Department of Oceanography and Limnology, Federal University of Rio Grande do Norte, Via Costeira, Mãe Luiza, Natal, RN, 59014-002, Brazil.
Biodiversity Conservation Center, Environmental Research Institute, Av. Miguel Estéfano 3687, Água Funda, São Paulo, SP, 04301-902, Brazil.
Mar Environ Res. 2022 Jun;178:105662. doi: 10.1016/j.marenvres.2022.105662. Epub 2022 May 22.
Increased greenhouse gas concentrations in the Earth's atmosphere have resulted in global change, such as ocean warming and sea level rise. Increased salinity in estuaries is expected as a result of sea level rise and warming. Thus, we analysed the interactive effects of increased temperature and salinity on multiple physiological responses of Bostrychia montagnei and B. calliptera from two biogeographic provinces, Tropical Southwestern Atlantic (TSA) and Warm Temperate Southwestern Atlantic (WTSA). Macroalgae were cultured under three salinities (15, 25 and 35 PSU) and three temperatures: mean sea surface temperature (SST: 27 °C for TSA and 24 °C for WTSA), an RCP8.5 ocean warming scenario (SST + 5 °C), and a maximum temperature to test the algal upper thermal tolerance limits (RCP8.5 + 2 °C). Macroalgae from both localities decreased their growth under increased temperature and salinity. RCP8.5 + 2 °C was lethal for both macroalgae from TSA. RCP8.5 and RCP8.5 + 2 °C at 35 PSU were lethal for B. calliptera from WTSA, due to the interactive effects between increased temperature and salinity. Overall, increased salinity decreased the effective quantum yield and relative electron transport rate in algal photosynthesis. Our results demonstrated that the macroalgae synthesized proteins, carbohydrates (polysaccharides and low molecular weight carbohydrates), and antioxidants to tolerate detrimental temperatures and salinities. Our results also demonstrated that the macroalgae adjusted their pigment contents (phycobiliproteins, total carotenoids, and chlorophyll a) for efficient light-harvesting under thermal and saline stress. Our findings suggest that ocean warming and increased salinity in estuaries will be detrimental to B. montagnei and B. calliptera populations from both biogeographic provinces, especially to those from TSA that already live closer to their upper thermal tolerance limits.
地球大气中温室气体浓度的增加导致了全球变化，如海洋变暖以及海平面上升。海平面上升和变暖预计会导致河口盐度增加。因此，我们分析了温度和盐度升高对来自两个生物地理区（热带西南大西洋（TSA）和暖温西南大西洋（WTSA）的两种石莼科海藻（Bostrychia montagnei 和 B. calliptera）的多种生理反应的交互影响。将大型藻类在三种盐度（15、25 和 35 PSU）和三种温度下培养：海面平均温度（对于 TSA 为 27°C，对于 WTSA 为 24°C）、RCP8.5 海洋变暖情景（SST+5°C）和最大温度以测试藻类的上限热耐受极限（RCP8.5+2°C）。来自两个地区的大型藻类在温度和盐度升高的情况下生长减少。RCP8.5+2°C 对来自 TSA 的两种大型藻类均具有致死性。RCP8.5 和 RCP8.5+2°C 在 35 PSU 下对来自 WTSA 的 B. calliptera 具有致死性，这是由于温度和盐度升高的相互作用。总体而言，盐度升高降低了藻类光合作用的有效量子产率和相对电子传递率。我们的结果表明，大型藻类合成蛋白质、碳水化合物（多糖和低分子量碳水化合物）和抗氧化剂来耐受有害的温度和盐度。我们的结果还表明，大型藻类调整了它们的色素含量（藻胆蛋白、总类胡萝卜素和叶绿素 a）以在热胁迫和盐胁迫下进行有效的光捕获。我们的研究结果表明，海洋变暖以及河口盐度增加将对来自两个生物地理区的 B. montagnei 和 B. calliptera 种群造成不利影响，尤其是对那些已经接近其上限热耐受极限的来自 TSA 的种群。
