I. 



CB 



rl d 



a n 



iJaT aanaaanja 



111-, im" 



iJn n[i[i[i(iaLi™[lciciQi 



__ c=a ca [lb 



1 



n J 



J I I s 



I9E4-SS 



Figure 11. — River discharge, precipitation, and hydro- 

 logical properties at station 10, Caloosahatchee River, 

 Fla., January 1964 to January 1965. (Open bars= sur- 

 face; solid bars = bottom.) 



Concentrations of total phosphorus in individual 

 samples for all stauons ranged from 3.1 jug.at. per 

 liter in the Caloosahatchee River (station 10) to 

 62.9 fig.&t. per Uter in the Peace River (station 8). 



The differences between surface and bottom 

 values of total phosphorus varied from 0.0 to 15.4 

 ;ig.at. per liter. In the Hillsborough River (station 

 1) values were higher near the bottom than at 

 the surface due to upstream intrusion of Hills- 

 borough Bay water, in which phosphorus concen- 

 trations exceeded those in Hillsborough Bay (fig. 

 2, table 2). Salinity differences at surface and 

 bottom substantiate the conclusion. This obser- 

 vation agrees with previous studies (Dragovich 

 and May, 1962; Odum, 1953). 



Vertical differences in salinity in the Alafia 

 River (station 2) were not reflected in a pro- 

 nounced vertical stratification of phosphorus (fig. 

 3). Concentrations of phosphorus in the river 



FLORIDA'S WEST COAST TRIBUTARIES 



markedly exceed those in Hillsborough Bay 

 (table 1). The discharge waters of the Alafia 

 River are the chief source of phosphorus for 

 Hillsborough Bay (Dragovich and May, 1962). 



The Little Manatee River empties into the 

 upper portion of Tampa Bay, and the Manatee 

 River into the lower portion. Phosphorus con- 

 centrations in the upper and lower bays were 

 similar to those in the Little Manatee and Manatee 

 Rivers (table 1). Thus, the vertical stratification 

 of phosphorus in these two rivers was usually 

 moderate (figs. 4 and 5). 



Phosphorus values generally were higher at the 

 surface at stations 7 and 8. Differences between 

 sm^ace and bottom at stations 5 and 6 were 

 slight. Values were higher at the bottom oc- 

 casionally at both stations in the Caloosahatchee 

 River. This situation may arise from the bottom 

 sediment which enters the lower portion of the 

 water colimin during periods of turbulence. 



Monthly variations in total phosphorus showed 

 no trend. Mean concentrations of total phosphorus 

 at each river were multiplied by flow to estimate 

 changes in the total monthly quantity of phos- 

 phorus. Combined calculations for all rivers showed 

 maximiun quantities in February, March, August, 

 and September — the months with maximum run- 

 off; values were low during the minimum runoff 

 in June and November (table 4). It appears, 

 therefore, that the quantity of phosphorus added 

 to the bays and the adjacent sea depends more on 

 volume of river flow than on concentrations of 

 phosphorus in the streams. An exception was the 

 Alafia River — ^the total quantity of phosphorus 

 was much higher than in the Hillsborough River 

 despite greater flow rate in the latter. 



Geological formations influence the phosphorus 

 content of the river water (fig. 12). The high 

 phosphorus values are directly attributable to 

 di-ainage areas that are highest in CaP04. Quanti- 

 ties were highest in the Peace and Alafia Rivers 

 which flow primarily through Hawthorne phos- 

 phatic formations. Relatively high phosphorus 

 concentrations in the Manatee, Myakka, and 

 Peace Rivers may be explained by the fact that 

 they flow through jjhosphorus-bearing formations 

 (Bone Valley and Hawthorne). Higher values at 

 the Hillsborough River station result from mixing 

 of relatively phosphorus-rich bay water with 

 river water. Concentrations were lowest in the 

 Caloosahatchee River, only part of which drains 



471 



319-171 O - 68 - 3 



