Consumer adaptation mediates top-down regulation across a productivity gradient

Area of Science:

• Ecology
• Evolutionary Biology
• Environmental Science

Background:

• Human activities, such as increased nutrient loading, have globally altered ecosystem productivity.
• Eutrophication consequences like harmful algal blooms are well-documented, but the role of organismal adaptation in ecosystem response is understudied.
• Most research focuses on short-term ecological responses, neglecting the evolutionary timescales of adaptation.

Purpose of the Study:

• To test if adaptation in a generalist consumer (Daphnia pulicaria) to toxic prey (cyanobacteria) influences plankton community responses to nutrient enrichment.
• To investigate how consumer genotype (tolerant vs. sensitive Daphnia) and prey traits affect ecosystem stability under eutrophication.

Main Methods:

• Experimental manipulation of nutrient levels in aquatic ecosystems.
• Assessing the top-down effects of different Daphnia pulicaria genotypes on primary producer biomass.
• Evaluating the influence of toxic cyanobacteria presence and abundance on consumer-prey dynamics.

Main Results:

• The top-down control by Daphnia on primary producers strengthened with increased nutrient enrichment.
• The effectiveness of Daphnia's control was dependent on both the consumer's genotype and the prevalence of toxic cyanobacteria.
• Tolerant Daphnia genotypes significantly suppressed toxic cyanobacteria in nutrient-rich conditions, while sensitive genotypes did not.
• Both tolerant and sensitive Daphnia genotypes had similar impacts on producer biomass when toxic cyanobacteria were absent.

Conclusions:

• Organismal adaptation plays a crucial role in mediating ecosystem-level responses to anthropogenic perturbations like nutrient enrichment.
• Adaptive capacity of consumers can stabilize plankton communities by regulating populations of toxic cyanobacteria.
• Understanding adaptation is essential for predicting the long-term ecological consequences of environmental change.