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Cyanobacteria and other Harmful Algal Blooms

Cyanobacteria can form dense surface scums or suspensions in the water | Photo: Sue WatsonHarmful algal blooms (HABs) result from the proliferation of algae in environmentally stressed systems, where conditions favour opportunistic growth of one or few noxious species which displace more benign ones. In both marine and freshwater environments, HABs can be caused by a species of green and golden-brown algae, diatoms, dinoflagellates and other motile cells. In freshwaters, cyanobacteria (blue-green algae) typically cause the HABs of most concern because some of these species can produce potent toxins, foul odours and seriously degrade water quality.

Cyanobacteria are bacteria, but like true algae and plants, can harness the sun’s energy to grow, developing dense surface scums or suspensions in the water or mats on plants, stones or the bottom. Many cyanobacteria are highly beneficial to food webs, but some of these species can develop noxious blooms, particularly in extreme or nutrient-polluted environments where their ability to control their buoyancy, resist desiccation and avoid predation gives them a competitive edge over more benign algae. Widespread deforestation, waste production, urbanization, agricultural development and use of fertilizers are resulting in an increasing number of HABs across inland waters in Canada and worldwide.

HABs have wide-ranging consequences on drinking and food-processing water quality, recreational uses, tourist activities, real estate value, livestock drinking water and aquaculture industries. Some strains of cyanobacteria produce toxins, which can affect the liver, nervous system or skin. Exposure most often occurs through ingestion, although direct contact can cause skin and membrane inflammation.

Cyanobacteria can produce a foul ‘muddy/musty’ taste and odour in water and fish, because of their ability to produce certain volatile organic compounds. Although these substances are non-toxic, they result in substantial costs for water treatment plants as they induce a negative consumer perception of the quality and safety of drinking water supplies.

HABs also affect ecosystem integrity through alteration of food webs, modified water chemistry and reduced oxygen content as algae decay.

Water S&T Research 

Mats of filamentous cyanobacteria are sampled by raking the riverbed | Photo: Christiane HudonTo gain a better understanding of distribution, abundance, and seasonal variations of planktonic (free living) and benthic (filamentous mats) cyanobacteria in both large and small water bodies, studies are being conducted in a diversity of surface waters across Canada, including Lake Winnipeg, Lake of the Woods, the Great Lakes, Prairie, Shield and Maritime lakes and the St. Lawrence, Detroit and Maumee rivers.

Researchers are using both remote and in situ instrumentation to contribute to the development of new monitoring techniques.  This involves the use of automated probes, satellite imagery to detect blooms over large areas, and remote sensing of their specific pigments. In addition, new predictive HAB models are being developed through studies linking cyanobacterial abundance to environmental variables such as land use, meteorological and hydrological conditions, climate, physical water quality, and nutrient concentrations (forms of phosphorus, nitrogen, and iron). Scientists are also working with provincial, municipal and local partners to evaluate the relative size and availability of different nutrient inputs to surface waters (such as wastes, soil, sediment and agricultural runoff) and investigate how they help to favour the development and toxicity/odour capacity of HABs species.

Foul taste and odour in water, induced by cyanobacteria and other nuisance algae, are being studied to determine the levels in source water and drinking water and the primary environmental and food web related causes and controls.

Environment Canada researchers are working in partnership with other agencies to develop analytical standards for measurements of known toxins and to identify and characterize the molecular structure of unknown toxins. The developed analytical methods will allow studies on the fate and transformation of toxins in aquatic ecosystems. Researchers are also collaborating with national and international partners to develop genetic probes to allow rapid screening of different water bodies for the presence of important HAB species which can produce toxins or odour.

Scientists are assessing both the toxicity of HABs, as well as their impact on the trophic network. Those toxins will be assayed across several taxonomic groups including decomposers (bacteria), primary producers (micro-algae), as well as primary and secondary consumers (micro-invertebrates and fish). These investigations will aid in quantifying the effects of algal proliferation on aquatic ecosystem functions.


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