Species invasions can disrupt aquatic ecosystems by re-wiring food webs. A trophic cascade triggered by the invasion of the predatory zooplankter spiny water flea (Bythotrephes cederströmii) resulted in increased phytoplankton due to decreased zooplankton grazing. Here, we show that increased phytoplankton biomass led to an increase in lake anoxia. The temporal and spatial extent of anoxia experienced a step change increase coincident with the invasion, and anoxic factor increased by 11 d. Post-invasion, anoxia established more quickly following spring stratification, driven by an increase in phytoplankton biomass. A shift in spring phytoplankton phenology encompassed both abundance and community composition. Diatoms (Bacillaryophyta) drove the increase in spring phytoplankton biomass, but not all phytoplankton community members increased, shifting the community composition. We infer that increased phytoplankton biomass increased labile organic matter and drove hypolimnetic oxygen consumption. These results demonstrate how a species invasion can shift lake phenology and biogeochemistry.

中文翻译：

---

富营养化湖泊物种入侵后缺氧加剧

物种入侵可能会通过重新连接食物网来破坏水生生态系统。捕食性浮游动物带刺水蚤（Bythotrephes cederströmii）的入侵引发了营养级联反应，导致浮游植物吃草减少，导致浮游植物数量增加。在这里，我们发现浮游植物生物量的增加导致了湖泊缺氧的增加。缺氧的时间和空间范围随着入侵而出现阶跃变化，缺氧因子增加了11 d。入侵后，由于浮游植物生物量的增加，春季分层后缺氧更快地形成。春季浮游植物物候的变化包括丰度和群落组成。硅藻（Bacillaryophyta）推动了春季浮游植物生物量的增加，但并非所有浮游植物群落成员都增加了，从而改变了群落组成。我们推断，浮游植物生物量的增加增加了不稳定的有机物并驱动了低湖区的耗氧量。这些结果证明了物种入侵如何改变湖泊物候和生物地球化学。