|Stable carbon isotopic composition of Mytilus edulis shells: relation to metabolism, salinity, d13CDIC and phytoplankton|
|Gillikin, D.P.; Lorrain, A.; Bouillon, S.; Willenz, P.; Dehairs, F.A. (2006). Stable carbon isotopic composition of Mytilus edulis shells: relation to metabolism, salinity, d13CDIC and phytoplankton. Org. Geochem. 37(10): 1371-1382. dx.doi.org/10.1016/j.orggeochem.2006.03.008|
|In: Organic Geochemistry. Elsevier: Amsterdam. ISSN 0146-6380, more|
Carbon isotopes; Metabolism; Phytoplankton; Salinity; Shells; Mytilus edulis Linnaeus, 1758 [WoRMS]; Marine
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- Validation of alternative marine calcareous skeletons as recorders of global climate change, more
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Bivalve shells can potentially record the carbon isotopic signature of dissolved inorganic carbon (d13CDIC) in estuarine waters, thereby providing information about past estuarine biogeochemical cycles. However, the fluid from which these animals calcify is a ‘pool’ of metabolic CO2 and external dissolved inorganic carbon (DIC). The incorporation of respired 13C-depleted carbon into the skeletons of aquatic invertebrates is well documented, and may affect the d13C record of the skeleton. Typically, less than 10% of the carbon in the skeleton is metabolic in origin, although higher amounts have been reported. If this small offset is more or less constant, large biogeochemical gradients in estuaries may be recorded in the d13C value of bivalve shells. In this study, it is assessed if the d13C values of Mytilus edulis shells can be used as a proxy of d13CDIC as well as providing an indication of salinity. First, the d13C values of respired CO2 (d13CR) were considered using the d13C values of soft tissues as a proxy for d13CR. Along the strong biogeochemical gradient of the Scheldt estuary (The Netherlands–Belgium), d13CR was linearly related to d13CDIC (r2 = 0.87), which in turn was linearly related to salinity (r2 = 0.94). The mussels were highly selective, assimilating most of their carbon from phytoplankton out of the total particulate organic carbon (POC) pool. However, on a seasonal basis, tissue d13C varied differently than d13CDIC and d13CPOC, most likely due to lipid content of the tissue. All shells contained less than 10% metabolic carbon, but ranged from near zero to 10%, thus excluding the use of d13C in these shells as a robust d13CDIC or salinity proxy. As an example, an error in salinity of about 5 would have been made at one site. Nevertheless, large changes in d13CDIC (>2‰) can be determined using M. edulis shell d13C.