Under current levels of global warming most demersal species in the Northeast Atlantic are experiencing tropicalization, meridionalization or borealization of their distributions, leading to profound changes in demersal communities. We explore these changes using the Community Weighted Mean Temperature (CWMT), an index to link the thermal preference of demersal fish communities and temperature. The CWMT is calculated as the summation of the mean temperature of each fish species distribution weighted by its relative abundance in the community. The relative abundance is based on the community composition data obtained by the International Bottom Trawl Surveys (IBTS) in the Southern Bay of Biscay between 1983 and 2015. Our analyses show that the CWMT responds to the actual temperature of the water column reproducing its space–time trends in the study area: (i) an increase from SW to NE, towards the inner Bay of Biscay, (ii) a decrease with depth, except in the SW area characterized by an intense upwelling, (iii) a general increase along the time series. Applying a k-means classification to the CWMT data we identified warm-, temperate- and cold-communities over the shelf and slope and their spatial changes in the last decades. The area occupied by warm communities has expanded 268.4 km²/yr since the 80 s, while the cold communities have retracted at a speed of −155.4 km²/yr. The CWMT was able to capture the community dynamics in relation to environmental temperature at different temporal and spatial scales, highlighting the potential of this index to explore and anticipate the effects of climate change in demersal communities under different scenarios of global warming.

在目前的全球变暖水平下，东北大西洋的大多数海底物种正在经历其分布的热带化，子午化或寒带化，从而导致了海底群落的深刻变化。我们使用社区加权平均温度（CWMT）探索这些变化，CWMT是将沉鱼鱼类群落的热偏好与温度联系起来的指数。CWMT计算为每种鱼类分布平均温度的总和，以其在社区中的相对丰度加权。相对丰度是根据1983年至2015年南比斯开湾国际海底拖网调查（IBTS）获得的群落组成数据得出的。我们的分析表明，CWMT对水柱的实际温度做出了响应，从而再现了研究区域的时空趋势：（i）从西南向NE向比斯开湾内湾增加，（ii）随着深度的增加而减少，但在西南部地区以剧烈上升为特征，（iii）沿时间序列总体增加。通过对CWMT数据进行k均值分类，我们确定了架子和斜坡上的暖，温带和冷社区及其在过去几十年中的空间变化。温暖社区所占面积扩大了268.4公里 近几十年来，陆架和斜坡上的温带和冷带群落及其空间变化。温暖社区所占面积扩大了268.4公里 近几十年来，陆架和斜坡上的温带和冷带群落及其空间变化。温暖社区所占面积扩大了268.4公里自80年代以来为² / yr，而寒冷社区以-155.4 km ² / yr的速度退缩。CWMT能够在不同的时空尺度上捕捉与环境温度相关的群落动态，突显了该指数在探索和预测气候变化对全球变暖不同情景下的沉没社区的影响方面的潜力。