The Influence of Terrestrially-Derived Humic Substances on Dissolved Organic Matter in the Gulf of Maine
George
R
Aiken, U.S. Geological Survey, graiken@usgs.gov
(Presenting)
William
M
Balch, Bigelow Laboratory for Ocean Sciences, bbalch@bigelo.org
Barnard
Andrew, WET Labs, Inc, andrew@wetlabs.com
Thomas
G
Huntington, U.S. Geological Survey, thunting@usgs.gov
Collin
Roesler, University of Maine, collin.roesler@maine.edu
Huijie
Xue, University of Maine, hxue@maine.edu
The chemical nature of aquatic humic substances (HPOA) exported to the Gulf of Maine by the Penobscot River is being studied as part of a project focusing on quantifying and characterizing optical proxies for a range of specific dissolved organic matter (DOM) pools in the Penobscot watershed and the receiving waters of the Gulf of Maine. Optical measurements (specific ultraviolet absorbance (SUVA254), absorption coefficient (350nm and 412nm) and fluorescence), in combination with DOC and DOC fractionation and isotopic analyses, were used to determine the amount and nature of DOC in the Penobscot River, Penobscot Bay and the Gulf of Maine. DOC fractionation data indicate the amount of HPOA material in the Penobscot River (60% of DOC) is much greater and more aromatic than that found in the Gulf of Maine (25% of DOC). However, SUVA254 determined on HPOA fractions from the Gulf of Maine (SUVA254 = 1.5 L mgC-1m-1) is greater than for a sample collected from the Sargasso Sea (SUVA254 = 0.75 L mgC-1m-1) or a similar sample from the Pacific Ocean near Hawaii (SUVA254 = 0.6 L mgC-1m-1), indicating the Gulf of Maine is more strongly influenced by terrestrial sources than samples from the open ocean. This observation is consistent with isotopic data that indicated δ 13C values for the HPOA fractions from the Gulf samples (δ 13C= -27 and -25) were considerably lighter than the whole DOM sample (δ 13C = -19) and are more similar to those from the terrestrial sources.
NASA Carbon Cycle & Ecosystems Active Awards Represented by this Poster: