Current Harmful Algal Bloom Status at Blue Marsh Lake - WATCH

Conditions at the lake make the water susceptible to harmful algal blooms. Be alert and avoid areas that are noticeably green or blue green, have algae-like scum, foam, mats, or clumps present, or have a paint spill like or streaked appearance. Do not ingest the water.  
This status can change quickly during the season as regular testing is completed to monitor the water conditions. Be sure to check current water conditions before your visit. 

Current Harmful Algal Bloom Status at Blue Marsh Lake - ADVISORY

Current Harmful Algal Bloom Status - WARNING

Algal Bloom Examples

Aerial images can capture the extent of algal blooms. Here you can see that the algal bloom is widespread throughout the lake, with large concentrations of algal bloom congregating along the bend of one of the Blue Marsh Lake arms. The main channel of the lake flows faster along the upper portion of the image, whereas the slower moving water along the bottom of the image shows how water movement affects algal blooms. Photo taken in 2019 by visitor Jim Demsko in his airplane.
This photo displays an algal bloom occurring along the shoreline of the Blue Marsh Lake Swim Beach, Leesport PA. Wind and wave action can push algal blooms up along a shoreline making them very noticeable. Photo taken on 06 October 2021.
Harmful algal blooms can have a streaking or paint-like appearance on the surface of the water. Photo taken on 29 August 2021 at Blue Marsh Lake, Leesport PA.
Harmful algal blooms can look like a can of green paint was spilled on the surface of the water. Wind and wave action pushes the algae up along the shoreline making it more noticeable. Photo taken on 27 August 2020 at Blue Marsh Lake, Leesport PA.
Harmful algal blooms can appear to look like paint spilled on the surface of the water. Here the algal bloom is widespread but with clumping characteristics. Photo taken on 30 July 2018 at Blue Marsh Lake, Leesport PA.
Harmful algal blooms can have a thick scum or mat-like appearance on the surface of the water. Photo taken on 27 August 2020 at Blue Marsh Lake, Leesport PA.
Thick layers of algae can clump together and is an indicator of a harmful algal bloom. Photo taken on 04 August 2021 at Blue Marsh Lake, Leesport PA.
Algal blooms can be different colors including blue, blue-green, bright green, brown, and red. Here the harmful algal bloom has a blue-green appearance with streaking of light green and white. Photo taken in 2019 by visitor Chad Steinman while fishing.
Algal blooms can occur year round. Here a small algal bloom occurs during the winter months. Photo taken on 04 November 2021.

Blue-Green Algae & Harmful Algal Bloom Facts

Blue-green algae, also known as cyanobacteria, are microscopic organisms found naturally in all types of water. In warm, nutrient-rich environments, cyanobacteria can multiply quickly, creating blooms that spread across the water's surface. 

Harmful algal blooms, or HABs, are known as the intense, rapid growth of algae or cyanobacteria in the water with the potential to harm human health or aquatic ecosystems. Some cyanobacteria can produce toxins that are harmful to people and animals. 

You may or may not be able to see algal blooms. They sometimes stay below the water's surface, or they may float on the water's surface. Some blooms can look like foam, scum, or mats, particularly when the wind blows them toward a shoreline. Harmful algal blooms sometimes look like paint streaked on the water's surface and can be different colors. The blooms can be blue, bright green, brown, or red. As cyanobacteria in a bloom die, the water may smell bad, similar to rotting plants, as they decompose in the water. 

Heavy rainfall and significant runoff conveys nutrients to the reservoir. When followed by hot weather, blue-green algae can thrive and multiply. 

When in doubt, stay out!

  • Avoid water contact in areas where the water is discolored or where you see foam, scum, or mats of algae on the water’s surface.
  • Children and pets are especially susceptible to the harmful effects of the toxins produced by blue-green algae. Do not allow children or pets to play in or drink discolored/scummy water.
  • If you have contact with water that might contain harmful cyanobacteria, rinse off with fresh water as soon as possible afterwards.

Algal blooms are an annual occurrence at Blue Marsh Lake. Algae can be present year round within the lake, however large algal blooms and HABs typically occur and persist throughout the summer months (June - September). Generally, algal blooms disappear in late September or early October once water temperatures start cooling off. 
Throughout the summer, algal bloom conditions can worsen or improve depending on:

  • air and water temperatures (hotter = more severe)
  • rainfall and lake sediment input of nutrients (more = more food for reproduction and growth)
  • wind action mixing of the surface waters (more = break up of algae colonies)

Algal bloom statuses change depending on the current conditions present within the lake. Risks to humans and animals increase as a status increases from Watch to Advisory to Warning. Algal bloom statuses can change quickly throughout the season, especially from June through October.

WATCH - The conditions for an algal bloom to occur are present, however there has not been a HABs sighting/report. 

ADVISORY -  Algal blooms are currently occurring in the lake and the conditions for a HAB are present.

WARNING - Harmful algal blooms are currently occurring in the lake. 

Contact Information

Blue Marsh Lake Office
1268 Palisades Drive
Leesport, PA 19533-9750