Researchers representing the National Water Research Institute, Environment Canada and Ontario Ministry of the Environment began their research into the origin of late summer taste and odour (T&O) in western Lake Ontario in 1999 and are continuing their intensive research efforts in 2005.

Research Objectives

• Identify the mechanisms that promote the production of Geosmin and/or modify the severity of the T&O experienced by consumers
• Determine the time course of T&O events and associated major water quality parameters
• Intensive monitoring of Toronto area/lakewide survey for nutrient effects on algae and T&O
• Survey utilities around the Great Lakes to determine their experience with T&O, including control
• Determine the biological origin of T&O caused by elevated levels of Geosmin and MIB in Lake Ontario
• Develop a mechanistic model to predict outbreaks

Key Research Findings

Study Sites (2003)
Intensive monitoring of physical, chemical and biological parameters continued at a series of sampling sites offshore of the Region of Peel.

Additional sampling of the whole lake including Hamilton Harbour, the Bay of Quinte and the upper St. Lawrence River was carried out during the annual lakewide survey conducted in late summer. Samples were taken at the surface, thermocline and hypolimnion and analyzed for Geosmin, phytoplankton biomass and species, and nutrient levels.

Cause of Taste and Odour Production
There is strong evidence to suggest that the main contributor of Geosmin in the western basin of Lake Ontario is the bluegreen alga, Anabaena lemmermanii. Samples of this algae were taken from Lake Ontario and cultured under various conditions: nutrient levels, temperature and light. Results showed distinctive variations in:
1. Morphology
2. Growth/abundance
3. Geosmin produced / cell

Although A. lemmermanii is known to be a Geosmin producer, the samples isolated from Lake Ontario have yet to yield high levels of Geosmin. Intensive work is underway to culture this alga under varying environmental conditions and findings may lead to the development of control options and/or early warning tools.

In 2004, researchers were able to develop a protocol to measure short-term Geosmin production rates through their work with A. lemmermanii isolates from Lake Ontario and one from the United States. Genetic typing of the isolates is ongoing in 2005 with the goals of developing a genetic-based method to identify Geosmin-producing cyanobacteria in environmental samples and determining if there are different producing and non-producing A. lemmermanii strains in Lake Ontario.

Deep Water Free of Geosmin
Intensive sampling over five years has confirmed that the lower layer of water (hypolimnetic layer) in Lake Ontario is essentially free of T&O. Water intakes at 30 metres depth, or greater, can consistently draw hypolimnetic water and should not be impacted by taste and odour.

Annual Geosmin Peak
A Geosmin peak occurs annually usually at the end of August each year, but the intensity of the peak varies between years. 1998 & 1999 showed the highest recorded Geosmin peaks with levels reaching over 100 ng/L, while peaks since have averaged around 10 ng/L.

In 2003, the T&O peak occurred on Sept. 17th approximately 2 weeks later than seen in previous years. Geosmin showed its highest peak levels since the severe T&O events in 1998 and 1999. At the time of the peak, the Geosmin levels within the upper mixing layer (thermocline) were similar to levels found in surface waters and odour was detected in public water supplies in some member municipalities. The abundance of A. lemmermanii increased in offshore samples during this time although overall biomass of the alga was not high.

In 2004, there was a significant T&O event, which elicited consumer complaints, press releases and media coverage. Geosmin levels at the water treatment plant intakes began to increase coincident with a downwelling event during the last week in August. The annual LIMNOS Lake Ontario cruise was carried out the week following the initiation of the downwelling. The survey reported major patches of surface odour (verified using a kettle assay), which corresponded with increased densities of A. lemmermanii. Geosmin levels over much of the western basin were high at this time, particularly in the near inshore area between Hamilton and Oshawa. As in other years, MIB was generally low or undetectable over most of the Lake.

Delivery to Water Treatment Intakes through Downwelling
Intensive field investigation continued in 2003 to gain insight into the physical delivery of geosmin from the open lake to the water treatment plant intakes. The 2002 current and temperature data showed that high levels of Geosmin at the intakes coincided with an increase in intake temperature. These findings supported the data collected in 2000. Further analysis of data lead researchers to believe that Geosmin is being produced in the open lake and is delivered to the near shore zone, and water intakes, by downwelling events driven by easterly winds.

In 2004, researchers focused on the hypothesis that upwelling-relaxation (calm conditions/low turbulence in the upper water column due to weak winds) followed by downwelling events coincided with both the production and transport of Geosmin to the intakes. Two temperature moorings with thermistors at LV2 and LV3 were deployed. As observed in the previous year, the T&O event coincided with downwelling, preceded by an upwelling event.

Hydrolab profiling and field observations suggest that Geosmin production may be modified by the rapid upward movement of algal cells during the upwelling and their subsequent trapping at the surface, because of low turbulence during the calm period. These rapid changes in light and temperature may help in determining why conspicuous aggregations of A. lemmermanii are not always reported as odourous.

Daily monitoring and reporting of wind patterns have served as an effective early warning of downwelling and subsequent Geosmin increase to participating utilities along the NW shore. Values of major parameters such as light, temperature, conductivity, current, insulation, nitrogen, phosphorus, chlorophyll a and algal community assemblages collected during the 2000-2005 field work will be used in multivariate analyses with the aim to identify the most important drivers and modifiers of these events, and thereby develop a model to predict their timing and severity.

Survey of the Great Lakes Water Utilities
In July and August of 2004, the Ontario Clean Water Agency, at the request of the member utilities, conducted a survey of both Canadian and American Great Lakes water utilities to determine the location, frequency and severity of T&O problems, and the success of various treatment methods. The results of the survey are available here.

Cumulative Surface Water Temperature and T&O
A rapid increase in the spring cumulative surface water temperature was seen in both 1998 and 1999. Although there was a considerable T&O event in 2003, the spring cumulative temperatures did not follow this same trend. In 2003, a prolonged cool early spring and summer were followed by very warm weather and a rapid increase in surface water temperature in early fall.

Surface water temperature in 2005 is showing a similar trend with 1998 and 1999, although the rapid increase in temperature previously seen in the spring occurred slightly later (June). Cumulative surface water temperature in August is the highest recorded since 1998 and may indicate the onset of a large T&O event. Researchers are preparing for the annual LIMNOS lakewide survey and continue to monitor the Lake closely with the help of the member utilities.

2005 Research Plan

• Continue to collect field data on timing and severity of T&O events in Lake Ontario
• Determine if the intensity and timing of Geosmin peaks/ abundance of A. lemmermanii in offshore waters is moderated by thermal regime, high light intensity/UV and/or reduced NO3 levels
• Establish more A. lemmermanii isolates to examine:
  • the robustness of Geosmin production and its response to changes in light and temperature,
  • taxonomy and odour production of A. lemmermanii using morphometric and genetic criteria, and
  • whether strains of odour and non-odour producers are of the same species or if several species are involved

This study was carried out with assistance from the Green Municipal Enabling Fund which in turn is funded by the Government of Canada and is administered by the Federation of Canadian Municipalities (FCM).

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