EVERYTHING YOU NEED TO KNOW ABOUT METAPHYTON

By Scott Williams, Aquatic Biologist

Many Maine lakes were clearer than normal this summer and that can be attributed to an unusually warm, sunny and dry summer. Rainfall was nearly nonexistent and dry weather positively affects lake clarity. Without rain, there is no stormwater runoff. Runoff is the primary means by which most pollutants from the watershed reach the lake.

The nutrient phosphorous is the pollutant of greatest concern. Phosphorus stimulates the growth of algae (microscopic plants) which in turn affect the overall clarity of lake water. Another component of stormwater runoff influencing water clarity is sediment from eroding soil. The combination of phosphorous and sediment can cause dramatic reductions in water clarity.

But warm, sunny weather sometimes causes in increase in other forms of plant growth in lakes. Metaphyton is a wispy, filamentous form of algae that grows in shallow areas near the shoreline. In appearance, metaphyton is sometimes described as "green cotton candy." This common algae often forms large billowing clouds in the water. But there is little substance in the clouds, as anyone who has tried to pull them from the water can attest. Last summer Maine people reported an increase in metaphyton, probably because of the unusually warm weather.

While it’s impossible to control weather, it certainly is possible to minimize stormwater runoff to the lake. Many simple conservation practices can be applied to capture, filter and reduce runoff. These include planting vegetated buffers along the shoreline and diverting runoff from roads and driveways to wooded areas. Wouldn’t it be nice if our lakes could be clear every summer?