Microcystis is the predominant genus of harmful cyanobacterium in both Lake Erie and Saginaw Bay of Lake Huron and has the capacity to regulate the buoyancy of its colonies, sinking under certain conditions while floating towards the surface in others. Understanding the factors that control buoyancy is critical for interpretation of remote sensing data, modeling and forecasting harmful algal blooms within these two systems. To determine if Microcystis colony buoyancy in the two lakes responds similarly to diurnal light cycles, colony buoyant velocity (floating/sinking terminal velocity in a quiescent water column) and size were measured after manipulating the intensity of sunlight. Overall, there were more positively buoyant (floating) colonies in Lake Erie while most of the colonies in Saginaw Bay were negatively buoyant (sinking). In Lake Erie the colonies became less buoyant at increased light intensities and were less buoyant in the afternoon than in the morning. In both lakes, apparent colony density was more variable among small colonies (< 200 µm), whereas larger colonies showed a diminished response of density to light intensity and duration. These findings suggest that colony density becomes less plastic as colonies increase in size, leading to a weak relationship between size and velocity. These relationships may ultimately affect how the bloom is transported throughout each system and will help explain observed differences in vertical distribution and movement of Microcystis in the two lakes.

微囊藻是伊利湖和休伦湖萨吉诺湾中有害蓝藻的主要属，能够调节其菌落的浮力，在某些条件下下沉，而在其他条件下则浮到水面。了解控制浮力的因素对于解释遥感数据、建模和预测这两个系统内的有害藻华至关重要。确定是否有微囊藻两个湖泊中的菌落浮力对昼夜光循环的响应相似，在操纵阳光强度后测量了菌落浮力速度（静止水柱中的漂浮/下沉终端速度）和大小。总体而言，伊利湖中有更多的正浮力（漂浮）菌落，而萨吉诺湾的大多数菌落负浮力（下沉）。在伊利湖，随着光照强度的增加，菌落的浮力变小，并且在下午的浮力低于早上。在这两个湖中，小菌落（< 200 µm）的表观菌落密度变化更大，而较大的菌落则显示密度对光强度和持续时间的响应减弱。这些发现表明，随着菌落大小的增加，菌落密度的可塑性降低，导致大小和速度之间的关系很弱。这些关系可能最终会影响花朵在每个系统中的传输方式，并将有助于解释观察到的垂直分布和运动的差异。两个湖泊中的微囊藻。