河口/近海区域低氧形成的物理机制研究进展

Advances in the Study on Physical Mechanism of Hypoxia Formation in Estuary and Coastal Sea

低氧/缺氧已成为严重威胁河口/近海与陆架浅海生态系统安全的要素之一。生物地球化学过程大量耗氧与水体分层限制表、底层水体交换是河口/近海低氧/缺氧问题的直接原因;而河口/近海和陆架海的各种物理过程控制了营养盐和有机质输运、水体层化,成为导致低氧/缺氧发生的根本原因之一。先讨论了近几年来国内外主要大河河口/近海和陆架浅海低氧现象发生的物理机制:径流冲淡水、潮汐、风、环流对低氧的影响,以及低氧对海-气大尺度变化和气候变化的响应等。再以长江口为例,重点分析了水动力过程对长江口夏季底层低氧的具体影响,同时对溶解氧统计模型和动力学模型的研究工作进行了阐述。最后对各种研究方法的优缺点进行总结,对长江口外海夏季底层低氧的研究工作进行了展望。

Hypoxia/anoxia is one of the most important factors that has exerted seriously affacting to the ecosystem safety in the estuary/coastal sea.The hypoxia in the estuary/coastal sea is considered to be directly related to the large amount of oxygen comsumption caused by biogeochemical processes and the restriction of surface-bottom water exchange due to water stratification,but the essential reason for leading to the formation of hypoxia/anoxia in the estuary,coastal and shelf seas is the controlling of various physical processes to the transportation of nutrents and organic matter and the water stratification envolpe.In the present paper,the studies published domestically and abroad in the last few years on physical mechanisms of the formation of hypoxia occurring in the estuaries of main large rivers and in the coastal and the shelf seas are summarized and discussed,which include the influences of diluted water from runoffs,tides,winds and circulations to the formation of hypoxia,the response of hypoxia to the large scale air-sea interactions and the climate changes,and so on.In addition,taking the estuary of the Changjiang River as an example,the influence of the hydrodynamic processes to the bottom hypoxia formed in the Changjiang River estuary in summer is analyzed in detail and the studies on the statistical and dynamical models for dissolved oxgen are synthesized simultaneously.And then,the advantages and limitations of different research methods are summarized and the future researches on the bottom hypoxia in the area out of the Changjiang River estuary are prospected.