Department of Integrative Biology, University of California, 3040 Valley Life Sciences Building #3140, Berkeley, CA, 94720-3140, USA.
Estuary & Ocean Science Center and Department of Biology, Romberg Tiburon Campus, San Francisco State University, 3150 Paradise Drive, Tiburon, CA, 94920, USA.
Sci Rep. 2022 Jun 30;12(1):11034. doi: 10.1038/s41598-022-14503-4.
Giant clams produce massive calcified shells with important biological (e.g., defensive) and ecological (e.g., habitat-forming) properties. Whereas elevated seawater temperature is known to alter giant clam shell structure, no study has examined the effects of a simultaneous increase in seawater temperature and partial pressure of carbon dioxide (pCO) on shell mineralogical composition in these species. We investigated the effects of 60-days exposure to end-of-the-century projections for seawater temperature (+ 3 °C) and pCO (+ 500 µatm) on growth, mineralogy, and organic content of shells and scutes in juvenile Tridacna squamosa giant clams. Elevated temperature had no effect on growth rates or organic content, but did increase shell [Mg]/[Ca] as well as [Ca] in newly-formed scutes. Elevated pCO increased shell growth and whole animal mass gain. In addition, we report the first evidence of an effect of elevated pCO on element/Ca ratios in giant clam shells, with significantly increased [Ba]/[Ca] in newly-formed shells. Simultaneous exposure to both drivers greatly increased inter-individual variation in mineral concentrations and resulted in reduced shell N-content which may signal the onset of physiological stress. Overall, our results indicate a greater influence of pCO on shell mineralogy in giant clams than previously recognized.
巨蛤产生大量钙化外壳，具有重要的生物学（例如防御）和生态学（例如，形成栖息地）特性。已知海水温度升高会改变巨蛤壳的结构，但没有研究检查同时增加海水温度和二氧化碳分压（pCO）对这些物种壳矿物成分的影响。我们研究了 60 天暴露于本世纪末海水温度（升高 3°C）和 pCO（升高 500 µatm）对幼年砗磲巨蛤贝壳和鳞片生长、矿物成分和有机含量的影响。高温对生长率或有机含量没有影响，但确实增加了壳[Mg]/[Ca]和新形成鳞片中的[Ca]。升高的 pCO 增加了壳的生长和整个动物的质量增加。此外，我们报告了首次证明升高的 pCO 对巨蛤壳中元素/Ca 比值的影响的证据，新形成的壳中[Ba]/[Ca]显著增加。同时暴露于这两个驱动因素大大增加了个体间矿物浓度的差异，并导致壳中 N 含量降低，这可能表明生理压力的开始。总体而言，我们的结果表明，pCO 对巨蛤壳矿物成分的影响比以前认识到的更大。
