A. The rate of photosynthesis depends on light intensity, and light intensity falls off with increasing water depth. B. Greater numbers of oxygen-consuming organisms that do not photosynthesize are found at the bottoms rather than the surfaces of aquatic environments.
C. Oxygen preferentially collects at the surface of aquatic environments, leaving deep water oxygen-free.
D. Increasing water pressure at greater depths increasingly inhibits the rate of photosynthesis.

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