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Description: The School for Marine Science and Technology
Department of Estuarine and Ocean Sciences
Master's Thesis Defense Announcement

"Seasonal carbon and nitrogen mineralization in sediments receiving bio-deposition from oyster aquaculture in shallow temperate estuaries"

By
Nicholas Uline

Advisor
Brian Howes, School for Marine Science and Technology, University of Massachusetts Dartmouth

Committee
Miles Sundermeyer, University of Massachusetts Dartmouth
David Schlezinger, University of Massachusetts Dartmouth
Craig Taylor, Woods Hole Oceanographic Institution

Friday, April 1, 2022
9:00 am to 10:00 am
SMAST East Rooms 101/102
New Bedford, MA
and via Zoom

Abstract:
Over the past 80 years, nitrogen (N) enrichment has been increasing with human population and shifts in land use near temperate coastal systems. Managers currently seek new infrastructure tools to control N while also improve marine habitat. Recently, the use of intensive aquaculture has been proposed, but few quantitative studies integrate both the mechanisms and extent that bivalves mitigate the impact of nutrient enrichment in general. Specifically, in New England’s coastal estuaries, oyster growth and filtration are well known, however, biodeposition from active feeding bivalves has been shown to also
modify the benthic-pelagic coupling of carbon (C) and N. The present study investigated the seasonal response of C and N cycling in sediments receiving labile organic matter through biodeposits from suspended oyster aquaculture, Crassostrea virginica, in two temperate estuaries. In addition to field measurements of sediment-water column exchange of oxygen and N, a long-term
sediment incubation was conducted over 351 days, where sediments received daily additions of field collected biodeposits for the length of the growth season (208 days). Further, a separate experiment incubated only the biodeposits to directly assess the decay rate at a constant temperature. The overall results showed similar seasonal trends in both field and long-term laboratory sediment
incubations, with temperature being the driving force in the annual pattern of C and N mineralization. Results indicated 45 – 65 % of C and 28 – 33 % of N in biodeposits were remineralized, including N loss through denitrification. The isolated biodeposits had a half-life for labile organic C of 11.25 – 15.92 days. Through the impact of oyster biodeposition, seasonal changes in temperature
appear to effect the volatility of mineralization rates and the biogeochemical cycle of sediments. Especially when eutrophication is less pronounced, C and N deposited through the summer continues releasing to the water column during cooler winter periods.
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For additional information, please contact Sue Silva at s1silva@umassd.edu.