TECHNICAL


Oxygen is used by the pond to clean itself of excess nutrients through the action of aerobic bacteria. In


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oxygen depleted ponds, some metals - and the nutrients phosphorous and ammonium (a nitrogen compound) - become


These before and after shots show how canals, ponds and lakes can be transformed with Otterbine aerators.


increasingly soluble and


are released from the pond sediments to recycle through the water


3. Oxygen


The third and final mechanism is oxygen. Oxygen is used by the pond to clean itself of excess nutrients through the action of aerobic bacteria. In oxygen depleted ponds, some metals - and the nutrients phosphorous and ammonium (a nitrogen compound) - become increasingly soluble and are released from the pond sediments to recycle through the water. Mixing events, such as cold fronts with winds and cold rains, can transport some of these released nutrients to the lake surface where they can stimulate increased algae production.


Organic nutrients


containing phosphorous and nitrogen are essential to pond plant life, but you must keep the nutrient level in an ideal balance to avoid severe weed and plant growth


” 138 PC June/July 2019 2. Nutrients


Like any living body, ponds accumulate and digest organic matter. Organic nutrients containing phosphorous and nitrogen are essential to pond plant life, but you must keep the nutrient level in an ideal balance to avoid severe weed and plant growth. A pond may become eutrophic, which is too rich in dissolved nutrient, due to run off from nearby turf areas, leeching fertilisers, or from domestic septic systems, leaves, grass clippings or other organic waste blown or dumped into the pond. In addition, the algae and aquatic weeds living in the pond will eventually die and contribute to the nutrient level. As the nutrient levels rise, the rate of plant growth will also increase, initiating the gradual consumption of the pond by organic sludge.


As a pond ages and the nutrient level rises, the amount of algae and aquatic plant life increases. Naturally, these plants will die and sink to the bottom of the pond and begin to decompose. This is referred to as a biomass problem. However, due to thermal stratification, the upper and lower layers of the pond do not mix and therefore the oxygen needed to support pond life does not reach the bottom of the pond. An oxygen depletion problem in the lower layers of the pond is now created and may result in aquatic life problems such as fish kills, leading to foul odours and stagnant water.


Pond problem solving


There are several methods available to help solve some of the problems ponds and lakes are subject to:


Mechanical control can be used to remove algae, aquatic plants and their root systems. This solution is best facilitated in medium to large ponds and would be achieved by dredging, weed harvesting, roto-tilling or


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