Does the presence of an algae bloom always mean the water is contaminated?
No. Just as not all cyanobacteria have blooms that are visible, not all cyanobacteria produce harmful toxins. Between 30 and 50 percent of blooms are from non-toxic species of cyanobacteria. Samples of the bloom must be analyzed in a laboratory before a body of water can be declared safe. All cyanobacterial blooms are potentially toxic, so it is best to stay away from contaminated water until it has been tested and declared safe. Health effects of exposure to toxins When cyanobacteria are present in high numbers, some bathers may experience eye, ear, or skin irritation, or gastrointestinal problems like vomiting and diarrhea. Some species of cyanobacteria can also produce poisons or toxins. These toxins may cause nerve or liver problems in people or animals that are exposed to them in large amounts. Signs of poisoning appear between a couple of hours to several days following exposure. When large amounts of the toxins are ingested, it can kill animals. Poisoning is more severe the smal
