Green, red, yellow or other discolouration of water or filamentous strands in water.
Blue-green Algae can cause spectacular blooms in fresh water bodies and may be toxic.
The toxic Blue-green Algae include:
Anabaena circinalis is usually well dispersed up to 70 cm deep in water but may forms scum where concentrated by currents or wind. It has a musky to earthy smell.
Microcystis aeruginosa form an emerald green scum in water and when dried looks like pale blue paint. It has a musky to earthy smell.
Nodularia spumigena form a green suspension in water or may form a scum in sheltered areas where they are concentrated by currents or wind. It has a musky to earthy smell. This species regularly occurred in spring/summer in the Peel-Harvey inlet since the early sixties.
Species Affected:
Biology:
Blue-green algal blooms are favoured in shallow, warm, calm water that is hard, alkaline and rich in nitrogen, phosphates, carbonates and organic matter.
Life Cycle:
Origin and History:
Distribution:
Significance:
Some species are toxic to stock and humans.
Toxicity:
Stock poisonings usually occur in summer when stock drink infested water.
Fish deaths may be caused by the toxin, depletion of oxygen, release of hydrogen sulphide or ammonia as algal cells decompose or by clogging of the gills.
Anabaena species are reported to be toxic to stock, birds and fish and implicated in eye and skin irritations in dogs and humans.
Anacystis species are reported to be toxic to stock, birds and fish and have been implicated in "hay fever" like symptoms in humans.
Aphanizomenon species are reported to be toxic to stock, birds and fish.
Lyngbya species are reported to cause "hay fever" like symptoms in humans.
Microcystis species (formerly Anacystis) are reported to be toxic to stock, birds and fish and have been implicated in "hay fever" like symptoms in humans.
Nodularia species are reported to be toxic to stock, birds and fish and implicated in eye and skin irritations in dogs and humans.
Nodularia spumigena has been implicated in stock losses. Fish, crabs and birds are not usually affected as they seem to avoid the floating algal masses. Problems with fish toxicity are more likely when the level of water is lowered and the fish can't avoid contact with the algae.
Toxic products released from Blue-green Algae are suspected to cause unexplained gastro-enteritis in humans.
Symptoms:
In sheep, Nodularia spumigena and Microcystis aeruginosa causes difficult breathing, muscular weakness, signs of paralysis or nervous muscle twitching followed by coma and quiet death. In the field sheep are often found dead close to the infested water source and may have algal scum around the mouth, forelegs and brisket. Post-mortem examination often shows haemorrhage from small blood vessels under the skin and between the muscles. Pale areas may be seen throughout the liver.
Fish are usually found dead or gasping at the surface and may have small haemorrhages throughout the body.
Sudden death.
Treatment:
Shift stock slowly and quietly to another water source.
Management and Control:
Get algae identified by submitting a fresh sample of 100 mL of infested water in a screw top bottle to the Dept of Agriculture. If the sample needs to be preserved then add 3 mL formalin per 100 mL water.
Apply copper based products or triazine herbicides.
In farm dams 1-2 ppm of Copper or Triazine will provide good control. Treatment may cause a release of algal toxins which lasts for several days. Don't use water for stock for at least a week after treatment and test with a few stock before introducing the main mob. Avoid the use of Copper treatments if stock have copper bullets or may have suffered liver damage or there is desirable aquatic life in the water body. Ensure the Triazine or copper is thoroughly mixed through the surface layers. This may be done by premixing in a large quantity of water and applying by a fire fighter pump or using an outboard motor to mix the products in the dam after applying to the surface.
Chlorination of the water using calcium hypochlorite is preferred in water that may be used for human consumption. The rate depends on conditions and 12 grams of the 70% product per 1000 L water is often used. This may kill fish and crustacea.
Ferric alum can also be used in late winter to prevent an algal bloom. Moor a block of ferric alum in a Hessian bag on a float in the middle of the dam so it may float around. This removes phosphate from the water by precipitation and thus reduces algal growth. In severely polluted waters the treatment may need to be reapplied in October.
Straw and especially Barley straw in the dam is often used to prevent Algae building up in dams. Spread about 100 grams of straw per 1000 L water over the dam in late winter. It is not effective once the algae has bloomed.
Reduce the inflow of nutrients and sewerage into the dam.
Cover tanks to exclude light.
Make dams deeper and increase catchment area so dams overflow each season.
Reduce nutrient, sewerage and manure contamination of water sources.
Related and Similar Species:
References:
Main, D. C. (1994) Toxic algal blooms. Farmnote 43/94. Western Australian Department of Agriculture.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 for more information.