When do aquatic plants contribute the most dissolved oxygen to water?
A. during the night B. during the day C. during periods when plants die D. production of oxygen by plants is uniform E. plants do not produce oxygen, they consume oxygen 6. If a pond has an unstable level of dissolved oxygen, the best method of correction would be . A. to add fertilizer to the pond. B. to add algae to the pond. C. to add fish to the pond. D. to pump air into the pond. E. to expose the pond to direct sunlight. 7. One liter of water weighs . A. one pound B. one kilogram C. one ounce D. one milligram E. one pint 8. You are standing on the banks of a large lake where dozens of different kinds of fish are floating dead on the surface. Which of the following things is most likely to have occurred? A. Bacteria in the water infected the fish causing them to die. B. Nitrates in the water poisoned the fish. C. The dissolved oxygen levels dropped below 2 mg/L and the fish suffocated. D. The fish ate algae and died from toxins produced by the algae. E. The temperature of the lake
