Report on Algae at Otty Lake

Murray Hunt

On July 25, 2009 I participated in an algae workshop organized by Peter Au of the Rideau Round Table. Paul Hamilton of the Canadian Museum of Nature, an expert on algae, led the workshop

The workshop was designed to enable the participants to learn the general types of algae and to use microscopes to identify specific examples. The general conditions that promote algae growth were discussed at length. Participants were representatives from local lakes and various organizations concerned with water quality.

I brought samples of algae from two locations on Otty Lake for identification. All samples were identified as types of Green Algae. None of these are toxic. In a sample taken at the docks at MapleGlen, two algae were identified, Rhopalodia and Maugeotia. In the bay north of Conlon Island, Gloeocystic Baneergattensis was identified.

It is apparent that algae have been present in abundance in lakes and rivers in Eastern Ontario this year. The samples brought by various lake representatives contained various species of Green Algae. The general consensus of the "experts" appears to be that these algae are the types that form in the spring after ice-out. The view is that the wet and cool "spring-like" weather conditions that persisted in the early part of the summer provided ideal conditions for these algae.

There is also a view that the presence of zebra mussels also contributes to the growth of algae due to the clarity of the water column (more sunlight penetration) and the concentration of pseudo-feces (i.e. nutrients) of zebra mussels in shallow areas.

Nevertheless, although the conditions in any particular water body will change from time to time depending on weather, the level of nutrient loading in the waterbody also affects the growth of algae. The higher the level of nutrients, the more algae blooms will be present in the lake.

These are some of the things that will limit man-made nutrient loading

Septic waste from humans is a major contributor of nutrients to a lake due to the proximity of septic systems to the shoreline and it is important to:

 have properly designed and functioning septic systems o the septic re-inspection program is a key element to identify leaking and sub- standard systems o regular pump-outs - two to four years is recommended  also use phosphorous-free soaps

Develop buffer strips

o the roots of the plants can absorb soluble nutrients flowing in the shallow topsoil o the plants will impede the direct flow of nutrients into the lake during rain runoff o leave the leaf litter in the buffer strip- it helps o bigger is better, 5 or even 15 metres width is often recommended - I realize that is impractical on smaller properties on Otty, but every centimeter helps Do not use fertilizers - you cannot assume that all the nutrients will remain in your garden (or your lawn).