Oceanography (2+1)

Phosphorus

                  Phosphorus is an essential element to all life forms. It is a structural and functional component of all orgnisms. It provides phosphate ester backbone of DNA andRNA.Marine organisms contain phosphorus in the form of orthophosphoric acid in complex organic compounds such as phosphoproteins, nucleo proteins, nucleic acids, and phospholipids. The turnover rate of phosphorus in the surface layers is quite rapid. In the upper layers of the oceans chemical decomposition of simple excretory products may occur, by bacterial decomposition of simple excretory products .Bacterial decomposition of organic debris and organic compounds is the most important regenerative process. The phosphorus regeneration rate is thus a function of water temperature and the phytoplankton population. Laboratory experiments have shown that 35 to 55 percent reduction of plankton to phosphate can occur in 17 to 35 days, very little organic phosphate is found in the oceans below 300m.

The  above figure shows the vertical distribution of phosphate in the various oceans. The four layers described previously are clearly visible. In the Atlantic Ocean, water below about 1000m exhibits a decrease in phosphate as one move from south to north. The maximum phosphate concentrations are found at about 1000m depth in the Atlantic Ocean. In the Pacific Ocean maximum phosphate concentrations (0.33ppm) are found north of the equator. The Antarctic areas contain about 0.19ppm phosphate at all depths.

The phosphate in the phototrophic regions of the oceans is normally depleted somewhat during spring and summer because of phytoplankton growth. Death of the organisms, with subsequent phosphorus regeneration, increases the concentration later in this season.