2001 Strategic Environmental Assessment SEA2 Technical report - An overview of plankton ecology in the North Sea

This report is a contribution to the Department of Trade and Industry's (now Department of Energy and Climate Change) Strategic Environmental Assessment SEA2. It gives an overview of the phytoplankton and zooplankton community composition in the North Sea and how this has fluctuated through the latter half of the 20th Century in response to environmental change. The study is based on a unique long-term dataset of plankton abundance in the North Atlantic and the North Sea acquired by the Continuous Plankton Recorder (CPR). The dinoflagellate genus Ceratium dominates the phytoplankton community in the North Sea, but diatoms are also important, especially in the southern part. The normal annual blooms of plankton are discussed, as are harmful algal blooms (HABs), which appear to be on the increase, possibly due to a combination of climatic variability and eutrophication. Among the zooplankton, copepods are particularly important and constitute a major food resource for many commercial fish species, such as cod and herring. Calanus is the dominant copepod genus in the North Atlantic. Other important components of the plankton, meroplankton, picoplankton and megaplankton are also reviewed. Very small picoplankton (~1 micron in diameter) and much larger gelatinous members of the megaplankton (e.g. jellyfish and ctenophores) are poorly sampled by the CPR. Although the picoplankton represents a sizeable fraction of total primary production, its role in the marine ecosystem is poorly understood. The introduction of non-indigenous plankton in ship's ballast water has been in progress for about a century. There is growing concern about the risk of alien species, and the importance of protecting native biodiversity.

本报告为贸易与工业部（现能源与气候变化部）的战略环境评估（SEA2）项目贡献了一份重要成果。报告概述了北海浮游植物和浮游动物群落组成，及其在20世纪后半叶对环境变迁的响应变化。研究基于连续浮游生物记录仪（CPR）收集的独特长期数据集，对北大西洋和北海的浮游生物丰度进行了分析。在北海的浮游植物群落中，硅藻门的角藻属占主导地位，但硅藻类亦具有重要地位，尤其在南部地区。报告讨论了浮游植物的常规年度爆发，以及日益增多的有害藻华（HABs），其出现可能归因于气候变率和富营养化的综合影响。在浮游动物中，桡足类尤为重要，它们构成了许多商业鱼类物种，如鳕鱼和鲱鱼的主要食物来源。桡足类的角甲藻属在北大西洋中占主导地位。此外，还回顾了浮游生物的其他重要组成部分，如甲壳浮游生物、微型浮游生物和大型浮游生物。连续浮游生物记录仪对极小型的微型浮游生物（直径约1微米）和大型凝胶状的大型浮游生物（例如水母和栉水母）的采样不足。尽管微型浮游生物代表了总初级生产量的一大部分，但其海洋生态系统中的作用尚不明确。非本地浮游生物通过船舶压载水引入已有近一个世纪，对异种生物风险的担忧日益增加，保护本地生物多样性变得尤为重要。