varied from 100 to 190 percent. Greatest varia- 

 tions were at Hillsborough Bay and 18.5 km. 

 offshore; minimum variations were in Terra 

 Ceia Bay and in upper Tampa Bay. 



CONSTITUENTS OF ZOOPLANKTON 



The zooplankton consisted of holoplankton 

 (53.5 percent), meroplankton (46.2 percent), 

 and hypoplankton (0.3 percent). Most (87 per- 

 cent) of the zooplankters in these categories 

 were decapod crustaceans. Sixteen species, 24 

 genera, 30 families, and 21 taxonomic divisions 

 higher than family were identified. 



On the basis of abundance and frequency of 

 occurrence the plankton is treated in three 

 groups: major plankton; less abundant but 

 frequently occurring and widely distributed 

 organisms ; and forms caught rarely. 



MAJOR PLANKTON 



Lucifer faxoni, larval porcellanids, and lar- 

 val brachyurans, each of which accounted for 

 10 percent or more of the total number of 

 organisms, were classified as major plankters. 

 Collectively these taxa represented 83.5 percent 

 of the zooplankton. 



L. faxoni constituted 45.6 percent of the total 

 number of zooplankters (table 5). It was the 

 dominant zooplankter in Tampa Bay and was 

 the only sergestid found. Most of the speci- 

 mens were in the mastigopus phase, although 

 protozoea and acanthosoma types were seen. It 

 was collected at all stations and taken in num- 

 bers up to 1,051 per m.^*; 52 percent of L. 

 faxoni were collected from the upper and cen- 

 tral areas of Tampa Bay. This species was the 

 most numerous organism in the fall, winter, 

 and summer (fig. 4). As a result of its large 

 size and numbers, L. faxoni accounted for 18.5 

 percent of plankton biomass. The monthly 

 peaks in its displacement volume corresponded 

 generally with the monthly peaks in the total 

 volume of plankton. 



Porcellanid larvae (zoea and megalops 

 stages) formed the second most abundant 

 group of organisms. They accounted for 27.4 

 percent of the total number of zooplankters 

 and were collected in numbers up to 2,634 per 

 m.3 They were most numerous in upper Tampa 

 Bay and lower Hillsborough Bay and during 



1 



■s 



i 



FALL WINTER SPRING SUMMER I2M0NTHS 

 SEPI 1961 — AUG 19BZ 



■ Lucifer taioni 



2 Porcellanid larvae 



[^ Brachyuran larvae 



■ Sagitia hrspida 

 § CopepDds 



Figure 4. — Zooplankton taxa from Tampa Bay and the 

 adjacent Gulf of Mexico that accounted for 5 percent 

 or more of the organisms found during the periods 

 shown, September 1961 through August 1962. 



the spring were the dominant organism in the 

 area of investigation. 



Except for Dromiidae, larval brachyurans 

 were not identified to family and were classed 

 only as zoea or megalops. Collectively they 

 constituted 10.5 percent of the total number of 

 zooplankters, and were the third-most-abun- 

 dant taxon. Zoea and megalops were collected 

 in numbers up to 251 per m.' and 51 m.^ re- 

 spectively. They were found at every station 

 but appeared most abundantly in upper Tampa 

 Bay and least abundantly in upper Old Tampa 

 Bay. During the winter, megalops were absent 

 at all stations in the upper portion of the area 

 (stations 9 through 14). 



In another and concurrent study, Dragovich 

 and Kelly (1964) noted 2 species of adult Por- 

 cellanidae (Petrolisthes galathinus and P. 

 armatus), 23 species of adult brachyurans 

 (many of which were gravid), and a large 

 number of juvenile portunids. Of the com- 



MACRO-ZOOPLANKTON IN TAMPA BAY AND ADJACENT GULF 



215 



