McCallister, S. SMS/VIMS, College of William and Mary, leigh@vims.edu
Bauer, J. SMS/VIMS, College of William and Mary, bauer@vims.edu
Ducklow, H. W.. SMS/VIMS, College of William and Mary, duck@vims.edu

 
BIOAVAILABILITY OF DISSOLVED ORGANIC MATTER IN THE YORK RIVER ESTUARY: AN ENZYMATIC AND STOICHIOMETRIC STUDY
 
The bioavailability and stoichiometric decomposition of dissolved organic matter (DOM) along a transect in the York River Estuary was determined through experimental incubations. Previous studies focusing solely on dissolved organic carbon (DOC) dynamics alone have overlooked the contributions of other potentially labile sources of DOM to bacterial production. Surface water was collected from the mouth, a mid- salinity (8 ppt) and a freshwater site, filtered to remove grazers, and incubated in the dark in sealed glass ampules. Changes in the DOC, dissolved organic nitrogen, and dissolved organic phosphorous components of the DOM coupled with bacterial production and abundance were monitored over several months. Additionally fluorogenic substrates were employed to determine potential ectoenzyme activities. Results show C:N and N:P ratios of DOM to be substantially higher than Redfield stoichiometry. Decomposition incubations indicate increases in the C:P ratio implying preferential mineralization of P relative to C. Potential peptidase hydrolysis rates were elevated relative to glucosidase and phosphatase activities and exhibited a summertime maximum at the river mouth. Both phosphatase and the glucosidases demonstrated an opposing trend with peak hydrolysis rates at the freshwater endmember. Bacterial transformation of DOM in estuaries plays a crucial role in mediating the flux of recycled and potentially C enriched production to the adjacent continental shelves.
 
Day: Monday, Feb. 1
Time: 04:45 - 05:00pm
Location: Eldorado Hotel
 
Code: SS34MO0445E