Murky vs Polluted
Murky vs. Polluted: Why a "Dirty" Looking Lake Might Actually Be Healthy
Summary: Many people assume that if they can't see their toes in three feet of water, the lake must be polluted. This is a myth. Murkiness, or Turbidity, is often caused by natural factors like suspended silt, tannins, or healthy populations of microscopic life. A perfectly crystal-clear lake can sometimes be "dead" (oligotrophic), while a murky-looking lake might be a thriving, nutrient-rich environment for fish and wildlife. "Dirty" water is only a concern when it’s caused by man-made runoff or toxic chemicals.
The Science Behind It: The Science Behind It: Turbidity is a measure of water clarity influenced by Suspended Particulate Matter (SPM). This includes both organic materials (like algae) and inorganic materials (like clay or silt). According to environmental research, natural turbidity can be caused by wind-driven resuspension of bottom sediments or "marl" (calcium carbonate) precipitation in hard-water lakes. High turbidity can actually be a defense mechanism for a lake; suspended silts can bind to excess phosphorus, making it unavailable for harmful blue-green algae blooms. Scientists distinguish between "natural turbidity" and "anthropogenic pollution" by testing for specific contaminants like heavy metals or high fecal coliform counts. Therefore, a lake that is "murky" due to healthy algae levels is providing the base of a food web that supports larger game fish.