Guest Column - April 2007
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A Delicate Balance

Understanding water quality problems in lakes and ponds

By Angela Hopko


Oxygen

The third essential factor in lake water quality is the role oxygen plays.

Oxygen is important to all forms of life in the lake, and supports the food chain including the natural decomposition process. A lake is supplied with oxygen from several sources, but primarily through photosynthesis, and wave and wind action.

Immediate reactions to oxygen depletion would be fish kills or odors. Long-term issues include nutrient buildup, sludge accumulation and a chemical imbalance. Oxygen depletion or stress situations occur for different reasons, but most typically happen:

  • Late at night and just before dawn
  • On cloudy and still days
  • On hot and humid days
  • When the lake's nutrient content is high
  • After a chemical application

Nature has provided a cleanup process that will metabolize or decompose excess nutrients. This is called organic digestion. This involves two types of naturally occurring bacteria present in all lakes and ponds: aerobic and anaerobic.

The most effective of these bacteria are aerobic bacteria, which only live in the presence of oxygen. Highly efficient, they are roughly seven times faster in organic digestion than anaerobic bacteria.

Anaerobic bacteria exist in oxygen-deficient pond water and soil, are much slower in breaking down nutrients and allow soluble organic nutrients to recycle into the water column. Noxious byproducts such as methane, ammonia and hydrogen sulfide are created by anaerobic decomposition.

Find your balance

Balance is critical to the aquatic ecosystem. Without it, your pond or lake will suffer.

There are many steps that can prevent an imbalance, and knowing the causes will assist in determining the best solution for your application. Some methods include proper pond construction, chemical applications and the addition of oxygen through aeration systems and devices.



ABOUT THE AUTHOR

Angela Hopko is marketing manager for Otterbine Barebo Inc., a leader in pond and lake management for more than 50 years. Otterbine takes a scientific approach to develop natural, energy-efficient, versatile, technologically advanced and easy-to-use water treatment methods. For more information, visit www.otterbine.com.