长江口及其邻近海域有害藻华的发生情况、危害效应与演变趋势

STATUS, IMPACTS AND LONG-TERM CHANGES OF HARMFUL ALGAL BLOOMS IN THE SEA AREA ADJACENT TO THE CHANGJIANG RIVER ESTUARY

长江口及其邻近海域是我国近海有害藻华高发区之一。自2000年以来,由东海原甲藻(Prorocentrum donghaiense)、米氏凯伦藻(Karenia mikimotoi)和亚历山大藻(Alexandrium spp.)等甲藻形成的大规模有害藻华连年暴发,对海水养殖业、人类健康和生态安全构成了严重威胁。以往调查和研究工作表明,长江口及其邻近海域藻华优势类群近年来已由硅藻逐渐转变为甲藻,同时,有害藻华原因种也表现出明显的年际变异特征和有毒有害藻种增多的态势,亟待解析其演变机理、趋势和驱动因素。长江口及其邻近海域受长江径流影响,富营养化问题突出,是大规模有害藻华形成的重要原因。同时,该海域也受到来自台湾东北部黑潮分支的影响,但对其与有害藻华的关系所知甚少。在中国科学院战略性先导科技专项"热带西太平洋海洋系统物质能量交换及其影响"支持下,针对这一问题开展了较为系统的调查和研究工作,本文对研究中得到的科学认识进行了初步总结。结果表明:东海黑潮分支能够到达长江口及其邻近海域赤潮区,影响该海域赤潮生物多样性状况;黑潮分支对长江口及其邻近海域甲藻赤潮发生过程具有重要调控作用;长江冲淡水和黑潮分支的共同作用决定了长江口及其邻近海域有害藻华的发生过程和演变趋势。在现有结果基础上进一步分析和讨论了未来长江口及其邻近海域有害藻华的研究方向,以期为进一步解析有害藻华演变趋势、提升有害藻华的监测和预警能力提供依据。

The sea area adjacent to the Changjiang（Yangtze） River estuary is the most notable region for harmful algal blooms in the coastal waters of China. Large-scale blooms of dinoflagellates Prorocentrum donghaiense, Karenia mikimotoi, and Alexandrium spp. started to occur from the year 2000, and posed significant threats to mariculture industry, the health of human beings, and marine ecosystems. Previous studies indicated significant changes of dominant blooming microalgae from diatoms to dinoflagellates, obvious inter-annual variations of blooming dinoflagellate species, and apparent increase of noxious or toxic species. However, the mechanisms, trend, and driving forces for the changes of harmful algal blooms yet need to be elucidated. The sea area adjacent to the Changjiang River estuary has a serious problem of eutrophication driven by excessive nutrients from the Changjiang River, which is the basis for the formation of large-scale dinoflagellate blooms. In addition, it is also affected by a branch of the Kuroshio from the sea area northeast to Taiwan Island, but the impacts on harmful algal blooms are poorly understood. Focusing on this issue, systematic investigations were organized in the East China Sea supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, and the primary findings of this project were summarized. It has been confirmed that the branch of Kuroshio could reach the ＂red-tide zone＂ in the sea area adjacent to the Changjiang River estuary, and affect the diversity of bloom-forming microalgae. The variation of the Kuroshio branch has a strong regulative effect on the dynamics of dinoflagellate blooms. The combined effects of the Changjiang River diluted water and the Kuroshio branch together determined the occurrence and long-term changes of harmful algal blooms in the sea area adjacent to the Changjiang River estuary. Based on these findings, the research perspectives were put forward to further resolve issues related to the prediction, early-warning, and long-term changes of harmful algal blooms in this region.