Environmental Drivers of Zooplankton Distribution and Community Assembly in the Eastern Indian Ocean During the Inter‐Monsoon

Abstract As a crucial component of ecosystems, the distribution of zooplankton is closely related to environmental conditions and ocean currents. Despite its unique role in global circulation, zooplankton data for the Eastern Indian Ocean (EIO) remain scarce. To better characterize zooplankton composition and distribution in EIO, we conducted a survey in the region between 5°S and 14°N and 80°−93°E from March–May 2022. To our knowledge, this is among the first applications of ecological models to reveal the preliminary characteristics of zooplankton community assembly mechanisms in EIO. Through microscopic examination, we identified 427 species of adult zooplankton and 24 zooplankton larvae taxa. The zooplankton abundance in the surveyed ranged from 137 to 1,326 ind./m 3 . Among them, copepods, particularly small‐bodied species, were the dominant components, contributing most significantly to the abundance and species richness of EIO zooplankton. Redundancy Analysis (RDA) and Random Forest (RF) results indicated that Dissolved oxygen (DO), temperature, and chlorophyll a were the primary factors influencing the abundance and diversity of EIO zooplankton. According to cluster analysis, the EIO zooplankton could categorized into three ecological groups: Group A (GA), Group B (GB) and Group C (GC). The results of Neutral Community Model revealed that the community assembly of EIO zooplankton was primarily influenced by stochastic processes. However, certain deterministic factors still influence the community assembly mechanisms of GA and GB. Correlation analyses between environmental factors and characteristic species in each group showed that deterministic assembly in GA is mainly driven by interspecific interactions, whereas in GB it is primarily driven by environmental selection.