Islanders encouraged to support Lake Manitou

To the Expositor:

The Lake Manitou Area Association (LMAA) was established in 1993. Its activities include monitoring the ecological health of Lake Manitou and related educational activities. We wish to share with Expositor readers our serious concern with Lake Manitou’s continued ability to support its provincially significant lake trout fishery.

A lake that is oligotrophic (high water quality) is low in nutrients (especially phosphorus) that stimulate aquatic plant/biomass production. One result of low biomass production is high water clarity (measured by a Secchi disk). Another is that the inevitable death and decomposition of the biomass—which consumes oxygen—is low enough so that ample oxygen remains to support coldwater fish such as lake trout.

Coldwater fish are especially sensitive because lakes become stratified into distinct layers in the summertime and these fish exist only in the deeper, colder layer (hypolimnion) that receives no mixing, and therefore no new oxygen supplies, during the period of summertime stratification. In Lake Manitou, this is generally from early/mid July through late September. If coldwater fish do not have sufficient oxygen during this period, they cannot survive.

LMAA has for years conducted monitoring for water clarity and nutrient levels (phosphorus) under the “Lake Partner” program coordinated by the Ministry of Environment (MOE). Although results for these parameters continued to suggest high water quality, this monitoring is based on a ‘model’ that was developed mainly from research in granite-basin lakes. Those lakes have different water chemistry than lakes such as Lake Manitou, which are situated in limestone geology. It has become apparent that the ‘model’ and related monitoring does not accurately predict the extent of biomass production (from nutrient loading) and subsequent, oxygen-consuming decomposition.

MOE has taken direct measurements of deepwater oxygen levels in 2007, 2009, 2010 and 2011, and the results are of serious concern. The average concentration is approximately 3 mg/L in the Lake Manitou’s west basin, while the east basin is approximately 6 mg/L. What is enough?

The provincial objective for maintaining lake trout fisheries at full viability is 7 mg/L. Adult lake trout can carry out various life cycle activities (feeding, respiration, reproduction, etc.) in the range of 5-6 mg/L, but at lower activity levels and increasing impairment. Juvenile lake trout tend to remain near the lakebed where the oxygen levels are still lower than the average for the deep water layer.

Lake Manitou clearly supports a lake trout fishery at the present time. Equally obvious is that deepwater oxygen levels are wholly inadequate in the west basin, and lower than the provincial objective in the east basin, which could follow suit to the west basin if further nutrient loading (from further shoreline development) is not halted. In addition to its value as a key component of the Lake Manitou ecosystem, the lake trout fishery helps support lake trout fisheries across the province though the operations at the Blue Jay Creek Hatchery Station, which in one location or other has been active since at least the mid-1950s. Lake Manitou has been designated as a “provincially significant” lake trout fishery, with good reason.

Against this background, the municipality of Northeastern Manitoulin and the Islands (NEMI) approved re-zoning that would allow a 20+/- lot subdivision development in the Green Bay area of Lake Manitou. This was done despite the Ontario Municipal Board (OMB) refusing a similarly-sized development a few years ago. It was also done despite objections from the ministries of Natural Resources and Environment. The NEMI action requires approval from the Ministry of Municipal Affairs and Housing (MAH), which has in effect referred the matter to the OMB. An OMB pre-hearing is scheduled for May 1 in Little Current, with the timing and scope of a full hearing to be determined at the pre-hearing.

LMAA will be present to participate and express our objections. We understand that the objections of the ministries of Natural Resources and Environment (already on record at MAH) will also be tabled. The OMB rules apparently do not allow participation by persons or parties who have not already established standing. We nevertheless encourage all who value the lake and the integrity of its ecosystem and fisheries to make their opinions known to NEMI, the Manitoulin Planning Board and provincial representatives.

It is not too late to protect this valuable and unique resource, but further development should be halted.

Rob Coulter, M.Sc.

Lake Manitou Area Association

Mindemoya and Rochester Hills, MI