important of these are the corals, Solenaster 

 hyades, two species of OcuZina coral, and vari- 

 ous species of the alga Halimeda. The clam. 

 Area zebra, is also important for it is found 

 attached in great quantity on the bar rock, and 

 on some bars is of importance for the attach- 

 ment of wool sponges. 



Calcareous sediments form from the break- 

 down of these corals and the various animals 

 that live on the central parts of the sponge bars. 

 Sorting of these sediments is brought about by 

 wave activity, and there is a gradation of the 

 sediments from coarse to fine from the central 

 areas of the bars to the edges. 



To assess the effect of the large produc- 

 tion of calcareous material in the loose sedi- 

 ments, series of sediment samples were taken 

 at evenly spaced intervals from the central 

 part of the bar area to the edge. The results 

 of two such series, one selected from an iso- 

 lated bar in 25 feetof water off Piney Point and 

 the other from a bar in 1 6 feet of water off the 

 mouth of the Aucilla River, represent the ex- 

 tremes of the samples taken (table 6). 



Samples from the central portion of the bar 

 had large percentagesof the sediments over 0.5 

 mm. in size. This coarse material was made up 

 primarily of fragments of coral, moUusk 

 shells, sea urchin tests, and other skeletal re- 

 mains. Toward the edge of the bar and in the 

 grassy area around the bar, the sediment size 

 was finer. The sample series from the isolated 

 bar shows the effect of the shifting of the finer 

 sediments, principally quartz particles, onto 

 the bar area. This particular series was taken 

 after very rough weather which upset the 

 normal sorting action described above. 



The series of samples taken from a bar in a 

 very rocky area off the Aucilla River reflects 

 the effect of the addition of large amounts of 

 calcium to the sediments in the area. In this 

 case the sediment sample taken from the grassy 

 region off the bar area contains more cal- 

 careous material than did the central part of the 

 bar in the series from Piney Point. 



Although much variation in sediment dis- 

 tribution across a bar is to be expected, the 

 sample series from the Aucilla River area 



indicates the importance of a bar area in the 

 production and addition of calcareous material 

 by animals and plants to the unconsolidated 

 sediments. This was apparent from visual 

 observation of the sediments. 



ECOLOGICAL RELATIONSHIPS 



Salinity Tolerances of Sponges 



Little is known about the salinity tolerances 

 of commercial sponges other than wool 

 sponges. A number of wool sponges shown to me 

 by divers had lost most of the living material, 

 leaving the remainder of the sponge with clean 

 skeletal fibers. The divers attributed the dying 

 of the sponges to "fresh" water. Such sponges 

 were not more than normally odoriferous, but 

 there were no signs of decay or disease even 

 when examined microscopically. Such sponges 

 are commonly found west of the mouth of the 

 Suwannee River in the area where fresh- water 

 discharge would be expected. Salinity data from 

 the Red Tide Cruise of June 1956, carried out 

 by the Marine Laboratory of the University of 

 Miami, show salinities as low as 27.7 %q , in 

 this area extending as much as 5 miles from 

 land. 



In October 1956, during a sponge investiga- 

 tion field trip to the area just north of the 

 Steinhatchee River, a large number of sponges 

 appeared to be affected in much the same way 

 as those off the mouth of the Suwannee River. 

 Later the hookers and divers reported that 

 large numbers of wool sponges in the shallow 

 water zones from Piney Point to St. Marks had 

 been killed. There was every indication that the 

 destruction of the wool sponges was related in 

 some way with a tropical storm which had 

 passed northward through the New Orleans 

 area a few days before. Tagged sponges at one 

 of the buoyed stations were examined and found 

 healthy before the storm. Seven days later they 

 were dying off. Within this period the Stein- 

 hatchee River (fig. 10) had begun to flow for 

 the first time in 4 years; the initial flow was 

 particularly strong, following exceptionally 

 heavy rainfall. 



Water samples from St. Marks to Stein- 

 hatchee taken 6 days after the beginning of the 

 outflow showed lowered salinities throughout 



35 



