Phytoplankton Groups and Eutrophication Status in the Southeastern Liaodong Bay
|School||First Institute of Oceanography of State Oceanic Administration|
|Keywords||harmful algal bloom phytoplankton nutrition NQI index eutrophication|
Phytoplankton is the elementary producers of the ocean, its kind’s composition and change of quantity are restricting the development of marine productivity directly or indirectly, thus play an important instruction role in the development and utilization of the marine living resources. The kind of the marine phytoplankton and cell quantity can be regarded as the rich or poor index of aquatic resources of sea area, and because different kinds have different biological characteristics, is often used for as the index of some environmental factors. Eutrophication is the unusual phenomenon of ecology appearing in the ocean, as a material factor which initiates the harmful algal bloom. Eutrophication is an unusual phenomenon, and the frequency of harmful algal bloom on marine biological resources, such as the enormous harm; timely prediction and discovery of water eutrophication, the protection of the marine ecological balance, and prevention of disasters such as harmful algal bloom , avoid loss of fisheries is significant.This text based on the survey data of many ecological factors on the four cruises of April、Julys September、December of 2006 in the waters of hongyan river, southeast of the Liaodong Bay. Physical and chemical environments, the species composition of phytoplankton, cell abundance are all discussed and analysised. The results are as followed:The temperature difference, seasonal changes of the temperature of the research waters are dominant. But the vertical changes of the temperature are not dominant. The average salinity is 31.3—31.9.The fluctuation of the salinity is small during the spring-neep tide and the seasonal change. At the same time the salinity of the surface layer is almost the same as the bottom layer. The suspension of the bottom layer is more than the surface layer. The mean-value and variable-amplitude of the suspension is the biggest in spring. The water transparency is lower in spring and autumn, high in summer.The exchange of PH in the research waters is dominant: the mean-value of spring, summer, autumn is 7.95、8.21 and 8.13. The variable-amplitude is smaller than 0.2. The exchange of DO is dominant: the DO in spring is higher than in summer and autumn. The exchange of DO is also showed in the spring-neep tide, but the difference of surface and bottom layer is not obvious. The horizontal distribution of DO in the open sea is higher than in the seashore in spring, but the situation is just contrary in the summer and autumn. The exchange of COD is also dominant: the horizontal distribution of COD in the research waters is higher in the seashore. The distribution of COD in summer is complex: the seashore is higher and there are higher and lower distribution in the open sea. In autumn the COD is higher in the south of Donggang Town.DIN mainly comes from NO3-N. The exchange of it is dominant: the highest is spring, then winter, autumn, and summer in turn. There is only a little difference in the surface and bottom layer and in the spring-neep tide. The horizontal distribution is higher in the seashore of the Donggang Town and in the outer of Fuzhou Bay. PO4-P is lower. The seasonal changes is dominant. The situation of PO4-P is almost the same as the situation of the DIN.The seasonal exchange of chl-a in the research sea is remarkable. The change of chl-a is highest in spring, then summer, autumn, and winter in turn. The chl-a value of the seashore near the Donggang Town is high.It is estimated that the primary productivity of research sea is highest in summer,then autumn, spring in turn. The primary productivity of the sea near Donggang Town is usually high.The dominate species of phytoplankton is diatoms. There are seasonal variations. But the dominate species is similar in autumn and in winter. The dominate species of the water sample near Donggang Town is diatoms, but the dominate species in summer is also including dinoflagellates. There are seasonal variation of the dominate species. But notiluca scienllans and ceratium tripos are dominate spicy in spring and summer.The quantity of net-phytoplankton change is obvious during the seasonal exchange. The exchange is highest in spring, then autumn, spring, and winter in turn. There is a big difference in the spring-neep tide. The horizontal distribution of net-phytoplankton quantity is higher in the seashore near Donggang Town. But the quatity is low near Wentuozi Island in winter. The average biodiversity index in spring, summer, autumn, and winter is 1.59、1.11、1.94、1.82 in turn. The quatity variation of phytoplankton of water sample is dominant during the seasonal variation. The variation of spring is highest, then summer, autumn and winter in turn. The quatity of phytoplankton is increasing from north to south. The biodiversity index of spring, summer, autumn and winter is 0.44、2.69、1.99、2.11 in turn.Harmful algal bloom is not found during the investigation period, but 27 species of harmful algal bloom organisms are found. Harmful algal bloom organisms exist during the year. There are more harmful algal bloom organisms’ species in spring, summer and autumn. Harmful algal bloom organisms of athecate dinoflagellates and diatoms are found in the water sample near Donggang Town in spring and summer. Noctiluca sinicus is the main harmful algal bloom organisms in summer and autumn. Otherwise, some dominate species of the phytoplankton in the research sea are not harmful algal bloom organisms in this area but the harmful algal bloom organisms of other sea areas.According to the above data, the trophic state of the study sea is "meso to oligo -trophic waters with local area eutrophicated", assessed with the Nutritional Quality Index (NQI). The result is similar to the result that the study area is a "potential problem area, with risk of eutrophication", given by assessment with the EU "Comprehensive Evaluation Process of Eutrophication" (OSPAR-COMPP)".