Abstract
Benthic fauna, as ecosystem engineers, can strongly affect microbial-driven ecosystem biogeochemical cycling. However, the effects of benthic fauna, especially epifauna, on CH4 cycling remain still elusive. In this study, CH4 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 CH4 efflux was significantly increased with snail density. Likewise, the stimulating effects of freshwater snails on CH4 effluxes were evident in the homogenised indoor microcosms. These results show that snails can stimulate CH4 efflux in the freshwater lake ecosystem. Moreover, the average efflux of CH4 emitted from snails’ habitats has reached 15.33 mg CH4-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 CH4 in a freshwater ecosystem. This study suggests identifying and modeling epifauna activity as a function of CH4 cycling could improve the mechanistic understanding of wetland biogeochemical cycling responses to climate change.
Highlights
Benthic fauna are known as ecosystem engineers, whose activities can create unique microniches for microorganisms to inhabit (Laverock et al, 2011), and increase resource availabilities for microbial metabolism (Mermillod-Blondin and Rosenberg, 2006)
A higher CH4 efflux in the habitat with a greater snail density suggests that snail could stimulate CH4 efflux in the largest freshwater lake in China (Figure 1)
Promoted potential of CH4 production and suppressed potential of CH4 oxidation across the gradient of snail density (Figure 2) suggest that snail-induced changes in microbial functioning relative to CH4 cycling are expected to result in more greenhouse gas effects, potentially contributing to a positive climate feedback
Summary
Benthic fauna are known as ecosystem engineers, whose activities can create unique microniches for microorganisms to inhabit (Laverock et al, 2011), and increase resource availabilities for microbial metabolism (Mermillod-Blondin and Rosenberg, 2006). Altered microbial community structure and composition due to fauna activities could largely influence microbial-driven ecosystem biogeochemical cycling (MermillodBlondin and Rosenberg, 2006; Laverock et al, 2011). Wetland CH4 effluxes are primarily driven by net effects of two microbial processes, the CH4 production and oxidation (Whalen, 2005). The effects of benthic fauna, especially epifauna, on CH4 cycling are very limited (Weyhenmeyer et al, 2009). Present study was planned to establish the effects of epifauna on CH4 cycling in freshwater ecosystems. Understanding the potential roles of epifauna in regulating CH4 cycling can fully reveal the dynamic processes of CH4-cycling in freshwater ecosystems, and throw a new light on their ecosystem processes in the process-based CH4 models (Cao et al, 1996)
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