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Hahn, S.; Rodolfo-Metalpa, R.; Griesshaber, Erika; Schmahl, Wolfgang W.; Buhl, D.; Hall-Spencer, J. M.; Baggini, C.; Fehr, K. T.; Immenhauser, A. (2012): Marine bivalve shell geochemistry and ultrastructure from modern low pH environments: environmental effect versus experimental bias. In: Biogeosciences, Vol. 9, No. 5: pp. 1897-1914


Bivalve shells can provide excellent archives of past environmentalchange but have not been used to interpret ocean acidification events.We investigated carbon, oxygen and trace element records from differentshell layers in the mussels Mytilus galloprovincialis combined withdetailed investigations of the shell ultrastructure. Mussels from theharbour of Ischia (Mediterranean, Italy) were transplanted and grown inwater with mean pHT 7.3 and mean pHT 8.1 near CO2 vents on the eastcoast of the island. Most prominently, the shells recorded the shock oftransplantation, both in their shell ultrastructure, textural andgeochemical record. Shell calcite, precipitated subsequently underacidified seawater responded to the pH gradient by an in part disturbedultrastructure. Geochemical data from all test sites show a strongmetabolic effect that exceeds the influence of the low-pH environment.These field experiments showed that care is needed when interpretingpotential ocean acidification signals because various parameters affectshell chemistry and ultrastructure. Besides metabolic processes,seawater pH, factors such as salinity, water temperature, foodavailability and population density all affect the biogenic carbonateshell archive.