A Range of Impacts from Harmful Algal Blooms
Taste and Odor
These problems are often encountered in freshwater ecosystems. One of the Impacts from harmful algal blooms is foul smelling odor and may affect the taste of water even if the compounds are not toxic; this is caused by the compounds produced by the many algal species found in harmful algal blooms. The USGS and the U.S. EPA provide some understanding and guidance on taste and odor issues related to (among other things) harmful algae.
Decreased Aesthetics and Economics
In addition to off-putting taste and odor, certain algal species form foams or surface mats that affect the aesthetics of the environment. These issues can affect water use, as high accumulations of algae, even if they are not toxic, can make the water unpleasant for swimming, boating, fishing and other activities. In recent years, some of these problems have moved beyond purely aesthetic considerations and have resulted in negative economic impacts, even in the absence of truly toxic conditions. For instance, studies have shown that harmful algal blooms can lead to decreases in property values:
Animal and Health Risk
Some algal-based compounds are sufficiently toxic that they pose risks to human and animal health, sometimes even when there is no visible discoloration of the water. This latter situation is particularly true in marine ecosystems where filter-feeding organisms such as clams, mussels and other shellfish can concentrate the algal cells via their feeding activities and present health risk through their consumption.