Keynote lecture: Interactive effects of elevated CO2, temperature and salinity on physiology and shell properties of hard shell clams Mercenaria mercenaria

Ocean acidification has been shown to increase mortality, alter energy metabolism and respiration, and diminish shell mechanical properties of marine calcifiers. In estuaries, fluctuations in environmental parameters such as salinity and temperature are common, which can affect ocean chemistry and modify or exacerbate the effects of ocean acidification on calcifying organisms. Here, we tested if elevated CO2 levels combined, with either increased temperature or decreased salinity alter physiological and shell mechanical properties of the hard clam, Mercenaria mercenaria. The effect of temperature was tested in adult clams. Shell formed during exposure to increased PCO2 (800 ppm) at an elevated temperature (27 °C) showed significantly reduced hardness, compared to shell formed during exposure to increased PCO2 or temperature alone. The effect of salinity was tested in juvenile clams. Increased PCO2 (800 and 2000 ppm) at reduced salinity (15 ppt) leads to profound differences in shell physical properties. After 8 weeks of exposure, clam shells appeared chalky with considerable pitting and flaking. After 16 weeks, the hinge region had deteriorated in a large number of individuals, resulting in separation of shell valves. Such changes in shell properties may compromise survival of hard clams under future ocean conditions. Supported by NSF award IOS-0951079 to E.B. and I.M.S.

Sokolova I., Ivanina A., Matoo O., Dickinson G. & Beniash E., 2012. Keynote lecture: Developmental and reproductive adaptation to CO2-induced ocean acidification scenarios: a multi-generational study using the marine copepod Calanus finmarchicus. 28th Congress – European Society for Comparative Physiology and Biochemistry – Cellular and molecular mechanisms for physiological adaptation to multiple stress, Bilbao, 2-5 September 2012. Abstract.

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