AB 9:77-84 (2010)  -  DOI: https://doi.org/10.3354/ab00228

ABSTRACT: We measured δ¹⁵N values in the acid-insoluble organic portion of shells from Crassostrea virginica transplanted at increasing distance from a major wastewater treatment plant in Mobile Bay, Alabama. To determine whether δ¹⁵N in shell material recorded local spatial variation in wastewater influence, we compared δ¹⁵N in newly deposited oyster shell to δ¹⁵N values in wastewater effluent and in suspended particulate matter in receiving waters. We compared δ¹⁵N values in shell to δ¹⁵N in adductor muscle and whole tissues to determine the isotopic relationships between shell and soft tissues for this previously untested species. δ¹⁵N values in oyster shell reflected differences in wastewater influence relative to distance from the wastewater treatment plant within 38 d of transplanting. δ¹⁵N values in shell were enriched by 2.4‰ compared to available foods, consistent with a trophic shift from food source to consumer. δ¹⁵N values in shell also were significantly correlated with δ¹⁵N values in soft tissues, but were enriched by 1.9‰ compared to whole tissues and 0.8‰ compared to adductor muscle. Overall, δ¹⁵N values in oyster shell were a better proxy for adductor muscle than whole tissues. If applied with care, oyster shells provide an ecologically and commercially meaningful wastewater detection tool that may be effective over relatively short spatial and temporal scales. δ¹⁵N values in shell material may be particularly useful to enable anthropogenic source tracing and refine food web reconstructions in areas with remnant shells where oysters or other bivalves have been severely depleted or already lost.

KEY WORDS: Nitrogen · Stable isotopes · Bivalve · Anthropogenic · Oyster