Research Scientist, Biogeochemistry
Virginia Institute of Marine Science
College of William and Mary

Title: Impact of increasing terrestrially-derived dissolved organic matter inputs on carbon and nitrogen cycling in the coast Arctic

Abstract:The Arctic is warming at nearly twice the global average, leading to increases in permafrost thawing, discharge of terrestrially-derived dissolved organic matter (tDOM) from rivers, and increases in coastal erosion. The tDOM released from rivers is carbon (C)-rich and dark in color, giving it the ability to serve as a C source for bacterial growth and to attenuate light required for photosynthesis. Once thought to be highly refractory, several studies have found that at least a portion of Arctic tDOM is bioavailable to coastal microorganisms on time scales of weeks to months. However, due to tDOM’s high C:N ratio, additional nitrogen is required for microorganisms to utilize all of the labile carbon. This need for additional nitrogen in a seasonally nitrogen limited system may exacerbate the competition between autotrophs and heterotrophs for available resources. A series of experiments conducted in the coastal Chukchi Sea near Barrow, Alaska explored the impacts that increasing tDOM will have on C and nitrogen cycling and community composition of coastal Arctic microbial communities. Results show that not all coastal Arctic microorganisms will thrive under higher tDOM conditions, altering the current state of C and nitrogen cycling in coastal Arctic ecosystems.