Functional diversity and substrate composition shape primary productivity and decomposition patterns in an aquatic ecosystem

Abstract

The relationship between biodiversity and ecosystem function has emerged as a vital concept in conservation biology. Elevated biodiversity has been shown to influence critical ecosystem processes; however, the identity of species composing a community may be more important than the absolute number of species. We assessed the effects of consumer species richness on aquatic ecosystem processes under different habitat contexts in a mesocosm experiment. Species richness and habitat substrate were manipulated using a 3x2 factorial design. Substrate was either sand or gravel, and 3 species (amphipods, water boatmen, and snails) were maintained at 0, 1 and 3 species across 54 plastic tubs. After 21 days, increasing richness from one to three species significantly decreased periphytic biomass by 22%, periphytic chlorophyll by 25%, and suspended chlorophyll by 19%. Enhancing richness also resulted in increased leaf breakdown. No single species effect equaled or exceeded the 3-species treatment, suggesting facilitation and compimentarity between species. Substrate type caused differences in fine particulate organic matter (FPOM) and turbidity; however, no significant interactions between substrate and species richness were detected. This experiment suggests that increasing species, and more importantly, functional diversity may be important for understanding algal dynamics, primary production, and decomposition rates in aquatic ecosystems.