Nitrous oxide emission by aquatic macrofauna.
A large variety of aquatic animals was found to emit the potent greenhouse gas nitrous oxide when nitrate was present in the environment. The emission was ascribed to denitrification by ingested bacteria in the anoxic animal gut, and the exceptionally high N(2)O-to-N(2) production ratio suggested delayed induction of the last step of denitrification. Filter- and deposit-feeding animal species showed the highest rates of nitrous oxide emission and predators the lowest, probably reflecting the different amounts of denitrifying bacteria in the diet. We estimate that nitrous oxide emission by aquatic animals is quantitatively important in nitrate-rich aquatic environments like freshwater, coastal marine, and deep-sea ecosystems. The contribution of this source to overall nitrous oxide emission from aquatic environments might further increase because of the projected increase of nitrate availability in tropical regions and the numeric dominance of filter- and deposit-feeders in eutrophic ecosystems.
Stief
Peter
P
Section of Microbiology, Department of Biological Sciences, Aarhus University, DK-8000 Aarhus C, Denmark. pstief@mpi-bremen.de
Poulsen
Morten
M
Nielsen
Lars Peter
LP
Brix
Hans
H
Schramm
Andreas
A
D000818:Animals; D001419:Bacteria / Q000378:metabolism; D017753:Ecosystem; D004785:Environmental Pollutants; D005618:Fresh Water; D041981:Gastrointestinal Tract / Q000382:microbiology; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D012623:Seawater
D004785:Environmental Pollutants; D009566:Nitrates; D009609:Nitrous Oxide