Romberg Tiburon Center, San Francisco State University, 3150 Paradise Drive, Tiburon, CA 94920, USA.
J Exp Biol. 2013 Apr 15;216(Pt 8):1412-22. doi: 10.1242/jeb.078162.
Absorption of elevated atmospheric CO2 is causing surface ocean pH to decline, a process known as ocean acidification (OA). To date, few studies have assessed the physiological impacts of OA on early life-history stages of intertidal organisms, which transition from habitats with fluctuating pH (intertidal zone) to relatively stable (pelagic zone) pH environments. We used the intertidal crab Petrolisthes cinctipes to determine whether metabolic responses to year 2300 predictions for OA vary among early developmental stages and to examine whether the effects were more pronounced in larval stages developing in the open ocean. Oxygen consumption rate, total protein, dry mass, total lipids and C/N were determined in late-stage embryos, zoea I larvae and newly settled juveniles reared in ambient pH (7.93 ± 0.06) or low pH (7.58 ± 0.06). After short-term exposure to low pH, embryos displayed 11% and 6% lower metabolism and dry mass, respectively, which may have an associated bioenergetic cost of delayed development to hatching. However, metabolic responses appeared to vary among broods, suggesting significant parental effects among the offspring of six females, possibly a consequence of maternal state during egg deposition and genetic differences among broods. Larval and juvenile metabolism were not affected by acute exposure to elevated CO2. Larvae contained 7% less nitrogen and C/N was 6% higher in individuals reared at pH 7.58 for 6 days, representing a possible switch from lipid to protein metabolism under low pH; the metabolic switch appears to fully cover the energetic cost of responding to elevated CO2. Juvenile dry mass was unaffected after 33 days exposure to low pH seawater. Increased tolerance to low pH in zoea I larvae and juvenile stages may be a consequence of enhanced acid-base regulatory mechanisms, allowing greater compensation of extracellular pH changes and thus preventing decreases in metabolism after exposure to elevated PCO2. The observed variation in responses of P. cinctipes to decreased pH in the present study suggests the potential for this species to adapt to future declines in near-shore pH.
大气中二氧化碳浓度的升高导致表层海水 pH 值下降，这一过程被称为海洋酸化（OA）。迄今为止，很少有研究评估 OA 对潮间带生物早期生活史阶段的生理影响，这些生物从 pH 值波动的栖息地（潮间带）过渡到相对稳定的（浮游带）pH 值环境。我们使用潮间带螃蟹 Petrolisthes cinctipes 来确定代谢对 2300 年 OA 预测的反应是否因早期发育阶段而异，并检查这些影响在浮游幼虫阶段是否更为明显。在环境 pH 值（7.93 ± 0.06）或低 pH 值（7.58 ± 0.06）中饲养的晚期胚胎、Zoea I 幼虫和新定居的幼体中，测定了耗氧量、总蛋白、干质量、总脂和 C/N。在短期暴露于低 pH 值后，胚胎的代谢和干质量分别降低了 11%和 6%，这可能会导致孵化发育延迟的相关生物能量成本。然而，代谢反应似乎因幼虫而异，这表明在 6 只雌蟹的后代中存在显著的母代效应，这可能是由于产卵期间母代状态和幼虫之间的遗传差异所致。幼虫和幼体的代谢不受短期暴露于高 CO2 的影响。在 pH 值为 7.58 的条件下饲养 6 天的个体中，氮含量减少了 7%，C/N 增加了 6%，这可能代表在低 pH 值下从脂质到蛋白质代谢的可能转变；这种代谢转变似乎完全覆盖了对高 CO2 做出反应的能量成本。在低 pH 值海水中暴露 33 天后，幼体的干质量不受影响。Zoea I 幼虫和幼体对低 pH 值的耐受性增加可能是由于增强的酸碱调节机制所致，这允许对细胞外 pH 变化进行更大的补偿，从而防止在暴露于高 PCO2 后代谢降低。在本研究中，观察到 P. cinctipes 对 pH 值降低的反应存在差异，这表明该物种有可能适应近岸 pH 值下降。
