the area between Sarasota and Charlotte Harbor. A sample of this bloom 

 collected with a bucket contained 10.20 ug-at/L of total phosphorus but a 

 scarcely measurable amount of inorganic phosphorus . A portion of the 

 sample was filtered and the filtrate showed the same low concentration of 

 inorganic phosphorus. The quantity of total phosphorus found in this bloom 

 was within the range reported for the red tide samples. 



Throughout the present investigations there was never any evidence of 

 sudden increases in inorganic or total phosphorus immediately preceding any 

 of these blooms of Trichodesmium . It seems necessary to conclude that Tricho- 

 desmium is able to live in water of very low phosphate concentration and 

 that by drifting about it can accumulate phosphorus from a large volume jf 

 water. The phosphorus content of the bloom itself, then, bears no dir" 

 relation either to the phosphorus content of the water in which it is grow- 

 ing or to that of the entire column of water underlying it. 



Since Trichodesmium drifts about like so much Sargassum, it would be 

 as inaccurate to include floating Trichodesmium in a sample of water for 

 total phosphorus analysis as it would be to include a piece of floating 

 Sargasso Weed. In neither case would the floating plants represent an 

 integral part of the underlying water column as does the suspended plankton. 



Table 6.— Analysis of Trichodesmium blooms. 



1/ Estimated 



Trichodesmium can be concentrated by the winds and tide into long 

 narrow bands several hundred yards wide and miles long. This much has been 

 observed. If conditions suddenly became unfavorable for the survival of 

 this organism a great mass of organic matter would suddenly become available 

 to the biological cycle in the sea. The decomposition of this material 

 would release large quantities of nutrients for the growth of other organisms, 

 Blooms of other organisms would be expected under such conditions. 



Since Gymncdinium brevis was not found during the period of these inves- 

 tigations and a red tide did not occur during that time, the relation of 

 concentrations of Trichodesmium t o red tide could not be ascertained. The 

 results of analysis of Trichodesmium are presented here simply to focus 

 attention on the occurrence of concentrations of phosphorus in living 

 material floating on offshore waters of extremely low phosphorus content. 



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