Rangia Cuneata Shells as An Environmental Proxy: Variations in Elemental Concentrations within Populations

Rangia cuneata is an endobenthic clam typically found in brackish water estuaries of the Atlantic and Gulf of Mexico coasts of North America. Its shell may potentially be useful as an archive for elemental water pollution for many coastal areas, due to its wide salinity tolerance. Soft tissue analysis for anthropogenic pollutants in this species is presently used to monitor environmental health. However, before R. cuneata shells can be developed as a proxy archive some fundamental characteristics need to be better assessed. For example, it is uncertain if different individuals within a population grown at the same place and time record similar concentrations of contaminates in their shells. To address this issue, samples of living R. cuneata were collected in two sites in the Mobile-Tensaw Delta (Gulf of Mexico coast, Alabama, USA) where previous data existed on several key metal pollutants, in addition to some soft tissue elemental analysis of other R. cuneata samples. Time-equal sections of shell as identified through growth increment analysis, will be measured via LA-ICP-MS for calcium-substituting elements such as Cd, and Pb, to assess if concentrations of these metals vary significantly between individuals. Factors such as age difference and growth rates will be considered as potential sources of variation.