Nutrients enter the urban system in a variety of
ways, including landscaping practices (commercial and home), leaks
from sanitary sewers and septic systems, and animal wastes. The
nutrients most often identified in storm water runoff are phosphorus
and nitrogen.
Excess
nutrients can cause algae blooms. When algae die, they sink
to the bottom and decompose in a process that removes oxygen
from the water. Fish and other aquatic organisms die when
their oxygen levels are depleted.
