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Title: Top–down effects of a grazing, omnivorous minnow ( Campostoma anomalum) on stream microbial communities

We report top–down control exerted by macroconsumers can strongly affect lower trophic levels and ecosystem processes. Studies of effects on primary consumers in streams have been focused on algae, and effects on bacteria are largely unknown. We manipulated the density of an omnivorous, grazing minnow, the central stoneroller (Campostoma anomalum), in experimental stream mesocosms (treatments with 0, 1, 2, 3, 4, 5, 6, or 7 individuals) to understand consumer effects on algal and bacterial abundance (chlorophyll a [Chl a] extraction, bacterial cell counts, biomass measurements) and bacterial diversity and community composition (via Illumina MiSeq sequencing of the V4 region of the 16S ribosomal RNA gene). Increasing C. anomalum density reduced algal biomass until density reached ~2 fish (5 g fish biomass/m 2), and higher fish densities did not affect algal biomass. Fish biomass did not affect bacterial cell counts. Biofilm organic matter decreased with increasing C. anomalum biomass. Bacterial community composition was not affected by fish biomass, but variation in community composition was correlated with shifts in bacterial abundances. Evenness of bacterial operational taxonomic units (OTUs) decreased with increasing C. anomalum biomass, indicating that bacterial communities exhibited a greater degree of OTU dominance when fish biomass was higher. These findingsmore » suggest that this grazing fish species reduces algal abundance and organic matter in low-nutrient streams until a threshold of moderate fish abundance is reached and that it reduces evenness of benthic bacterial communities but not bacterial biomass. Finally, given the importance of biofilm bacteria for ecosystem processes and the ubiquity of grazing fishes in streams, future researchers should explore both top–down and bottom–up interactions in alternative environmental contexts and with other grazing fish species.« less
ORCiD logo [1] ;  [2] ;  [2] ;  [2]
  1. Kansas State Univ., Manhattan, KS (United States). Division of Biology; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
  2. Kansas State Univ., Manhattan, KS (United States). Division of Biology
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Freshwater Science
Additional Journal Information:
Journal Volume: 37; Journal Issue: 1; Journal ID: ISSN 2161-9549
University of Chicago Press
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; 16S rRNA sequencing; stream biofilms; C. anomalum; chlorophyll a; bacterial cell counts; AFDM; Konza Prairie
OSTI Identifier: