DO Percent Saturation values of 80-120 % are considered to be excellent and values less than 60% or over 125% are considered to be poor.
Low DO levels may be found in areas where organic material (dead plant and animal matter or oil) is decaying. Bacteria require oxygen to decompose organic waste, thus, deplete the water of oxygen. Areas near sewage discharges sometimes have low DO levels due to this effect. DO levels will also be low in warm, slow moving waters.
http://www.ciese.org/curriculum/waterproj/saturation.shtml
What is dissolved oxygen (DO) and why would dispersant application monitoring be stopped if DO levels dropped?
Dissolved oxygen (DO) analysis measures the amount of gaseous oxygen (O2) dissolved in the water. Adequate dissolved oxygen is necessary for good water quality. Normal ranges for DO in the Gulf area are 4 mg/l. The lower the concentration of dissolved oxygen, the greater the stress is on aquatic life. The evaluation criteria to determine further use of subsea dispersant include DO levels that are < 2mg/l and the results of toxicity tests.
http://www.epa.gov/bpspill/dispersants.html#q011
Question 2: Which organisms would you most expect to see while snorkeling in the Gulf of Mexico at 2 ppm DO? 4 ppm DO?
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