dc.description.abstract | Algae grow wherever there is water; in
oceans, freshwater lakes, rivers, streams and
pools. They underpin aquatic food webs,
providing nutrition for animals in the system,
and along with microbes, are responsible
for cycling energy and nutrients throughout
the environment. Problems arise when algae
bloom, which is often the result of excess
nutrients. These nutrients may come from
a range of sources, including rainfall and
associated runoff from fertilizer application
and land erosion, as well as discharge from
sewage and other high-nutrient sources.
One of the key groups of algae that can bloom
in freshwaters, marine and brackish waters is
cyanobacteria (also known as blue-green algae).
Cyanobacteria are technically not algae, as
they are a more ancient lifeform, but they share
characteristics in common with algae, including
needing sunlight for photosynthesis. They are
particularly prolific in calm waterbodies, such as
lakes, ponds, weirs and reservoirs, or slow flowing
rivers. Cyanobacteria can proliferate in these
environments because longer water residence
times allow many of them to grow and form
blooms. They can also float on the water surface
more readily than other algal groups.
One of the major problems with cyanobacterial
blooms, or cyanoHABs, is that some species
can be toxic. Their toxins (cyanotoxins) can
have diverse health effects on people and
animals, ranging from mild to serious, and
impacts on whole ecosystems. Water intended
for human and animal consumption generally
needs to be treated to remove toxins before
drinking, significantly adding to the cost of
supply. In many countries, testing methods for
cyanotoxins are not available and people may
inadvertently be exposed to these health hazards.
Even when blooms are not toxic, their use of
oxygen at night (= respiration), and bloom
decay can result in low-oxygen conditions
which kill fish and other animals. They can
cause earthy/musty or bad odours via excretory
products and decomposing blooms, e.g.
rotten egg smells, and can wash up on shores
and affect recreational use. They can also
cause severe skin irritation for swimmers.
There is a wide range of within pond/lake system
management and mitigation products, methods
and tools available for controlling cyanoHABs
blooms. However, it is often difficult to determine
which products and approaches may be most
effective for a particular waterbody. This provides
an overview of the products and and physical,
chemical and biological solutions available for
control of cyanoHABs, and some detail on their
benefits and relative costs. It also points to other
publications with more detailed information. | en_US |