What happens to DOM when a big river, the Yukon, meanders through a big delta and out into the big ocean?
Abstract
Seasonal samples (spring freshet, early and late summer) were collected in the Yukon River delta out to salinities in the coastal zone as high as 22 in order to characterize changes in DOM composition due to organic matter inputs from the delta itself as well as salinity-induced changes such as flocculation. Preliminary laboratory mixing experiments showed the potential for ~10% losses in DOC due to flocculation, while water mass balance calculations, (precipitation - evapotranspiration) X delta area, demonstrate intriguing potential for runoff from the delta to be large enough to impact DOM chemistry in the Yukon River during at least some parts of the year. Our sample set also included potential endmembers of these delta sources, i.e. streams, seeps, and tundra lakes. Preliminary DOC and optical data across salinity gradients shows nonconservative mixing, with losses that could be due to flocculation. DOC from the delta sources in late summer were much higher than the Yukon River mainstem (3.5 to 4.5 mg/L), with DOC as high as 48 mg/L. This presentation will focus on changes in DOM composition as reflected in lignin biomarkers and optical analyses. Lignin parameters from wetland-dominated deltas have previously been shown to contrast with upstream river chemistry, and we predict that the same will hold for a tundra-dominated delta as well, such that we should be able to detect whether delta DOM sources are overprinting the Yukon River.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B43J2628H
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0442 Estuarine and nearshore processes;
- BIOGEOSCIENCES;
- 0497 Wetlands;
- BIOGEOSCIENCES;
- 4825 Geochemistry;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL