Size-dependent pH effect on calcification in post-larval hard clam Mercenaria spp.
Size-dependent pH effect on calcification in post-larval hard clam Mercenaria spp.
复制标题
尺寸依赖性 pH 对硬蛤幼体 Mercenaria spp 钙化的影响。
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
Mark A. Green
中科院分区：
文献类型：
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作者：
G. Waldbusser;Heather Bergschneider;Mark A. Green
大气中二氧化碳的增加可能会降低世界海洋的PH值。具有重大生态和经济重要性的沿海和河口钙化生物处于危险之中；然而，几个生物地球化学过程决定了这些生境的pH值。特别是，即使上覆水饱和，由于有机物再矿化率高，沿海和河口沉积物的碳酸钙含量往往不饱和。因此，海洋双壳贝类幼体后阶段必须能够在对贝壳具有腐蚀性的条件下沉积新的贝壳材料。用碱度异常法测定了5种规格(0.39、0.56、0.78、0.98和2.90 mm壳高)硬壳贝的钙化速率。通过用空气-二氧化碳混合物鼓泡来控制实验水的酸度，获得的pH值分别为8.02、7.64和7.41，对应的二氧化碳分压为424、1120和1950微米。这些pH值是在许多近岸陆源海洋沉积物中发现的典型pH值。我们的结果表明，在所测量的5个大小类别中，钙化率随着pH的降低而降低。我们还发现大小对钙化率有显著的影响，较小的仔鱼不能克服溶解压力。随着尺寸的增加，钙化速度的增加使得较大的尺寸可以克服溶解压力，并在腐蚀条件下沉积新的外壳材料。PH对钙化作用的大小依赖可能是由于器官发生和贝壳矿物学的发育变化发生在幼虫后阶段。此外，我们发现用于这些实验的两种来源的硬蛤的钙化率显著不同，很可能是由于基因差异。我们的发现证实了这种重要的双壳类早期生活阶段对pH下降的敏感性，并揭示了先前研究中发现的与溶解压力有关的仔贝幼体死亡率增加的机制。
Increasing atmospheric carbon dioxide threatens to decrease pH in the world's oceans. Coastal and estuarine calcifying organisms of significant ecological and economical importance are at risk; however, several biogeochemical processes drive pH in these habitats. In particular, coastal and estuarine sediments are frequently undersaturated with respect to calcium carbonate due to high rates of organic matter remineralization, even when overlying waters are saturated. As a result, the post-larval stages of infaunal marine bivalves must be able to deposit new shell material in conditions that are corrosive to shell. We measured calcification rates on the hard clam, Mercenaria spp., in 5 post-larval size classes (0.39, 0.56, 0.78, 0.98, and 2.90 mm shell height) using the alkalinity anomaly method. Acidity of experimental water was controlled by bubbling with air-CO2 blends to obtain pH values of 8.02, 7.64, and 7.41, corresponding to pCO2 values of 424, 1120, and 1950 µatm. These pH values are typical of those found in many near-shore terrigenous marine sediments. Our results show that calcification rate decreased with lower pH in all 5 size classes measured. We also found a signif- icant effect of size on calcification rate, with the smaller post-larval sizes unable to overcome dissolu- tion pressure. Increased calcification rate with size allowed the larger sizes to overcome dissolution pressure and deposit new shell material under corrosive conditions. Size dependency of pH effects on calcification is likely due to organogenesis and developmental shifts in shell mineralogy occurring through the post-larval stage. Furthermore, we found significantly different calcification rates between the 2 sources of hard clams we used for these experiments, most likely due to genotypic dif- ferences. Our findings confirm the susceptibility of the early life stages of this important bivalve to decreasing pH and reveal mechanisms behind the increased mortality in post-larval juvenile hard clams related to dissolution pressure, that has been found in previous studies.