Biodiversity increases ecosystem functions despite multiple stressors on coral reefs

Area of Science:

• Marine Ecology
• Conservation Biology
• Ecosystem Science

Background:

• Biodiversity and ecosystem functioning (BEF) relationships are crucial for ecosystem services.
• Human activities are causing rapid biodiversity loss, threatening ecosystem functions.
• Understanding how multiple stressors impact BEF relationships is limited, especially in natural systems.

Purpose of the Study:

• To investigate the robustness of BEF relationships in natural coral reef fish assemblages under multiple stressors.
• To determine how extreme heatwaves and invasive species affect BEF relationships and ecosystem functioning.
• To elucidate the pathways through which stressors impact ecosystem functioning.

Main Methods:

• Utilized remote coral reef fish assemblages to study biodiversity and ecosystem functioning.
• Assessed the impact of an extreme heatwave (coral bleaching) and invasive rats on BEF relationships.
• Quantified effects on fish biomass and productivity as key ecosystem functions.

Main Results:

• Demonstrated strong, non-saturating positive relationships between fish biodiversity and ecosystem functions (biomass, productivity).
• These BEF relationships remained robust despite an extreme heatwave and the presence of invasive rats.
• Both stressors reduced ecosystem functioning, but through different mechanisms: heatwave reduced biodiversity, while invasive rats disrupted nutrient subsidies.

Conclusions:

• Positive BEF relationships are resilient to major stressors in natural high-diversity assemblages.
• Human-caused stressors can reduce ecosystem functioning through multiple pathways, including direct impacts and biodiversity loss.
• Conservation of biodiversity remains essential for maintaining ecosystem functions and services.