Controls on boron isotopes in a cold-water coral and the cost of resilience to ocean acidification
Controls on boron isotopes in a cold-water coral and the cost of resilience to ocean acidification
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DOI：
10.1016/j.epsl.2020.116662
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发表时间：
2021-01-15
影响因子：
5.3
通讯作者：
Stewart, Joseph A.
中科院分区：
文献类型：
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作者：
Gagnon, Alexander C.;Gothmann, Anne M.;Stewart, Joseph A.
珊瑚骨骼生长对环境变化敏感，可能会受到海洋酸化的不利影响。然而，生理过程也可以缓冲外部条件下的生物矿化，为某些物种提供明显的酸化恢复能力。这些相同的生理过程会影响骨骼组成，并可能影响古环境指标。因此，了解珊瑚钙化机制对于预测不同珊瑚对海洋酸化的脆弱性以及准确解释基于珊瑚的气候记录至关重要。在这里，我们利用对养殖冷水珊瑚的硼同位素 (delta B-11) 测量，解释了珊瑚钙化的基本特征及其对环境变化的敏感性。硼同位素是过去海水 pH 值最广泛使用的替代物之一，我们观察到 delta B-11 和 pH 值之间的预期敏感性。令人惊讶的是，我们还发现珊瑚三角洲 B-11 对海水溶解无机碳 (DIC) 独立敏感。如果我们将硼酸跨细胞膜的扩散引入生物矿化地球化学模型中作为新的通量，我们就可以解释这种新的 DIC 效应。该模型独立预测 delta B-11-pH 代理的灵敏度，无需接受这些数据的训练，即使钙化液 pH (pH(CF)) 是恒定的。硼酸扩散可以解释为什么 delta B-11 是一系列钙化器（包括有孔虫）的有用代理，即使钙化液 pH 值与海水不同。我们的模型表明 delta B-11 不能明确地解释为 pH(CF) 的直接示踪剂。恒定的 pH (CF ) 意味着随着海水 pH 值的降低，钙化率相似，这可以解释一些珊瑚对海洋酸化的恢复能力。然而，我们表明，这种弹性具有隐藏的能量成本，使得钙化在酸化海洋中变得不那么有效。 (C) 2020 Elsevier B.V. 保留所有权利。
Coral skeletal growth is sensitive to environmental change and may be adversely impacted by an acidifying ocean. However, physiological processes can also buffer biomineralization from external conditions, providing apparent resilience to acidification in some species. These same physiological processes affect skeletal composition and can impact paleoenvironmental proxies. Understanding the mechanisms of coral calcification is thus crucial for predicting the vulnerability of different corals to ocean acidification and for accurately interpreting coral-based climate records. Here, using boron isotope (delta B-11) measurements on cultured cold-water corals, we explain fundamental features of coral calcification and its sensitivity to environmental change. Boron isotopes are one of the most widely used proxies for past seawater pH, and we observe the expected sensitivity between delta B-11 and pH. Surprisingly, we also discover that coral delta B-11 is independently sensitive to seawater dissolved inorganic carbon (DIC). We can explain this new DIC effect if we introduce boric acid diffusion across cell membranes as a new flux within a geochemical model of biomineralization. This model independently predicts the sensitivity of the delta B-11-pH proxy, without being trained to these data, even though calcifying fluid pH (pH(CF)) is constant. Boric acid diffusion can resolve why delta B-11 is a useful proxy across a range of calcifiers, including foraminifera, even when calcifying fluid pH differs from seawater. Our modeling shows that delta B-11 cannot be interpreted unequivocally as a direct tracer of pH(CF). Constant pH(CF )implies similar calcification rates as seawater pH decreases, which can explain the resilience of some corals to ocean acidification. However, we show that this resilience has a hidden energetic cost such that calcification becomes less efficient in an acidifying ocean. (C) 2020 Elsevier B.V. All rights reserved.