Lake Water Quality 2006 Report - Lakefield Herald

plants. In the Kawartha Lakes area, the limestone is Paleozoic and often containsfossils of sea creatures.Parts per billion (ppb) – A measure of concentration used for extremely smallquantities of one substance within another substance. One part per billion ofphosphorus means one unit of phosphorus within a billion units of water, whichcorresponds to one drop of water in an Olympic-sized swimming pool. For ourpurposes, micrograms per litre and parts per billion are equal.Phosphorus – A widely occurring chemical element that stimulates the growth ofterrestrial and aquatic plants as well as algae. Much phosphorus in the Kawarthascomes from the atmosphere, from within the bedrock (especially the limestone), aswell as from decaying vegetation on the bottoms of lakes and streams. Much may alsobe coming from human sources.Phytoplankton (“floating plants”) – Tiny free-floating algae that can turn lake watergreenish, and are fed upon by zooplankton, zebra mussels, baby fish, etc.Regression analysis – A statistical method of modeling the association betweendifferent variables.Safe swimming level – The Ontario Ministry of Environment’s stated level of 100E.coli bacteria per 100 millilitres of lake or river water. At that level or higher,beaches are posted as unsafe for swimming.Secchi disk – A circular disk with alternating black and white quarters, which islowered to specific depths in surface water and used to estimate water clarity.Trophic gradient – A gradual change in the level of nutrients (usually phosphorus) andautotrophs (phytoplankton or macrophytes) in the water. The gradient in theKawarthas is established by higher phosphorus concentrations in lakes fed byagricultural watersheds mixing with lower phosphorus water fed by watersheds ofthe Canadian Shield.Water column – A hypothetical cylinder of water from the surface to the bottom ofa stream, river or lake, within which scientists measure physical and/or chemicalproperties.90