Algae Blooms

If you've walked by the shore of Greenwich Bay at low tide, you've probably seen it: mats of green stuff appropriately nicknamed "sea lettuce."

If you've waded or swum through it, or tried to run your boat engine in it, you know that in some places there is a lot of it and that it can be a nuisance. When it grows in large numbers, it can also block sunlight to other plants such as eelgrass and when it dies, the bacteria that break down the dead plants can use up large amounts of dissolved oxygen in the water.

Sea lettuce—Ulva lactuca—is one type of macroalgae: simple aquatic or marine plants that are large enough to be seen with the naked eye. Under certain conditions, these algae can grow in enormous numbers, causing some of the problems mentioned above. This growth is called an algae bloom.

Blooms of macroalgae are not only a problem in and of themselves. They are also a very important symptom of a larger process that may affect many more parts of the Greenwich Bay ecosystem: eutrophication.