| Summary: | Many of the difficulties associated with establishing generalisations for marine ecosystem function arise because such systems are large, complicated and poorly studied in comparison with their terrestrial counterparts. Nevertheless, the increasing prominence of meta-analyses, combined with the development and consolidation of large biological and environmental databases is starting alter this perspective. By seeking signals that predictably arise from biological time series in response to hypothesised ecological mechanisms, inferences can be made regarding corresponding ecological processes. If these signals are consistently present in separate areas covering gradients in biological and environmental characteristics, generalisations may be proposed. Recent ground-breaking work along these lines focused on the northeast Atlantic because this is one of the few regions for which appropriate data are available. Using the Continuous Plankton Recorder Survey database, the holoplanktonic community was divided into three functional groups (phytoplankton, herbivorous copepods and carnivorous zooplankton), each corresponding to a trophic level in a linear conceptual foodweb. Although taxonomic, temporal and spatial resolutions were coarse, and only part of the pelagic community was studied, the analysis nevertheless demonstrated that changing sea surface temperatures had predictable impacts on phytoplankton abundance and that these propagated up the planktonic foodweb by bottom-up forcing. Here we report on the challenges and advances associated with taking the next step along this analytical path: we extend the conceptual foodweb to include planktonic and piscivorous fish. In so doing, we introduce the possibility of assessing the impact on marine pelagic communities of a second major external forcing factor, namely commercial fishing.
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