What effect can fertilizer runoff have on an aquatic ecosystem?

a. increased plant growth leading to a decrease in fish populations

b. increased plant growth leading to an increase in fish populations

c. decreased plant growth leading to a decrease in fish populations

d. decreased plant growth leading to an increase in fish populations

a. increased plant growth leading to a decrease in fish populations. Fertilizer runoff degrades aquatic system by promoting growth of algae, phytoplanktons and other aquatic plants. A phenomenon called 'algal bloom' will take place, increasing oxygen consuming bacteria and lessening the available oxygen for plants and animals in the area.