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，在缅因州海湾发生了异常有毒的鞭毛藻亚历山德里亚毛线藻的强烈繁殖。水华达到高浓度（从数十万到一百万个细胞L ^-1），使水变色，并且超出正常水华浓度的1000倍。使用中分辨率成像光谱仪（MERIS）图像处理到目标叶绿素浓度（> 2 µg L ^-1），浓烈的A. catenella斑​​点确定的浓度与从船舶调查中观察到的高度局部细胞浓度一致。水华斑块通常与高吸收的沿海水域对齐。密集的水华斑块响应下沉事件而移到了岸上，持续了大约一周，然后在几天内迅速散开，没有再出现。耦合的物理生物学模型模拟表明，强迫风是在岸上运输细胞的重要因素。向上游泳行为促进了水平细胞的聚集，使模拟的最大深度整合细胞浓度增加了多达40倍。细胞的垂直会聚，归因于A. catenella的活跃游泳从地下到顶层，可以解释达到达到使水变色的水华浓度所需的额外25倍强度（25×40 = 1000倍）。考虑向上游泳的模型模拟高估了强聚集下游的细胞浓度。模型与观察到的浓度之间的差异表明，与囊化开始相对应的时间，水柱中的细胞丢失。这些结果表明，向上游泳，水平收敛和风流共同作用导致了红水事件，这可能促进了包囊过程之前的有性生殖事件。