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Chesapeake Bay News

Sep
03
2010

What do algae blooms mean for water quality?

Welcome to the latest installment of the BayBlog Question of the Week! Each week, we take a question submitted on the Chesapeake Bay Program website or a frequently asked question and answer it here for all to read.

This week’s question comes from Peg: “We have a second home on a creek in Virginia. While there last week, I noticed an unusual quality in the water. The water appeared unusually murky and quiet and there was a large ribbon of a reddish brown color, very distinct, stretching through our cove.  Contrary to normal situations there was a period of time where there were no fish noticeably jumping or swimming and no birds fishing. Could this have been some sort of red tide or algae bloom and what does that mean as far as water quality?”

Each spring and summer in the Chesapeake Bay region, low-oxygen “dead zones” and harmful algae blooms appear in various parts of the Bay and its creeks and rivers. The size and severity of algae blooms and dead zones in the Bay depend on the amount of water that flows into the Bay. That water brings excess nutrients and sediment from the land. Combined with high temperatures, the excess pollutants can fuel the growth of algae blooms and cause the water to become clouded and discolored.

The water condition Peg may have observed is called a mahogany tide, which can cause the water to appear reddish brown. Mahogany tides may also deplete the water of oxygen, which may be why Peg did not see fish in the water as she normally does. Algae blooms make conditions difficult for much of the aquatic life in the Chesapeake Bay. 

Algae blooms can be very detrimental to the health of the Bay. Some are considered harmful algae blooms (HABs) and can be toxic to aquatic life such as fish, oysters and crabs. They can also cause skin irritation or other sickness to people who come into contact with them.

Even if algae blooms aren’t toxic, they can still be harmful to the Bay. When algae blooms get dense enough, they block sunlight from reaching bay grasses growing at the bottom of the Bay. Of course, bay grasses are vital to the Bay's health, so when fewer bay grasses grow, the cycle of poor Bay health continues. When algae blooms die they create more problems, as the decomposition process sucks up most of the oxygen that fish, oysters and crabs needs to survive.

Since algae blooms are fueled by excess nutrients, you can do your part to help prevent algae blooms in your local waterway by taking small steps to decrease polluted runoff. Small steps such as not fertilizing your lawn, picking up your pet's waste and planting more trees in your yard can make a difference.

Do you have a question about the Chesapeake Bay? Ask us and we might choose your question for the next Question of the Week! You can also ask us a question via Twitter by sending a reply to @chesbayprogram! Be sure to follow us there for all the latest in Bay news and events


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