Shell decay rates of native and alien freshwater bivalves and implications for habitat engineering

Abstract

SUMMARY1. Spent shells of bivalves can provide habitat for other organisms, as well as playing important roles in biogeochemical cycles. The amount of spent shell material that will accumulate at a site depends on rates of both shell production and decay, although the latter is rarely considered. 2. We measured the instantaneous decay rates of four species of freshwater bivalves across a range of sites in south-eastern New York, and found that rates varied by more than 500-fold across sites and species. 3. Differences in decay rates were related to water chemistry (Ca, pH, dissolved inorganic C), the presence of a current, and the size of the bivalve shell. 4. Combining these decay rates with estimates of shell production derived from the literature, we conclude that the Unionidae, Corbicula, and Dreissena are all capable of producing large accumulations (>10 kg dry mass m )2 ) of spent shells, while members of the Sphaeriidae probably rarely will produce such large accumulations. 5. Hence the replacement of native unionid bivalves by the alien Corbicula and Dreissena may have little effect on standing stocks of spent shells, unless the aliens invade sites where unionids are scarce or absent.

Habitat engineering by the invasive zebra mussel Dreissena polymorpha (Pallas) in a boreal coastal lagoon: impact on biodiversity

“…For shell deposits only samples devoid of live mussels were analyzed. Only species with statistically signiWcant correlation of abundance with either zebra mussel biomass or dry weight of shell deposits are presented (correlation coeYcients are shown next to genus name) calcium carbonate production rates for D. polymorpha ranges from 10 to 10,000 gDW/m 2 year, depending on the population size (Strayer and Malcom 2007). Based on this, the density of calcite and aragonite, assuming shells have a calcite/aragonite ratio of 1:1 (Gutierrez et al 2003), zebra mussels may deposit 0.035-3.5 mm of CaCO 3 per year.…”

Contrasting decay rates of freshwater bivalves’ shells: Aquatic versus terrestrial habitats

“…The input of shells can lead to profound consequences at different ecological levels, from individuals to ecosystems (e.g. Gutiérrez et al, 2003;Strayer and Malcom, 2007), given that the physical structure of shells can provide habitat to a myriad of organisms (Werner and Rothhaupt, 2008) and play an important role in the carbon cycling (Gutiérrez et al, 2003;Sousa et al, 2009).…”

Linking calcification by exotic snails to stream inorganic carbon cycling

“…Melanoides shells will take several years to dissolve after death, especially with high Ca concentrations (Ca 2? ) and pH in Kelly Warm Springs, which impede CaCO 3 dissolution (Strayer and Malcom 2007). We do not have sufficient data to quantify how dissolving shells contribute to the net impact of Melanoides on stream CO 2 fluxes.…”