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Pike Conservation District: What Are Harmful Algal Blooms? Climate Change Makes Them More Prolific, Intense

The latest newsletter from the Pike County Conservation District includes two timely articles on harmful algal blooms that release toxins into bodies of water.

Look for more information on the District's Instagram and Facebook during its Harmful Algal Blooms Month.  

What Are Harmful Algal Blooms?

By: Rachael Marques, PCCD Watershed Specialist

A harmful algal bloom (HAB or cyanoHAB) can occur when a naturally occurring cyanobacteria, or blue-green algae, begins to grow out of control in its environment.

Some species of cyanobacteria naturally have the potential to create toxins and, when they bloom, the toxins can be released within water bodies. These HABs often are mistaken for green algae which is also naturally occurring but does not produce toxins.

The large issues with HABs are that they can lead to fish kills due to low oxygen in the water as well as illness in people and animals due to the toxins produced. It is also possible for cyanotoxins to leach into drinking water sources.

Harmful algal blooms tend to occur in our area in the late summer to early fall when the water is warmer.

Their frequency is on the rise nationwide, and this is generally linked to increases of human activities such as point-source discharges and nonpoint source pollution from stormwater and surface runoff.  

Climate change is also thought to be a suspect.

Additionally, we have all probably experienced walking in a parking lot during the summer heat. When rainwater washes over these areas it can unintentionally cause rainwater to heat up before it reaches a stream.

The combined factors listed above lead to the perfect conditions for HABs since cyanobacteria like warm, slow-moving water and extra available nutrients to grow.

Several practices may limit the growth of HABs including the installation of riparian buffers which filter excess nutrients in runoff before it reaches local water bodies.

Management of nonpoint source pollution from urban areas as well as from areas with heavy nutrients such as farm fields and over-fertilized lawns can also help prevent these blooms.

It is important to note that algae and cyanobacteria are naturally occurring and play a critical role in aquatic ecosystems.

They play the role of the base of our aquatic food webs, like the one below, and produce more oxygen on planet Earth than trees!

Without these cyanobacteria and algae (shown as phytoplankton in the diagram) our aquatic ecosystems would not function.

The key is to maintain the natural balance of these aquatic ecosystems through best management practices like those listed in the previous paragraph. 

If you suspect there is a HAB in your local waterway, e-mail the Pennsylvania HABs Task Force at  and/or report it to your local community manager.

Visit the CDC HABs webpage or the state Department of Health HABs webpages for additional information regarding the health effects of HABs.

When going to water bodies for recreation, keep an eye out for HABs warning signs and advisories. It is best to avoid recreating in bodies of water where a HAB is suspected.

Resources Links:

-- DEP - What Are Harmful Algal Blooms?

-- EPA - Interactive HABs Map

-- Penn State Extension - Harmful Algal Blooms video 

Climate Change and Harmful Algal Blooms

By: Devan George, Communications Coordinator

Climate change is the long-term shift in temperatures and weather patterns, often resulting in more frequent and severe weather events.

This shift is predicted to have a massive impact on freshwater and marine environments, affecting the plant and wildlife that live there, as well as humans.

As a result, Harmful Algal Blooms can become more prolific and more intense.

Harmful Algal Blooms are overgrowths of algae in the water that can produce dangerous toxins..

These toxins pose a danger to humans, pets, wildlife, and entire aquatic habitats. It is because of these adverse health effects that everyone should be on the lookout for HABs in local water bodies.

There are three things that HABs need to be successful in an ecosystem-- sunlight, slow-moving water, and nutrients like nitrogen and phosphorus.

These nutrients can come from human activities, such as agriculture, stormwater, wastewater, and from individual properties..

These nutrients are often in high levels as a result of human activity, encouraging blooms that are more severe and more frequent.

Climate change adds to these nutrients, supporting the growth and intensity of HABs, making the perfect conditions for proliferation.

Harmful Algal Blooms typically bloom in the warm summer season, when sunlight is most available, and toxic blue-green algae prefers warm water.

As Climate Change creates warmer weather conditions, it warms surface waters as well. Warmer water also leads to less water mixing in surface water, allowing algae to grow thicker and faster.

As Climate Change continues to contribute to warmer weather and humans continue to add nutrients to surface waters, Harmful Algal Blooms will become more intense and more frequent in water bodies across the globe, and here in Northeast Pennsylvania.

For more information on services to landowners and other environmental topics, visit the Pike County Conservation District website.  Click Here to sign up for regular updates.

[Posted: July 1, 2022]


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