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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.