A marine scientist observes that dissolved oxygen decreases with increasing ocean depth. he concludes that deep sea creatures must require less oxygen than those at shallower depths. why is this an invalid scientific conclusion?

The dark, cold waters of much of the deep sea have adequate oxygen. This is because cold water can dissolve more oxygen than warm water, and the deepest waters generally originate from shallow polar seas. In certain places in the northern and southern seas, oxygen-rich waters cool off so much that they become dense enough to sink to the bottom of the sea.