Mannino, A. Chesapeake Biological Laboratory - UMCES, antonio@cbl.umces.edu
Harvey, R. Chesapeake Biological Laboratory - UMCES, harvey@cbl.umces.edu

 
STRUCTURAL COMPOSITION OF HIGH MOLECULAR WEIGHT DISSOLVED ORGANIC MATTER ALONG AN ESTUARINE GRADIENT: SOURCES AND IMPLICATIONS FOR DOM REACTIVITY
 
Identifying the structural composition of DOM is critical to understanding the cycling of carbon and nitrogen within coastal systems. DOM was collected throughout the Delaware Estuary and fractionated by ultrafiltration into 1-30 kDa (HDOM) and 30 kDa-0.2 um (VHDOM) nominal molecular weight fractions and compared to particles collected in parallel. Considerable portions of organic carbon have been identified from each fraction: 30-90% of POC, 40-70% of VHDOM-C and 20-40% of HDOM-C, primarily as carbohydrates, amino acids, lipids and lignin phenols. Hydrolyzable amino acids comprise 10-45% of dissolved organic nitrogen in VHDOM and HDOM, indicating that organic nitrogen is highly modified within the dissolved pool. Lability appears to decline with molecular size. The composition of amino acids and distribution of polysaccharides are consistent with enrichment of vascular plant and algal cell wall material within DOM. Characterization of organic matter by thermochemolysis showed that lignin concentrations in particles and DOM declined between the middle estuary and coastal ocean, whereas higher concentrations of amino acids, polysaccharides and lipids (including chlorophyll) were observed in the lower estuary. Lower concentrations of lignin phenols in particles versus DOM, especially within the coastal ocean demonstrate the importance of dissolved matter as a conduit for exporting terrestrial organics into the ocean.
 
Day: Tuesday, Feb. 2
Time: 11:15 - 11:30am
Location: Eldorado Hotel
 
Code: SS34TU1115E