| Bohai Sea, the largest inland sea of China, is a semi-closed shelf marginal sea which has poor seawater exchange capacity and bad self-purification capacity. With the high-speed development of economy in the pan-Bohai Sea provinces, large amount of heavy metal pollutants were poured into the sea, and the environment of Bohai Sea has become more and more serious. Therefore, people have to face some problems: How serious the pollutant situation in Bohai Sea area is? If heavy metal pollutants have some effect on phytoplankton or not, and how serious the degree is? Aiming at this spotlight, an investigation at the scene of heavy metal in Bohai Sea was carried on, and a model as the effect of heavy metal on phytoplankton depending on nutrient factor in lab was created. At the same time, The rule of heavy metal pollutants' distribution and the effect of heavy metal on the growth of marine phytoplankton in Bohai Sea could be studied on. The main work and the results are shown as follows:1. After the large scale voyage surveys of Bohai Sea in August 2002 and August 2003, the average concentration and the complanate distribution of dissolved heavy metals of Pb, Cu, Cd, Hg, As, Zn were analyzed systematically. Combining with the concentration value in previous reports, we drew a conclusion of the status quo of heavy metals pollution in Bohai Sea. 1.1 In 2003, the average concentrations of 6 different dissolved metals arelower than in 2002, which coincided with the trend that reported by State Oceanic Administration in Coastwise Heavy Metal Investigation of Bohai Sea from 1998 to 2003. The main resource of this kind of pollution is terrestrial input, such as river runoff, industry wastewater, life wastewater, pesticide and fertilizer. With the serious concern over the environmental quality and corresponding treatments by the governments at provincial, municipal and local levels around Bohai Sea Area, such as "The Plan of Cleaning Bohai Sea" "The Project Of Renovating Bohai Sea", the contents of the heavy metals in the whole Bohai Sea Area have been steadily decreased and the situation of the heavy metal pollutions has been improved.1.2 According to the State Sea Water Quality Standard, when analyze the heavy metal concentration in coastline and sea area, we find that the pollution situation in sea area is not as serious as that in coastline; the typical heavy metal pollutants in Bohai Sea are Pb and Hg, while it is only in some partial spot that the concentration of Cu, Cd, Zn and As are overrun.1.3 In Bohai Sea, the horizontal distributions of Pb, Cu, Cd, Hg, As and Zn from 2002 to 2003 showed that the high concentration value areas were mainly found in 3 Bays(which influenced deeply by human activity), estuaries, west part of Central Sea Area (vicinity of Qinhuang Island) and northeast part of Central Sea Area (vicinity of Fuzhou Bay). Compared with the rule of these 3 layer distribution, we can find that: Normally, the high-value of heavy metal in appearance occurs in shore, especially in 3 Bays and estuaries; The high-value in middle layer occurs in Central Sea Area mainly, while the situation is quite complex in bottom distribution.2. During the lab simulation process, we studied on the effect of heavy metal on marine phytoplankton. By making use of phytoplanktongrowth-rate parameter, concentration dynamic formula, and the correlation formula between phytoplankton terminative biomass and heavy metal concentration dynamic formula, a marine phytoplankton growth model under the influence of nutrient factor is built up. Furthermore, the effect of heavy metals on phytoplankton in fluctuant nutrient environment is described.2.1 Using one-off cultivation experiment in lab, we carried on a study about the effect of Pb, Cu, Cd, Hg, Zn, Cr on 5 species of red-tide algae and 3 species of bait-algae. The results indicated: High concentration can holdback the growth of phytoplankton, while low concentration may play a stimulative role. On base of Logistic Curve, after importing heavy-metal-concentration item, a Heavy Metal-Phytoplankton Growth Model was built to describe the growth process of phytoplankton under the control of heavy metal. Thereinto, Lorentz formula can be used to describe the effect of heavy metal concentration fluctuation on phytoplankton growth rate parameter, while GaussAmp formula is suitable to describe the effect of fluctuation on phytoplankton terminative biomass.2.2 In different nutrient conditions, we worked on the effect of Pb, Cu, Cd, Hg, Zn, Cr on the growth of typical phytoplankton, Chaetoceros curvisetus and Skeletonema costatum. The results showed that: High concentration can obstruct the progress, while low concentration may play a stimulative role. The change of concentration also has a direct effect on the inhibition rate of heavy metal. On the base of Heavy Metal-Phytoplankton Growth Model, a nutrient salt impact factor was imported to build a model in changed nutrient environment. An accurate description can be made to describe the phytoplankton growth situation in condition of the existence of nutrients.3. In this report, on basis of the heavy metal pollution situation, a HeavyMetal-Phytoplankton Growth Model was applied to estimate the effect of heavy metals (Pb, Cu, Cd, Hg, Zn, Cr) on 2 typical phytoplankton, Chaetoceros curvisetus and Skeletonema costatum, in 2002 and 2003. The data indicated that Pb and Zn had a promotive effect on Chaetoceros curvisetus during this period. In 2002, Pb(24(ig-dm"3) owned a 5% promotive rate in Yingkou coastline (the highest concentration site in 2002). Additionally, in 3 different concentration, Cu, Hg, Cd had a negative effect on Chaetoceros curvisetus and Skeletonema costatum, and Pb, Zn could holdback the growth rate of Skeletonema costatum. In 2002, Cu (105ug-dm"3) restrained the growth of Skeletonema costatum at rate of 24%, while other kind of heavy metal didn't have a significant effect on these 2 species in 3 different concentration.
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