| Dianshan Lake is one of the main water sources in Shanghai, in the past10years, due to the rapid economic growth around Dianshan Lake, the eutrophication degree was intensified, which brought bad influences to the residents and the ecological environment, since1985, the algal blooms became normally,so the comprehensive eutrophication-treatment approaches should be explored. This paper based on the investigations of phytoplankton community space-time distribution of Dianshan Lake to evaluate the implementation of the ecological restoration project.this research also reveals the predominance of the "EU Water Framework Directive" and sum up the experience and deficiencies to provide induction forsubsequent research on ecological governance in Dianshan Lake.The main conclusions of this paper are as follows:1. In recent years, the species composition, quantity change, dominant species, diversity index, evenness, chlorophyll a content and other phytoplankton community characteristics of in Dianshan Lake show the Similarities with the historical records, but,the dominant species show both coincidence and succession. The main results are as follows:1in recent years, the species composition, quantity change, dominant species, diversity index, evenness, chlorophyll a content and other phytoplankton community characteristics of in Dianshan Lake show the Similarities with the historical records, but,the dominant species show both coincidence and succession.The main results are as follows:(1)A total of8phylum,339species of phytoplankton were identified (with varietas and metatype). The phytoplankton community was mainly composed of Chlorophyta. And, Bacillariophyta and Euglenophyta followed. The species composition of Galbana, Dinoflagellate, Xanthophyta and Cryptophyta are less, and their quantities are more stable.The dominated species were mainly Chlorella vulgaris, Ulothrix flaccidum,Ulothrix implexa,Chamydomonas.sp in Chlorophyta; Melosira ambiuga,Melosira varians,Cyclotella.sp,Synedra acus in Bacillariophyta; Microcystis.sp, Oscillatoria subtrillissima in Cyanophyta; Chroomonas acuta,Cryptomonas erosa,Cryptomonas ovate,Cryptomonas rostrata in Cryptophyta.Chroomonas acuta and Chlorella vulgariswere the dominated species during the investigation. The number of phytoplankton species shows a distribution rules:Northern Lake> Western Lake> Southwestern Yuan Dang Lake> Central Lake> Southern Lake> Eastern Lake.(2)During October2010to March2011,the phytoplankton density was on average10.06×106cells/L, varing between2.09×106～31.66×106cells/L,the minimum appears in October2010and the maximum appears in May2011. We can suggest from the phytoplankton density that during the investigation, Chlorophyta showed a declining trend in the proportion, the Bacillariophyta showed the growing trend in the proportion,the Cryptophyta showed relatively stable proportion, Cyanophyta showed fluctuating trends in the proportion, The proportion of Galbana, Dinoflagellate, Xanthophyta and Euglenophyta are less and stable.Spatial distribution showed the characteristics of Northern Laket> Eastern Laket> Southwestern Yuan Dang Lake> Central Lake Lake Central> Southern Lake> Eastern Lake.(3)During October2010to March2011, the chlorophyll-a content of phytoplankton was on average12.47mg/m3, varing between2.07-27.57mg/m3, showing an fluctuating tendency which have a similar tendency with the density. In space, the minimum appeared in the lake Yuandang which is located in the southwest of the lake Dianshan, the maximum appearsed in the lake5which located in the east of the lake Dianshan, Spatial distribution showed the characteristics of The North side of Eastern Lake> Northeastern Lake> South side of Eastern Lake> Central Lake> Southwest Lake. (4)During the investigation, from October2010to December2010,Lake Dianshan was at middle to high nutrition level, February2011to August2012was at middle to especially high nutrition level. In space, level, except for the north, northeast, southwest of the lake were at middle to high nutrition level, other areas had a higher nutrition level which were at middle to especially high nutrition level.2.Dianshan Lake eutrophication has increased year by year, Main causes of eutrophication of water body and lead to the proliferation of phytoplankton is nitrogen and phosphorus, the input channel is divided into endogenous pollution and exogenous pollution, the exogenous pollution occupies the main status.3.In order to solve the endogenous pollution and exogenous pollution problems, the relevant departments started the ecological restoration demonstration projects in Dianshan Lake Areas, which include the pre-reservoir projects, Phytoplankton-control project,the comprehensive ecological restoration demonstration project, etc. The comprehensive treatment measures have certain effects, but there is also some insufficient, for exemple,the cycle, the supplying for follow-up project, the interdisciplinary research, the imperfect river basin water environment management system, the eutrophication evaluation index system,etc, These problems are worth to be explorated.4.Combined with the experience of the EU Water Framework Directive", the eutrophication prevention measures of Dianshan Lake should include the following aspects: the baseline surveys, thef public participation platform, the digital regional water management decision support system, the strict punitive measures, regular maintenance of the facilities,the guidance of lake ecological restoration demonstration projects, the water quality tendency chart, expanding sources of funds, strengthen the controlling of the sources, the cross river basin comprehensive management system,etc. |
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