FROM THE GUT OF AN INSECT TO THE GLOBAL CLIMATE: DENITRIFICATION AND NITROUS OXIDE PRODUCTION INSIDE LAKE CHIRONOMIDAE P. Stief, L.P. Nielsen, N.P. Revsbech, A. Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Denmark Denitrifying bacteria in lake sediments drive an environmentally relevant ecosystem function by reducing nitrate to dinitrogen gas. Thereby, they remove inorganic nitrogen that originates from organic matter mineralisation and anthropogenic pollution. Nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide, is emitted from lakes only as a minor fraction of the nitrate reduced. However, when lake sediments are densely colonised by macrofauna, the rates of nitrous oxide emission increase significantly. We hypothesise that the guts of bacterivorous macrofauna represent short-term habitats in which high denitrification activity and preferential nitrous oxide production are induced. Our investigation indeed revealed the guts of Chironomus plumosus, a widely distributed insect larva, as microsites of microbial denitrification by providing anoxic conditions and enrichment of organic carbon. Both the larvae and their dissected guts emitted considerable amounts of nitrous oxide. Most notably, the emission rate of nitrous oxide was up to two times higher than that of dinitrogen. Despite the small scale at which these processes occur, their contribution to overall sediment denitrification and nitrous oxide production is significant. Lake sediment inhabited by C. plumosus larvae emitted up to seven times more nitrous oxide than control sediment. Nitrous oxide emission was also found in a range of other macrofauna species, in particular among highly abundant filter- and deposit-feeders of freshwater and coastal marine ecosystems. Given the increasing nitrate pollution of these ecosystems, the gut of benthic invertebrates might constitute an increasingly important yet hitherto overlooked link in the global nitrous oxide budget.
Hidden Powers - Microbial Communities in Action. Proceedings of the 11th International Symposium on Microbial Ecology (isme-11), 2006
Main Research Area:
11th International Symposium on Microbial Ecology (ISME-11), 2006