Limnological annual cycle inferred from physical-chemical fluctuations at three stations of Lake Tanganyika
Limnological annual cycle inferred from physical-chemical fluctuations at three stations of Lake Tanganyika
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DOI：
10.1023/a:1003762119873
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发表时间：
1999-07-01
期刊：
影响因子：
2.6
通讯作者：
Coenen, E
中科院分区：
文献类型：
--
作者：
Plisnier, PD;Chitamwebwa, D;Coenen, E
在一年(1993-1994年)期间，在坦噶尼喀湖(东非)的三个地点每月至少测量两次10个变量。在5月至9月的干燥多风季节，在湖的南部观察到了上升流。层结的强度是不同的，但总是出现在北部。枯水期湖底明显倾斜(南部为0-20m，北部为60-70m)。在这段期间之后，当来自东南风的强风停止时，水团向平衡方向振荡。电导率和pH的波动表明振荡减弱，特别是在湖的末端。尾流向产生和/或再增强内波的平衡位置移动。这些波浪是从湖泊的化学和物理特征的波动中推断出来的。沉积物中无机磷和无机氮的浓度波动一般在3倍以上。长周期内波周期估计为28-33天。浊度的变化表明，脉搏产生是由内波引起的，内波与营养物质和生物体中的非随机斑块有关。由高动态物理事件引起的湍流也会导致水组成中的随机斑块。湖水一般在表层附近表现为贫营养特征，但在深水中营养物质浓度较高。结果表明，坦噶尼喀湖的营养状态，就像海洋一样，似乎在很大程度上取决于再生过程。坦噶尼喀湖的年度湖水循环似乎与气候条件密切相关。
Ten variables were measured at least twice per month at three locations of Lake Tanganyika (East Africa) over one year (1993-94). Upwelling was observed in the south of the lake during the dry, windy season from May to September. Stratification was variable in strength but always present in the north. The lake showed a marked tilting of the epilimnion during the dry season (0-20 m in the South, 60-70 m in the North). This period was followed by oscillations of water masses towards an equilibrium when the strong winds from the south east ceased. Conductivity and pH fluctuations indicated dampened oscillations, particularly at the ends of the lake. Movements of the epilimnion toward an equilibrium position generated and/or re-inforced internal waves. These waves were inferred from fluctuations of chemical and physical characteristics of the lake. The concentrations of inorganic P and N commonly fluctuated by a factor of 3 or more in the epilimnion. The period of long-period internal waves was estimated to be ca. 28-33 days. Turbidity changes suggested pulse production caused by internal waves linked to non-random patchiness in nutrients and organisms. Turbulence resulting from highly dynamic physical events also induce random-patchiness in water composition. The lake water generally showed oligotrophic characteristics near the surface but had high concentrations of nutrients in deep water. The results showed that the trophic state of Lake Tanganyika, like that of the oceans, seems to depend largely on regeneration processes. The annual limnological cycle in Lake Tanganyika appears closely linked to the climatic conditions.