Nutrient cycling in a freshwater marsh: The decomposition of fish and waterfowl carrion

Abstract

We measured decomposition rates and nutrient loss sequences of rainbow trout (Oncorhynchus mykiss) and pintail duck (Anas acutas) carcasses in a Wyoming marsh over a 10‐month period (July–May). Data on carcass mass loss were fit to single‐ and double‐exponential decomposition models. Fish carrion decomposed more rapidly and completely than waterfowl carrion; after 10 months, fish carcasses had lost 85% of their initial dry mass (leaving only scales and bones), while duck carcasses had lost only 30% (leaving feathers and bones). Fish carrion lost 95% of the original carcass N and 60% of carcass P; waterfowl carrion lost 65% of carcass N, but only 30% of carcass P. The sequence of total elemental loss rates from carcasses was K > Na > N > S > P > Ca Mg and was similar for fish and waterfowl carrion. Percentage elemental compositions of carcasses changed temporally with K, Na, and N decreasing in concentration and Mg, Ca, P, and S increasing. Vertebrate carrion decomposition differed from plant litter decomposition, both qualitatively (different nutrient loss sequences) and quantitatively (faster mass loss rates). We suggest that vertebrate carrion can function as a nutrient source for some elements (N, K, Na, and S) and as a partial nutrient sink for others (P, Ca, and Mg). Although the quantitative importance of carrion‐derived elements to ecosystem nutrient budgets is site‐specific, studies have shown that in aquatic environments supporting large vertebrate populations, carrion decomposition can contribute significant amounts of important nutrients that ultimately influence the structure and functioning of the aquatic ecosystem.