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Freshwater Algae & Cyanobacteria

The growth of algae, cyanobacteria and other aquatic plants and animals can affect the quality of water in several ways. They can cause unsightly scums, impart tastes & odours, produce toxins, block filters, increase turbidity and restrict flow in pipes and channels. Cyanobacteria are of most concern, because some species can produce toxins which may have adverse health effects.

The AWQC provides a comprehensive service for the monitoring and assessment of algae and cyanobacteria in source waters for drinking supplies, wastewaters and in fresh and marine waters used for recreation and agricultural/aquaculture use. The Algal Laboratory is NATA accredited for a range of phycological services, including the collection of planktonic and non-planktonic samples, the microscopic identification and enumeration of algal and cyanobacterial taxa and the estimation of their biomass (refer table below).

The majority of samples analysed for algae and cyanobacteria should be received in the laboratory within 24 hours of collection, unless preserved upon collection. Customers can choose from a range of turnaround times for reporting of results, including a same day service for samples requiring urgent attention.

Phytoplankton and periphyton are identified from morphological criteria and enumerated by estimation of cell abundance per unit volume. Identification is generally to genus level, but toxin and odour producing taxa of cyanobacteria can be identified to species level, as required for compliance reporting against national water quality guidelines. A choice of algal scans (identification only), partial algal counts (selected species), total cyanobacteria and full algal counts are available, depending on the objective of the monitoring program and customer instructions. The uncertainty of measurement in algal enumeration is largely attributable to the clumped distribution of cells in colonies and filaments and sample preparation prior to enumeration can include disaggregation of large aggregates. A measure of cell viability of a cyanobacterial population (eg immediately following algicide treatment) can be determined by microscopic examination of auto-fluorescence.

Total algal biomass is an indicator of trophic status of environmental waters and can be analysed by spectrophotometric determination of chlorophyll pigments (chlorophyll a, chlorophyll b and phaeophytin). Estimates of cyanobacteria biovolume are a useful indicator of potential health risk and can be offered as a measure of species specific biomass, using microscopy and analysis of digitised images.

Certain algae and cyanobacteria produce characteristic odours when present in high numbers and the Biology Unit offers olfactory analysis of hot (60oC) and cold odours, categorised by descriptor and intensity rating as a complementary test to microscopic identification.

TEST METHOD UNITS

TYPES OF SAMPLES

Algal Scan (Identification)* Microscopic species level for noxious cyano-bacteria; otherwise genus level Phytoplankton or benthic algae in freshwaters, marine waters, estuaries, and wastewaters
Algal Identification and Full Enumeration* Microscopic cells/mL ID as above As above
Algal Identification and Partial Enumeration* Microscopic cells/mL ID as above As above
Cyanobacterial Identification & Enumeration* Microscopic cells/mL ID as above As above
Algal Biovolume* Microscopic mm3/L Phytoplankton
Chlorophyll - a & b* Spectrophotometric determination ug/L Phytoplankton in fresh-waters, marine waters, estuaries and wastewaters
Chlorophyll a & Phaeophytin* Spectrophotometric determination ug/L Phytoplankton in fresh-waters, marine waters, estuaries and wastewaters
Hot and Cold Odour Olfactory determination descriptor and intensity rating Range of Waters
Algal Viability Fluorescence Microscopy N/A Samples assessed for physiological status

* NATA Accreditation held

Algae Fact Sheet