最近的媒体报道将北海描述为一个濒临崩溃的生态系统。幼年鳕鱼的存量达到20年来的最低点，很多海鸟遭遇到有记录以来的最坏的繁殖季节。关于浮游生物种群及其生命周期事件所发生的时间的研究，可用作气候变化的一种指标。这种方法 1958-2002年间曾被用于一项关于北海中66个浮游生物类别的研究，结果显示，海洋食物链的根部发生了很大变化，可能是由全球变暖引起的。浮游植物和其他海洋生命形式的生产力增长在时间上的不一致，可能是导致鱼类、海洋哺乳动物和海鸟种群数量下降的一个因素。
Impact of climate change on marine pelagic phenology and trophic mismatch
Phenology, the study of annually recurring life cycle events such as the timing of migrations and flowering, can provide particularly sensitive indicators of climate change1. Changes in phenology may be important to ecosystem function because the level of response to climate change may vary across functional groups and multiple trophic levels. The decoupling of phenological relationships will have important ramifications for trophic interactions, altering food-web structures and leading to eventual ecosystem-level changes. Temperate marine environments may be particularly vulnerable to these changes because the recruitment success of higher trophic levels is highly dependent on synchronization with pulsed planktonic production2, 3. Using long-term data of 66 plankton taxa during the period from 1958 to 2002, we investigated whether climate warming signals4 are emergent across all trophic levels and functional groups within an ecological community. Here we show that not only is the marine pelagic community responding to climate changes, but also that the level of response differs throughout the community and the seasonal cycle, leading to a mismatch between trophic levels and functional groups.
Figure 1 Changes in phenology throughout the pelagic season. a, Examples of seasonal cycles for two of the 66 taxa—the dinoflagellate Ceratium fusus and the diatom Cylindrotheca closterium—used in the analysis for the periods 1958–1980 and 1981–2002. The timing of the seasonal peaks, using the indicator of central tendency, is also shown. b, Inter-annual variability of the seasonal peak for the above two species from 1958 to 2002. c, The change in the timing of the seasonal peaks (in months) for the 66 taxa over the 45-yr period from 1958 to 2002 plotted against the timing of their seasonal peak in 1958. For each taxon, the linear regression in b was used to estimate the difference between the seasonal peak in 1958 and 2002. A negative difference between 1958 and 2002 indicates seasonal cycles are becoming earlier. Standard linear regression was considered appropriate because there was minimal autocorrelation (determined by the Durbin–Watson statistic) in the phenology time series.
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Figure 2 The relationship between the interannual variation in the timing of the seasonal cycle for various functional groups during the summer stratified period and SST. Note the high correlations for dinoflagellates and meroplankton. The time series of the timing of the seasonal cycle for each functional group was represented by principal component analysis of all constituent taxa. Negative standard deviations represent earlier seasonal cycles.
