Konghao Zhu

Climate warming, nutrient loading, and pesticide pollution are major anthropogenic stressors affecting community dynamics and trophic interactions in aquatic ecosystems. However, the complex interplay among these stressors remains poorly understood as most studies focus on a single stressor and overlook the effects of temporal variations. To address this knowledge gap, we first conducted a long‐term outdoor experiment to examine the effects of climate warming, nutrient loading, and a neonicotinoid pesticide (imidacloprid) on the responses of the common predator–prey pair cyclopoid copepods and rotifers. Additionally, a follow‐up laboratory experiment was conducted to assess the dose‐dependent impact of imidacloprid on the predation rate of cyclopoid copepods on rotifers, and to explore mechanistic alterations in biotic interactions resulting from predator responses to varying neonicotinoid concentrations. The neonicotinoid pesticide was the most influential stressor, significantly reducing cyclopoid copepod populations thereby positively affecting rotifer abundances due to a release from predation. Nutrient loading boosted copepod abundances but weakened their top‐down control on rotifer prey, disrupting predator–prey dynamics. Warming had negligible effects on copepod abundances, but ultimately increased rotifer abundances. Warming predominantly influenced rotifer abundances during the establishment phase, whereas the effects of the pesticide became more pronounced during subsequent growth and reproduction phases. Conversely, the neonicotinoid pesticide consistently emerged as the primary stressor impacting cyclopoid copepods throughout the experiment. Our study underscores the importance of considering temporal dynamics when assessing the combined effects of multiple stressors for understanding responses among interacting organisms and highlights the significance of organism life history stages in their distinct reactions to specific compounded threats over time.

Recent studies have shown a decoupling in the way community composition and functions respond to environmental changes. A common pattern observed is that aggregated functions at the community level are more stable than community composition, which is likely the result of functional compensatory dynamics driven by interspecific differences in response to environmental change. However, the mechanisms by which these patterns emerge remain largely unexplored. Here we investigated in a mesocosm experiment for four weeks the compositional and functional responses of edible phytoplankton (<64 μm) and cladoceran zooplankton communities to climate warming (a constant increase of +3.5°C plus heat wave) and eutrophication (nutrient additions) from a size‐based perspective. Our results show that warming increases small‐sized taxa and decreases large‐sized taxa within both phytoplankton and zooplankton community composition. We found that such opposite responses of different‐sized taxa contributed to the stability of planktonic community functions and thereby resulted in a decoupling between compositional and functional changes. We also found that nutrient additions increased the abundance of all‐sized algal taxa, while phytoplankton community function remained stable. Nutrient additions did not alter the zooplankton community, neither compositionally nor functionally. Under the combined stress of warming and nutrient additions, the compositional and functional responses of planktonic communities were mainly driven by warming. In a broader perspective, our findings reveal a size‐dependent compensation mechanism and suggest that functional stability relies on compensatory effects among different‐sized taxa, and it is therefore important that communities host a large range of taxa differing in size to withstand an increasingly more variable environment in the future.

Under the influence of human activities, eutrophication has become an increasingly serious global phenomenon, especially in shallow lakes. Many studies have shown that aquatic macrophytes play a significant role in controlling eutrophication, but only few of these studies are ecosystem based. In this paper, we applied a mass-balance ecosystem model to a shallow eutrophic lake (Lake Datong, China) as a case study with the aims of evaluating the status of ecosystem restoration via the recovery of aquatic vegetation and providing adaptive management suggestions. Results showed that the ecosystem was immature with weak energy flows and nutrient cycling largely due to the excessive submerged macrophytes and the lack of fish as consumer. In the early stages of restoration, the number of fish should be reduced, and aquatic vegetation needs to be recovered to mitigate eutrophication. When the aquatic vegetation community tends to be stable, herbivorous and omnivorous fish should be moderately stocked, and dead aquatic macrophytes should be harvested to maintain the healthy and sustainable development of the ecosystem. This study provided insights for the ecological restoration of shallow eutrophic lakes and revealed the urgent need for ecosystem-based restoration.