In July 2009, an unusually intense bloom of the toxic dinoflagellate Alexandrium catenella occurred in the Gulf of Maine. The bloom reached high concentrations (from hundreds of thousands to one million cells L⁻¹) that discolored the water and exceeded normal bloom concentrations by a factor of 1000. Using Medium Resolution Imaging Spectrometer (MERIS) imagery processed to target chlorophyll concentrations (>2 µg L⁻¹), patches of intense A. catenella concentration were identified that were consistent with the highly localized cell concentrations observed from ship surveys. The bloom patches were generally aligned with the edge of coastal waters with high-absorption. Dense bloom patches moved onshore in response to a downwelling event, persisted for approximately one week, then dispersed rapidly over a few days and did not reappear. Coupled physical-biological model simulations showed that wind forcing was an important factor in transporting cells onshore. Upward swimming behavior facilitated the horizontal cell aggregation, increasing the simulated maximum depth-integrated cell concentration by up to a factor of 40. Vertical convergence of cells, due to active swimming of A. catenella from the subsurface to the top layer, could explain the additional 25-fold intensification (25 × 40=1000-fold) needed to reach the bloom concentrations that discolored the water. A model simulation that considered upward swimming overestimated cell concentrations downstream of the intense aggregation. This discrepancy between model and observed concentrations suggested a loss of cells from the water column at a time that corresponded to the start of encystment. These results indicated that the joint effect of upward swimming, horizontal convergence, and wind-driven flow contributed to the red water event, which might have promoted the sexual reproduction event that preceded the encystment process.

2009 年 7 月，缅因湾发生了一场异常强烈的有毒甲藻链状亚历山大藻的大量繁殖。水华达到高浓度（从数十万到一百万个细胞L ^-1 ），使水变色并超出正常水华浓度 1000 倍。使用中分辨率成像光谱仪 (MERIS) 处理图像以达到目标叶绿素浓度 (>2 µg L ^-1 ），鉴定出强烈的链环链状杆菌浓度斑块，这与从船舶调查中观察到的高度局部细胞浓度一致。水华斑块通常与具有高吸收能力的沿海水域边缘对齐。由于下降流事件，密集的水华斑块移动到岸上，持续了大约一周，然后在几天内迅速消散，并且没有再次出现。物理-生物耦合模型模拟表明，风力是细胞向陆地输送的重要因素。向上游动行为促进了水平细胞聚集，使模拟的最大深度积分细胞浓度增加了 40 倍。由于链状线虫从地下到顶层的主动游动，细胞的垂直聚集可以解释需要额外25倍的强化（25×40=1000倍）才能达到使水变色的水华浓度。考虑向上游泳的模型模拟高估了强烈聚集下游的细胞浓度。模型和观察到的浓度之间的这种差异表明，在与包囊开始相对应的时间，细胞从水柱中丢失。 这些结果表明，向上游动、水平辐合和风驱动流的共同作用促成了红水事件，这可能促进了包囊过程之前的有性生殖事件。