Abstract:

Aims: Pteropods (Mollusca: Gastropoda) play a key role in marine ecosystems and biodiversity, contributing to critical processes such as the marine food web and carbon cycle. However, their diversity and distribution in the South China Sea (SCS) remain poorly understood. To address these gaps and enhance the understanding of their regional biogeography, this study aimed to systematically investigate the species diversity and spatial distribution patterns of pteropods (Mollusca: Gastropoda) in the South China Sea. 

Methods: Zooplankton samples were collected during four cruises across various ecological regions, including estuarine, shelf, basin, and island/reef areas of the South China Sea between 2022 and 2023. Species were identified based on morphological examination using stereomicroscopy and scanning electron microscopy. Ecological indices, including species richness, Shannon-Wiener diversity index, Pielou evenness index, and dominance index, were calculated to analyze community structure. 

Results: A total of 26 pteropod species belonging to 13 families and 18 genera were identified, including four new records for the South China Sea: Diacavolinia elegans van der Spoel, Bleeker & Kobayasi, 1993, Desmopterus gardineri Tesch, 1910, Notobranchaea tetrabranchiate Bonnevie, 1913, and Cliopsis krohnii Troschel, 1854. Notable regional heterogeneity was observed: the Pearl River Estuary–western shelf area showed the highest species richness (22 species), while the northern island/reef area had the lowest (6 species). Horizontally, coastal areas exhibited higher abundance but lower diversity, whereas open-sea areas showed the reverse pattern. Vertically, pteropods were predominantly concentrated in the 0–200 m layer, with abundance and diversity declining sharply with depth. The composition of dominant species varied markedly among different ecological regions. 

Conclusions: This study updates the species checklist of pteropods in the South China Sea and reveals clear spatial partitioning in their community structure, reflecting adaptations to distinct habitats. The findings provide essential baseline data for understanding regional marine biodiversity and monitoring ecosystem changes in this marginal sea.

Key words: Pteropoda, zooplankton, new records, species diversity, South China Sea