your head
deep 1 in the river bed 2

oxygen diffuses slowly through water and takes time
to move from the surface to deeper areas

    2 contaminated sediments can accumulate
at the bottom of the river

where flow is slow
& sedentary 3

3 sediments on the river bed where water
movement is limited are usually oxygen poor


your body
stir waters               

breathing is moving 4
moving is breathing 5

those living in low oxygen environments often
use movement to bring oxygenated water into contact with their bodies

5 they absorb oxygen from the water across the skin
or from air bubbles held against the body


breathe in 
breathe in 6

6 some freshwaters can go from oxygen rich to virtually
no oxygen over the course of 24 hours

through your skin
breathe in 7

7 heat and the decay of excessive plant and algal growth
deplete oxygen and can be considered pollution