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Abstract

Several freshwater and terrestrial inver-tebrate species emit the greenhouse gas nitrous oxide(N2O). The N2O production associated with these ani-mals was ascribed to incomplete denitrification byingested sediment or soil bacteria. The present studyshows that many marine invertebrates also emit N2O atsubstantial rates. A total of 19 invertebrate species col-lected in the German Wadden Sea and in Aarhus Bay,Denmark, and 1 aquacultured shrimp species weretested for N2O emission. Potential N2O emission ratesranged from 0 to 1.354 nmol ind.–1h–1, with an averagerate of 0.320 nmol ind.–1h–1, excluding the aquacul-tured shrimp Litopenaeus vannamei, which showedthe highest rate of N2O emission measured so far forany marine species (3.569 nmol ind.–1h–1), probablydue to very high nitrate concentrations in the rearingtanks. The N2O emitted by L. vannameiwas almostexclusively produced in its gut by incomplete denitrifi-cation. Statistical analysis revealed that body weight,habitat, and exoskeletal biofilms were important deter-minants of animal-associated N2O production. Thesnail Hinia reticulataemitted about 3.5 times moreN2O with an intact exoskeletal biofilm on its shell thanwith an experimentally cleaned shell. Thus, the N2Oproduction associated with marine invertebrates isapparently not due to gut denitrification in every spe-cies, but may also result from microbial activity on theexternal surfaces of animals. The high abundance andpotential N2O emission rates of many marine inverte-brate species suggest significant contributions to over-all N2O emissions from coastal marine environmentsand aquaculture facilities.