Agricultural pressures impair trophic link between aquatic microorganisms and invertebrates

Abstract

Decadal declines in aquatic ecosystem health prompted monitoring efforts and studies on effects of human practices on aquatic biodiversity, yet a consideration of ecological processes and trophic linkages is increasingly required to develop an in-depth understanding of aquatic food webs and its vulnerability to human activities. Here, we test in laboratory incubations using natural organic matter whether agricultural practices have an effect on two interacting ecological processes (i.e., decomposition and invertebrate growth) as the relevant temporal components of the trophic linkage between aquatic microbial communities and aquatic invertebrates. We further assess whether these altered trophic interactions are visible on ecologically relevant scales. We observed clear patterns in agricultural constraints on microbial decomposition, which coincided with reduced invertebrate growth and an unexpected increase in invertebrate consumption of organic matter. Similar differences in invertebrate length depending on land use were observed in our field survey, thereby providing important clues on the relevance and vulnerability of interdependent processes that can serve to improve future forays in monitoring ecosystem health.