PHOSPHORUS CONTENT OF WATERS ALONG THE WEST COAST OF FLORIDA 



Mass mortality of fish along the west coast of Florida during I9U6 

 and 19k7 , caused by an intense water bloom of Gymnodinium brevis Davis in 

 the form of a "red tide", stimulated an active interest in the causes of 

 such plankton blooms (Galtsoff, 19^8; Gunter, et al, 19h7; Gunter, Smith, 

 and Williams, 19>i7; Smith, 19k9) • In 19U8 the Fish and Wildlife Service 

 established a laboratory at Sarasota, Fla., dedicated to the study of the 

 ecology of the local plankton, particularly the causes of plankton blooms. 



Of the many hypotheses offered to explain the red tide, the one m 

 generally accepted was that unusual enrichment of the coastal waters oc irred, 

 resulting in abnormal growth of plankton in general, and of G^ brevis in par- 

 ticular. 



Ketchum and Keen (19h8) analyzed a number of surface samples from the 

 red tide of 19U7* Their analyses showed total phosphorus values ranging 

 from about 5 jig-at/li' in water of light amber color to more than 20 _ug-at/L 

 in water of deep amber color. As Ketchum and Keen pointed out, the total 

 phosphorus content of waters containing d ense Gymnodinium populations was 

 from 2-1/2 to 10 times the maximum to be expected in the sea. To find such 

 concentrations of phosnhorus in subtropical surface waters was very unusual. 

 They offered two possible explanations for these high values in surface 

 samples: either a surface swarming of organisms which had absorbed all the 

 phosphorus in the water column, or an enormous contamination or fertilization 

 of the coastal waters. They tended to rule out terrigenous contamination 

 because the quantities of phosphorus necessary would be unreasonably great. 



In red tide sampler, the total phosphorus was high but the inorganic 



phosphorus was generally low. At least some of the water in which the red 



tide occurred contained no measurable amount of inorganic phosphorus 

 (Gunter, et al, 19U7; Smith, 19h9) • 



Enrichment of the Gulf waters with phosphorus by way of river drain- 

 age fmm phosphate mines in the interior was early suspected as a con- 

 tributing cause of the red tide, but the importance of this contamination 

 was later minimized as the red tide spread in extent, and as early histori- 

 cal records of occurrences of noxious red water along the Florida west 

 coast came to light (Smith, 19U9)« 



The program of the red tide laboratory at Sarasota included a hydro - 



graphic and biological survey of certain waters along the west coast of 



Florida. A saries of river, coastal, and offshore stations were established 



and were occapied at regular intervals. Water samples were analyzed for 



salinity, oxygen, pH, inorganic and total phosohorus. Quantitative plank- 

 ton samples were also taken. 



1/ jig-at/L (microgram atom per liter) ■ micrograms per liter divided by the 



gram-atomic weight. 

 2/ W.W. Anderson was in charge of the Red Tide Investigations during the 



planning stages and directed the surveys during the first year of 



operations. 



