Question

how can you distinguish between high chlorophyll concentration in the ocean and high chlorophyll concentration on land

Answer 1

maybe this will assist
The highest chlorophyll concentrations, where tiny surface-dwelling ocean plants are thriving, are in cold polar waters or in places where ocean currents bring cold water to the surface, such as around the equator and along the shores of continents. The polar–equator difference intensifies in the hemisphere experiencing summer. For example, the difference in chlorophyll concentration between the Southern Ocean and equatorial ocean areas is bigger in December than September. In polar waters, nutrients accumulate in surface waters during the dark winter months when plants can’t grow. When sunlight returns in the spring and summer, the plants flourish in high concentrations.
http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MY1DMM_CHLORA&d2=MYD28M