Water Quality

What is good water quality? It depends on what the water is used for. Water, one of the most abundant substances on earth, is all around us. Yet only 0.01% of all of the earth's water resources (equal to 0.4% of all freshwater) is stored in lakes and rivers. This water is used for everything from drinking to recreation to industrial cooling and power generation. Each water use demands a different level of water quality. Bacteria levels don't affect water's usefullness in hydroelectric power generation, but have serious implications for drinking water supplies (people and animals that consume enteric bacteria will become sick.) Even within your own home, all water is (hopefully) treated to a level acceptable for drinking and cooking, even though 95% of domestic water use is for applications like laundry and toilet flushing that could use water of a lesser quality (CMHC, 1991).

Lake Water

For these reasons, even a lake in an apparently pristine condition should not be used as a source of drinking water. Add to this thousands of humans who build their homes, drive their boats, cut down their trees, fertilize their lawns, and process their sewage around the lake, and you can get a picture of why water quality in the Muskoka Lakes could be concerning.

Eutrophication

Eutrophication is defined as "biological effects of an increase in concentration of plant nutrients on aquatic ecosystems" (Harper, 1992). Predictive limnology, especially on the Precambrian Shield, is particularly concerned with cultural eutrophication; a catalysis of a natural aging process that usually takes thousands of years.

The term eutrophication was introduced to scientific literature by Weber's study of bogs in 1907. The term began to be more widely used in the 1940s (Harper, 1992).

Oligotrophic lakes are poor in plant nutrients (Cole, 1994). The sparse soils and granitic rock of the Precambrian Shield contain lakes that are mostly of this type, including most lakes in Muskoka. Some lakes, such as Brandy Lake near Port Carling, are nutrient rich due to in thick glacial till in their watersheds (Downing, 1986). When plant nutrient (phosphorus) levels increase, lake communities become more productive, but less diverse. Water also becomes more turbid and algal blooms are common.

Some research shows that most oligotrophic lakes naturally eutrophy over thousands of years (Glynn and Heinke, 1996), but debate over this hypothesis is still fervent. Paleolimnology has proven that several lakes are less productive now than they have been in the past, and the trophic status of some lakes has declined steeply in only a few years since anthropogenic nutrient sources have been attenuated (Cole, 1994; Munson et al, undated).

Normal eutrophication that does take place over an extended time period has little effect on a human temporal scale (changes to the ecosystem are barely noticeable). However, anthropogenic eutrophication, which can be very rapid, became a problem in the middle to late 20th century (Harper, 1992).

The first proof that changes to lakes were related to urban and agricultural runoff (land use) was published by Sawyer in 1947, whose study focussed on the Madison Lakes in Wisconsin (Sawyer, 1947 in Vollenweider and Dillon, 1974). This study showed that phosphorus (P) was likely the most important nutrient, although he studied general enrichment. Other early studies were focussed on how lake surface area, depth and flushing rate effect eutrophication (Vollenweider and Dillon, 1974). Later it was shown that P is the plant nutrient that limits biomass production in most freshwater (Harper, 1992). Although there is a wide range of natural sources of P, urban and agricultural sources (both anthropogenic) are usually considered to be the most important (Harper, 1992).

Adverse effects of eutrophication are now wide-spread and well known. Major effects include an increase in the standing crop of phytoplankton (increasing turbidity) (Vollenweider and Dillon, 1974), algal blooms (Harper, 1992), decreased dissolved oxygen levels in the hypolimnion (Schiefer, 2001), odours and nuisance adult insect swarms (Harper, 1992). Apart from the nuisance and inconvenience of these effects, a decrease in dissolved oxygen can severely affect cold water fish populations (Schiefer, 2001) and benthic biodiversity (Harper, 1992). Moreover, some algae that take over eutrophic and hypereutrophic ecosystems (cyanobacteria) can be toxic or pose a risk of botulism (Harper, 1992).

Autochthonous, oligotrophic lakes (that naturally produce most organic material internally) are particularly susceptible to eutrophication by anthropogenic nutrient loading. These lakes often exhibit a direct relationship between an increase in P and an increase in algae (Clark, 2002a).

In lieu of an inherent understanding of the value of ecosystem health, economics and aesthetics may be the most important implications of eutrophication. Changes are much more important from a human perspective where human demands are placed on the lake system. As recreational demands increase, eutrophication effects can therefore be measured in economic terms (Harper, 1992). A decrease in property values and tourism revenues are both examples of possible economic consequences of eutrophication.

Clearly, good water quality is realised in various ways including looks, smells and tastes. All of these are affected by algae blooms and other effects of nutrient enrichment. But good water quality is also determined by the presence of bacteria.

Bacteria

Bacteria also have an important impact on human health as humans and other species are susceptible to infection by bacteria. While it is not the intent of the MWQI to determine the safety of recreational water bodies, it is important to have an understanding of how safety is related to bacteria counts.

Water is a good vector for the transmission of bacteria if it is untreated. The Province of Ontario accordingly sets standards for acceptable bacteria levels in recreational and drinking water. These standards do not guarantee that no one will be infected by enteric pathogens if they swim in "safe" water. Rather, they represent an acceptable risk of infection given normal ambient water quality and economic factors (disinfection costs).

It would be nearly impossible and very uneconomical to attempt identifying every possible pathogen present in surface water on a routine bases (Glynn and Heinke, 1996). Indicator organisms are therefore used. The indicator most commonly used to represent the probable presence of enteric pathogens is total coliforms, which include E.Coli (Madigan et al, 2000). These are the two bacterial indicators the MWQI monitors.

Coliform include a variety of bacteria. In practice, detectable coliforms are usually enteric (Madigan et al, 2000). Total Coliform are a good indicator because they are prolific in the intestinal tracts of humans and other warm-blooded species (organisms originating in warm-blooded species are most likely to infect warm-blooded species). Coliform eventually die if exposed in surface water, but last longer than other organisms that present serious threats like salmonella and shigella (Madigan et al, 2000).

According to the Province of Ontario, surface water is safe for recreational purposes if there are less than 1000 Coliform counts/100 mL, however a concentration of 200 Coliform counts/100 mL is indicative of deteriorating water quality (Schiefer, 2001). Given that these standards are essentially arbitrary and simply represent an acceptable threshold of risk, an objective of 100 Coliform counts/100 mL has been suggested for oligotrophic lakes in the District of Muskoka (Schiefer, 2001). This objective is suggested because the ambient water quality in Muskoka is very good (a higher standard represents a more reasonable threshold of concern). Moreover, the high demands for swimming and other recreational activities of Muskoka lakes imply a higher rate of infection given similar contamination (Schiefer, 2001).

Escherichia Coli (E.Coli) is a subset of total coliforms, and is exclusively associated with faecal waste (Schiefer, 2001). There are several different strains of E.Coli; most waterborn strains are themselves not harmful, but some (such as E.Coli O157:H7) can cause serious illness (OMH, 2001).

E.Coli has been Health Canada's standard water quality indicator since 1993 (Schiefer, 2001). It makes an excellent indicator because its source is limited to faecal waste, the density of the organism is directly related to faecal contamination of water, it is able to survive longer than other coliforms and it is resistant to disinfectant (Madigan et al, 2000). Unfortunately, it is impossible to distinguish between human and animal sources of E.Coli using conventional scientific techniques (Schiefer, 2000).

The Ontario government considers water with less than 100 E.Coli counts/100 mL safe for recreational purposes. Similar to the previous discussion about total coliforms, a more stringent objective of 10 E.Coli counts/100 mL has been suggested for lakes in Muskoka (Schiefer, 2001).