It is a substance called Chlorophyll, the most wonderful substance in our world. A world without chlorophyll would be a world without the higher forms of life, and in such a world no life, save perhaps that of the lowest bacteria, could possibly endure. In fact, without this remarkable pigment the living world as at present constituted could not exist.
Sir Arthur E. Shipley (1923)
Chlorophyll concentrations in the world’s oceans are important indicators for the presence of algae and other plant-like organisms that carry out photosynthesis. Variations and changes in the chlorophyll levels are relevant for the study of the ecology of the sea. Changing chlorophyll levels can also indicate changing sea temperatures and other changing conditions in the oceans that cover about 72% of the planet’s surface.
The map highlights the increasing levels at most of the coastal zones of the continents which appear as bizarrely distorted white islands in the sea.
Higher levels can be seen along the west coasts of the Americas as well as Africa where rising cold water streams lift nutrients from the ocean floor that support phytoplankton growth. Coastal upwellings also influence the high chlorophyll concentrations of the surface waters in the Baltic Sea. This is also case for the largest lakes, such as Lake Victoria in Africa. In contrast, the dark band of low chlorophyll levels around the Equator eastwards the coast of South America is influenced by the easterly trade winds that also help the upwelling of deeper water layers.