Award: OCE-1401349

Changes in the amount of dissolved oxygen and acidity of the surface ocean threaten the health of fisheries in several coastal environments in the US. This exploratory research award enabled a set of laboratory experiments to develop single and multi-elemental geochemical proxies for mussel larval exposure to high pCO2 and low O2 conditions. In particular, the emphasis of this project was to develop geochemical fingerprints that would allow researchers to determine pH exposure history for living organisms in their larval state. Is the chemical composition of mussel larvae a faithful recorder of such chemical changes in seawater? In order to assess this possibility, this research project aimed at establishing differences in the chemical composition of mussel larvae reared under different environmental conditions using a range of instruments. Measurement of boron isotopes using secondary ion mass spectrometry. Measurement of calcium isotopes using multi-collector inductively coupled mass spectrometry. Measurement of boron-to-calcium ratios using laser ablation inductively coupled mass spectrometry. The major results of this project (presented at meetings, written up as undergraduate theses, or in preparation as papers) assess all aspects of this research project. The results of this research project indicate that there is little change in the calcium isotopic or boron isotopic composition of mussel larvae in response to changes in pH or O2 conditions. While the results of the laser ablation inductively coupled mass spectrometry measurements indicate that the elemental composition of mussel larvae holds promise as an indicator of environmental change, the lack of an appropriate standard hampers progress in this area of research. Hence, from the current results, it is inconclusive as to whether elements ratios record environmental conditions in mussel larvae. Further work is needed to determine whether new standard material can help improve accuracy and precision of such measurements. The award supported several related secondary projects that provided further baseline information about elemental chemistry of calcareous shells and improved analytical approaches. The award contributed substantially to the training of two undergraduate students in field and laboratory methods, as well as in mass spectrometric analyses, enhancing the skilled scientific workforce. Lastly, PI Herrmann conveyed the results and importance of this research project to students in the undergraduate class he teaches at LSU ("History of the Biosphere"). Last Modified: 04/12/2016 Submitted by: Achim D Herrmann