Assessing meroplankton assemblage interannual variations in the Southern Yellow Sea, China: Key environmental factors and climate-related drivers

Meroplankton significantly influences both benthic and pelagic ecosystems. This study investigates interannual variations of meroplankton in the Southern Yellow Sea (SYS), China, during summertime from 2012 to 2023 (noncontinuous), focusing on the interannual variations of key groups and their environmental factors under climate change. Findings revealed that meroplankton abundance was lower in June than in July, with peak abundances recorded in 2013 for June and 2012 for July, respectively. Spatial distribution patterns showed higher abundance in coastal shallow waters (<50 m) and lower in the Yellow Sea Cold Water Mass (YSCWM) (>50 m). Gastropoda and Bivalvia larvae were the most predominant and widely distributed groups, while body length of Bivalvia larvae varied across the surveyed periods; Gastropoda and Polychaeta larvae exhibited minimal differences. Brachyura and Echinodermata larvae showed no significant body length variations. Key environmental factors affecting meroplankton included sea bottom temperature (SBT), sea bottom salinity (SBS), and depth. Notably, SBT correlated positively with increased abundance of most groups, whereas SBS and depth were associated with decreased abundance. This study reveals the broad influence of the Pacific Decadal Oscillation (PDO) on the meroplankton abundance in the Yellow Sea, to which echinoderm larvae show significant sensitivity. This research highlights the significant interactions between environmental factors and meroplankton dynamics, providing valuable insights into their ecological roles in response to climate change in the SYS. By elucidating these relationships, the study enhances our understanding of meroplankton ecology and benthic-pelagic coupling, positioning meroplankton as important ecological indicators for assessing the impacts of climate change on marine ecosystems.