188 THE OCEAN RIVER 



South Africa is a notable example of such a place — and here 

 is a major fishery. The seas off the west coast of Portugal and 

 Morocco are likewise areas of up-welling waters that provide 

 the nutrition for tuna and sardine fisheries. In the Gulf of 

 Mexico the major fishing area of the Campeche Bank is also 

 an area of divergent water flow. 



One of the main reservoirs of the ocean is the deep Sargasso 

 Sea at the center of the great Atlantic eddy. The blue surface 

 waters of this central sea are like those of the Gulf Stream 

 poor in fertilizer and therefore poor in plankton. Compared to 

 coastal waters they are the deserts of the ocean. Drifting Sar- 

 gassum weed provides a home for small fishes, crabs, and snails 

 camouflaged by color pattern and by weird shapes to resemble 

 the fronds of their hiding place, but the aggregate quantity of 

 life is small. Beneath the surface, however, as the dying weed 

 sinks down and as the impoverished plankton rains its nour- 

 ishment into the waters below, the depths become richer in 

 food, so that at a depth of three or four thousand feet — 

 according to Hjort — a greater quantity of life is supported 

 than in equal depths of the more easterly ocean. Sometimes 

 the nutrient from this cold, deep Sargasso water may be 

 brought back to foster life where the Gulf Stream eddies drag 

 it to the surface. The arctic and antarctic waters, however, are 

 the great sources of fertilizer, in sufficient quantity to nourish 

 the huge amounts of plankton needed by the whales in their 

 subpolar feeding grounds. From the arctic coasts and rivers of 

 Siberia great quantities of fresh water drain into the sea, carry- 

 ing with them the debris of vegetation and the raw materials 

 for ocean food. Thus the Arctic Sea is a carrier of food mate- 

 rial, while the less fertile Gulf Stream acts as a carrier of heat. 

 Millions of years ago the action of glaciers wore down the 

 most ancient rocks of Canada, the Canadian shield, and car- 

 ried great masses of rock and gravel to the edge of the conti- 

 nent, where they now form the floor of the wide, shallow 



