Botany Department, Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth 6031, South Africa; DSI/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela University, Port Elizabeth 6031, South Africa.
Botany Department, Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth 6031, South Africa; DSI/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela University, Port Elizabeth 6031, South Africa.
Sci Total Environ. 2022 May 1;819:152038. doi: 10.1016/j.scitotenv.2021.152038. Epub 2021 Nov 30.
Nutrient pollution is facilitating the encroachment of invasive aquatic plants in various water bodies globally. This study investigated seasonal aquatic macrophyte responses in two temporarily closed estuaries with different nutrient inputs. Consistent effluent discharge from the upstream wastewater treatment works (WWTW) facilitated the establishment of numerous freshwater invasive alien aquatic plants (IAAPs) in the uThongathi Estuary. IAAPs (Myriophyllum aquaticum, Pistia stratiotes and Pontederia crassipes) were only displaced from the estuary after high flow events (>5 m s). In the less polluted uMdlotane Estuary nutrient pulses (>1 mg/L DIN) associated with high rainfall changed the aquatic macrophyte composition. The nutrient tolerant non-rooted Ceratophyllum demersum outcompeted the rooted submerged macrophyte Stuckenia pectinata. Species composition changed in response to flow and nutrient inputs, with the exception of emergent macrophytes, such as the grass Echinochloa pyramidalis, that remained consistent in cover and distribution in the uMdlotane Estuary. This study demonstrated that aquatic macrophytes are more responsive to nutrient inputs in unimpacted estuaries compared to consistently nutrient-rich systems where flow is an important driver of IAAPs community dynamics. Many temporarily closed estuaries are subjected to nutrient pollution from WWTWs and restoration efforts such as diversion of discharges to constructed wetlands needs urgent implementation.
营养物污染正在促进全球各种水体中入侵水生植物的蔓延。本研究调查了两个具有不同养分输入的暂时封闭河口的季节性水生大型植物的响应。上游污水处理厂（WWTW）持续的废水排放，促进了大量淡水入侵外来水生植物（IAAPs）在乌通加蒂河口的建立。只有在高流量事件（>5 m s）后，IAAPs（狐尾藻、凤眼蓝和水鳖）才会从河口被排挤出去。在污染较少的乌姆德拉通河口，与强降雨相关的营养脉冲（>1 mg/L DIN）改变了水生大型植物的组成。耐营养非根生的金鱼藻胜过了有根的沉水大型植物水盾草。除了芒草等浮水大型植物外，物种组成会因水流和养分输入而发生变化，而芒草在乌姆德拉通河口的覆盖和分布保持一致。本研究表明，与始终富含养分的系统相比，水生大型植物对未受影响的河口的养分输入更敏感，而在这些系统中，水流是 IAAPs 群落动态的重要驱动因素。许多暂时封闭的河口受到 WWTWs 的营养污染，需要紧急实施将排放物分流到人工湿地等修复工作。
