Long-term changes in the pelagic carbon cycle of the Gulf of Maine, as documented by GNATS (Gulf of Maine North Atlantic Time Series)
William
M.
Balch, Bigelow Laboratory for Ocean Sciences, bbalch@bigelow.org
(Presenting)
Aiken
R.
George, U.S. Geological Survey,, Water Resources Division,, graiken@usgs.gov
David
T.
Drapeau, Bigelow Laboratory for Ocean Sciences, ddrapeau@bigelow.org
Bruce
C.
Bowler, Bigelow Laboratory for Ocean Sciences, bbowler@bigelow.org
Emily
S.
Booth, Bigelow Laboratory for Ocean Sciences, ebooth@bigelow.org
“GNATS” (Gulf of Maine North Atlantic Time Series) is a coastal time series that documents the carbon cycle across the Gulf of Maine (NASA N. American Carbon Cycle project). Now in its tenth year, GNATS regularly samples biological, bio-optical and chemical variables across the Gulf, all targeted for clear sky days to maximize concurrent satellite and ship measurements. The GNATS provides a valuable test bed for satellite algorithm development as well as an important ocean end member for a study of carbon flow from the Maine watershed (NASA IDS project with G. Aiken, A. Barnard, T. Huntington, C. Roesler, and H. Xue). Here we document long-term variability in hydrography, nutrients, DOC, phytoplankton standing stocks and carbon fixation in the GoM, in response to several years of extreme river discharge. Changes have been documented in phytoplankton community structure along with decreases in nutrients, phytoplankton biomass and primary production during 2005 (wettest year in 105 years) and 2006 (eighth wettest year in 105 years). Colored dissolved organic matter increased in response to the increased river run off. During wet years, fresh water appears to have capped the surface euphotic layer, impeding the upward diffusion of nutrients, thus limiting phytoplankton biomass and growth. Total GoM and Georges Bank phytoplankton photosynthesis was estimated from the Aqua-MODIS time series to be 38.12 Tg C per year and total calcification was 0.55 Tg C per year, yielding a ratio of calcification to photosynthesis of 1.44%. Regional variability in primary production and calcification will also be discussed.
NASA Carbon Cycle & Ecosystems Active Awards Represented by this Poster: