were available on the bottom, the bottom water should show high values 

 during periods of high thermal stratification and the entire water column 

 should show an increase in phosphorus when the thermocline disappears and 

 wind-stirring extends to the bottom,, No increase was found in the deeper 

 water except the expected increase below the euphotic zone and no increase 

 in values was found during the months when the water "turned over" from sur- 

 face to bottom. From November to April the convection zone extended from 30 

 to 50 meters depth yet during these months the phosphorus concentration of 

 the water was less, rather than more, at stations inside the IiO-fathom line. 

 There seems to be no evidence of the bottom contributing phosphorus to the 

 Gulf waters in any measurable degree. 



Total phosphorus in column 



Since Kalle (1937) and Armstrong and Harvey (l°5o) have used total 

 phosphorus concentration in the water column as an indicator of water masses, 

 it is interesting to study the changes in the total phosphorus in the body of 

 water in the Gulf. 



The integral mean concentrations of total phosphorus for the water 

 columns at Stations 5 to 8 are shown in table Jj. At Station 8, 120 miles 

 offshore, there war, an indication of a different water mass from November 

 19^9 to May 195>0. Although data were obtained for only three months of that- 

 period, the integral means were consistently about 65 percent of the values 

 for the rest of the year. 



At Station 7 where observations were more complete, 8I4 miles offshore, 

 there was a greater and a more irregular variation in the integral mean con- 

 centration throughout the period of study and the fluctuations do not corres- 

 pond to those found at Station 8. Either the water masses passing through the 

 two regions were quite independent of each other or else the changes occurred 

 at some particular level. Changes at particular- levels would not be accu- 

 rately reflected in the total phosphorus-integral means because of the redis- 

 tribution of phosphorus by the vertical migrations of the zooplankton and 

 the sinking of organic detritus. 



At Stations $ and 6 there was also a wide range in mean values from 

 month to month although values were always comoaratively low except in a 

 few instances at Station 5", the station closest inshore of this series. It 

 is impossible to explain these fluctuations in our present state of knowledge. 

 They may be related to tidal and irregular along-shore currents. The tremen- 

 dous migrations of Gulf shrimp and other fish no doubt are important in the 

 redistribution of phosphorus in the water and may have to be taken into con- 

 sideration in any attempt to explair. the horizontal distribution. 



39 



