Snails promote methane release from a freshwater lake ecosystem

Abstract

Benthic fauna, as ecosystem engineers, can strongly affect microbial-driven ecosystem biogeochemical cycling. However, the effects of benthic fauna, especially epifauna, on CH 4 cycling remain still elusive. In this study, CH 4 effluxes were both measured along a gradient of snail density in a freshwater lake ecosystem in China, and monitored in manipulated laboratory microcosms with and without snails. Field CH 4 efflux was significantly increased with snail density. Likewise, the stimulating effects of freshwater snails on CH 4 effluxes were evident in the homogenized indoormicrocosms. These results show that snails can stimulate CH 4 efflux in the freshwater lake ecosystem. Moreover, the average efflux of CH 4 emitted from snails' habitats has reached 15.33mg CH 4 -C m -2 d -1 . By comparing with those emitted from vegetated coastal marsh and alpine wetland, this data indicates that snails' habitats are strong sources of CH 4 in a freshwater ecosystem. This study suggests identifying and modeling epifauna activity as a function of CH 4 cycling could improve the mechanistic understanding of wetland biogeochemical cycling responses to climate change.