识别人为富营养化和引入非本地物种的生态系统变化和食物网动态对于确保渔业和湖泊生物多样性的长期可持续性是必要的。维多利亚湖富营养化的先前研究,东非,在过去的几十年里,人们一直关注当地鱼类生物多样性的丧失,但同时浮游生物群落的变化仍不清楚。为了填补这个空白,我们检查了富营养化沉积物的沉积物核心,姆万扎海湾,以确定过去一个世纪浮游植物和浮游动物组合变化的时间和幅度。生物地球化学代理表明营养富集开始于〜1920CE左右,并导致初级生产迅速增加,我们对光合色素的分析揭示了三个区域:富营养化前(1920年之前),随着所有色素的增加,富营养化开始(1920-1990CE),和以蓝藻为主的持续富营养化(1990年CE至今)。Cladoceran遗骸表明,在1960年左右,生物量突然下降,为了应对富营养化和湖泊水位上升的累积效应,在1980年代单倍色胺丽鱼科动物崩溃之前。Alona和Chydorus,通常是底栖沿海类群,自1960年代以来一直保持在相对较低的丰度,而博斯米纳的丰富,通常是浮游分类单元,在1990年代,单倍色胺丽鱼鱼的生物量回收同时增加。总的来说,我们的结果表明,在过去的一个世纪中,姆万扎湾浮游植物和浮游动物群落的生物量结构和分类组成发生了重大变化,提供历史食物网的观点,可以帮助了解最近的变化,并为维多利亚湖生态系统未来的资源管理决策提供信息。
■在线版本包含补充材料,可在10.1007/s10021-024-00908-x获得。
Discerning ecosystem change and food web dynamics underlying anthropogenic
eutrophication and the introduction of non-native species is necessary for ensuring the long-term sustainability of fisheries and lake biodiversity. Previous studies of
eutrophication in Lake Victoria, eastern Africa, have focused on the loss of endemic fish biodiversity over the past several decades, but changes in the plankton communities over this same time remain unclear. To fill this gap, we examined sediment cores from a eutrophic embayment, Mwanza Gulf, to determine the timing and magnitude of changes in the phytoplankton and zooplankton assemblages over the past century. Biogeochemical proxies indicate nutrient enrichment began around ~ 1920 CE and led to rapid increases in primary production, and our analysis of photosynthetic pigments revealed three zones: pre-eutrophication (prior to 1920 CE), onset of
eutrophication with increases in all pigments (1920-1990 CE), and sustained
eutrophication with cyanobacterial dominance (1990 CE-present). Cladoceran remains indicate an abrupt decline in biomass in ~ 1960 CE, in response to the cumulative effects of
eutrophication and lake-level rise, preceding the collapse of haplochromine cichlids in the 1980s. Alona and Chydorus, typically benthic littoral taxa, have remained at relatively low abundances since the 1960s, whereas the abundance of Bosmina, typically a planktonic taxon, increased in the 1990s concurrently with the biomass recovery of haplochromine cichlid fishes. Overall, our results demonstrate substantial changes over the past century in the biomass structure and taxonomic composition of Mwanza Gulf phytoplankton and zooplankton communities, providing a historical food web perspective that can help understand the recent changes and inform future resource management decisions in the Lake Victoria ecosystem.
UNASSIGNED: The online version contains supplementary material available at 10.1007/s10021-024-00908-x.