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首页> 外文期刊>Journal of Paleolimnology >Biomarker evidence of macrophyte and plankton community changes in Zeekoevlei, a shallow lake in South Africa
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Biomarker evidence of macrophyte and plankton community changes in Zeekoevlei, a shallow lake in South Africa

机译：南非浅湖Zeekoevlei中大型植物和浮游生物群落变化的生物标志物证据

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摘要

Zeekoevlei is the largest freshwater lake in South Africa and has a century-long history of anthropogenic impact that caused hyper-eutrophic conditions. We used biomarkers (alkanes and pigments), stable isotopes (δ13C and δ15N), rates of primary palaeoproduction and total inorganic carbon (TIC) accumulation rates in the lake sediments to investigate changes in plankton and macrophyte communities in response to anthropogenic activities in this shallow lake. Specific alkanes (ΣC15,17,19, pristane, phytane and n-C29-C17 ratio) and pigment (chlorophyll a, β,β-carotene, echinenone, fucoxanthin and zeaxanthin) concentrations in lake waters indicated the present-day hyper-eutrophic condition and seasonal fluctuations of cyanobacteria, zooplankton and diatom populations. Eutrophic conditions were initiated in the lake with the start of recreational activities and construction of a sewage treatment plant in the early 1920s. The lake transformed from a eutrophic to a hyper-eutrophic waterbody following damming, pondweed eradication and accelerated catchment-derived nutrient input. The change in lake trophic state was recorded by a sharp decline in the terrestrial to aquatic ratio (TAR) of specific n-alkanes, low carbon preference index (CPI) and increased δ13C values in the sediment core. In addition, the aquatic macrophyte n-alkane proxy (Paq) values (~1) indicated a slow takeover by floating macrophytes after the eradication of submerged pondweeds in 1951. Elevated n-alkane (ΣC15,17,19), total alkane and pigment (chlorophyll a, β,β-carotene, zeaxanthin and zeaxanthin to β,β-carotene ratio) concentrations, low δ15N values and low TIC accumulation rates in the upper middle section of the core indicated the beginning of intense cyanobacterial blooms after the dredging in 1983. Although the cyanobacterial population has decreased in recent years, hyper-eutrophic conditions are reflected by low CPI <0.04 and TAR <1 values at the top of the sediment core.
机译：Zeekoevlei是南非最大的淡水湖，拥有长达一个世纪的人为影响历史，造成了富营养化状况。我们使用了生物标志物（烷烃和色素），稳定同位素（δ 13 C和δ 15 N），一次古生速率和总无机碳（TIC）积累速率。湖泊沉积物，以调查该浅湖中浮游生物和大型植物群落对人为活动的响应。特定烷烃（ΣC 15,17,19 、,烷，植烷和nC 29 / nC 17 的比例）和色素（叶绿素a，β，湖水中的β-胡萝卜素，海胆烯酮，岩藻黄质和玉米黄质）的浓度表明了当今的富营养化状况以及蓝细菌，浮游动物和硅藻种群的季节性波动。随着休闲活动的开始以及1920年代初期污水处理厂的建设，湖泊开始出现富营养化的状况。在筑坝，消灭杂草和加速集水源性养分输入之后，该湖从富营养化的水体转变为富营养化的水体。湖泊营养状态的变化记录为特定正构烷烃的陆地与水的比率（TAR）急剧下降，低碳优先指数（CPI）和沉积物中δ 13 C值增加核心。此外，水生植物正链烷烃代用品（P aq ）值（〜1）表示在1951年消灭淹没的草草后，漂浮的水生植物缓慢吸收。正链烷烃（ΣC 15,17,19 ），总烷烃和色素（叶绿素a，β，β-胡萝卜素，玉米黄质和玉米黄质与β，β-胡萝卜素的比例）浓度，低δ 15 N岩心中上部的TIC值和TIC积累率低表明1983年疏after后开始出现强烈的蓝藻水华。尽管近年来蓝藻菌数量有所减少，但低CPI <0.04和TAR反映了高营养状态沉积物核心顶部的<1值。

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