (A) Catenula adhaerens; (B) Amphora eximia; (C) Amphora cf. marina; (D) Amphora incrassata; (E) Amphora sp. 1; (F) Amphora sp. 2; (G) Amphora abludens; (H) Amphora americana; (I) Amphora laevissima; (J) Amphora proteoides f. varians; (K) Seminavis robusta; (L) Seminavis exigua; (M) Tetramphora lineolata; (N) Amphora holsaticoides; (O) Halamphora coffeiformis; (P) Halamphora aponina; (Q) Halamphora sp. 1; (R) Halamphora sp. 2; (S) Halamphora tenerrima. Scale bar = 10 μm.

Figure 7. (A) Nitzschia reversa; (B) Nitzschia capitellata; (C) Nitzschia palea; (D) Nitzschia hybrida; (E) Nitzschia cf. sicula; (F) Nitzschia bicapitata; (G) Nitzschia aequorea; (H) Nitzschia frustulum; (I) Nitzschia amabilis; (J) Nitzschia valdestriata; (K) Entomoneis paludosa; (L) Campylodiscus neofastuosus; (M) Tryblionella hungarica; (N) Tryblionella apiculata; (O) Psammodictyon constrictum; (P) Cymbellonitzschia szulczewskii; (Q) Homoeocladia volvendirostrata; (R) Homoeocladia distans; (S) Bacillaria socialis. Scale bar = 10 μm.

Figure 7. (A) Nitzschia reversa; (B) Nitzschia capitellata; (C) Nitzschia palea; (D) Nitzschia hybrida; (E) Nitzschia cf. sicula; (F) Nitzschia bicapitata; (G) Nitzschia aequorea; (H) Nitzschia frustulum; (I) Nitzschia amabilis; (J) Nitzschia valdestriata; (K) Entomoneis paludosa; (L) Campylodiscus neofastuosus; (M) Tryblionella hungarica; (N) Tryblionella apiculata; (O) Psammodictyon constrictum; (P) Cymbellonitzschia szulczewskii; (Q) Homoeocladia volvendirostrata; (R) Homoeocladia distans; (S) Bacillaria socialis. Scale bar = 10 μm.

4. Discussion

In comparison to several previous reports on the epiphytic diatoms of Z. marina, the species richness in our study (112 taxa) is higher than that reported from the southern coast of Korea (77 taxa), Sanggou Bay, China (10 taxa) and Arikawa Bay, Japan (76 taxa) [7,14,20], but lower than the numbers reported in two reports from France and Mexico, where 199 and 235 taxa were recorded, respectively [12,30]. Furthermore, species in our samples are distinctly different from these studies which only share 11, 2, 7, 23 and 22 same taxa, respectively. It should be acknowledged, however, that these comparisons are subject to certain limitations due to the absence of spring and summer data in our study.

Chung & Lee (2008) [20] proposed that the species composition of epiphytic diatoms should be closely linked with the lifespan and surface structure of seagrass leaves. Similarly, da Rosa & Copertino (2022) [21] noted that the abundance and diversity of epiphytic communities were influenced by the host plant, as different seagrass morphologies could create distinct microhabitats for these epiphytes. However, Sullivan (1979) [1] and Sterrenburg et al. (1995) [31] suggested that the stochastic effects play a key role in the colonization of seagrasses by diatoms which utilize seagrass as a substratum for attachment purposes. The sediment likely serves as the key reservoir for individuals colonizing seagrass surfaces [6,32]. In a survey of epiphytic diatoms associated with seaweeds, a total of 62 diatom species, belonging to 36 genera, were identified in the coastal waters of Qingdao [33]. The overlap of 19 species with diatoms characterized in this study suggests that these epiphytic diatoms originate, at least in part, from the sediment. In light of this, our results are consistent with the previous observation that epiphytic diatoms on seagrasses generally resemble those found in adjacent meadow sediments.

As expected, species of the genus Cocconeis were present in all studied samples. Our examination revealed five species, which included C. costata Gregory, C. notata Petit, C. scutellum Ehrenberg, Cocconeis sp. 1 and Cocconeis sp. 2. Cocconeis is a monoraphid diatom genus characterized by heterovalvar morphology [34]. Its frustule features a single functional raphe on only one valve (the raphe valve), while the other valve (the sternum valve or rapheless valve) bears only a sternum [35]. Members of this genus are common and widespread in marine attached diatom communities, inhabiting diverse substrata such as rocks, plants, and animals [36]. Most Cocconeis taxa typically attach via their raphe valve, thereby directly exposing the rapheless valve to the environment [15]. Similar studies have frequently recorded Cocconeis spp. as the characteristic taxa in the epiphytic diatom assemblages on seagrasses, with C. scutellum often being a dominant species [37]. Notably, Majewska et al. (2014) [18] identified as many as 32 species and varieties of Cocconeis in the epiphytic diatom samples collected from Posidonia oceanica Delile in the Mediterranean Sea. The Cocconeis species often grow rapidly to dominate uninhabited surfaces, forming a crust that is recognized as pioneer vegetation on Zostera leaves [9,38]. The development of the pioneer community was suggested to be influenced by competition for space and light [39]. Yet, they could be protected from grazing by their firm attachment to the leaf surface, resulting in lower consumption rates than other diatoms [9,40].

From a habitat point of view, most of the newly recorded taxa in this study are marine benthic or periphytic diatoms. The exceptions are Amphora eximia, a freshwater diatom found in the Scottish lake sediments, and Cyclotella litoralis, a planktonic species originally described from the South Atlantic waters [41,42]. Monoalveoneis convexa and Navicula flebilis were previously reported as epiphytic diatoms on seaweeds in Japan [43,44]. Sandy sediments have been documented as the habitats for Plagiogrammopsis crawfordii, Pierrecomperia catenuloides and Navicula arenaria var. rostellata [26,45,46]. Amphora abludens has been found in the epilithon along the Middle Adriatic coast [47]. Both Parlibellus delognei and Amphora americana were recorded from scrapings of glass slides [48,49]. Navicula eidrigiana was commonly observed in the salt marshes of the Gulf of Gdansk [26], while Nitzschia aequorea was identified during an epipelic diatom bloom on a muddy tidal flat in Japan [50]. Amphora proteoides f. varians and Achnanthes fimbriata have been reported from European sediment [26,51]. Ellerbeckia sol (as Melosira sol (Ehrenberg) Kützing) was documented as an epizoic diatom on Kemp’s ridley turtle [52]. Finally, Donkinia carinata was recorded from artificial substrates in the Crimean coastal waters of Black Sea [53]. In general, a number of the recorded taxa and their habitats reveal that the diatom flora living on seagrasses, while quite extensive, does not constitute a unique community composition.

5. Conclusions

Epiphytic diatom flora found on Z. marina leaves in Qingdao Bay were composed of 112 taxa in the 19 orders, 31 families and 57 genera, including 16 newly recorded taxa for China. The best-represented genera were Navicula (12), Amphora (10), Nitzschia (10), Cocconeis (5), Halamphora (5), and Licmophora (4), collectively accounting for 41% of the total taxa recorded in this study. As the pioneer vegetation, species of the genus Cocconeis occurred in all samples. According to our findings, these epiphytic diatoms may be derived from sediment reservoirs. Nevertheless, this report improved the knowledge of epiphytic diatom diversity associated with Z. marina meadows in China. Future studies should therefore focus on elucidating how environmental factors shape the composition of epiphytic diatom communities.