Mbonde Athanasio S, Sitoki Lewis, Kurmayer Rainer
Tanzania Fisheries Research Institute (TAFIRI), Kigoma centre, P.O. Box 90, Kigoma, Tanzania.
Technical University of Kenya, P.O. Box 52428 - 00200, Nairobi. Kenya.
Aquat Ecosyst Health Manag. 2015;18(2):212-220. doi: 10.1080/14634988.2015.1011030. Epub 2015 Feb 3.
This study was carried out in order to investigate the spatial variation of algal toxin (microcystin) concentrations along the shoreline of Lake Victoria. A total of 16 nearshore stations differing in connectivity to the main lake basin were categorized as either closed bays (ratio of bay area to bay opening < 1) or open bays (ratio ≥ 1) and sampled during November and December 2009. Water samples were analyzed for total phosphorus (TP), chlorophyll , phytoplankton community composition and concentrations of microcystin (MC). Open and closed bays were significantly different for phytoplankton abundance and composition: Average phytoplankton biovolume was higher for closed bays (45 mm L ± 11 SE) than open bays (5 ± 2 mm L). Cyanobacterial biovolume (mainly spp. spp. and spp.) also was significantly higher in closed bays (82 ± 9% of total biovolume) than in open bays (44 ± 5%). In contrast, diatom biovolume was lower in closed bays (7 ± 1%) than in open bays (36 ± 6%). MCs were found only among sites from closed bays and concentrations ranged from 0.4 to 13 μg L MC-LR equiv. and coincided with high abundance of spp. It is concluded that the level of water exchange from individual bays to the main basin is an important factor influencing eutrophication and microcystin production in nearshore habitats of Lake Victoria.
本研究旨在调查维多利亚湖沿岸藻毒素（微囊藻毒素）浓度的空间变化。总共16个与主湖盆连通性不同的近岸站点被分类为封闭海湾（海湾面积与海湾开口的比率<1）或开放海湾（比率≥1），并于2009年11月和12月进行了采样。对水样分析了总磷（TP）、叶绿素、浮游植物群落组成和微囊藻毒素（MC）浓度。开放海湾和封闭海湾在浮游植物丰度和组成方面存在显著差异：封闭海湾的浮游植物平均生物量（45立方毫米/升±11标准误）高于开放海湾（5±2立方毫米/升）。封闭海湾中的蓝藻生物量（主要是 属、 属和 属）也显著高于开放海湾（占总生物量的82±9%），而开放海湾为（44±5%）。相比之下，封闭海湾中的硅藻生物量（7±1%）低于开放海湾（36±6%）。仅在封闭海湾的站点中发现了微囊藻毒素，浓度范围为0.4至13微克/升（以MC-LR当量计），并且与 属的高丰度一致。得出的结论是，各个海湾与主湖盆之间的水交换水平是影响维多利亚湖近岸栖息地富营养化和微囊藻毒素产生的一个重要因素。
