452 



114 



OCEANOGRAPHY IN THE NEXT DECADE 



FIGURE 3-6 World ocean primary production according to Koblents- 

 Mishke and coworkers on an equal area projection. Productivity catego- 

 ries are, from low to high, <36, 36-54, 54-90, 90-180, >180 gC/m^/yr. 

 Note that most of the areas of high productivity are located on the ocean 

 margins. From Berger (1988). 



often deposited on the continental shelves, although they are some- 

 times transported to the slopes and deep ocean later. Sedimen- 

 tary conditions on the shelf are far from static: numerous physical 

 and biological processes can lead to reworking of the sediments 

 and to their eventual transport to other locations. New evidence 

 suggests that the shelf can be a source of particulates that accu- 

 mulate within estuaries together with sediments delivered to the 

 estuaries by rivers and shoreline erosion. Over geological time 

 scales, the fates of sediments can vary widely with sea level; shelf 

 processes can differ markedly, depending on how much of the 

 shelf (or slope) is exposed above the sea surface. Coastal waters 

 also receive chemicals and particulates weathered from continen- 

 tal rocks and transported to the ocean by rivers, groundwater, and 

 winds. When these chemicals reach the coastal ocean, they are 

 transformed or removed, so that although the properties of the 

 estuarine waters may differ from those of the open ocean, shelf 

 waters closely resemble open ocean water. 



