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首页> 外文期刊>Estuarine Coastal and Shelf Science >Long-term decline of the canopy-forming algae Gelidium corneum, associated to extreme wave events and reduced sunlight hours, in the southeastern Bay of Biscay
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Long-term decline of the canopy-forming algae Gelidium corneum, associated to extreme wave events and reduced sunlight hours, in the southeastern Bay of Biscay

机译：在比斯开湾东南部，与极端海浪事件和日照时间减少有关的冠层藻类角质层的长期下降

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Canopy-forming macroalgae are experiencing large biogeographical shifts due to climate change. One of them (Gelidium corneum) has shown a dramatic decline in biomass in northern Spain, in the past 20 years. We investigate here two most plausible hypotheses to explain its decline: (i) a combination of increasing wave energy and decrease of irradiance in the growth season; and (ii) a combination of increasing light in summer and decreasing nutrient concentration. Using a dataset of biomass and environmental variables (1993-2016), in three sectors and three water depths, we have determined that the variables explaining more biomass variability were: suspended solids, nitrate, sunlight hours, significant wave height threshold exceedances (Hs5m), temperature, silicate, and nitrite. When undertaking multiple regression analyses for the whole depth range, only the model including sunlight hours with Hs5m was selected, being highly significant (p 0.0001) and explaining 37% of the variability. When comparing the macroalgal biomass between the initial period of the series (where the biomass was stable) and final period (showing biomass decline), 45% decrease was observed while the Hs5m increase was 41%, detaching the algae from the substratum during the growth season. The decline rate in biomass with time, at each sector and depth, was highly correlated (p 0.001) to the wave energy flux received at each depth, which was higher at 5 m in all sectors, decreasing with depth. In turn, nutrients, instead of decreasing, have increased, and only nitrate presented a significant negative correlation with G. corneum biomass, which was not significant after detrending. The significant (p = 0.001) increase in rainfall over the studied period can explain the increase of those nutrients. Hence, we question whether the effect of nutrients is such, as already described. The most likely factor explaining the decline of this macroalga was the combination of sunlight hours decrease and Hs5m increase. (C) 2018 Elsevier Ltd. All rights reserved.
机译：由于气候变化，形成冠层的大型藻类正在经历较大的生物地理变化。其中之一（角质层）在过去20年中显示了西班牙北部生物量的急剧下降。我们在这里研究两个最合理的假设以解释其下降：（i）波能增加和生长季节辐照度降低的结合； （ii）夏季增加光照并减少养分浓度。使用生物量和环境变量（1993-2016年）的数据集，在三个部门和三个水深中，我们确定了解释更多生物量变异性的变量是：悬浮固体，硝酸盐，日照时间，显着的波高阈值超标（Hs5m） ，温度，硅酸盐和亚硝酸盐。在对整个深度范围进行多元回归分析时，仅选择了模型，其中包括Hs5m的日照小时数，具有很高的显着性（p <0.0001），并解释了37％的变异性。比较系列初始阶段（生物量稳定）和最终阶段（生物量下降）之间的大型藻类生物量时，观察到减少了45％，而Hs5m的增加为41％，使藻类在生长过程中脱离了基质季节。在每个扇区和深度处，生物量随时间的下降率与在每个深度处接收到的波能通量高度相关（p <0.001），在所有扇区中，波能通量均较高，在5 m处，随深度而减小。反过来，养分却没有减少，反而增加了，只有硝酸盐与角质层生物量呈显着负相关，而去趋势后则无显着性。在研究期间，降雨的显着增加（p = 0.001）可以解释这些营养素的增加。因此，我们已经质疑营养素的作用是否如此。解释这种大型藻类减少的最可能因素是日照时间减少和Hs5m增加的综合作用。 （C）2018 Elsevier Ltd.保留所有权利。

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