Over the last 50 years, the amount of nitrogen (N) and phosphorus (P) pollution entering our nation’s waters has escalated significantly.  This type of pollution, referred to as nutrient pollution, now affects 30% of U.S. streams.  When excess nutrients enter streams and lakes, increases in N and P concentrations may trigger algal blooms.

Algae are a natural component of the aquatic food chain and are typically not harmful to people. However, some algal species, known as Harmful Algal Blooms (HABs), may cause harm through the production of toxins.  HABs can cause illness or irritation – sometimes even death – in pets, livestock, and humans.  Most HABs are caused by planktonic bacteria called cyanobacteria, which are commonly known as “blue-green algae.”  Cyanobacteria often float to form scums on or near the surface, forming colonies that often look like bright green paint.  Not all algal blooms are HABs and cyanobacteria should not be confused with small harmless aquatic plants called duckweeds or other true algae.  The blooms can also be blue, brown, or red; most look like paint floating on the water. Some blooms may not affect the appearance of the water.

Many HAB-forming organisms are native to Ohio, but only cause problems with environmental conditions (often human-induced) favor them. Factors that contribute to HABs include an overabundance of nutrients, sunlight, low water, calm water, warmer temperatures, and low salinity.  Nutrients that contribute to HABs and other algal blooms come from many sources, including agriculture, lawn fertilizers, wastewater treatment plants, sewer overflows and leaking septic systems.  In addition to these external sources, the internal cycling of nutrients within lakes and ponds can also trigger algal blooms.

HABs can occur almost anywhere there is water: lakes, ponds, stormwater retention basins, rivers, streams or reservoirs.  HABs can cause taste and odor problems in drinking waters, pollute beaches with scum, reduce oxygen levels for fish and other animals, causing processing problems for public water supplies, and may generate toxic chemicals.  Cyanobacteria can cause a range of problems for recreation and the environment, but at their worst they can cause health problems because of their ability to produce toxins.  It’s important to note that the mere presence of cyanobacteria does not necessarily mean that toxins are being produced. The level of toxicity depends on the strains of cyanobacteria present and environmental factors (i.e. the amount of nutrients, light, temperature, etc.).

The Ohio EPA, Ohio Department of Health and Ohio Department of Natural Resources are monitoring HABs across the state and working to educate local communities.  The State issues advisories when toxins released by cyanobacteria are detected and exceed health standards for recreational use.  People and pets are advised to minimize contact with and avoid ingestion of the lake water.

For more information, visit: http://epa.ohio.gov/habalgae.aspx