Eutrophication is the process
that can happen in a water body,
like a river or a lake,
when too many nutrients are added to the system.
Eutrophication starts with fertilizers, which are rich in
nutrients like nitrate and phosphate,
are washed into the river or lake system.
This leads to an increase in nutrient concentrations in the water.
The nutrients are food for algae.
The algae grow and reproduce quickly,
forming a thick green bloom in the water.
This algal bloom will absorb sunlight shining on the water
so the sunlight can't reach the bottom.
Plants who need this light to photosynthesis will die.
The algae will also start to die when
they eat up all of the nutrients
and run out of food.
Next,
bacteria start to breakdown the dead plants and algae.
That releases more nutrients
back into the water
continuing the Algal Bloom Cycle.
The bacteria, with a continuing supply of food,
reproduce into much larger numbers
consuming oxygen as they grow and respire.
There is not much oxygen in the water to begin with
so when the bacteria consume it quickly
it might run out completely.
Water without oxygen is called Anoxic.
If the water turns anoxic
all non-bacterial life in the water,
including fish and other animals, will die.
So,
eutrophication happens when nutrients are added to water
which causes an algal bloom,
cutting off sunlight and feeding bacteria.
The bacteria use up oxygen in the water
which becomes an anoxic,
causing everything living in the water to die.
Eutrophication is one reason why we need to be carefull
with fertilizers when we are growing crops.