Text Size: A  A  A

Chesapeake Bay News


The ABCs of HABs: How Harmful Algal Blooms Impact the Bay

Algae are a vital component of the Bay's ecosystem—these free-floating plants make up the base of the food chain. Their size ranges from tiny microscopic cells floating in the water column (phytoplankton) to large mats of visible "macroalgae" that grow on bottom sediments. Algae behave much like land plants, soaking up the sun's rays to produce energy while converting carbon dioxide to oxygen during photosynthesis.

However, when algae populations explode to unusually high numbers they create what are called harmful algae blooms (HABs), which can:

  • Block sunlight that is vital for underwater bay grasses.
  • Impede filter-feeders from obtaining food.
  • Produce smelly surface scum.
  • Consume dissolved oxygen when the algae die and decompose.

In addition, certain algae can also produce harmful chemicals that are toxic to humans, wildlife and aquatic life. Fortunately, of the more than 700 species of algae in Chesapeake Bay, less than two percent of them are believed to have the ability to produce toxic substances.

HABs are primarily fueled by excess nutrients (nitrogen and phosphorous) in area waterways, which come from agriculture, air deposition, septic systems and sewage treatment plants, and runoff from lawns, gardens and paved surfaces.

While phytoplankton form the base of the food chain, the amount of nutrients now entering the Bay is overwhelming the system. Oysters and other filter feeders can't consume all the phytoplankton in the water. Unconsumed phytoplankton sink to the bottom of the Bay and are decomposed by bacteria in a process that depletes the water of oxygen. Decomposing phytoplankton, combined with high summer water temperatures, can cause large swaths of the deepest parts of the Bay's mainstem to have little or no oxygen to support fish, crabs and other marine life.

Residents of the Bay watershed can help give the Bay's crabs, fish and other species some relief from HABs by taking simple actions to reduce nutrient pollution, including driving less, upgrading septic systems, picking up pet waste and reducing the use of lawn fertilizers.

Bay Program partners actively monitor the region's waterways for HABs, so that if one occurs the public can be notified to protect human health. Citizens are also asked to keep a watchful eye out for possible HABs and are urged to report suspected HABs to their respective state environmental agency:

  • To report HABs in Maryland call (877) 224-7229.
  • To report HABs in Virginia call (888) 238-6154.

Keywords: algae, phytoplankton



Dina says:
January 25, 2012

Hi! My name is Dina and I am doing a projest in science class. It is on Phytoplankton and I found out some really neat things. I got inspired when my science teacher showed me a video of how to save the C. Bay. I then went to the local pet store and asked them for a tank of salt water. I then called many people but I found someone who breeded aquatic animals. I asked if I could have a special order of 72 oysters to breed. I mean, this tank was huge! I had to fill it up! However, I had to be very patient and wait for the oysters to be old enough to reperduce. I finally got the call and headed to pick them up. I put them in the tank and so sediment, plants, and bay-familiar fish. Now, I basically have my own coral reef!


Daniil German says:
September 15, 2016

My hypothesis…
  Big sharks were killed a number of years ago leading to increase in ray and small shark populations which lead to a decrease in the rays food - mollusks, which now can not help control the algal population.

Post A Comment:



410 Severn Avenue / Suite 112
Annapolis, Maryland 21403
Tel: (800) YOUR-BAY / Fax: (410) 267-5777
Directions to the Bay Program Office
Terms of Use | Privacy Policy
©2012 Chesapeake Bay Program | All Rights Reserved