three others were taken but not in these areas. 

 Of the 59 identified species collected by us, 

 34 were different from those recorded in 1948 

 in the same areas. In all, 11 species taken by 

 the 1948 survey in the same general areas ex- 

 plored by the present investigation were not 

 recorded as being taken a second time. 



The temperatures are based on the nearest 

 permanent tide station data. Check of the cruise 

 data of the Red Tide project at the Marine 

 Laboratory indicates that temperature data are 

 accurate for the areas indicated. 



In table 10 the lesser number of species re- 

 corded from area A may be partly due to the 

 fact that although very intensive work was done, 

 only a few bars were surveyed. The population 

 make-up of individual bars will vary greatly 

 even within a limited area, and it would there- 

 fore be necessary to examine a large number 

 of bars to obtain a true population sample. 



In area F the several stations southwest of 

 the Cape Romano buoy yielded a number of 

 sponges which could not be identified with cer- 

 tainty. These stations were in an area where 

 the flow of the tidal current was strongest. Gen- 

 erally speaking, the sponges found at these sta- 

 tions were growing more profusely, the shape 

 and texture varying greatly from that of the 

 same species in zones where the tidal flow was 

 less. These differences in shape, texture, and 

 internal structure (purely ecological varia- 

 tions) made identification of many of the species 

 difficult. 



Sponges recorded from area G represent 

 those species collected in the upper Keys from 

 Miami to Plantation Key. The combination of the 

 collections made in areas F and G were used to 

 make the comparison with the 1948 collection 



from the Key West and Ten Thousand Islands 

 areas. 



Area G is the only ecological zone that differs 

 physically from all the others. This area is the 

 coral reef zone of the upper Keys, and the 

 slope of the bottom, nearness to land, and 

 proximity to the Gulf Stream and deep open 

 ocean set this zone apart ecologically from 

 the others. The lesser number of species found 

 indicate that this is an unfavorable habitat for 

 many sponges. 



A comparison of the number of species in 

 each area with the yearly mean temperature 

 (table 10) suggests that the optimum water 

 temperature for the growth and existence of 

 most species of sponges is about 75° to 76° F. 

 Of greater importance ecologically than the 

 mean temperature of an area is the tempera- 

 ture range. There is a difference of 52° F. 

 between the lowest and highest recorded 

 monthly temperature in area A while the dif- 

 ference is 35° F. in area F. In addition, as 

 indicated by a study of yearly weather condi- 

 tions, there is far more likelihood of sudden 

 changes in area A than in area F. In the case 

 of Florida sponges, (1) some species are in- 

 capable of reproducing effectively in colder 

 water, (2) the mature sponges are killed by 

 sudden water temperature changes, and (3) the 

 prolonged low water temperatures of the winter 

 found in the northern Gulf kill the sponges or 

 drastically deter growth. 



Sponging Grounds and Zones 



A full description of individual productive 

 sponge beds has been made by Moore (1910a). 

 Little can be added to that description as the 

 names or areas have not changed appreciably. 



Table 10. — Distribution of species by number in each area 



^ Based on U.S. Department of Commerce Special Publication No. 278. 

 Average between Cedar Keys and St. Petersburg recordings. 



44 



