The Effects of Winter Storm Cato on the Composition and Flux of Carbon at the Marsh-Estuarine Interface

Abstract:

By the end of this century, the IPCC predicts that mid-latitude regions will experience increases in precipitation accompanied by more intense and frequent storm events. These extreme events will likely result in changes in magnitude, direction, and composition of carbon fluxes in coastal habitats. This study focused on understanding variability in carbon pools at the tidal marsh-estuarine interface at Taskinas Creek, VA, during baseline and storm event conditions. Measurements of carbon concentration and composition were made during November and December 2014 (baseline) and during different phases of Winter Storm Cato, which affected northeastern USA during late November 2014 and delivered ~32.5 mm of precipitation to Taskinas Creek. Particulate organic carbon (POC), dissolved organic carbon (DOC), chlorophyll-a (chla), phaeopigments (phaeo), and colored dissolved organic matter (CDOM) optical properties were measured. Using tidal prism flux calculations and concentrations measured during the 18-hr storm, Taskinas Creek exported ~32.9 kg DOC and 25.2 kg POC. The annual net export of DOC from Taskinas for water year 2014 was ~334 kg, indicating that ~10% of the annual DOC flux was exported during the 18-hr event. In contrast, while the Taskinas marsh generally acts as a sink for POC it acted as a source of POC to the adjacent estuary during the Cato event. CDOM concentrations during precipitation were similar to baseline but increased after precipitation. Post-precipitation CDOM had lower spectral slopes than during November, December, and during precipitation, indicating an increase in higher molecular weight organic matter after the precipitation event. These results highlight the fact that storms events impact the magnitude of fluxes, cause shifts in carbon pool source and composition, and have the potential to change the function of coastal regions from sinks to sources, and thus should be better integrated into carbon flux budgets.