Answer:
A - Fertilizer runoff can cause micro-organisms such algae to bloom out of control. B - Algae blooms suffocate the ecosystem if there is too much.
Step-by-step explanation:
A - Not all fertilizer nutrients is used in agricultural production and so some of it makes its way into the excess water and therefore runs into creeks and rivers. It is also toxic to many animals in high concentrations as well as more sensitive native plants.
B - Algae blooms take a lot of oxygen out of the water, therefore suffocating natural wildlife. The decay that results from such large blooms is also problematic and takes away oxygen. Many algae likes slow moving water with little flow and in these optimal conditions with excess nutrients (Nitrogen, Phosphorus, and Potassium, NPK are the main ones) cause it to become out of control