Stazione Zoologica Anton Dohrn of Naples, Integrative Marine Ecology Department, Branch office 'Villa Dohrn', Punta S. Pietro, 80077 Ischia, Naples, Italy.
Department of Biology, University of Naples Federico II, Via Cinthia, 80126 Naples, Italy.
Sci Total Environ. 2020 Aug 20;731:138896. doi: 10.1016/j.scitotenv.2020.138896. Epub 2020 May 5.
The ocean acidification may severely affect macroalgal communities of the shallowest coastal habitats where they play relevant structural and functional roles. In this paper were investigated the physiological traits of two populations of Dictyota dichotoma var. intricata, living at two different pH for several generations to assess the reasons of the algae reduced abundance at current (8.1) compared to low pH (6.7). Besides, through transplant experiments, the two populations were analysed for the stress response and reversibility of physiological performance at different pH. The long-term acclimation to high pCO/low pH favours an ecotype characterised by low energetic costs, higher photochemical efficiency and more resistance to the oxidative stress, compared to individuals living at current pH. These traits promoted the growth and reproduction of the community living at pH 6.7, favouring a lower macroalgal diversity, but a higher ecological success under ocean acidification. The similar behaviour observed between Dictyota living at pH 6.7 and transplanted thalli from pH 6.7 to 8.1, suggested a high tolerance to pH changes in the short-term. On the contrary, adaptive responses may have favoured molecular adjustments on the long-term, as showed by the significant differences between the wild populations at pH 8.1 and 6.7. The overall data indicate that both plasticity and adaptive mechanisms may be the reasons for the success of the brown seaweeds under future high pCO/low pH. The plasticity due to photochemistry adjustments is likely involved in the early response to environmental changes. Conversely, modifications in the photosynthetic biochemical machinery suggest that more complex adaptive mechanisms occurred in the current population of Dictyota living at pH 6.7. Further studies on population genetics will reveal if any differentiation is taking place at the population level or a local adaptation has already occurred in Dictyota and other brown algae under chronic low pH.
海洋酸化可能会严重影响到最浅沿海栖息地的大型藻类群落，因为它们在这些栖息地中发挥着重要的结构和功能作用。在本文中，我们研究了两种生活在不同 pH 值下的长松萝（Dictyota dichotoma var. intricata）种群的生理特征，这些种群已经在当前（8.1）和较低 pH（6.7）条件下生活了多代，以评估藻类在当前条件下减少的原因。此外，通过移植实验，我们分析了这两个种群在不同 pH 值下的应激反应和生理性能的可逆性。与生活在当前 pH 值下的个体相比，长期适应高 pCO₂/低 pH 值有利于形成一种生态型，其特点是能量成本低、光化学效率高、对氧化应激的抵抗力强。这些特征促进了生活在 pH 6.7 条件下的群落的生长和繁殖，导致大型藻类的多样性较低，但在海洋酸化条件下具有更高的生态成功。在 pH 6.7 条件下生活的长松萝和从 pH 6.7 移植到 pH 8.1 的长松萝之间观察到的相似行为表明，它们在短期内对 pH 值变化具有较高的耐受性。相反，适应反应可能在长期内促进了分子调整，这表明生活在 pH 8.1 和 6.7 的野生种群之间存在显著差异。总的来说，这些数据表明，可塑性和适应性机制可能是棕色海藻在未来高 pCO₂/低 pH 值条件下成功的原因。由于光化学调整而产生的可塑性可能涉及对环境变化的早期反应。相反，光合生化机制的改变表明，在生活在 pH 6.7 的当前长松萝种群中发生了更复杂的适应性机制。进一步的种群遗传学研究将揭示是否在种群水平上发生了任何分化，或者长松萝和其他棕色海藻在慢性低 pH 值条件下是否已经发生了局部适应。
