Estimated distribution of Trichodesmium in the world's oceans. The dashed line represents the approximate limit to polewards penetration of Trichodesmium's distribution. Trichodesmium occurs in the hot, nutrient-poor waters of the tropical and sub-tropical oceans. It tends to be absent from the nutrient-rich upwelling waters that occur along the eastern edges of most oceans. The map projection used here exaggerates the fraction of the oceans that is out of bounds to Trichodesmium [check]; in fact the area within the dashed lines is more than 50% of the surface waters of the world's oceans. The coloured areas, arrows and numbers correspond to specific scientific studies of Trichodesmium. Reproduced with permission from (DG Capone et al, 1997, "Trichodesmium, a Globally Significant Marine Cyanobacterium", Science, vol 26, pgs 1221-9)
The Sargasso Sea, the Caribbean, the ocean west of west Africa, the east and north coasts of Australia, the seas around Fiji, the Red Sea and the Arabian Sea are some areas of the highest concentrations of Trichodesmium.
Much of the information about the distribution of Trichodesmium comes from sampling carried out along long trans-oceanic cruises, for instance this German expedition a century ago. Image from Ed Carpenter/Doug Capone (copied from Wille N, 1904, Ergeb. Humbolt-Stift. 4:1).
Or this set of cruises carried out almost a century later. AMT stands for Atlantic Meridional Transect, a programme which has carried out 10 cruises between about 50S and 50N in the Atlantic.
