The most significant way oxygen is introduced into the aquatic eco-system is through photosynthesis. Additional oxygen is absorbed through water movement which acts to “stir” the aquatic environment causing oxygen molecules in the air to dissolve into the water. The more turbulent the water, the more oxygen is introduced. Oxygen is depleted through wildlife respiration and the decomposition of organic material by bacteria and fungi. Together, this system of oxygen production and depletion traverse an unsteady course of maintaining the proper amount of oxygen throughout the entire ecosystem.
Photosynthesis, plants using the sun’s energy to convert carbon dioxide into sugar and oxygen, is the greatest source of H2O. Because photosynthesis requires sunlight, oxygen introduced through this method can only occur during the day. When the sun sets, the process of photosynthesis ceases while decomposition and wildlife respiration continue. As night wears on, the oxygen levels in the water are slowly depleted until dawn breaks and photosynthesis can resume. Large amounts of decomposing organic matter along with an overpopulation of wildlife can easily shatter the delicate balance of oxygen levels, literally, overnight.
Though the majority of lakes in Florida are relatively shallow, understanding the role size and depth plays in making up the anatomy of a lake is also essential. Oxygen is primarily produced in the top layer of a lake where sunlight penetrates the water, driving photosynthesis. Winds further increase oxygen absorption as they push their way across the water, mixing in oxygen as they create waves and eddies along the surface.
At the lake bottom, rotting organic matter collects and decomposes, using vast amounts of oxygen in the process. Sunlight and winds are unable to reach these murky depths, leaving this lower level dark and still. This lack of light and movement keeps the water cool and, even though cooler water has the ability to hold more oxygen than warmer water, it lacks the oxygen produced through photosynthesis and motion. Because of this, little oxygen is available to replenish that which is used in decomposition and respiration, leaving the lake bottom depleted. The lake becomes stratified, creating horizontal columns of water with varying oxygen levels - plenty of oxygen near the top but practically none near the bottom.
This is where water temperature, and therefore seasons, plays a key role in affecting the lake’s ability to regulate adequate oxygen concentrations. Because cooler water has the capability to hold more oxygen than warm water, as water temperature increases, it holds less and less dissolved oxygen. This increase in temperature usually isn’t a serious problem as long as adequate sunlight and winds can penetrate the surface and maintain the supply of oxygen. However, when high temperatures combine with little wind and high cloud cover, fish become trapped in a squeeze that often result in massive fish kills.
Cloud cover reduces the process of photosynthesis and lack of wind movement restricts oxygen penetration from the atmosphere. Water near the surface of the lake quickly becomes anoxic as oxygen is consumed from the bottom up. The warm temperatures of late spring and summer limit the water’s ability to “hold” the small amount of oxygen that is produced. As the sun sets, the process of photosynthesis ceases completely as decomposition and respiration continue, further taxing an already stressed lake. Fish become ensnared in an eco-system that can no longer maintain the levels of oxygen necessary to sustain life.
In an attempt to juggle the many varying factors at play, mechanical aeration becomes a valuable tool in helping maintain adequate oxygen levels. However, there seem to be as many different ways to aerate a body of water as there are companies who supply solutions. And determining which system works best can be confusing. So let’s break it down…MORE>>
Art Of Juggling Oxygen - Shelly Steck
