WATER QUALITY: ALGAE AND WEED CONTROL

The Association employs a limnologist (a specialist in lake ecology) to monitor the health of the lake. Monitoring includes annual checks of the lake’s ecological balance, together with tests of its water with regard to acidity, oxygen, organic matter, and trace elements. This information is used by the Association’s Lake Committee in its recommendations for maintaining the health of the Lake. Like all lakes, natural or man-made, Lake Sagamore is constantly under pressure from physical and biological processes. There are many things Association members can do to prevent or minimize undesirable changes. (For more about the water quality of Lake Sagamore, see Handbook Part IV, Section D.)

The overall condition of the Lake, in recent years, has been good if not exceptional. Oxygen, temperature, and acidity are within the desirable limits for a small, moderately deep lake such as ours, indicating that circulation and bacterial action are normal. Nutrients (phosphates and nitrates, primarily) are also within acceptable limits, such that algae, whether solitary microscopic forms (i.e. diatoms) that make the water green and clouded or the stringy mats of colonial forms, are not overly abundant.

Submerged water weeds are a constant concern, and recent years have seen an increase in density and affected area. The plant ecology has also shifted, from mixed stands with American milfoil and elodea to almost 100 percent native pondweed, Potamogeton illinoensis (although not the invasive “curly leaf” pondweed). At present, the Association is attempting to control weed growth with triploid (i.e., genetically sterile) grass carp, a vegetarian species from Siberia. This approach has been successful at Lake Mahopac and Lake Carmel, and was approved by DEP subject to construction of an effective barrier below the dam to keep the fish from entering the reservoir system. Eight hundred young fish were introduced in the fall of 2003, but success has been limited so far. It may be that even two years later the carp have not had enough time to do their job. It may be that the necessary number of fish was underestimated, but predation is also a factor. The fish, at 24 inches or more, are too big for osprey or snapping turtle, but several otter kills have been found and more are likely. In the summer of 2005, it was decided by the Board of the Association to add more fish — and more may be added in the future. As an additional measure of control, the membership of the Association approved the application of a biodegradable, environmentally neutral defoliant to the worst hit parts of the lake. This measure was taken in June, 2006. Lowering the level of the lake in the winter to expose and kill pondweed is yet another measure adopted by the Association.


Eight hundred young fish were introduced in the fall of 2003, but success has been limited so far. It may be that the carp have not had enough time to do their job. It may be that the necessary number of fish was underestimated, but predation is also a factor.