Realistic changes in seaweed biodiversity affect multiple ecosystem functions on a rocky shore

Area of Science:

• Marine Ecology
• Ecosystem Functioning
• Biodiversity Research

Background:

• Understanding biodiversity's impact on ecosystem functions is crucial due to current biodiversity threats.
• Realism in biodiversity studies is often limited, hindering the connection between research findings and real-world biodiversity loss.
• Seaweed assemblages are vital primary producers in rocky shore ecosystems.

Purpose of the Study:

• To incorporate realism into biodiversity research by using observed seaweed assemblages.
• To compare ecosystem functions (nitrate uptake, photosynthesis) in realistic versus random seaweed assemblages.
• To investigate how species richness affects ecosystem functioning in realistic scenarios.

Main Methods:

• Constructed realistic seaweed assemblages (2, 5, 8 species) mirroring observed patterns on a rocky shore.
• Compared realistic assemblages to random assemblages from the same species pool.
• Measured nitrate uptake rates and photosynthetic rates as functions of nitrate concentration and irradiance, respectively.

Main Results:

• Ecosystem functioning changes along a richness gradient were only observed in realistic assemblages.
• Realistic assemblages showed higher maximum nitrate uptake rates (Vmax) and photosynthetic light use efficiency (alphap) than random assemblages.
• Overyielding effects, influencing Vmax and alphap, were evident in realistic assemblages and varied with species richness.

Conclusions:

• Ecosystem functions may be maximized at lower species richness levels in realistic assemblages.
• The range of diversity values, not just diversity per se, is important for sustaining multiple ecosystem functions.
• Species identity and overyielding effects significantly influence ecosystem functioning along richness gradients.