charges of the Hillsborough River ^ — the major 

 source of river water to the bay (fig. 2) . 



■^ River discharge data (tig. 2) and rainfall data used in this 

 section were taken from the 1961 and 1962 Surface Water Records 

 of Florida, Vol. 1 : Streams, compiled by the U.S. Department of 

 the Interior. Geological Surve.v, and from the 1961 and 1962 Annual 

 Summaries of Local Climatological Data for Tampa. Florida, pub- 

 lished by the U.S. Department of Commerce. Weather Biireau. 



J 3 

 30 



27 

 24 



2 I 



1 8 - 

 I 5 

 1 2 

 36 

 33 

 ; 30 



27 

 24 

 21 

 1 8 



WtlER lEMPEXTURE 



HI ItSeOROUCH RIVEII DISCHARGE 



WINTER I SPRING ' SUMMER 

 SEPI IJSI — AUC IIE2 



Figure 2. — Mean monthly discharge rate for the Hills- 

 borough River and monthly surface water tempera- 

 ture and salinity for upper Hillsborough Bay (station 

 14) and 10 nautical miles offshore (station 1), Sep- 

 tember 1961 through August 1962. Mean values for 

 temperature and salinity are given when two meas- 

 urements of these variables were made in a month. 



CLIMATOLOGY 



Climatological data were taken from the 

 records of the U.S. Weather Bureau for Tampa, 

 Fla. 



Rainfall was abnormally low during the 

 study. From September 1961 through August 

 1962 total rainfall at Tampa, Fla.. was 95.3 

 cm., 35.7 cm. below the climatological normal. 

 Half of this amount (47.7 cm.) fell during the 

 summer. 



Mean monthly air temperatures at Tampa 

 from September 1961 through August 1962 

 varied from 15.8° C. in January to 28.3° C. in 

 July. Seasonally, mean air temperatures were 

 23.3° C. (fall), 16.7° C. (winter), 21.9° C. 

 (spring), and 27.4° C. (summer). 



ZOOPLANKTON VOLUMES 



In 267 plankton tows, the volume of zoo- 

 plankton per tow ranged from < 0.5 (consider- 

 ed as 0.25 ml. in all statistical treatments) to 

 92.0 ml. and averaged 7.0 ml. per sample. The 

 greatest concentrations of macrozooplankton 

 were in upper Tampa Bay, central Tampa Bay, 

 lower Hillsborough Bay, central Old Tampa 

 Bay, and 6.5 km. 3-i 2 nautical miles) offshore 

 (fig. 3. 



The abundance and composition of zooplank- 

 ton varied widely by season and location. 

 Twenty-five percent of the total volume was 

 collected in the fall, 5 percent in the winter, 18 

 percent in the spring, and 52 percent in the 

 summer (values adjusted for different num- 

 bers of tows per season). Coefllicients of 

 variation in zooplankton volume were calculat- 

 ed for each station to compare the areal vari- 

 ability of volumes (table 4). These coeflRcients 



Table 4.- 



-Mean zooplankton volumes and the coefficients of variation of individual zooplankton volumes taken in Tampa Bau and the 

 adjacent Gulf of Mexico. September 1H61 through Augu.'st 1962 



MACRO-ZOOPLANKTON IN TAMPA BAY AND ADJACENT GULF 



213 



