4.15 understand the biological consequences of pollution of water by sewage including increases in the number of microorganisms causing depletion of oxygen

 Sewage is rich in nutrients such as nitrogen and phosphorous, when it spills into a body of water it

causes eutrophication. Eutrophic means nutrient rich and eutrophication is when there is an excessive

amount of nutrients in a body of water.

-        Sewage run off or agricultural run off is leached into the body of water

-        The nutrients encourage the growth of algae, resulting in an algal bloom

-        The algal bloom covers the surface of the water, depletes oxygen levels and prevents sunlight from reaching other plants.

-        This results in the plants dying and there is a loss of habitat

-        The plants are decomposed by bacteria which use up more oxygen

-        Fish and other organisms die due to suffocation