Spatial and temporal distribution of diatoms in sediments of Lake Malawi, Central Africa, and ecological implications
Spatial and temporal distribution of diatoms in sediments of Lake Malawi, Central Africa, and ecological implications
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DOI：
10.1007/bf00197031
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发表时间：
1992
影响因子：
2.1
通讯作者：
R. Owen;R. Crossley
中科院分区：
文献类型：
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作者：
R. Owen;R. Crossley
马拉维湖位于中非的一个主要裂谷，深约700米，长约550公里。1984 ~ 1989年共采集了242个岩心和111个抓斗样品，为研究该湖盆硅藻分布提供了数据基础。沉积物包括均质的碳酸盐岩、浮游碳酸盐泥、纹状碳酸盐-泥偶、浊积岩、沿岸的砂席和广泛的铁锰结核沉积物。化石硅藻显示出湖的南部、中部和北方地区之间的主要时间和区域差异。南部湖泊沉积物中有多种Aulacoseiras种。在北部，Nkhotakota地区通常以Stephanodiscus和Aulacoseira为特征，偶尔有由Aulacoseira或Nitzschia组成的纹层。湖的中部显示出最大的变化，与Stephanodiscus，NitzeriaandAulacoseira都是突出的。北方以Aulacoseira nyassensis为主，硅磷比、硅浓度、湍流度和透光度控制着这些组合的变化。这些因素本身的影响，在湖混合的深度和持续时间的差异，由于风的强度，假潮和底部地形之间的不同区域的湖泊和从全湖的环流模式的变化。
Lake Malawi lies in a major rift valley in Central Africa that is some 700 m deep and 550 km long. A total of 242 cores and 111 grab samples were recovered between 1984 and 1989 and form the data base for a study of diatom distribution in this lake basin. The sediments consist of homogeneous diatomites, pelagic diatomaceous muds, varved diatomite-mud couplets, turbidites, littoral sand sheets and extensive deposits of ferro-manganous nodules.Fossil diatoms show major temporal and regional contrasts between the southern, central and northern areas of the lake. A wide variety ofAulacoseiraspecies occur in the southern lake sediments. To the north, the Nkhotakota region is generally characterised byStephanodiscusandAulacoseira, with occasional diatomite laminae composed ofAulacoseiraorNitzschia. The central parts of the lake show the greatest variation, withStephanodiscus, NitzschiaandAulacoseiraall being prominent. The northern region is dominated byAulacoseira nyassensisthroughout most core sequences.Variability in these assemblages appears to be controlled by Si:P ratios, Si concentrations, turbulence and light penetration. These factors themselves are influenced by differences in the depth and duration of lake mixing due to variations in wind strength, seiches and bottom topography among different regions of the lake and from lakewide circulation patterns.