Abundance of phytoplankton, heterotrophic nanoflagellates and bacteria through the water column at time series station L4 in the Western English Channel. 2007-2011

The marine laboratories in Plymouth have sampled at two principle sites in the Western English Channel for over a century in open-shelf (station E1; 50° 02'N, 4° 22'W) and coastal (station L4; 50° 15'N, 4° 13'W) waters. These stations are seasonally stratified from late-April until September, and the variable biological response is regulated by subtle variations in temperature, light, nutrients and meteorology. Station L4 is characterized by summer nutrient depletion, although intense summer precipitation, increasing riverine input to the system, results in pulses of increased nitrate concentration and surface freshening. The winter nutrient concentrations at E1 are consistent with an open-shelf site. Both stations have a spring and autumn phytoplankton bloom; at station E1, the autumn bloom tends to dominate in terms of chlorophyll concentration. The last two decades have seen a warming of around 0.6°C per decade, and this is superimposed on several periods of warming and cooling over the past century. In general, over the Western English Channel domain, the end of the 20th century was around 0.5°C warmer than the first half of the century. The warming magnitude and trend is consistent with other stations across the north-west European Shelf and occurred during a period of reduced wind stress and increased levels of insolation (+20%); these are both correlated with the larger scale climatic forcing of the North Atlantic Oscillation.

普利茅斯的海洋实验室一个多世纪以来，一直在英吉利海峡西部的两个主要站位开展采样工作，站位分别位于开阔陆架海域（E1站；北纬50°02′，西经4°22′）与近岸海域（L4站；北纬50°15′，西经4°13′）。这两个站位自4月下旬至9月会出现季节性层化现象，其生物响应的动态变化受温度、光照、营养盐与气象条件的细微波动调控。L4站的典型特征为夏季营养盐耗尽，但夏季强降水与不断增加的河流输入会引发硝酸盐浓度脉冲式升高与表层海水淡化现象。E1站冬季的营养盐浓度符合开阔陆架站位的特征。两个站位均存在春季与秋季浮游植物藻华；其中E1站的秋季藻华在叶绿素浓度层面通常占据主导地位。近二十年来，该海域每十年升温约0.6℃，这一趋势叠加于过去一个世纪内多次冷暖波动之上。总体而言，英吉利海峡西部海域20世纪末的水温较该世纪前半叶高出约0.5℃。此次升温的幅度与趋势与西北欧陆架其他站位的观测结果一致，其发生时段伴随风应力减弱与日照辐射增加（增幅达20%）；这两项变化均与北大西洋涛动（North Atlantic Oscillation）的大尺度气候强迫效应相关。