Abstract: Abstract:  Planktonic larvae of zooplankton represent a significant component of zooplankton communities in coral reef ecosystems, primarily consisting of the temporary planktonic stages of various nektonic and benthic organisms. They play a crucial role in maintaining biodiversity, supporting ecological processes, and facilitating resource replenishment in coral reefs. However, their distribution patterns and influencing factors across different reef habitats remain limited. Based on zooplankton samples collected from six coral atolls in the central South China Sea during May–June 2015, this study systematically analyzed the distribution characteristics of planktonic larvae in two distinct habitats—the lagoon and the reef slope—and identified the main factors driving community differences in relation to environmental variables. The results revealed that fish eggs dominated the reef slope (41.1%±10%), whereas Macrura larvae were predominant in the lagoon (76.7%±9.2%). Generalized additive model (GAM) analysis indicated a significant positive correlation between the abundance of Macrura larvae and salinity in the lagoon (p < 0.05), while fish egg abundance was negatively correlated with temperature on the reef slope (p < 0.05). These findings suggest that larval abundance in the lagoon is mainly regulated by salinity, whereas on the reef slope, it is more closely associated with temperature. The observed differences in larval distribution between the lagoon and reef slope are likely driven by a combination of environmental factors, hydrodynamics, and predation pressure. This study provides important scientific insights for the conservation and management of coral reef ecosystems.

Key words: Planktonic larvae, Zooplankton, Community structure, Coral reef, Habitat selection