The eggs and larvae of marine animals tend to require water with more dissolved oxygen in it than the adults do. If water flows from a freshwater source into a salt water bay, what effect would this have on the population of marine animals? The freshwater would decrease the populations of marine animals because it would deplete the salt water of oxygen. The freshwater would decrease the populations of marine animals by decreasing both salinity and oxygen levels. The freshwater would increase the populations, thereby decreasing the levels of oxygen and marine animals. The freshwater would increase the populations of marine animals because it holds more oxygen than the salt water.