Eutrophication and predation mediate zooplankton diversity and network structure

Anthropogenic activities such as eutrophication and fishing have prominent effects on freshwater ecosystems. However, the ways in which ecosystem function and biodiversity respond to multiple drivers from eutrophication and top-down predation remains inconclusive. We studied zooplankton communities in 102 subtropical shallow lakes in the eastern plain of China and further examined the joint effects of nutrient enrichment and predation on biodiversity and ecological networks. We found that alpha diversity was negatively influenced by nutrient conditions (such as total phosphorus and total nitrogen [TN]), whereas beta diversity (beta-diversity) was positively related to nutrients and was also structured by omnivorous fish showing a unimodal pattern. Furthermore, the network skewness of zooplankton increased with nutrient enrichment, especially TN, and was negatively related to omnivorous fish. This skewness is more sensitive than beta-diversity, whereas negative skew is primarily caused by omnivorous fish. Our results demonstrated that top-down effects were dominant for zooplankton communities and resulted in structural adjustment of zooplankton communities, mainly with an increase in fish predation. A negative skewed network indicates the presence of more generalist species and stronger connections among the zooplankton assemblages, as well as decreased beta-diversity.

Automated summary

Anthropogenic activities such as eutrophication and fishing have significant impacts on freshwater ecosystems. A study of zooplankton communities in subtropical shallow lakes in eastern China revealed that nutrient enrichment and predation have joint effects on biodiversity and ecological networks. Our findings show that nutrient conditions negatively affect alpha diversity, while beta diversity and network skewness are influenced by nutrients and omnivorous fish, with top-down effects dominating the structural adjustment of zooplankton communities.