Closed waters: Managing toxins in Alberta’s surface waters will be far from simple

Closed waters: Managing toxins in Alberta’s surface waters will be far from simple

A recent study about high microcystin concentrations in lakes across the country hit the media recently.  The study found that lakes across Canada and many in Alberta had high levels of the liver toxin often exceeding guidelines for potable use and recreational water quality. Microcystin is created by cyanobacteria (blue-green algae) which are often found in surface waters rich in nutrients, nitrogen and phosphorus. (See a map of eutrophic or hypereutrophic lakes in Alberta).

The study found that microcystin levels occurred where there was low ratios of nitrogen to phosphorus (N:P) and decreased as the ratio increased;  however, the causal connection between the low ratio and creation of microcystin has not been established. How are we to respond at a policy or regulatory level to such a finding?

Measuring and managing nitrogen and phosphorus inputs into surface water is an intensive and often complex task, with both natural and anthropogenic and point and non-point sources.  From a regulatory standpoint Alberta does little to regulate phosphorus from non-point sources and has various standards embedded in approvals for phosphorus from point sources (such as effluent streams from waste treatment plants).  Nitrogen garners additional regulatory coverage in Alberta (see, for example, the Standards and Administration Regulation under the Agricultural Operations Practices Act) but we don’t know whether these regulatory standards are resulting in appropriate outcomes when it comes to nitrogen in surface water.   The government has also initiated a multi-stakeholder pilot project on the Bow River in an attempt to manage phosphorus.

The microcystin study adds to the complexity of potential management by raising questions about whether we must move towards managing the ratio itself.  The study suggests

that subsequent experiments should manipulate N:P ratios – at scales relevant to ecosystem management – as the outcome may be germane to the ongoing debate regarding the need for a “dual –nutrient management strategy.”

This in turn leads to more questions. If management strategies merely focus on one nutrient, to acquire a high N:P ratio with the aim of minimizing mycrocystin production, what unforeseen or unintended consequences on aquatic ecology might result?

Further, we can barely get our collective effort around managing one nutrient, let alone the ratios between N and P, as additional study might suggest is needed. However, if we want to swim, we must commit to trying.

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