Algal blooms

Algae-related diseases are very rare. Most algae-related health effects are not from freshwater blue-green algae but instead are linked to marine (saltwater) algae, such as the red-tide algae.

Their type and abundance are influenced by the availability of essential nutrients such as nitrogen and phosphorus, the amount of sunlight and other factors such as mixing and turbidity.

Most algae-related poisonings come from eating tainted seafood such as clams, oysters, and predatory fish, which accumulate the toxins in their bodies but don't get sick themselves.

Occurrence of blooms

An algal bloom is essentially a population explosion, indicating an abundance of nutrients and ideal growing conditions. Generally these are naturally occurring although there is an apparent increase in their frequency and distribution worldwide. They are a natural occurrence and can occur in the spring and early summer. Some of the species which have been observed include:

Phaeocystis - can bring ashore gelatinous material and in rougher weather / windy conditions can cause foam. The blooms are non-toxic, but can cause aesthetic problems such as an unpleasant cabbage type smell when the algae are dying.

Chaetoceros - which is a long chain algae with spines and spears. It is an irritant to fish gills, thereby affecting the fish and causes some fish deaths. It is non-toxic to humans.

Noctiluca - it is non-toxic, but can turn the sea bright red, light green, orange or black and be phosphorescent.

Cyanobacteria - (Blue-green algae) are natural inhabitants of many inland waters, estuaries and the sea. In certain conditions they form blooms and can produce a surface scum. Blooms and scums are capable of producing toxins and are known to have caused the death of wild animals, farm livestock, domestic pets and have been major contributors to fish kills. Rashes have occurred on humans following skin contact and illnesses have occurred when blue-green algae have been swallowed. Although blooms and scums are not always toxic, it is not possible to tell from their appearance whether a particular one is harmful or not, as there is at least a one in two chance of it being toxic.

Common-sense, practical precautions around algae blooms are the following:

Don't wade or swim in water containing visible blooms, and avoid direct contact with dense mats of algae.
Don't drink the untreated water or let children, livestock or pets get into or drink the untreated water.
Make sure children are supervised at all times when they are near water.
Drowning, not exposure to algae, remains the greatest hazard of water recreation.
If you do come into contact with the algae or the water around a bloom, simply rinse off with fresh water as soon as possible.

Further information can be obtained from the Environment Agency (http://www.environment-agency.gov.uk/).

Havant Borough Council, Civic Centre Road, Havant, Hampshire PO9 2AX