Journal Article

Filter-feeders have differential bottom-up impacts on green and brown food webs

Halvorson, Halvor M., Hamid, Ansley, Winebarger, Monica, Waters, Matthew N., Kuehn, Kevin A., Atkinson, Carla L.

2021

Overview

Nutrient recycling by consumers can strongly impact nutrient availability for autotrophic and heterotrophic microbes, thus impacting functions such as primary production and decomposition. Filter-feeding freshwater mussels form dense, multispecies assemblages in aquatic ecosystems and have been shown to play a critical role in nutrient cycling. Mussel excretion can enhance benthic primary production and influence algal species composition. However, the role of mussels in brown or detritus-based food webs and species-specific differences has received considerably less attention. Here, using mesocosm experiments, we assessed how three species of freshwater mussels that occupy three different phylogenetic tribes influenced benthic algal accrual, ecosystem metabolism, cotton strip decomposition, leaf litter (Acer saccharum) decomposition, and litter-associated fungal biomass measured as ergosterol. Additionally, we measured mussel excretion and biodeposition rates and assessed the stoichiometry (C:N, C:P, and N:P) of the benthic algae, cotton strips, and leaf litter. In comparison to controls without mussels, generally, mussel treatments had higher benthic algal biomass composed of more diatoms, higher gross primary productivity and net ecosystem production rates, and higher cotton strip tensile strength loss, but there was not a difference in ecosystem respiration rates, leaf litter decomposition rates, or fungal biomass. Benthic algae had lower C:N and higher N:P in mussel treatment tanks and cotton strip C:N was lower in mesocosms with mussels. Our results suggest that nutrient regeneration by mussels most strongly regulates green food webs, with some impacts to brown food webs, suggesting that consumers have interactive effects on microbial functioning in freshwaters.

• Publisher: Springer Science + Business Media,Springer Berlin Heidelberg,Springer,Springer Nature B.V
• Subject: Acer saccharum / Algae / Animals / Aquatic ecosystems / Benthos / Biomass / Biomedical and Life Sciences / Bivalvia / Closed ecological systems / Community composition / COMMUNITY ECOLOGY – ORIGINAL RESEARCH / Consumers / Cotton / Decomposition / Detritus / Diatoms / Ecology / Ecosystem / ecosystem respiration / Ergosterol / Excretion / Feeders / Food Chain / Food chains / Food chains (Ecology) / Food webs / Fresh water / Freshwater / Freshwater molluscs / fungal biomass / Fungi / gross primary productivity / Hydrology/Water Resources / Inland water environment / Leaf litter / Leaves / Life Sciences / Marine microorganisms / Mesocosms / Metabolism / Microorganisms / Mineral nutrients / Mollusks / Mussels / net ecosystem production / Nutrient availability / Nutrient cycles / Phylogeny / Physiological aspects / Phytobenthos / Phytosterols / plant litter / Plant Sciences / Primary production / Regeneration / Regeneration (biological) / Species composition / species diversity / Stoichiometry / Strip / Tanks / Tensile strength