| In recent years, the intense blooms of blue-green algae increased badly in Chinese inland waters, brought lots of inconvenience to the residents around. Therefore, people pay more and more attentions in researching of predicting and controlling the blooms now. Research shows the blue-green algae blooms could be very sensitive to the change of meteorological factors. So study the link between meteorological factors and the blue-green algae should be very helpful. We use a set of MODIS images during2000and2009to calculate the FAI (Floating Algae Index), in order to figure out the time and spatial distribution of the blue-green algae blooms in Lake Taihu, Lake Chaohu, and Lake Dianchi. With the daily meteorological data, we want to find out impact of temperature, sunshine duration, annual rainfall, wind speed and direction to the algae blooms, in order to reveal the mechanism of it. Specifically, we analyze the daily average temperature and the proportion of the blue-green algae blooms, the difference of proportion of the blue-green algae blooms in two consecutive days and the annual rainfall in the first day, the difference between two images of algae blooms got in different time of one day and the average wind speed direction of the highest wind speed the same day, and eventually verify the relationship between these meteorological factors and the blue-green algae blooms is very close.Generally, we get some conclusions:a. The distribution of blue-green algae blooms in inland waters has a certain seasonal law. Generally, it barely happens in spring and winter, and can cover part of the lake during autumn, as in summer, it always covers part of the lake, sometimes grows to cover most part of the lake. Besides, the frequency and scale of the blooms become higher and lager in all three lakes since2005.b. Blue-green algae blooms in different lakes always obey their own rule to show or fade, but the rules are generally cycling in a year time. Take Lake Taihu for instance, the bloom in it always shows up in south part of the lake, and then grows toward the north part of the lake along the shore in clockwise. It can reach the middle of the Lake Taihu when the blue-green algae reach the maximum in quantity. After that, the bloom begin to go back along its own way in counter-clockwise, and finally become what it looked like one year ago. The same phenomenon shows in Lake Chaohu and Lake Dianchi also, the only difference is the blooms start from northwest Lake Chaohu and the north part of Lake Dianchi. Furthermore, the blooms grow in counter-clockwise along the shore in Lake Chaohu, but go directly through the middle of the Lake Dianchi. These differences are caused by different hydrological characteristics, inflowing rivers, and location of the pollution sources in different areas.c. The higher the daily average temperature (DAT), as well as the longer the daily duration of sunshine (DDS) is, the higher the frequency and level of the blue-green algae bloom is. And both of them improve the blooms by accumulating. In Lake Taihu, sum of daily average temperature of the7days before the bloom minus the daily average temperature the bloomy day has a correlation coefficient is higher than the coefficient in Lake Chaohu and Lake Dianchi. But the correlation coefficient between DDS and PB in Lake Taihu is very small, which means the effect of DDS is so much weaker than the effect of DAT in Lake Taihu. But in Lake Dianchi, if the DDS is longer than one day and two days before, the blooms will be more likely to show. Moreover, the greater the difference is, the more blue-green algae bloom will be. The more rainfall, the less bloom shows the day after the rainfall. The reduce of area of the blue-green algae bloom reaches as much as71.8%in Lake Taihu,50.8%in Lake Chaohu, and58.9%in Lake Dianchi. Also, wind has the bloom move with it, or stirs the water, brings changes to the area covered by the blooms. The changes of bloom areas reach as much as28.5%in Lake Taihu,23.6%in Lake Chaohu, and37.9%in Lake Dianchi. |
PDF Full Text Request