Warming and resource enhancement shape food webs in South China Sea coral reef system

Abstract Coral reef ecosystems are being altered by rising ocean temperatures and increasing nutrient inputs, yet their combined influence on food-web structure is not well understood. Here we analyzed 130 coral reef food webs across the South China Sea, constructed from environmental DNA surveys integrated with trophic interactions. We grouped the food webs into surface-water, bottom-water and sediment habitats. Our analyses reveal pronounced structural differences among habitats: surface- and bottom-water webs exhibit significantly higher connectance and nestedness, whereas sediment webs are more compartmentalized. Using linear mixed-effects models, we find that temperature and productivity interact in nonlinear ways to shape food-web properties. In surface waters, higher temperature together with higher productivity tends to increase connectance, whereas in deeper waters the same conditions tend to lengthen trophic pathways and reduce stability. These results suggest that future environmental change may influence pelagic and benthic reef food webs in contrasting ways.