But sometimes the beauty of blooms can be deceiving.
Too many algae can overload waters: As they die, other bacteria eat them and use up oxygen in the water. This can create oxygen-depleted dead zones where "organisms cannot survive."
Meanwhile, cruise ships are reportedly still dumping sewage into the Baltic Sea. Along with fertilizers in agricultural runoff, this fuels bloom growth.
Climate change is draining more freshwater into the Baltic, which further encourages blooms to grow. So giant blooms appear somewhat regularly during the summer.
Addressing the problem will likely take the whole planet working together to reduce greenhouse emissions, slow climate change, and curb its disruption.