Cyanobacteria also produce similar toxins that overlap with several of these general categories, including neurotoxins and hepatoxins. Symptoms of exposure to these toxins include gastrointestinal, neurological, cardiovascular, and hepatological symptoms. The algae that produce these toxins, and the specific symptoms they cause, are summarized in Appendix A . Other harmful algal blooms produce toxins with no identifiable effects on humans but devastating impacts on coastal living resources. Predation is another way that several HAB species can impact coastal biota.
Predation occurs when one organism captures or feeds on another organism.
One example of a predatory HAB is Pfiesteria piscicida. Two of these toxic fractions are produced after the P. piscicida is exposed to fish secretions. The first fraction has neurotoxin-like properties that affect the fish's neurological system. The neurotoxin-like materials cause lethargy in the fish, and, when present in sufficient quantities, death. The dermonecrotic compounds apparently cause sloughing of the external skin layers, leading to lesions and perhaps secondary infections from fungi and other pathogens in the surrounding water.