Algae are photosynthetic microorganisms that are found in most aquatic habitats. Algae love runoff nutrients, and an algae bloom occurs when nutrient pollution and lots of sunlight create a rapid increase in the density of the algae. Algal blooms may occur in freshwater as well as marine environments.
Public Health Concerns
- When an algae bloom does happen, the stream, river, lake, or ocean becomes covered with algae, creating a thick mat of surface scum. Bright green colored blooms develop from cyanobacteria, which are also known as blue-green algae.
- Hence Impact of algal bloom are:
- Exposure to algal toxins may occur through consumption of tainted water, fish, or shellfish; recreational activities; or inhalation of aerosolized toxins.
- Algal toxins are known to cause illness immediately (hours to days) after exposure. In addition, several algal toxins are believed to be carcinogens or to promote tumour growth, although more research on the effects of long-term exposure is needed.
- HABs may impart a distinct colour to the water bodies. Colors observed are green, yellowish-brown, or red. Bright green blooms may also occur. These are a result of blue-green algae, which are actually bacteria (cyanobacteria).
- HABs may cause mortality of aquatic organisms because of low dissolved oxygen or algal toxins. Algal toxins also may cause mortality of terrestrial organisms using the water source.
- As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive. This results in a dead area.
Economic concerns associated with HABs include increased drinking-water treatment costs, loss of recreational revenue, loss of aqua cultural and fisheries revenue, and livestock sickness or fatalities.
Taste-and-odour compounds are of particular concern to drinking-water suppliers because of customer dissatisfaction with malodorous drinking water.
Also algae may clog filters, and produce nuisance slime growths on intake pipes and equipment.
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