| Summary: | Environmental archives provide records of natural and anthropogenic variation in the environment at different temporal and spatial scales. Lead (Pb) concentrations and isotopic ratios are useful tracers of anthropogenic emissions from industrial activities including mining, smelting, and leaded gasoline use, however, methods of measuring Pb are largely limited in low concentration media. In this study, measurement protocols and methods are developed in two environmental archives – oyster shells and ice – to improve geochemical analyses of Pb. Additionally, oyster fitness is examined to determine best management practices for culturing bivalves under worsening ocean acidification (OA) conditions. As a result of OA, periods of decreased calcite saturation state have increased in duration, intensity, and magnitude, making calcareous organisms such as oysters, vulnerable to changes in carbonate chemistry. In Chapter 2 condition indices in oyster shells were measured to examine the impacts of culturing practices on oyster fitness to mitigate impacts of worsening OA conditions. Oysters were cultured at varying tidal heights, either on rebar platforms, or on top of shell plantings. Results indicated that growing oysters off bottom without shell plantings produced the most positive influence on oyster fitness. Shell plantings negatively influenced summertime condition index results, but showed higher than predicted shell weights, likely suggesting these cultures produced higher quality shell compared to oysters cultured on rebar platforms. Thus, this work demonstrated that traditional methods of measuring oyster fatness, using condition indices, may be problematic in carbonate poor environments due to their reliance on shell weights, which may be impacted by dissolution of calcium carbonate shell. While laser ablation quadrupole inductively coupled plasma mass spectrometry (LA-Q-ICP-MS) offers a low cost, efficient, and powerful tool for direct elemental analysis of solid samples, Pb isotopic analyses are limited in ...
|
|---|