What Are the Effects of HABs
Human Health Effects Caused by the Most Common Toxin-producing HABs Species
When people are exposed to toxins, adverse health effects may range from a mild skin rash to serious illness or in rare circumstances, death. Acute illnesses caused by short-term exposure to cyanobacteria and cyanotoxins during recreational activities include hay fever-like symptoms, skin rashes, respiratory, and gastrointestinal distress. The table summarizes the health effects caused by common cyanobacteria toxins.
| Toxins | Acute Health Effects in Humans | Common Toxin producing Cyanobacteria |
|---|---|---|
| Microcystin-LR | Abdominal pain, headache, sore throat, vomiting and nausea, dry cough, diarrhea, blistering around the mouth, and pneumonia | Microcystis, Dolichospermum (previously Anabaena), Nodularia, Planktothrix, Fischerella, Nostoc, Oscillatoria, and Gloeotrichia |
| Cylindrospermopsin | Fever, headache, vomiting, bloody diarrhea | Raphidiopsis (previously Cylindrospermopsis) raciborskii, Aphanizomenon flos-aquae, Aphanizomenon gracile, Aphanizomenon ovalisporum, Umezakia natans, Dolichospermum bergii, Dolichospermum lapponica, Dolichospermum planctonica, Lyngbya wollei, Rhaphidiopsis curvata, and Rhaphidiopsis mediterranea |
| Anatoxin-a group | Tingling, burning, numbness, drowsiness, incoherent speech, salivation, respiratory paralysis leading to death (experimental animals) | Chrysosporum (Aphanizomenon) ovalisporum, Cuspidothrix, Raphidiopsis, Cylindrospermum, Dolichospermum, Microcystis, Oscillatoria, Planktothrix, Phormidium, Dolichospermum flos-aquae, A. lemmermannii Raphidiopsis mediterranea (strain of Raphidiopsis raciborskii), Tychonema and Woronichinia |
Treatment for People Who Have Been Exposed to Toxins
If you do come into contact with water that is known to be contaminated with cyanobacteria and/or cyanotoxins, the Centers for Disease Control (CDC) recommends that you rinse off with clean, fresh water as soon as possible. Seek medical treatment right away if you think you or someone you know might have been poisoned by toxins, especially when any of the symptoms mentioned above are recognized.
Ecosystem Effects Caused by HABs
High biomass blooms, whether of toxic or nontoxic species, can lead to very low oxygen levels in the water column (hypoxia) or even no oxygen (anoxia), resulting in higher mortality rates for plant, invertebrate, shellfish and fish populations. Hypoxia/Anoxia can also alter biochemical reactions that may further exacerbate algal blooms and release other pollutants from sediments (e.g., metals).
Learn more about hypoxia at Hypoxia 101.
The hypoxia/anoxia can be accompanied by a decrease in pH (increase in acidity) in the water that can exacerbate ongoing acidification caused by climate change. The acidity of the water affects a wide range of processes, including the growth of healthy algae, shellfish, and fishes.
- Learn more at Ocean and Coastal Acidification
The same blooms may also affect benthic flora and fauna due to decreased light penetration. Low light levels negatively affect the growth of macrophytes, seagrasses and corals, upon which a wide range of other organisms depend. If low light levels persist, they can cause a regime shift in these ecosystems that then require expensive restoration efforts to reverse.
Some toxins and toxin producing taxa may actual inhibit other algae and suppress of zooplankton grazing, leading to reduced growth and reproductive rates. These impacts can be transmitted through the food web causing changes in the community structure and composition, including impacts to recreationally and commercially important fishes.