Vertical variations of zooplankton functional traits and diversity in the tropical and subtropical northwestern Pacific

Abstract Zooplankton play a pivotal role in the marine biological pump, and vertical variations in their functional trait composition and functional diversity can affect the export of organic carbon. However, our comprehension of the vertical variations in functional traits and functional diversity of zooplankton in the northwestern Pacific is insufficient. This study examined the vertical distributions in the functional trait composition, functional diversity, and trait space of zooplankton in the tropical and subtropical northwestern Pacific. Zooplankton functional trait composition exhibited obvious vertical variations. The proportion of active‐feeding zooplankton increased with depth, while the proportion of ambush feeders decreased. The trophic groups of zooplankton shifted from omnivore–herbivore to omnivore–detritivore with depth. Zooplankton displayed high functional richness and functional dispersion in the 0–100 m layer, whereas narrow trait space but high functional evenness was observed in the 500–3000 m layer. The trait space of zooplankton within the 500–3000 m layer was nested within that of the epipelagic zone, indicating maintenance of the core functional structure. Environmental filtering and limiting similarity primarily governed zooplankton community assembly in the 0–100 m and 500–3000 m layers, whereas the process was more stochastic in other layers. These findings highlight the relationship between zooplankton functional traits and the biological pump, which could help explain the variations in biological pump strength among marine ecosystems.