Removing Metaphyton

Nutrient reduction and pond deepening are the most logical preventative approaches for reducing metaphyton abundance. There are also two general low-budget treatment options: 1) application of algicides, and 2) mechanical removal.

Metaphyton may be treated with the same algicides used to control phytoplankton. Slow diffusion of the algicide into the often dense clouds of metaphyton may delay algal death and necessitate higher dosage levels. If massive scums of metaphyton are present at the time of algicide application, their death and decomposition may cause severe oxygen depletion within the water column, resulting in fish kills and offensive odors.

boat metatphyton screen

Boat at a pond in East Bradford Township (left), outfitted with screen to move metaphyton to shore, where it is collected
for disposal outside the watershed; (right) a “lake rake” for removal of metaphyton and aquatic plants
(photo courtesy of The Pond Guy, Inc.).

An effective alternative approach that avoids the side effects of chemical treatment is the physical removal of floating mats using long-handled threshing rakes, seines, or specially designed screens. These may be operated either from shore or from boats.

A major advantage of this approach is that not only the algae but also their stored nutrients are removed from the pond. It should be recognized, however, that filamentous algae near the bottom in deeper areas of the pond are less easily collected and these will produce additional surface scums over time. Mechanical removal is also a lot of work!

An important planning consideration is what to do with the metaphyton once it is harvested. Piling the material near shore should be avoided, and the receiving area should ideally be out of the watershed. The material is rich in protein, and should potentially make excellent compost. To date, however, little is known about how to recycle metaphyton effectively.