我国近海藻华灾害现状、演变趋势与应对策略

Harmful Algal Blooms in the Coastal Waters of China: Current Situation, Long-term Changes and Prevention Strategies

有害藻华是近海常见的灾害性生态异常现象,不仅包括微藻形成的"赤潮"和"褐潮",也包括大型藻类形成的"绿潮"。在许多海域,有害藻华问题一旦出现,就会持续很长一段时间,对海水养殖、生态安全和人类健康构成威胁。在我国,有害藻华已成为一类突出的海洋生态灾害问题。渤海海域、长江口及其邻近海域和南海近岸海域是3个典型的赤潮高发区,大规模暴发的赤潮对海水养殖业造成了严重破坏,也威胁到海域生态安全和人类健康。近期在南黄海和渤海海域还出现了绿潮和褐潮等灾害性有害藻华现象,受到高度关注。综合分析我国近海的有害藻华问题可以看出,我国近海藻华原因种呈现出多样化、有害化和小型化的演变趋势,这给藻华的监测和管理带来了许多困难。为有效防控有害藻华,有必要加强针对有害藻华的基础研究,阐明藻华原因种的多样性状况、藻华发生与生态系统健康的关系、藻华的演变趋势及其驱动因子、藻华演变可能造成的生态效应等基础问题,同时,应进一步加强对藻华的观测预警和控制防范能力。

Harmful algal bloom （HAB） is an abnormal marine ecological phenomenon, which often associates with disastrous economic or ecological consequences. Typical HAB events include not only ＂red tides＂ or ＂brown tides＂ formed by microalgae, but also ＂green tides formed by some macroalgal species. Once HABs appear in some regions, they would last for a long time and lead to severe impacts on mariculture industry, marine ecosystems, even the health of human-beings. In China, HABs are among the most serious marine ecological problems. Red tides, brown tides, and green tides have been all reported in the coastal waters of China. The Bohai Sea, the Changjiang River estuary and its adjacent waters, and the coastal waters along the South China Sea are identified as three most notable regions for the occurrence of red tides. In the Bohai Sea, large-scale red tides of Gymnodinium sp., Ceratiumfurca and Phaeocystis sp., as well as the recently identified brown tides ofAureococcus anophagefferens, led to severe impacts on the mariculture industry and huge economic loss. Toxic algal blooms of Dinophysis spp. and Alexandrium spp. were also reported. In the Changjiang River estuary and its adjacent waters, large-scale blooms formed by dinoflagellates Prorocentrum donghaiense, Karenia mikimotoi and Alexandrium spp. started to appear from the beginning of the 21 century and also led to tremendous impacts. A single bloom event ofK. mikimotoi along the coast of Fujian Province in 2012 led to economic loss around 2 billion RMB. In the coastal waters of the South China Sea, the intensive blooms of Phaeocystis not only damaged the mariculture industry, but also posed potent threats on the operation of cooling systems of power plant. For the HABs recorded in China, it was also noticed that the bloom-forming species are getting more and more diversified over the last two decades. Besides the microalgal blooms formed by diatoms, dinoflagellates, haptophytes, cyanobacteria, cryptophytes, raphidophytes, and pelagophytes, blooms of macroalgae also occurred widely along the coast of China. More importantly, there are more and more blooms formed by toxic microalgal species, such as Alexandrium spp. and Dinophysis spp. Phycotoxins, such as paralytic shellfish toxins and diarrhetic shellfish toxins, are often detected from phytoplankton and shellfish samples. Besides, the cell size of bloom-forming species are getting smaller. Cell size of some bloom-forming species, such as Phaeocystis spp. and A. anophageffererns, is only about several micrometers, which make it difficult to carry out the routine monitoring based on traditional morphological approaches. The increasing severity of HABs in the coastal waters of China has a close relationship with the intensified eutrophication, especially in the estuaries and bays. Besides, the alteration of natural habitat by mariculture industry and other anthropogenic activities also contributes to the occurrence of some HAB events, such as the green tides in the southern Yellow Sea. Other factors like climate change also influence the distribution, dynamics, and impacts of HABs in the coastal waters of China directly or indirectly, through the effects on water temperature, stratification, and currents, However, such effects are still poorly understood compared to those of land-based anthropogenic activities. Base on the analysis of current situation and long-term changes of HABs in China, it is proposed to further strengthen the basic researches on HABs to answer some important questions, such as the diversity of bloom-forming species, the relationship between HABs and health of marine ecosystems, the trend of long-term changes of HABs and the major driving forces, and the economic and ecological consequences of HABs in the future. Meanwhile, observation system on HABs should be enhanced to improve the capabilities on prediction and early-warning of HABs, using both remote sensing and in situ real-time observation instruments based on molecular biological and morphological approaches. The techniques of modified clay have been successfully applied to control some HAB events in China, however, measures on controlling eutrophication and land-based pollution are still needed to prevent the HABs in the long run.