Would you expect the DO (dissolved oxygen) of water taken from a lake at 7pm to be higher or lower than 5pm?

Question

Would you expect the DO (dissolved oxygen) of water taken from a lake at 7pm to be higher or lower than samples taken at 5pm? Explain.

Answer 1

Give me the temperature of the water at each time, and I will tell you. (is 7pm cooler or warmer that 5 pm?)

Answer 2

I would say higher. The oxygen levels in water increase as temperature decreases. I would expect water to be colder at 7pm than 5pm

Answer 3

I think the DO will be lower because:

1. Organisms will be using oxygen at the same rate as earlier in the day, but photosynthesis will be much slower because the light intensity is much lower.
2. The temperature will not have dropped much because water resists temperature change and will stay relatively warm into the evening.

Answer 4

7pm will be high DO because it will be colder an atmospheric temperature.