Warmer Summers and Winters, More Great Lakes Algae Blooms

Here's a good explanation of algae blooms in the Great Lakes from Andrew Paterson, a senior scientist with the Ministry of the Environment in Canada.

There appears to be an increase in algae blooms across the Great Lakes...this is particularly evident in Lake Erie where an algae bloom visible from space is an annual occurrence, now. It should be noted that Paterson takes the cautious approach and says that algae blooms SEEM TO BE on the rise, but that could simply be a result of greater public awareness and more reporting.

When giving public lectures on the topic, I often hear the question: are algal blooms getting worse?

Anecdotally, this appears to be the case. With a few notable exceptions, I have yet to hear from a member of the public that their lake has fewer algal problems, or better water quality now than in the past.

The weird thing is, phosphorous levels are declining even as algae blooms appear to be on the rise, which is odd since algae blooms in the past have been associated with phosphorous levels.

So researchers are currently trying to figure out why there appears to be an increase in the number of algae blooms. Paterson seems to point to warmer, drier weather.

A rise in reports of algal blooms in Ontario is consistent with the observation that algal blooms are increasing in lakes throughout the world. Nutrient enrichment (in other words, increasing additions of phosphorus to lakes) is the leading cause globally, with blooms further exacerbated by climate change.

In Ontario, higher phosphorus concentrations are indeed part of the story. There are lakes near Sudbury, for example, where increased shoreline development and urbanization have contributed to higher phosphorus levels, and consequently, algal blooms.

However, in recent years, blue-green algal blooms have also been observed in lakes with low or declining phosphorus concentrations, suggesting that phosphorus is not the whole story.

Scientists are now beginning to report an increased likelihood and severity of algal blooms in summers that are warmer and drier. Warmer and longer summers, which are becoming more common in many parts of the province, can lead to warmer water temperatures, a longer ice-free season and more stable water columns in lakes. All of these factors favour blue-green algae and the development of algal blooms in general. My own research on Three Mile Lake found a link between the unusually warm and dry weather in late 2005, and the formation of an algal surface scum that year.

I'd like to point out the statement about longer ice-free seasons. Reduced ice cover is particularly of concern among Great Lakes researchers. The great thing about ice cover over the winter is it reduces evaporation. Greater evaporation over warmer winters creates the seemingly conflicting scenario where the winters are warmer....but you get more snow. Which seems to be what we have now. Climate change models for the Great Lakes predict less ice cover, more snow, and declining water levels. We may have to add more algae blooms to that list as well.