| Summary: | The burning of fossil fuels, and other natural processes, has led to an increase of carbon dioxide (CO2) in the atmosphere. The equilibration of atmospheric CO2 with surface waters causes the ocean pH to decrease from the current value of 8.1. Evidence suggests that as the ocean becomes more alkaline, organisms such as the bay scallop, Argopecten irradiansm, will become more stressed due to increased energy demands to maintain shell deposition and growth. This stress, as hypothesized here, may cause the deposition of S-bearing organic macromolecules to aid in mineralization as well as the potential for sulfate substitution and the deposition of gypsum (calcium sulfate) as opposed to calcite. I hypothesize that scallops raised under pH conditions predicted for the end of the 21st century will have higher total S content which may be due to the deposition of sulfate and/or deposition of high-S organic macromolecules. I will investigate this possibility as well as the possibility that the shift towards increased sulfur impacts the stable S isotopic composition of the inorganic and organic components of shells from organisms raised under high dissolved CO2 conditions as compared to “normal” pH.
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