Lake stratification (and chemistry)
Complete
circulation
of the water
column
Water column
is all the same
temperature
Lake stratification (and chemistry)
Circulation of
only the
surface water
Bottom water is
cold, isolated,
and stagnant
Lake stratification (and chemistry)
Warm,
mixed
Cold,
stagnant
Complete
circulation
of the water
column
Note temperature profile:
surface water is warmer,
less dense, and doesn’t
mix with bottom water
CO2 + H2O  CH2O + O2
(photosynthesis, shorthand)
Lake stratification (and chemistry)
As the weather cools in autumn, surface water cools and becomes more dense . . .
Lake stratification (and chemistry)
. . . and wind energy is able to mix the lake completely.
Some lakes never turn over. If
bottom water is very dense (due
to salt, for instance), temperature
doesn’t matter and the bottom
water remains permanently cut off
from the atmosphere – and
anoxic.
High levels of dissolved solids = high density