Table 6. — Percentage occurrence of sediments according to particle size and 

 percent calcium content in sediment samples from sponge bars 



■"- Numbers refer to samples taken at evenly spaced intervals from the central 

 part of the bar to the edge. 



the area. With normal salinities above 36 /q^ , 

 the samples showed that salinities just above 

 33 %Q were common. One salinity was 

 31.04 %„ . 



In addition to 

 sponges, almost 



the mortalities of the wool 

 all of the Styela plicata tuni- 

 cates had died as well. Since these are notably 

 intolerant to lowered salinities (Van Name, 

 1954), 1 believe that water conditions were the 

 cause of the wool sponge deaths. With the ex- 

 ception of two or three noncommercial sponges, 

 very few other sponges and sessile animals 

 showed any adverse effects. 



There is a possibility that the first heavy out- 

 flow of the river may have moved shorewise as 

 a parcel of low salinity water which would have 

 been dispersed or mixed only after a number of 

 days. The time lapse between the first outflow 

 and the sampling would have allowed sufficient 

 time for the lowest salinity water to have moved 

 out of the sampling area. 



Moore (1910b) in his experiments with culti- 

 vating sponges at Anclote Key determined that 

 salinities of 27.5 %^ were detrimental to wool 

 sponges while salinities of less than 26 /^^ 

 were lethal. In the Bahamas, W. Smith re- 

 ported that salinities of less than 32 °/ are 



'CO 



very harmful to sponges; however, his culti- 

 vated sponges were in water less than 6 feet 

 deep in a very different ecological situation. 



Elevated temperatures also have detrimental 

 effects on wool sponges, and it is probable that 

 the combined effect of elevated temperatures 

 and salinities not quite as low as 26 °/ would 

 be lethal. °° 



The commercial sponges appear to be able 



to withstand very high salinities. The salinity 



of the water over the Andros banks, a sponging 



area in the Bahamas, is often as much as 



46 °/ . 

 'oo 



Temperature 



Temperature effects on wool sponges ob- 

 served during the present investigation are: 



1. There is an optimum temperature range 

 in which wool sponges produce eggs in 

 quantity. 



2. There is a clinal effect on the size of the 

 wool sponges producing eggs. 



3. Sudden changes in temperature cause 

 withdrawal of the living tissue with re- 

 gression in size. 



The first two of these temperature relations 

 were discussed previously in the section on 

 reproduction. 



From the evidence at hand, commercial 

 sponges appear to have a tolerance range from 

 as low as 50° F., as observed during the study, 

 to at least 95° F. (W. Smith, personal com- 

 munication). 



During the laboratory experiment carried on 

 from September 1955 to June 1956, a number of 

 yellow sponges and wool sponge cuttings were 

 maintained in salt-water aquaria and the effect 

 of changes in temperature on these specimens 

 was observed. Photographs of these sponges 

 were made at 2-week periods and later at 



36 



