The USGS Water Science School[an error occurred while processing this directive]
Algal blooms are true to their name—they bloom for relatively short times. But just because they are less than permanent fixtures in the hydrologic landscape doesn't mean that they can't have a big, and nasty, impact on a poor lake subjected to them.
This picture below show Brookmill Park Lake, a pleasant country lake in a public park amid the urban settings near Greenwich in Great Britain. Water in the lake comes from streamflow from a nearby river. Certainly a pleasant pastoral setting for any person or duck. The picture, taken in October 2008, shows Brookmill Park Lake during normal conditions.
The picture below shows Brookmill Park Lake again, 11 months later in September 2009. A number of things—stagnant water movement, high temperatures, and/or an influx of nutrient material, such as lawn fertilizers—could have contributed to the explosive growth of algae to form this thick green mat. I'm not sure if odor was a problem at this time, but I'm sure even if no smells were present, the local residents did not sit by this lake for a pleasant family picnic. Well, at least the duck seems to be enjoying having this lake all to himself, unless he is stuck in the gooey mess and can't get out.