3. Harmful Algal Blooms

Algae on the news
What do these headlines tell you about the character of algae?

Algae - What are they?

Algae are photosynthetic organisms that occur in most habitats, ranging from marine and freshwater to desert sands and from hot boiling springs to snow and ice. They vary from small, single-celled forms to complex multicellular forms, such as the giant kelps of the eastern Pacific that grow to more than 60 meters in length and form dense marine forests (Smithsonian).

Good algae or bad algae?

From the news headlines you have probably infered that algae can be both - useful and harmful.
Algae are important as primary producers of organic matter at the base of the food chain. They also provide oxygen for other aquatic life. Algae contribute to economic well-being in the form of food, medicine and other products but they may also contribute to mass mortality of other organisms - in cases of algal blooms.

This chapter is about

• how algae form blooms and how they can become ocean polluters



• the effects of harmful algal blooms on marine life



• how harmful algal blooms may affect humans



• the use of remote sensing to detect and follow algal blooms

The chalky white exteriors of single-celled marine plants called coccolithophores are colouring the water of the Atlantic Ocean bright blue. Like other types of phytoplankton, coccolithophores are a source of food for marine organisms. Though coccoliths are small, they often form large, concentrated blooms that are visible from space. On June 15, 2004, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this image of a bloom off the coast of Brittany, France. The bloom had been developing for a few days before this image was taken.
Source: NASA, Credits: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC