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What are Algae and Algal Blooms?

Algae are naturally occurring microscopic organisms found in fresh and salt water. Many are beneficial to the environment in which they live because they are a major producer of oxygen and are food for other organisms.

There are different types of algae, some of which can be dangerous.  When environmental conditions are favorable, algae can multiply at a rapid rate.  When there is an overgrowth of algae in a single area, it is referred to as an algal bloom. These algal blooms are not necessarily toxic or harmful to humans or the environment.  Those that are harmful are known as Harmful Algal Blooms

Signs, Types and Effects of Harmful Algal Blooms?

Harmful Algal Blooms or HABs can change the color of the water most being red or brown, referred to as “red” or “brown” tides. They can cause discoloration or an odor to be prevalent. Depending on the type of algae, the HAB could produce bad smelling scum, foam, froth, or a film on the surface of the water. If any of these signs are showing, it is advised for humans and pets to stay out of the water.

Types of HABs include red tides, cyanobacteria blooms (also known as blue green algae), and golden algae. Golden algae have so far shown no signs of being harmful to humans but are responsible for massive fish kills.

Cyanobacteria can produce cyanotoxins that can result in health related problems depending on the type. They can cause a variety of issues to include neurological damage, liver damage, skin irritation or respiratory malfunction.

Effects of HABs include:

  • Production of dangerous toxins that can sicken or kill people and animals
  • Creation of dead zones in water
  • Raises in drinking water treatment costs 
  • Hurting of industries that depend on clean water
  • Blocking of sunlight in water bodies

Causes of Harmful Algal Blooms?

There are a variety of environmental conditions that influence the growth of a HAB, including:

  • Nutrient pollution
    • The overabundance of nutrients such as nitrogen and phosphorous from urban and rural runoff.
  • Wind and water flow modifications
    • The change in the natural movement or flow of water, this can create still water areas perfect for growth.
  • Changes in water temperature
    • Higher temperatures create a perfect area for algal and bacterial growth. The algal mats then block the surface of the sunlight which leads to warmer water and more growth.
  • Climate change
    • Climate change is increasing the duration and frequency of droughts, low levels of water create less flow and warmer temperatures.
  • Human Activity
    • Sewage or agricultural runoff influx directly into water sources.

What can we do?

As a community we can be more mindful of nutrient pollution, support green infrastructure and smart water policies and conservation. If you think you see an algal bloom you can report it on websites like the Virginia Department of Health and the EPA. Areas that are showing algal blooms can then be tested to see if it is in fact a HAB.  Click here for the Virginia Department of Health’s current HAB map and the link to reporting algal blooms.