Nutrients of Lake Biwa in the unusually cool and hot summers of 1993 and 1994
Nutrients of Lake Biwa in the unusually cool and hot summers of 1993 and 1994
复制标题
1993年和1994年异常凉爽和炎热的夏季琵琶湖的营养物
DOI：
10.1111/j.1440-1770.1996.tb00050.x
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
H. Hasegawa
中科院分区：
文献类型：
--
作者：
Y. Sohrin;T. Tateishi;S. Mito;M. Matsui;H. Maeda;A. Hattori;M. Kawashima;H. Hasegawa
在日本，1993年是一个异常凉爽多雨的夏天，1994年是一个异常炎热干燥的夏天。在这两年里，我们对琵琶湖水域的化学物种进行了调查。样本从中营养化的北部盆地Omimaiko附近和富营养化的南部盆地的疏浚区域垂直采集，另外三个站点也每隔大约一个月采集地表水样本。我们还研究了在南部盆地东南岸大津采集的降水中的化学物种，以及从南部盆地采集的沉积岩芯。湖水的性质很大程度上取决于夏季的气候。1993年，丰沛的降雨和微弱的热力层结支持了表层营养物质的高密度。1994年，盆地北部表层营养物质枯竭，出现了高透明度和低浓度的叶绿素a。这是因为降雨少，温跃层发达，养分供应有限。然而，南部盆地直到8月下旬才出现大量溶解活性磷(DRP)。1994年，由于水温高(30°C)和水位下降，大量大型藻类在南部盆地生长和退化，局部缺氧条件得到广泛发展。据推测，DRP是从缺氧沉积物中还原的锰铁氧化物中解吸出来的，DRP进入了湖水。虽然近二十年来，湖水中磷的浓度并没有显著增加，但沉积物中不断累积的磷对湖水的水质有很大的影响。
In Japan, there was an unusually cool and rainy summer in 1993, and an unusually hot and dry summer in 1994. We investigated chemical species in the waters of Lake Biwa during these two years. Samples were collected vertically from stations off Omimaiko in the mesotrophic northern basin and at a dredged area in the eutrophic southern basin, and surface water samples were also collected from three other stations at about one month intervals. We also studied chemical species in precipitation collected at Otsu, on the southeast shore of the southern basin, and sediment cores collected from the southern basin. The features of the lake water were very dependent on the summer climate. In 1993, abundant rain and weak thermal stratification supported high nutrient concentrations in the epilimnion. In 1994, nutrients were depleted and a high transparency and low concentration of chlorophyll a were observed in the epilimnion of the northern basin. This is because the supply of nutrients was limited owing to little rain and a well-developed thermocline. However, a great deal of dissolved reactive phosphorus (DRP) occurred until late August in the southern basin. Local anoxic conditions were extensively developed in 1994, since a large amount of macroalgae grew and regressed in the southern basin owing to a high water temperature (30°C) and decline in the water-level. Presumably DRP was desorbed from ferromanganese oxides that were reduced in the anoxic sediments and the DRP found its way into the lake water. Although it has been reported that the concentration of phosphorus in the lake water had not significantly increased in the last two decades, phosphorus which had steadily accumulated in the sediments had a crucial effect on the quality of the lake water.