compared to the deeper water sponges the 

 shallow-water wool sponges are very soft and 

 weak. A study of the microscopic structure of 

 the fibers shows that fibers from shallow-water 

 sponges are finer and more loosely connected 

 than those taken from sponges that grew in 

 deeper water. 



Competition for Space 



Two methods of evaluating bottom popula- 

 tions were attempted: (1) measuring the con- 

 centration in small quadrants using general 

 groupings of attached animals and plants and 

 (2) a more extensive study identifying plants 

 and animals in defined bar areas. 



In the first study the bottom flora and fauna 

 in a number of lO-foot squares were evaluated 

 quickly using an arbitrary method of division 

 of the bottom growth into groups (table 7). 

 Since loggerhead sponges are generally over 

 1-1/2 feet and up to 3 feet in diameter, these 

 sponges are listed separately as one group. 

 The average size of the other sponges is be- 

 tween 4 and 6 inches. The concentrations for 

 each area are also divided into two regions — 

 shallow- water, less than 21 feet, and deeper 

 water, more than 21 feet. 



There seems to be no direct connection 

 between a heavy bottom population and the 

 concentration of wool sponges. Rather it is the 

 indirect effect of concentrations of bottom 

 animals, which provide a sediment trap that 

 excludes the wool sponge from most areas of 

 higher concentrations of animals. This sedi- 

 ment is reduced or almost entirely removed 

 only during stormy weather, the heavy wave 

 action cleaning off the edges of the bar at the 

 same time and making these areas available 

 for wool sponges. 



Animals and Plants Associated with 

 Wool Sponges 



In addition to those animals and plants 

 intimately associated with the wool sponge as 

 cohabitants, there is a considerably larger 

 group of sessile forms found on the adjacent 

 bottom forming an ecological group to which 

 the wool sponge belongs. To determine this 

 group, collections of the sessile plants and 

 animals were made at each of the shallow- 

 water stations of the first two major field 

 trips. We intended that these collections would 

 establish a record of bottom forms by area 

 rather than by stations. Sponges were the only 

 group for which complete occurrence records 



Table 7. — IVpical concentrations of animals and plants in 10-foot squares 



on rock bars 



■"■ Areas are given in appendix. 



^ All sponges except loggerheads since these are three to six times average 

 size of other sponge species. 



39 



