Multiple stressors unpredictably affect primary producers and decomposition in a model freshwater ecosystem

Area of Science:

• Environmental toxicology
• Freshwater ecology
• Invasive species research

Background:

• Freshwater ecosystems face threats from contaminants like copper (Cu) and invasive species such as European carp (Cyprinus carpio L.).
• Copper and carp can disrupt crucial nutrient cycling processes, including primary production and decomposition.
• Understanding the combined impacts of these stressors is vital for effective environmental risk assessment.

Purpose of the Study:

• To investigate the individual and combined effects of copper and European carp on periphyton, macrophyte growth, and decomposition.
• To assess how these stressors influence critical ecosystem services within experimental ponds.

Main Methods:

• A controlled factorial experiment was conducted in outdoor ponds.
• The study examined periphyton cover, chlorophyll a, macrophyte growth (Vallisneria spiralis L.), and decomposition of leaf litter and cotton strips.
• Treatments included copper exposure, carp addition, and their combination at varying concentrations.

Main Results:

• Copper alone reduced macrophyte growth and decomposition. Carp alone negatively impacted plants outside cages but increased periphyton and chlorophyll a.
• Combined copper and carp eliminated aquatic plants due to toxicity, disturbance, and increased turbidity.
• Periphyton responses varied with copper concentration, and decomposition patterns were complex, indicating non-additive effects.

Conclusions:

• The interaction between copper and European carp poses a significant threat to freshwater plant communities and ecosystem functioning.
• Carp bioturbation exacerbates copper's negative effects by increasing turbidity and altering habitat conditions.
• Predicting the ecological consequences of multiple stressors requires detailed experimental studies due to complex, often non-linear interactions.