Oceans indispensable for our health

Scientists estimate that 50 to 80 % of the oxygen production on Earth comes from the ocean.The majority of this production is from oceanic plankton-drifting plants,algae and some plants that can photosynthesize.One particular species,Prochlorococcus,is the smallest photosynthetic organism on Earth.But this little bacteria produces up to 20% of the oxygen in our entire biosphere.That's a higher percentage than all of the tropical rainforests on land combined.