Nutrient loading associated with agriculture land use dampens the importance of consumer‐mediated niche construction

Abstract

The linkages between biological communities and ecosystem function remain poorly understood along gradients of human-induced stressors. We examined how resource provisioning (nutrient recycling), mediated by native freshwater mussels, influences the structure and function of benthic communities by combining observational data and a field experiment. We compared the following: (1) elemental and community composition (algal pigments and macroinvertebates) on live mussel shells and on nearby rocks across a gradient of catchment agriculture and (2) experimental colonisation of benthic communities on live vs. sham shells controlling for initial community composition and colonisation duration. We show that in near pristine systems, nutrient heterogeneity mediated by mussels relates to greater biodiversity of communities, which supports the notion that resource heterogeneity can foster biological diversity. However, with increased nutrients from the catchment, the relevance of mussel-provisioned nutrients was nearly eliminated. While species can persist in disturbed systems, their functional relevance may be diminished or lost.

Reestablishing a Host‐Affiliate Relationship: Migratory Fish Reintroduction Increases Native Mussel Recruitment

“…complanata has historically been considered a dominant species throughout the Atlantic Slope and remains so in the Susquehanna River Basin (Strayer and Jirka 1997, Nedeau 2008, Haag 2012. Both A. rostrata and E. complanata have been shown to perform key ecological functions in streams and rivers, and declines in abundance or loss of these species would likely have far-reaching impacts on community composition, diversity, water quality, and ecosystem dynamics (Spooner et al 2013). Our study has important implications for restoration and management, suggesting that simple species reintroductions, as are currently ongoing in the basin, may not necessarily restore host-affiliate relationships to their native state, partly because human influence has created novel environmental conditions (Seddon et al 2014).…”

Phosphorus body content in an herbivorous fish in environments with different trophic state

“…Differences in the organismal stoichiometry of populations from sites with different trophic status can lead to variations in the fish excretion rates, thus potentially affecting their role as nutrient recyclers. In disturbed sites, the ecological function of the species can change, with potential implications for the functioning of the ecosystem (Capps and Flecker, 2013;Spooner et al, 2013). Future studies should investigate if the trophic status of the environment has a direct or indirect effect on the fish body stoichiometry, to pin point the mechanisms generating the observed differences.…”

Consumer‐driven nutrient dynamics in freshwater ecosystems: an introduction

“…For example, Wheeler, Miller & Crowl () and Atkinson & Vaughn () directly addressed the effects of stream discharge on the roles of fish and mussel excretion on ecosystem processes in streams. Ambient nutrient concentrations may also influence the role organisms play in ecosystem processes (Wilson & Xenopoulos, ; Spooner et al ., ). In this issue, Datri et al .…”