Lake Assessments

The main water quality concerns relating to Pennsylvania lakes are conditions associated with eutrophication, particularly cultural eutrophication. All lakes undergo eutrophication, an ageing process that ensues from the gradual accumulation of nutrients and sediment resulting in increased productivity and slow filling of the lake with silt and organic matter from the surrounding watershed.

Human activity within the lake watershed hastens the eutrophication process and often results in increased algal growth stimulated by an increase in nutrients. Increased macrophyte growth can also ensue from this nutrient-rich environment along with expanding shallow areas resulting from high rates of sedimentation.

Wide fluctuations in pH and dissolved oxygen (DO) often result from increased photosynthesis and respiration by plants and biological oxygen demand (BOD) from the decay of organic matter.

Natural lake succession progresses through several increasing productivity stages: oligotrophic, mesotrophic, eutrophic, and hypereutrophic states.

• Oligotrophic lakes are typically nutrient-poor, clear, deep, cold, biologically unproductive lakes.
• Hypereutrophic lakes, at the other end of the spectrum, are extremely nutrient-rich, often with algal bloom-induced pea-soup conditions, abundant macrophyte populations in shallower areas, fish kills, and high levels of sedimentation.

Although lakes naturally go through the trophic states in a slow successional process, anthropogenic influences can greatly accelerate the progression, and is known as "cultural eutrophication". What normally takes thousands of years can be accelerated to decades when human influences are severe.