Seasonality of Dissolved Organic Matter in Lagoon Ecosystems along the Eastern Alaskan Beaufort Sea Coast
Abstract
Seasonality is a defining feature of the physicochemical environment in Arctic coastal regions, but fundamental understanding of temporal patterns in dissolved organic matter (DOM) among productive and highly valued estuarine ecosystems in the Arctic are lacking to date. Here we investigate seasonal patterns in the quantity and composition of DOM in lagoons along the Eastern Alaskan Beaufort Sea coast during full ice cover (April), ice break-up (late June), and open water period (August). We measured concentrations of dissolved organic carbon (DOC), ratios of DOC to DON (C:N), and chromophoric DOM optical properties, SUVA254 and S275-295, and found that the quantities and composition of DOM in Arctic lagoons vary markedly among seasons. We saw a general shift from low to high DOC, C:N, and SUVA254 values between April and June. These parameters were more variable during August, spanning the full range observed during the other two seasons. S275-295 values were lower and less variable during June and higher but more variable in August and April. These patterns reflect distinct seasonal transitions in ice-coverage, runoff from land, water column stratification, and connectivity with coastal waters of the Beaufort Sea that are coupled to dynamic changes in the sources and composition of DOM in Arctic lagoons. More specifically, lagoon DOM is strongly influenced by terrestrial inputs in the spring owing to large quantities of riverine freshwater and organic matter that inundate the Beaufort Sea coastline. The composition of DOM during the summer reflects variability in runoff and water exchange with the Beaufort Sea between spring and late summer. In some cases DOM concentrations build up beneath the lagoon ice over the winter, indicating that inputs of regenerated benthic material and/or the degradation of particulate organic matter retained in the water column are important contributors to the winter DOM pool. Across all seasons, DOM composition correlated with the composition of microbial communities, suggesting interaction between DOM and the primary consumers of this material. This work is part of a larger effort aimed at understanding how climate change impacts Arctic coastal ecosystems through effects on terrestrial inputs, nutrient cycling, and ocean mixing.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS24A..06C
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 4806 Carbon cycling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICALDE: 4235 Estuarine processes;
- OCEANOGRAPHY: GENERAL