Oiling impacts on salt marsh nitrogen cycling rates: insights from a large-scale marsh mesocosm experiment
Abstract
Coastal wetlands straddle the land/ocean interface, providing myriad ecosystem services yet are also especially vulnerable to disturbances across a range of time and space scales. Most disturbance studies rely on either large-scale comparisons between disturbed and undisturbed sites that may have other uncontrolled, underlying differences or on small-scale manipulations of individual processes in isolation from other relevant processes. Here we report results from a large-scale experiment using a salt marsh mesocosm facility capable of testing the impact of disturbances on intertwined ecosystem-scale processes against a backdrop of controlled and uniform environmental conditions. The facility consists of 12, hydrologically independent Spartina alterniflora marsh mesocosms (3m diameter) each with its own paired tidal surge tank capable of generating tidal cycles with ranges up to 50cm via an automated water control system of blowers and airlifts. Specifically, we report results on how oiling impacts salt marsh nitrification and denitrification rates by assigning three marsh tanks to each of four treatments: control plus light, moderate and heavy oiling levels scaled to the SCAT categories observed following the DWH spill. N cycling rate measurements were made every 1-2 months beginning one year prior to oiling in early July 2019 and extending through 4 months post-oiling. Water level, temperature, and salinity and soil temperature and redox potential are logged continuously. Other regular baseline measurements include: 1) soil physical and chemical properties; 2) porewater chemistry; 3) oil characterizations; 4) plant dynamics; 5) additional biogeochemical rates; 7) microbial abundances and composition; and 8) faunal abundances. This yearlong pre-oiling time series in a large-scale, highly monitored and controlled experiment provides a baseline against which we will track short- and long-term responses of marsh soil N cycling rates to a gradient of oil exposure.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC43A..07R
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0490 Trace gases;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE