Wednesday, August 27, 2008

Harmful algal blooms, or HABs

Harmful algal blooms, or HABs, in the new limno-lingo, represent a serious issue. When I was in lake school many years ago, we knew that certain algae could be hazardous. But these were marine algae that caused red tides or were rare events in freshwater, and then usually in cow ponds. Now HABs are front and center at many lakes.

The EPA report, Scientific Assessment of Freshwater Harmful Algal Blooms (available from EPA as a PDF) is the latest compendium of HAB science and is the techno-tell-all of what we know and what we no not know about HABs. We know for example that:
“Freshwater HAB toxins can have a broad range of negative impacts on humans, animals, and aquatic ecosystems. Many cyanobacteria can produce neurotoxic, hepatotoxic, dermatotoxic, or other bioactive compounds, and blooms of toxigenic cyanobacteria pose a particular threat if they occur in drinking water sources.”
A lot of new words and jargon that say in essence that these blooms can’t be good.

Seriously, as lake managers, we cannot ignore HABs. HABs pose threats beyond what we have traditionally dealt with as lake managers. HABs threaten water supplies, human health, and fish and wildlife.

What we don’t know or at least don’t know well includes risk assessment, analytical methods, toxicity pathways, or the appropriate response framework. The report provides an assessment and roadmap to better attend to these needs.

Of course, if we confront lakes experiencing HABs, we cannot wait for the answers to all the unknowns. We can fall back on our tried-and-true approaches to lake management - lake management basics – which ought to be relied upon to minimize and manage the impacts of HABs.

This means priority ought to be given to nutrient management. Specifically,
  • Top priority for watershed protection for those lakes not yet affected by HABs
  • For lakes already experiencing HABs, watershed rehabilitation may be too slow, so in addition, we should initiate in-lake nutrient reduction methods.
  • In cases where nutrient reduction may not be timely or sufficient, other in-lake techniques should be used.
These strategies and techniques are explained fully in the textbook, Restoration and Management of Lakes and Reservoirs or the manual, Managing Lakes and Reservoirs – both available in the NALMS Bookstore (currently off-line). You may also purchase Managing Lakes and Reservoirs through using the Lake Stewardship Store.

Article by Dick Osgood, President of the North American Lake Management Society (NALMS), used by permission. Read the latest NALMS' newsletter online.