title: Trophic complexity in aqueous systems: bacterial species richness and protistan predation regulate dissolved organic carbon and dissolved total nitrogen removal.
abstract: Loading of water bodies with dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) affects their integrity and functioning. Microbial interactions mitigate the negative effects of high nutrient loads in these ecosystems. Despite numerous studies on how biodiversity mediates ecosystem functions, whether and how diversity and complexity of microbial food webs (horizontal, vertical) and the underlying ecological mechanisms influence nutrient removal has barely been investigated. Using microbial microcosms accommodating systematic combinations of prey (bacteria) and predator (protists) species, we showed that increasing bacterial richness improved the extent and reliability of DOC and DTN removal. Bacterial diversity drove nutrient removal either due to species foraging physiology or functional redundancy, whereas protistan diversity affected nutrient removal through bacterial prey resource partitioning and changing nutrient balance in the system. Our results demonstrate that prey-predator diversity and trophic interactions interactively determine nutrient contents, thus implying the vital role of microbial trophic complexity as a biological buffer against DOC and DTN.
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, Leipzig 04318, Germany Department of Soil and Plant Sciences, University of Kentucky, Lexington, KY, USA.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Saleem
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, Leipzig 04318, Germany Stockholm Resilience Centre, Stockholm University, Stockholm 11419, Sweden.
authors.forename: Ingo
authors.initials: I
authors.lastname: Fetzer
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, Leipzig 04318, Germany German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, Leipzig 04103, Germany.
authors.forename: Hauke
authors.initials: H
authors.lastname: Harms
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, Leipzig 04318, Germany German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, Leipzig 04103, Germany antonis.chatzinotas@ufz.de.
authors.forename: Antonis
authors.identifier: http://orcid.org/0000-0002-0387-9802
authors.initials: A
authors.lastname: Chatzinotas
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D058440:Denitrification; D056890:Eukaryota / Q000378:metabolism*; D020387:Food Chain; D064307:Microbiota; D009584:Nitrogen / Q000378:metabolism*
chemical_list: D002244:Carbon; D009584:Nitrogen
keywords: biodiversity and ecosystem functioning; microbial model systems; nutrient removal; predator–prey interactions; trophic complexity and stability