Algae and cyanobacteria (blue-green algae) are microscopic protists that naturally occur in all aquatic environments. Being primary producers, they are vital components of these ecosystems. Most often, algal growth is regulated by factors such as nutrient availability and grazing pressure. However, when growth conditions are optimal, rapid growth can occur, resulting in a rapid increase in biomass – we call this an “algal bloom”.
Some common Types of algae
Algal blooms are a natural phenomenon but, in urbanised and agricultural areas, they are more often the result of human activities, particularly human induced eutrophication.
Algal blooms can affect ecosystem function by:
- absorbing all available nutrients and out-competing other primary producers (algae and submerged macrophytes);
- limiting light penetration and shading submerged macrophytes;
- stripping the oxygen out of the water overnight due to respiration, to the detriment of other organisms (especially fish);
- stripping the oxygen out of the water and harbouring pathogens as the algal biomass decomposes when the bloom “dies off”; and
- producing powerful toxins harmful to other organisms
Algal blooms also impact the amenity, function, ecological value and economic value of wetlands and other water sources from a human perspective.
Algal blooms are usually unsightly and associated with foul odours as well as creating conditions that encourage the growth and spread of mosquitoes and other biting insects. They create biofouling issues for process and industrial waters and they limit the practical uses of the water with respect to recreational activities, industrial uses, agricultural uses (irrigation, stock water etc.) and domestic uses (irrigation, drinking water etc.).
There are several different types of algal toxins and cyanotoxins, some with more than 50 structurally related forms (congeners). These toxins are generally grouped as neurotoxins (those primarily affecting the nervous system), hepatotoxins (those primarily affecting the liver) and dermatoxins (those primarily affecting the skin or exposed mucous membranes). Some algal/cyanobacterial toxins are also considered to promote the growth of tumours.
Some common types of algae capable of producing toxins
One significant endotoxin which is produced by all cyanobacteria (in all environments) is BMAA (β-Methylamino-L-alanine). BMAA is a neurotoxin and is currently being investigated as a potential environmental risk factor for neurodegenerative diseases, including ALS, Parkinson’s disease and Alzheimer’s disease. The mounting body of evidence regarding BMAA suggests both acute and chronic mechanisms of toxicity.
Undesirable tastes and odours resulting from compounds produced by algae are also an issue for managers of drinking water supplies however to a much lesser extent than cyanotoxins. Although undesirable in drinking waters, the compounds produced by algae which can cause off-tastes and odours are not harmful if ingested. These compounds, Geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol) are naturally produced within the cells of many types of algae and cyanobacteria.
There are four basic taste types associated with algae in drinking waters: sour, sweet, salty and bitter. There are also a variety of odour types including earthy, musty, grassy, cucumber, melon and fishy. The earthy and musty odours generated by geosmin and MIB are detectable by many people at concentrations as low as 5 to 10 parts per trillion.
Some common types of algae capable of producing taste and odour causing compounds
With respect to drinking waters, the concentration of algae in the water (species known to potentially produce toxins) does not have to be high such that we would consider it an algal bloom. To be a potential problem, the cell concentration of algae which produce toxins can be relatively low (by algal bloom standards), and there may not be any visible signs of these algae in the water.
Climate change is having and is predicted to have, a significant impact on the occurrence of harmful algae and harmful algae blooms worldwide.
The consensus among algal scientists is that the
– duration, and
of harmful algal blooms will all increase globally as a result of climate change.
As with many parts of Australia, the south-west of Western Australia is already impacted by a drying climate.
A continuing drying trend, coupled with an increase in temperature (milder winters and hotter summers) and an increase in the frequency and severity of summer storm events, are all conditions favourable to the above scenario with respect to harmful algal blooms.
Water managers and regulators and local, state and federal authorities need to start taking these predictions seriously if they are not already doing so.
Dalcon Environmental regularly refers to a number of current water quality guidelines pertaining to Algal and Cyanobacterial monitoring, including:
– National Health and Medical Research Council (NHMRC) – Australian Drinking Water Guidelines
– World Health Organisation – Guidelines for Drinking Water Quality
– National Health and Medical Research Council (NHMRC) – Guidelines for Managing Risk in Recreational Waters
– Department of the Environment – National Water Quality Management Strategy
In conjunction with monitoring in accordance with state, federal or agency-specific guidelines, Dalcon Environmental is also capable of adapting to suit client needs and client-specific monitoring programs, biodiversity surveys and environmental impact assessments through the use of palaeolimnological studies and targeted surveys.
We can analyse planktonic, benthic and periphytic algal communities for all types of algae including diatoms, chlorophytes, cyanobacteria, dinoflagellates and more.