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Effects of Three Variables on Dissolved O 2 Levels in Water. Three main variables that affect the amount of dissolved oxygen in water are temperature, sunlight, and the presence of nitrogen compounds. Temperature: - PowerPoint PPT Presentation
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Effects of Three Variables on Dissolved
O2 Levels in Water
Three main variables that affect the amount of dissolved oxygen in water are temperature, sunlight, and the presence of nitrogen compounds.
Temperature:
Because the solubility of gases in a liquid is lessened with
increasing temperature, warmer
water holds less dissolved oxygen than
does cooler water. The solubility of
oxygen at 0 degrees C is about twice the
solubility at 30 degrees C.
The temperature of the water is the single most important factor affecting DO levels. In summer
months when water temperatures are rising, competition for DO
increases, resulting in death of some organisms.
Sunlight
During daylight hours, underwater plants and phytoplankton add oxygen to the water through photosynthesis. At night or during cloudy periods, autotrophs consume oxygen for cellular respiration but don’t conduct much photosynthesis due to lack of sunlight.
Fishkills caused by low DO levels are common in the summer
months. Some species are more susceptible to fluctuations in DO
levels than others.
Nitrogen Compounds
Nitrate (NO3) and nitrite (NO2)
compounds often enter the water from agricultural areas. These
commonly come from fertilizers and animal fecal material.
These chemicals are often called “nutrients” because they enrich the water – providing resources
for algae.
The addition of these chemicals to the water causes large growths of algae known as algal blooms. These blooms block sunlight to submerged water plants. Without sufficient sunlight, plants and phytoplankton perform less photosynthesis and oxygen levels. in the water diminish. This is known as eutrophication.
Resources:http://aquaplant.tamu.edu/contents/dissolved_oxygen.htm
http://www.newton.dep.anl.gov/askasci/chem03/chem03334.htm
http://www.lenntech.com/periodic/water/nitrogen/nitrogen-and-water.htm#ixzz0zF5CBsgs
http://www.google.com/images
Biology (7th edition) by Neil Campbell and Jane Reece, 2006 Benjamin Cummings
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