Subtracting or applying the information from the graph that you need
Photosynthesis is this process
They ensured that balance in the ecosystem was maintained. They ensure that the genetic diversity and species is maintained. Sea otters applied natural selection pressures on the sea urchins population hence maintaining their level such that they will not overgraze on the kelps. Overgrazing would severely affect the sea urchin population and consequently severely affect the sea otters population too.
First they don't use oxygen, plants use the CO2 in the air and release oxygen out into the air after the plant used up the CO2
