Recall that areas with high net primary productivity not only produce high levels of biomass rapidly, they also take up large amounts of co2 and give off large amounts of oxygen. what is the likely result of the increasing amounts of fertilizers in the major rivers emptying into oceans?

The eutrophication of oceans.

Explanation:

This is the result of an increase in phosphates and nitrogen dissolved in water, at the end when it reaches the oceans, they are going to deposit in the bottom of the ocean and they are going to promote the production of algae.

With an increase of the population of algae, the sunlight will not reach the bottom, will consume the oxygen of the oceans, leaving a reduction in fish and other living things population.