The mass propagation of algae and cyanobacteria is called algal bloom. If this occurs, the water surface turns green, blue or red.
In this particular mass development, a single species of a
lgae or cyanobacteria accumulates directly below the water surface. In some species this is done by buoyancy but in others, such as the flagellated species of algae by actively searching the surface. The species of Euglena (Euglena sanguinea) can turn the surface fire red, an Oscillatoria species (O. rubescens) from blood to raspberry red, a Microcystis species sky blue.
The algae blooms reduces enormously the light at the surface, so not enough light for the photosyntosis is available. On the other hand, the drop in algae and the growing number of consumers significantly reduces oxygen. Yet another problem arises when algae and cyanobacteria develop toxic substances such as Mircoystins, which can be a major hazard to humans and animals.
In 2018, the “Red Tide” off the coast of Florida became a real environmental catastrophe. The deadly algal bloom there, was caused by Karenia brevis, which was a chemical defense substance that produced Brevetoxin, which had devastating effects on local marine fauna. Although this is a recurrent phenomenon, in 2018 it became an ecological disaster.
Beach visitors suffered from respiratory distress and skin irritation. The tourism industry in this part of the world suffered from the remaining guests. But the real victims were and are the sea creatures, because the highly toxic algal blooms cost the lives of innumerable fish, turtles, seabirds and marine mammals. The beaches were littered with dead marine life.
A true tragedy that could be avoided with sound agricultural action and sustainable policy choices. The cause of this phenomenon is, for example, an over-fertilization with phosphates, which then are taken by rivers into the sea. But scientists fear that climate change is also contributing to the strengthening of algal blooms.
By Fatima Kutzschbach