沿岸海域富营养化与赤潮发生的关系

综述了赤潮的发生与沿岸海域富营养化的关系。近几十年来,人类活动使得天然水体的富营养化进程大大加速。营养负荷的增加与高生物量水华的增多相联系。控制营养输入后,浮游植物生物量或有害藻类水华事件也相应减少。营养的组成与浮游植物的种类组成及水华的形成有密切联系。有机营养对有害藻类水华的促进作用受到关注。营养输入时机影响浮游植物种间竞争的结果,因而对浮游植物的群落演替具有深远影响。由于浮游植物存在生理差异,因而对营养加富的反应因种而异。营养在调控某些有毒藻类的毒素产量方面也发挥着重要作用。此外,营养输入与藻类水华之间存在复杂的间接联系。当然,营养状况并非浮游植物群落演替的唯一决定因素。研究结果提示,控制营养输入、减缓水域富营养化是减少有害藻类水华发生的有效途径,而深入研究典型有害藻类的营养生理对策则为防治并最终消除有害藻类水华提供了理论基础。

The relationships between the occurrences of red tides (HABs) and eutrophication in coastal waters

This paper summarizes the relationships between the occurrences of harmful algal blooms and the eutrophication in coastal waters. In recent years, eutrophication in coastal waters has increased rapidly because of human activities. The main sources of nutrients potentially stimulating algal blooms (HABs) include terrestrial runoff, aquaculture self-pollution and atmospheric deposition. Numerous evidences from all over the world reveal the linkage between the increases in nutrient loading and the occurrences of high biomass blooms. Lots researches suggest that nutrient composition could affect the species composition of phytoplankton as well as the development of some HABs. The changes in nutrient supply ratios, primarily N: P, often result in shifts in species composition. It has been further recognized that the organic nutrients could promote the growth of some HABs species, such as that dissolved organic nitrogen (DON) especially Urea played an important role in stimulating some HABs. Thus the nutrient ratios concept has been extended to include organic forms, and an elevation in the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC: DON) has been observed during several recent blooms in the Chesapeake Bay, US. Phytoplankton has the physiological capability of responding rapidly to nutrient pulses, so the timing of nutrient delivery may be of critical importance in determining the success of certain species. Furthermore, because the physiological response to nutrients enrichment could be species specific, the dominant species would represent the nutritional characteristics of the phytoplankton community. There are also some evidences suggest that nutrients can play a major role regulating the toxicity of some HAB species. In some cases, toxicity can vary dramatically with the concentration and composition of limiting nutrients. However, the occurrence of HABs are also related to other trophic levels in the aquatic ecosystem through top-down control, so nutrient itself state is not the determining factor for the succession of phytoplankton community. This paper suggests that the nutrient management could be an effective way to reduce the occurrences of HABs. However, understanding of the physiological response of HAB species to nutrients input is necessary for prevention and ultimate elimination of HAB incidents.