Investigating Hydrobiogeochemical Drivers of Salt Marsh Nitrogen Cycling
Abstract
Salt marshes are highly valued for their nutrient remediation ecosystem services, with implications for water quality, habitat quality, and carbon cycling. In particular, they exhibit a high potential capacity for nitrogen (N) processing, including microbial metabolic pathways that either remove N from the system (such as through denitrification, "DN"), or retain N as reactive species in the system (as in dissimilatory nitrate reduction to ammonium, "DNRA"). Interactions between saline surface water tidal fluctuations and seasonal precipitation-sourced freshwater dynamics in the subsurface create a spatiotemporal mosaic of nutrient cycling processes, and changes to the type and concentration of carbon substrates (i.e., electron donors) associated with different hydrologic sources, flowpaths, and residence times may significantly impact which N cycling processes (e.g., DN vs. DNRA) prevail in these systems. However, a mechanistic understanding of how converging hydrologic and sediment physicochemical characteristics drive N cycling processes and microbial communities remains elusive, challenging efforts to accurately model ecosystem function in the present and to predict impacts of anthropogenic climate change on salt marshes in the future. Using sequence-based microbial community analysis and N cycling process potential rates from isotope-labeled sediment slurries, we explore how spatiotemporal changes in surface and subsurface hydrology drive reactive N removal from (DN) or retention in (DNRA) the Elkhorn Slough salt marsh in Monterey Bay, California. We compare process rates and microbial community metrics across seasonal shifts in precipitation and plant phenology, with findings aimed at informing an understanding of hydrobiogeochemical drivers of nutrient cycling in salt marshes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.B52D0871R