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The role of oyster restoration and aquaculture in nitrogen removal within a Rhode Island estuary
Citation:
Ayvazian, S., A. Humphries, AND R. Fulweiler. The role of oyster restoration and aquaculture in nitrogen removal within a Rhode Island estuary. Coastal & Estuarine Research Federation (CERF) 23rd Biennial Conference, Portland, OR, November 08 - 12, 2015.
Impact/Purpose:
To understand the value of oysters in nutrient reduction in coastal waters.
Description:
Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster aquaculture and restoration are hypothesized to mitigate excessive nitrogen (N) loads via assimilation, burial, or benthic denitrification. Studies have not directly quantified the values of N removal for each potential pathway in New England, a region where non-point source runoff is high and increasing oyster aquaculture and restoration activity is taking place. Here, we examine tissue and shell N assimilation, and net N2 fluxes across the sediment-water interface in a shallow (~1 m) estuary in southern Rhode Island by collecting samples seasonally for one year using in situ 50 L chambers. Results indicate mean N assimilation in oyster tissue is 2.6% N g-1 DW, and does not differ between treatments. Denitrification rates from oyster restoration and aquaculture is greater than control treatments of bare sediment, but the difference is greater during summer and early fall than winter and spring. On average, oyster restoration and aquaculture enhance sediment denitrification in this system by 302 and 219 μmol m-2 h-1, respectively. These data demonstrate that shellfish can remove nitrogen in New England coastal systems via tissue assimilation and by increasing sediment denitrification rates, but nutrient processing may be seasonally dependent and tied to water temperature and the metabolism of oysters. These values will be important for managers as they incorporate oysters into nutrient reduction strategies.