Cyanobacteria and CyanoHABs
Finally, HABs are not always produced by dinoflagellates and diatoms. Cyanobacteria, or blue-green algae, another group of single-celled organisms, but one that is prokaryotic rather than eukaryotic, is also known to produce extremely potent toxins that can cause illness in fish, birds, and mammals including humans. Because of their potential to be harmful, this group is known as CyanoHABs. Cyanobacteria are some of the oldest species on Earth and are known to tolerate very tough conditions including hot, cold, salty waters and darkness. They live under ice sheets, near hydrothermal vents, and were some of the first organisms to colonize the ocedans after the massive asteroid that killed the dinosaurs.
Samples of CyanoHABs
Although the full scale of health effects of CyanoHABs on humans is not yet determined, the toxins may have gastrointestinal, respiratory, allergic, and neurological responses, and potentially lead to liver damage. In addition, prolific growth of cyanobacteria can block sunlight, which can harm other organisms, and use up oxygen which can lead to hypoxia and anoxia. As in the case of the HAB dinoflagellates, the growth of CyanoHABs may be stimulated by nitrogen loading from agricultural industrial runoff, as well as sewage disposal.