Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA 93106-9620, USA.
Mol Ecol. 2013 Mar;22(6):1609-25. doi: 10.1111/mec.12188. Epub 2013 Jan 14.
Some marine ecosystems already experience natural declines in pH approximating those predicted with future anthropogenic ocean acidification (OA), the decline in seawater pH caused by the absorption of atmospheric CO2 . The molecular mechanisms that allow organisms to inhabit these low pH environments, particularly those building calcium carbonate skeletons, are unknown. Also uncertain is whether an enhanced capacity to cope with present day pH variation will confer resistance to future OA. To address these issues, we monitored natural pH dynamics within an intertidal habitat in the Northeast Pacific, demonstrating that upwelling exposes resident species to pH regimes not predicted to occur elsewhere until 2100. Next, we cultured the progeny of adult purple sea urchins (Strongylocentrotus purpuratus) collected from this region in CO2 -acidified seawater representing present day and near future ocean scenarios and monitored gene expression using transcriptomics. We hypothesized that persistent exposure to upwelling during evolutionary history will have selected for increased pH tolerance in this population and that their transcriptomic response to low pH seawater would provide insight into mechanisms underlying pH tolerance in a calcifying species. Resulting expression patterns revealed two important trends. Firstly, S. purpuratus larvae may alter the bioavailability of calcium and adjust skeletogenic pathways to sustain calcification in a low pH ocean. Secondly, larvae use different strategies for coping with different magnitudes of pH stress: initiating a robust transcriptional response to present day pH regimes but a muted response to near future conditions. Thus, an enhanced capacity to cope with present day pH variation may not translate into success in future oceans.
一些海洋生态系统已经经历了与未来人为海洋酸化（OA）预测值相近的 pH 值自然下降，即由于大气 CO2 的吸收导致海水 pH 值下降。允许生物栖息在这些低 pH 值环境中的分子机制尚不清楚，特别是那些构建碳酸钙骨骼的生物。目前还不确定是否增强应对当前 pH 值变化的能力会赋予其对未来 OA 的抵抗力。为了解决这些问题，我们监测了东北太平洋潮间带栖息地内的自然 pH 值动态，证明上升流使居住物种暴露于预测到 2100 年才会在其他地方出现的 pH 范围。接下来，我们在 CO2 酸化海水中培养了从该地区采集的成年紫色海胆（Strongylocentrotus purpuratus）的后代，这些海水代表了当前和未来的海洋情景，并使用转录组学监测基因表达。我们假设，在进化历史上持续暴露于上升流将使该种群对 pH 值耐受能力有所增强，而它们对低 pH 值海水的转录组响应将为研究钙化物种 pH 值耐受机制提供线索。研究结果揭示了两个重要趋势。首先，S. purpuratus 幼虫可能会改变钙的生物利用度，并调整骨骼生成途径以维持在低 pH 值海洋中的钙化作用。其次，幼虫采用不同的策略来应对不同程度的 pH 值胁迫：对当前 pH 值范围启动强大的转录响应，但对未来条件的响应较弱。因此，增强应对当前 pH 值变化的能力可能不会转化为在未来海洋中的成功。
