National Oceanic and Atmospheric Administration, National Ocean Service, National Centers for Coastal Ocean Science, 1305 East-West Highway, Silver Spring, MD 20910, United States.
CSS, Inc. Under contract with National Oceanic and Atmospheric Administration, National Ocean Service, National Centers for Coastal Ocean Science, 1305 East-West Highway, Silver Spring, MD 20910, United States.
Harmful Algae. 2021 Mar;103:101999. doi: 10.1016/j.hal.2021.101999. Epub 2021 Feb 27.
Saginaw Bay and western Lake Erie basin (WLEB) are eutrophic catchments in the Laurentian Great Lakes that experience annual, summer-time cyanobacterial blooms. Both basins share many features including similar size, shallow depths, and equivalent-sized watersheds. They are geographically close and both basins derive a preponderance of their nutrient supply from a single river. Despite these similarities, the bloom phenology in each basin is quite different. The blooms in Saginaw Bay occur at the same time and place and at the same moderate severity level each year. The WLEB, in contrast, exhibits far greater interannual variability in the timing, location, and severity of the bloom than Saginaw Bay, consistent with greater and more variable phosphorus inputs. Saginaw Bay has bloom biomass that corresponds to relatively mild blooms in WLEB, and also has equivalent phosphorus loads. This result suggests that if inputs of P into the WLEB were reduced to similarly sized loads as Saginaw Bay the most severe blooms would be abated. Above 500 t P input, which occur in WLEB, blooms increase non-linearly indicating any reduction in P-input at the highest inputs levels currently occurring in the WLEB, would yield disproportionately large reductions in cyanobacterial bloom intensity. As the maximum phosphorus loads in Saginaw Bay lie just below this inflection point, shifts in the Saginaw Bay watershed toward greater agriculture uses and less wetlands may substantially increase the risk of more intense cyanobacterial blooms than presently occur.
萨吉诺湾和伊利湖西部流域（WLEB）是位于大湖地区的富营养化流域，每年夏季都会发生蓝藻水华。这两个流域具有许多共同特征，包括相似的面积、浅的水深和同等大小的流域。它们地理位置相近，且都从单一河流获得主要的营养供应。尽管存在这些相似之处，但两个流域的水华物候学却大不相同。萨吉诺湾的水华每年都在同一时间、同一地点、同一中度严重程度发生。相比之下，WLEB 的水华在时间、地点和严重程度方面表现出更大的年际变化，这与更大量和更可变的磷输入一致。萨吉诺湾的水华生物量与 WLEB 中相对温和的水华相当，且磷负荷也相同。这一结果表明，如果将 WLEB 的磷输入减少到与萨吉诺湾相同的负荷水平，最严重的水华将得到缓解。在 WLEB 中，磷输入超过 500 吨时，水华会呈非线性增加，这表明在 WLEB 目前最高的磷输入水平下，任何磷输入的减少都会导致蓝藻水华强度的不成比例的大幅减少。由于萨吉诺湾的最大磷负荷正好低于这个转折点，萨吉诺湾流域向更多农业用途和更少湿地的转变可能会大大增加比目前更严重的蓝藻水华的风险。
