Isotopic values in oysters indicate elemental sources constrained by multiple gradients

• Published in: Ecological indicators 2014-11, Vol.46, p.101-109
• Main Authors: Fertig, B., Carruthers, T.J.B., Dennison, W.C., Meyer, K.A., Williams, M.R.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Biological monitoring; Carbon; Citizen–scientists; Conservation, protection and management of environment and wildlife; Crassostrea virginica; Flushing; Fundamental and applied biological sciences. Psychology; General aspects; Invertebrates; Mollusca; Mouth; Oysters; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Physical factors; Shellfish; Signatures; Spatial scale; Stable isotopes; Synecology; Tributaries; Water quality
• ISSN: 1470-160X; 1872-7034
• DOI: 10.1016/j.ecolind.2014.06.004

•132 citizen–scientists grew oysters across 11,600km2 for δ15N and δ13C analysis.•δ15N varied by flushing, salinity, bioindicator size, water quality, and land use.•Nested spatial patterns constrained bioindication to scale of confounding factors.•At 100skm2, isotopic signatures can reveal elemental sources and transport.•Distributing bioindicators to citizen–scientists adds value to existing datasets. Stable nitrogen and carbon isotopes (δ15N and δ13C) and elemental content (% nitrogen, % carbon) in oysters (Crassostrea virginica) grown by a network of 132 citizen–scientists (11,600km2, 87.9km2site−1) were examined to test effects of land use, salinity, flushing time, and oyster size on bioindication of human and/or animal nitrogen sources. Oyster δ15N sampled from shallow waters sites throughout Chesapeake Bay and its tributaries exhibited nested spatial patterns: (1) decreasing toward the mouth of Chesapeake Bay (1000skm2) and (2) decreasing, increasing, and not changing toward tributary mouths (100skm2). Distinct isotopic ‘signatures’ in tributaries were associated with the composition of land use, water quality in tributaries and freshwater streams, human and/or animal nitrogen sources, and marine vs. terrestrial nitrogen and carbon sources. Yet at 1000skm2, oyster δ15N varied with flushing time, salinity, and bioindicator size, thus constraining the upper extent for inferring nitrogen sources from bioindicator δ15N to the scale of gradients in these confounding physical and biological factors. Nevertheless, at 100skm2 isotopic ‘signatures’ can be used to infer nutrient sources and transport mechanisms and might have implications for fishery management/enforcement. Ultimately, δ15N and δ13C in bioindicators distributed to citizen–scientists may add substantial value to existing and ongoing programs, networks, monitoring and databases, and might have some use for imputing data gaps where intensive water quality monitoring is lacking.