THE PARTICULATE ORGANIC DETRITUS CONTENT IN LAKE DONGHU, WUHAN

On the basis of morphological characteristics in degradation of the dominant plankters and macrophytes in Lake Donghu, Wuhan, Hubei Province, the content of particulate organic detritus(POD) from three sempling stations, which represent three different regions, i.e., a bay region, a pelagic zone, and a zone of luxuriant aquatic vegetation in the Lake was quantified according to the method adopted by Davis(1958) throughout the year 1980. The bits of organic detritus were considered as various geometrical shapes, and their overall volumes are expressed in cubic deeimillimeters per liter(dmm3/l, 1 dmm3=106μ3). The data for January to December, 1980 are presented in Table 1. The average values of Station Ⅰ, Ⅱ, and Ⅲ were 72,505, 18,125, and 52,398, respectively. Apparently, the quantity of POD in Station I was the largest, and smaller in Station Ⅲ. In Station Ⅱ it was the least, but appeared to be more regularly corresponding with the seasonal growth pattern of the phytoplankters, i.e., less in spring and winter, and richer in summer and autmnn (Fig. 2—5).Comparing with the average value (7,818 dmm3/l) of the western Lake Erie Region in the 1950s, the content of POD from the water columns in these three stations in Lake Donghu nowadays is 9 times, 2 times, and 7 times, respectively. It is obvious that eutrophication in Lake Donghu proceeds at a higher speed than in Lake Erie.