At certain times of the year, a normally clear lake can appear green and not so clear. You’re seeing the presence of algae in the water. In a healthy lake, algae are critical to the balance of life. But, as in life in general, the rule is: Everything in moderation.
Algae are tiny plants that have no stem or leaves but usually contain chlorophyll. They may attach to submerged rocks and branches, or they may float freely in the water. Algae provide food for the tiny creatures (zooplankton) that the fry of our favorite fish love to eat.
Algae exist when all conditions are right: temperature, sunlight, water pH and the balance of nutrients. A critical nutrient is phosphorus. It must be present in precisely the right amount. Too little and the algae will not thrive. Too much and algae will “bloom.” That reduces the lake clarity, appeal and natural balance.
There are several kinds of algae. Tiny green spots floating in the water are fine. Dense mats of stringy brown or green matter near the surface are filamentous algae. They aren’t pleasant to look at, but they cause few problems.
The trouble can come in mid to late summer, when lakes too rich in nutrients experience blooms of blue-green algae. These organisms are really bacteria that form suddenly and grow rapidly. They create a thick blue-green mat near the surface, forming wavelike patterns in quiet water. During certain times in their life cycle, these bacteria produce powerful toxins that can make you and your pet sick.
So, get to know the natural cycles of your lake. Know when to expect the welcome presence of beneficial algae. Be aware of sudden changes in algae growth. Don’t be alarmed by the presence of tree pollen on the cold lake surface in late spring.
Join your shoreline neighbors to help keep lake phosphorus in equilibrium. Don’t use phosphorus fertilizers and keep your septic system in good working order. Tend to your natural “shoreline buffer.”
In balance, algae is a good thing. Healthy lake life depends on it but too much may be a sign of a lake under stress.
Did You Know?
Blue-green algae blooms can deplete oxygen in lakes and kill fish.
NOTE: This is one in a series of articles sponsored by OCLRA (www.oclra.org) and will be made available to you on this website over the next ten months… with a new article appearing approximately every two weeks. OCLRA encourages the use and distribution of this material by lake associations, their members and other parties concerned about water quality.