Seagrasses support marine fauna across functional groups in the Yellow Sea

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Hanchen Wang, School of life sciences, Fudan University, Shanghai, China and Qiang He, Marine Laboratory, Duke University

Background/Question/Methods
Seagrass beds are widely thought to support marine food webs and provide critical habitat for marine faunal species. Previous assessments on the roles of seagrasses in supporting marine fauna have often focused on a single faunal group (e.g., fish) in some heavily studied regions such as Europe and the East Coast of North America. Whether seagrasses support marine fauna consistently across multiple functional groups, especially in less-studied marine ecoregions, requires further investigation. We surveyed faunal species in patches dominated by the dwarf eelgrass Zostera japonica and adjacent mudflats in different seasons in the Yellow River Estuary in the Yellow Sea, an extremely important fishing ground shared by China, South Korea, and North Korea. We estimated the abundance and biomass of different faunal species, determined their trophic levels using stable isotope analysis, and calculated multiple diversity indices (species richness, Shannon-Wiener diversity, and Pielou evenness). We tested if abundance, biomass, and diversity indices differed between eelgrass patches and mudflats for faunal species of different functional groups categorized according to life style (nekton, epifauna, and benthos) and trophic level (herbivores/omnivores, primary carnivores, and secondary carnivores), respectively.
Results/Conclusions
We found the abundance and biomass of all lifestyle and trophic groups were often times higher in eelgrass patches than in mudflats in summer. In autumn when eelgrass largely senesced, differences in the abundance and biomass of all functional groups became non-significant. In contrast, differences in species richness, Shannon-Wiener diversity, and Pielou evenness for all lifestyles and trophic groups were often non-significant. These results suggest that the dwarf eelgrass Z. japonica plays a significant role in enhancing marine fauna species and that this role is consistently evident across faunal life styles and trophic levels. As the majority of these faunal species (including many finfish, shrimps, and clams) are of high economic value, our results also underline the importance of conserving and restoring seagrass beds in the Yellow Sea for helping sustain fisheries in this important fishing ground.