Multistressor effects on river biofilms under global change conditions

Area of Science:

• Environmental Science
• Ecology
• Aquatic Biology

Background:

• Freshwater ecosystems are impacted by multiple chemical, biological, and physical stressors.
• Understanding combined stressor impacts is crucial for predicting ecosystem responses, but interactions remain poorly understood.
• The effects of co-occurring chemical and climate change-driven physical stressors on freshwater communities are largely unexplored.

Purpose of the Study:

• To investigate the combined effects of chemical and physical stressors on river biofilms using a microcosm approach.
• To identify the prevalence and nature of additive versus non-additive interactions between these stressors.
• To determine the role of physical stressors, particularly those linked to climate change, in driving biofilm responses.

Main Methods:

• Utilized a microcosm experimental setup to simulate river conditions.
• Exposed river biofilms to a combination of chemical and physical stressors.
• Quantified and analyzed the resulting community responses, distinguishing between additive and non-additive interactions.

Main Results:

• Additive responses were the most common outcome of combined stressors.
• Non-additive interactions occurred in 14.5% of responses, with antagonism (75%) more frequent than synergism (25%).
• Physical stressors, especially climate change-related ones, were dominant drivers in non-additive interactions and overall responses.

Conclusions:

• Combined stressors in freshwater ecosystems often lead to additive effects, but significant non-additive interactions exist.
• Physical stressors, exacerbated by climate change, play a critical role in modulating the effects of chemical stressors.
• The dominance of physical stressors in non-additive interactions suggests potential for unpredictable shifts in freshwater biofilm communities under future climate change scenarios.