ABSTRACT
The tropical seas are more blue than green precisely due to their relative lack of chlorophyll-containing, photosynthetically active radiation-absorbing phytoplankton. The legacies are vast and deep and began with a simple bioproductive blip that made Europe biologically isolated and the surrounding seas a testing-ground that would in the waning years of the fifteenth century allow Europeans to glimpse the promise of tropical productivity. The size and position of the gyres dominate the tropical oceans and make them, as a whole, relatively unproductive. But unlike nutrients arriving near the surface on upwelling currents, the phytoplankton blooms that sometimes accompany unnatural spikes in land-borne nutrients, often due to agro-chemical run-off or untreated sewage outfall, can be “counter-productive”. The rich biodiversity is arguably the most important factor in tropical forests achieving some of the highest levels of primary productivity recorded on the planet.
