Warming alters juvenile carp effects on macrophytes resulting in a shift to turbid conditions in freshwater mesocosms

1. Multiple stressors such as climate change and eutrophication are responsible for the global decline of macrophytes in lakes. The loss of this key component can result in turbid conditions and a loss of important ecosystem functions and services, particularly in shallow lakes. Benthivorous fish, which can increase in abundance during eutrophication, can adversely affect macrophytes through physical disturbance, cascading effects on turbidity, suspended and attached algae (phytoplankton and periphyton) and direct consumption. However, whether warming amplifies their effects on macrophytes and can trigger regime shifts remains unexplored.

2. Here, we tested the single and combined effects of warmer water (+4.5°C) and the widespread benthivorous juvenile common carp (Cyprinus carpio) on two different types of aquatic macrophytes in 24 mesocosms (2500 L each). We monitored phytoplankton, periphyton, turbidity and the abundance of the submerged curly-leafed pondweed (Potamogeton crispus...