Water advisories issued for blue-green algae at lakes and ponds

by Dave on June 15, 2010

The Department of Natural Resources and Environmental Control, the Department of Health and Social Services, Division of Public Health, and the Department of Agriculture have issued water advisories for Delaware state and municipal lakes and ponds to alert the public to the presence of blue-green algae, now being seen on local ponds, and its possible harmful effects on people and animals.

Blue-green algae – also known as cyanobacteria – are naturally occurring microscopic organisms that increase in density or “bloom” under certain environmental conditions, most commonly, an oversupply of nutrients, such as lawn chemicals and human and animals wastes, combined with warm water temperatures.

Blue-green algal blooms occur annually throughout Delaware on ponds and lakes of all sizes and some tidal freshwaters. They begin forming during summer and can continue through early autumn.

Blooms can form dense mats that appear most often as thick green, white or reddish-brown scum on the surface of the water that may be mistaken for a paint spill. The blooms or dense mats can cover entire areas of a pond or only certain portions such as along the shoreline or in isolated coves. When the algal blooms die and decay, the water can have a foul odor.

Certain strains of blue-green algae can produce toxins and the incidence of this occurrence is unpredictable. Although there have been no reported cases of human or animal illness in Delaware associated with exposure to blue-green algae, an inter-agency team developed educational water advisories as a common-sense, precautionary measure for the public. In addition, water advisory signs were posted at selected state and municipal lakes and ponds throughout the state.

Recreational activities that may inadvertently result in swallowing or inhaling droplets of water from blue-green algae blooms or areas of scum should be avoided. The best precaution is to avoid contact or exposure to blooms or scum. If contact is unavoidable or accidental, wash thoroughly.

Health effects to humans from skin contact can include rashes, hives and blisters, especially on lips and under swimsuits. Less frequent reactions reported nationally in individuals who have inhaled or swallowed water containing high concentrations of blue-green algae include, from inhalation: runny eyes and nose, sore throat, asthma-like symptoms or allergic reactions. If swallowed, reactions could include: diarrhea and vomiting, liver toxicity, kidney toxicity and neurotoxicity. If illness due to blue-green algae exposure is suspected, contact a physician.

Animals, both pets and livestock, may have the same adverse reactions as humans and should be washed after contact with the water. If illness is suspected, call a veterinarian and report possible contact with blue-green algae.

Toxins from blue-green algae have been documented in waters in other parts of the country where the algae is not visible or in full bloom. States from Massachusetts to Washington have developed guidance for the public who may recreate in fresh water bodies.

In Delaware, as elsewhere, dense blue-green algae blooms also contribute to lowered levels of dissolved oxygen, which can lead to fish kills. For more information including a fact sheet and Frequently Asked Questions, visit water advisories for blue green algae on DNREC’s website.

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