FISHERY BULLETIN: VOL. 73, NO. 1 



Figure 1. — Tampa Bay, Fla., showing location of study area 

 and sampling stations (hydrologic station • ; trawl sta- 

 tion « > ). 



of the canals was lower than at the surface in any 

 one sampling period. A definite thermocline was 

 noted in January and February with the most 

 inland stations exhibiting the greatest differences 

 between surface and bottom temperatures. The 

 greatest difference was at Station 5 in February 

 when the bottom was 4.0°C lower than the surface. 

 In the previous year's study, the greatest differ- 

 ence was at Station 4 (February 1971) when the 

 bottom was 1.8°C lower than at the surface (Lin- 

 dall et al. 1973). 



SALINITY 



Surface and bottom salinities at the control sta- 

 tion ranged from 19.1 to 28.0''/oo during the study 

 and were nearly identical in any one sampling 

 period (Figure 3). The greatest difference was in 

 May when the bottom was 0. 7*^/00 lower than the 

 surface. Surface salinities at canal stations were 

 similar to those at the control station, ranging 

 from 19.1 to 28.5%o. With few exceptions, how- 

 ever, salinity at the bottom of the canals was 

 higher than at the surface in any one sampling 

 period. The greatest difference was at Station 3 in 

 October when thd bottom was 4.5%o higher than 

 the surface. 



OCT. NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP 



Figure 2. — Monthly water temperature at the surface and bot- 

 tom of all hydrologic stations, October 1971-November 1972. 



Stratification of salinity was also noted in the 

 previous year's study (Lindall et al. 1973). Differ- 

 ences between surface and bottom were not as 

 pronounced during most of that study because 

 drought conditions prevailed throughout most of 

 the year. Heavy rains in August 1971 ended the 

 drought. Thus, greater differences between sur- 

 face and bottom salinities (as much as 15%o) were 

 recorded in the previous study than in the present 

 study. 



OXYGEN 



Dissolved oxygen levels at each station are 

 shown in Figure 4. Only at the control station 

 were surface and bottom values similar, differing 

 no more than 0.3 ml/liter in any one sampling 

 period. At this station the lowest observed con- 

 centration was 2.2 ml/liter (July 1972). Surface 

 oxygen values in the canals ranged from 2.4 to 6.2 

 ml/liter and were similar to those at the control 

 station throughout the year. Oxygen at the bottom 



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