Linking calcification by exotic snails to stream inorganic carbon cycling

Abstract

Biotic calcification is rarely considered in freshwater C budgets, despite calculations suggesting that calcifying animals can alter inorganic C cycling. Most studies that have quantified biocalcification in aquatic ecosystems have not directly linked CO(2) fluxes from biocalcification with whole-ecosystem rates of inorganic C cycling. The freshwater snail, Melanoides tuberculata, has achieved a high abundance and 37.4 g biomass m(-2) after invading Kelly Warm Springs in Grand Teton National Park. This high biomass suggests that introduced populations of Melanoides may alter ecosystem processes. We measured Melanoides growth rates and biomass to calculate the production of biomass, shell mass, and CO(2). We compared Melanoides biomass and inorganic C production with ecosystem C pools and fluxes, as well as with published rates of CO(2) production by other calcifying organisms. Melanoides calcification in Kelly Warm Springs produced 12.1 mmol CO(2) m(-2) day(-1) during summer months. We measured high rates of gross primary productivity and respiration in Kelly Warm Springs (-378 and 533 mmol CO(2) m(-2) day(-1), respectively); CO(2) produced from biocalcification increased net CO(2) production in Kelly Warm Springs from 155 to 167 mmol CO(2) m(-2) day(-1). This rate of CO(2) production via biocalcification is within the published range of calcification by animals. But these CO(2) fluxes are small when compared to ecosystem C fluxes from stream metabolism. The influence of animals is relative to ecosystem processes, and should always be compared with ecosystem fluxes to quantify the importance of a specific animal in its environment.

High rates of daytime respiration in three streams: Use of δ18OO2 and O2 to model diel ecosystem metabolism

“…where GPP is a positive rate of O 2 production (g O 2 m 22 d 21 ), ER is a negative rate of O 2 consumption (g O 2 m 22 d 21 ), z is mean stream depth (m), and K O 2 is the O 2 gas-exchange rate (d 21 ). O 2 saturation (O 2 sat t ð Þ ; g O 2 m 23 ) is calculated using water temperature (T ; uC) and barometric pressure (BP; mm Hg) for each measurement time (t; as in Hotchkiss and Hall 2010). All parameter descriptions and units are listed in Table 1.…”

Carbon dynamics of river corridors and the effects of human alterations

“…Calcifiers such as mollusks release a mole of CO 2 for each mole of carbonate fixed into their shells. This physiological process can release large amounts of CO 2 (Chauvaud et al 2003), although these CO 2 fluxes are likely small relative to daily variation in gross metabolic fluxes (Hotchkiss and Hall 2010). Variation in food web structure via a trophic cascade can alter CO 2 emissions from lakes by controlling rates of CO 2 fixation (Schindler et al 1997).…”

Quantity and quality: unifying food web and ecosystem perspectives on the role of resource subsidies in freshwaters

“…Fluxes that seem extraordinarily high when measured at a single trophic level may appear insignificant when compared to ecosystem-level fluxes. One example of such an analysis, although not specifically focused on subsidies, was conducted by Hotchkiss and Hall (2010), who studied an invasive freshwater snail with extremely high rates of secondary production in a Wyoming stream (Appendix D). Although this snail had tremendously high rates of biocalcification, this biocalcification contributed only 7% of the net daily CO 2 flux from the stream, with the rest of the flux being driven by ER.…”