Seasonal Variations of Dominant Phytoplankton, Chlorophyll a and Nutrient Levels in the Pelagic Regions of Lake Biwa
Seasonal Variations of Dominant Phytoplankton, Chlorophyll a and Nutrient Levels in the Pelagic Regions of Lake Biwa
复制标题
琵琶湖中上层主要浮游植物、叶绿素a及营养盐水平的季节变化
DOI：
10.3739/rikusui.45.26
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Y. Tezuka
中科院分区：
文献类型：
--
作者：
Y. Tezuka
为了阐明日本最大的单胞型湖泊-琵琶湖的营养现状，于1981年2月至12月对该湖北部（主）和南部（副）近海沃茨的优势浮游植物、叶绿素a和营养盐水平的季节变化进行了调查。在北部和南部盆地的Secchi盘透明度的年平均值分别为4.8和1.7米。两个流域冬季和早春以硅藻为主，其他季节以绿色藻类为主。除此之外，美洲弯尾藻和大孢鱼腥藻也在短时间内形成密集的水华。两个流域的表层水体中的叶绿素a浓度的两个高峰，一个在5月，另一个在10月。南北流域表层沃茨叶绿素a的年平均浓度分别为9.1和10.1 g El-1，而总磷的年平均浓度分别为9.2和16.7 g El-1。高浓度的硝酸盐和亚硝酸盐氮检测在两个流域除了三个月从8月到10月。结果表明，磷是一年中大部分时间浮游植物生长的最大限制性营养盐，但氮在8月至10月期间似乎也是限制性的。两个流域的营养化程度介于中营养和富营养之间的叶绿素a和总磷浓度。
In order to clarify the present trophic status of Lake Biwa, the largest, monomictic lake in Japan, seasonal variations of dominant phytoplankton, chlorophyll a and nutrient levels were surveyed for offshore waters of its north (main) and south (subsidiary) basins from February to December 1981. Annual means of Secchi disc transparency in the north and south basins were 4.8 and 1.7 m, respectively. In both basins, diatoms were most predominant in winter and early spring, and green algae in other seasons. Besides these algae, Uroglena americana and Anabaena macrospora formed dense blooms for short periods. Two peaks of chlorophyll a concentration in the surface water were observed in both basins, one in May and the other in October. Annual mean concentrations of chlorophyll a in the surface waters of the north and south basins were 9.1 and 10.1 g El-1, respectively, while those of total phosphorus were 9.2 and 16.7 g El-1, respectively. High concentrations of nitrate plus nitrite nitrogen were detected in both basins except for three months from August to October. It was concluded that phosphorus was the most limiting nutrient for phytoplankton growth for the most part of the year, but nitrogen seemed to be also limiting during August to October. Trophic degrees of both basins were intermediate between mesotrophic and eutrophic in terms of chlorophyll a and total phosphorus concentrations.