Salt Marsh Greenhouse Gas Fluxes and Microbial Communities Are Not Sensitive to the First Year of Precipitation Change

Abstract

AbstractChanging precipitation patterns are predicted to alter ecosystem structure and function with potential carbon cycle feedbacks to climate change. Influenced by both land and sea, salt marshes are unique ecosystems and their productivity and respiration responses to precipitation change differ from those observed in terrestrial ecosystems. How salt marsh greenhouse gas fluxes and sediment microbial communities will respond to climate‐induced precipitation changes is largely unknown. We conducted 1‐year precipitation manipulation experiments in the Spartina patens (high marsh) zone of two salt marshes and quantified ecosystem functions at both and microbial community structure at one. Precipitation treatments (doubled rainfall, extreme drought, and seasonal intensification) had a significant, although transient, impact on porewater salinity following storms at both sites, but most site conditions (nutrient concentrations, sediment moisture, and temperature) were unaffected. Extreme drought led to a subtle change in microbial community structure, but most ecosystem functions (primary productivity, litter decomposition, and greenhouse gas fluxes) were not affected by precipitation changes. The absence of ecosystem function change indicates functional redundancy (under extreme drought) and resistance (under doubled precipitation and seasonal intensification) exist in the microbial community. Our findings demonstrate that salt marsh ecosystems can maintain function (including ecosystem services like carbon sequestration) under even the most extreme precipitation change scenarios, due to resistance, resilience, and functional redundancy in the underlying microbial community.