title: Photoautotrophic microorganisms as a carbon source for temperate soil invertebrates.
abstract: We tested experimentally if photoautotrophic microorganisms are a carbon source for invertebrates in temperate soils. We exposed forest or arable soils to a (13)CO2-enriched atmosphere and quantified (13)C assimilation by three common animal groups: earthworms (Oligochaeta), springtails (Hexapoda) and slugs (Gastropoda). Endogeic earthworms (Allolobophora chlorotica) and hemiedaphic springtails (Ceratophysella denticulata) were highly (13)C enriched when incubated under light, deriving up to 3.0 and 17.0%, respectively, of their body carbon from the microbial source in 7 days. Earthworms assimilated more (13)C in undisturbed soil than when the microbial material was mixed into the soil, presumably reflecting selective surface grazing. By contrast, neither adult nor newly hatched terrestrial slugs (Deroceras reticulatum) grazed on algal mats. Non-photosynthetic (13)CO2 fixation in the dark was negligible. We conclude from these preliminary laboratory experiments that, in addition to litter and root-derived carbon from vascular plants, photoautotrophic soil surface microorganisms (cyanobacteria, algae) may be an ecologically important carbon input route for temperate soil animals that are traditionally assigned to the decomposer channel in soil food web models and carbon cycling studies.
authors.affiliation: UCD School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Republic of Ireland olaf.schmidt@ucd.ie.
authors.forename: Olaf
authors.identifier: http://orcid.org/0000-0003-0098-7960
authors.initials: O
authors.lastname: Schmidt
authors.affiliation: Centre for Stable Isotope Research and Analysis, Büsgen-Institute, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Dyckmans
authors.affiliation: Johann Heinrich von Thünen-Institute-Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Biodiversity, Bundesallee 50, 38116 Braunschweig, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schrader
mesh_terms: D000818:Animals; D001181:Arthropods / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D017753:Ecosystem; D020387:Food Chain; D049851:Gastropoda / Q000378:metabolism*; D007494:Ireland; D008027:Light; D009835:Oligochaeta / Q000378:metabolism*; D012988:Soil Microbiology
chemical_list: D002244:Carbon
keywords: carbon sequestration; energy channels; soil fauna; soil food webs; stable isotope tracer; terrestrial carbon cycle