Environmental DNA Reveals Fish Diversity Reestablishment of China’s Lake Ecosystem Driven by Extreme Drought and Human Intervention

Extreme droughts caused by current climate changes affect the diversity, composition and function of fish communities in lake ecosystems. Poyang Lake is the largest freshwater lake in China, and it is home to many important avian, fish and aquatic mammals. In 2022, Poyang Lake experienced one of the most severe droughts in recorded history. Understanding how fish communities responded to this event can offer key knowledge in developing strategies for coping with future climatic extremes, particularly given that the local government has been actively posting several middle- to long-term policies on managing the fish diversity of Poyang Lake, including fishery resource supplements and the well-known “ten-year fishing ban”. To understand how the fish diversity of Poyang Lake has been altered by climate change and human interventions, here, we analyzed the α- and β-taxonomic diversity (TD) and functional diversity (FD) of fish species using environmental DNA (eDNA), and we compared the fish diversity and community changes before and after the 2022 drought. In total, 77 native fish species and 4 invasive species were detected. The species richness and Shannon–Wiener index decreased significantly, and Simpson’s index had no significant difference post-drought. Rao’s Quadratic Entropy (Rao’sQE) index increased significantly, and the Functional Evenness (FEve) index decreased significantly. The differences in α- and β-TD and FD in the north part and south part of Poyang Lake also reflect the impact of drought. When calculating biodiversity contribution rates of the different species, we found that small-sized species were dominant pre-drought, while medium- and large-sized species were predominant post-drought. These patterns indicate that the fish community of Poyang Lake is undergoing a reestablishing process after the extreme drought. This fish community reestablishment post-drought does not correspond to the natural process of community recovery; instead, it is the result of human intervention while being affected by drought brought about by climate change.