Department of Biological and Environmental Sciences, University of Gothenburg, Fiskebäckskil 45178, Sweden; Department of Biological Sciences, Eduardo Mondlane University, Maputo CP257, Mozambique.
Department of Biological and Environmental Sciences, University of Gothenburg, Fiskebäckskil 45178, Sweden; IAEA Marine Environment Laboratories, Radioecology Laboratory, 4 Quai Antoine 1er, 98000, Monaco.
Sci Total Environ. 2024 Jul 20;935:173383. doi: 10.1016/j.scitotenv.2024.173383. Epub 2024 May 21.
A large body of evidence is documenting the impact of reduced pH on marine species and ecosystems. This information is used to infer the present and future impacts of ocean acidification. However, a vast majority of the studies were performed using constant pH and the high level of pH variability experienced by marine organisms on the coastal zone was often overlooked. Recent studies highlight the key role of this variability in driving biological response to pH as well as species sensitivity to ocean acidification. For example, it was hypothesized that because of local adaptation, the extreme of the present range of pH variability is a good predictor for local biological thresholds. Using a complex experimental design, we investigated what part of the pH variability is driving the biological response of the sea urchin Echinus esculentus larvae. Comparing stable (pH 8.13, 7.82, 7.53) and fluctuating treatments (12 h at pH 8.13 and 12 h at pH 7.53) following natural or inverted diurnal cycles, we were able to show that (i) under constant conditions, low pH deviating from the present range of natural variability had a negative effect on larval growth rate and calcification; (ii) under fluctuating conditions, a desynchronization of the pH variation with the photoperiod led to decreased larval growth rate and calcification; (iii) overall, larval fitness (survival, growth and calcification) was higher under fluctuating conditions as compared to constant. While these data do not support the hypothesis that the minimum pH is the main driver of the biological response, they provide evidence of adaptation to variability in a coastal species with associated a cost of plasticity but not a cost of canalization.
大量证据记录了 pH 值降低对海洋物种和生态系统的影响。这些信息被用来推断海洋酸化的当前和未来影响。然而，绝大多数研究都是在使用恒定 pH 值的情况下进行的，而海洋生物在沿海地区经历的高 pH 值变化水平往往被忽视。最近的研究强调了这种变异性在驱动生物对 pH 的反应以及物种对海洋酸化的敏感性方面的关键作用。例如，有人假设，由于局部适应，目前 pH 值变化范围的极端值是预测当地生物阈值的良好指标。本研究采用复杂的实验设计，调查了 pH 值变化的哪些部分驱动了海胆 Echinus esculentus 幼虫的生物学反应。通过比较稳定（pH 8.13、7.82、7.53）和波动处理（12 小时 pH 8.13 和 12 小时 pH 7.53），遵循自然或颠倒的昼夜节律，我们能够表明：（i）在恒定条件下，偏离当前自然变化范围的低 pH 值对幼虫生长率和钙化有负面影响；（ii）在波动条件下，pH 值变化与光周期不同步会导致幼虫生长率和钙化率降低；（iii）总体而言，与恒定条件相比，波动条件下幼虫的适应性（存活率、生长和钙化）更高。虽然这些数据不支持最小 pH 值是生物反应主要驱动因素的假设，但它们提供了证据证明了沿海物种对变异性的适应，同时存在可塑性成本但没有形态发生成本。
