.01 mm 



Figure 16. --Wool sponge fibers showing fiingal disease 

 growth. Fungal fibers attached by one end only. Liv- 

 ing materialof the sponge is indicated by the stippled 

 areas (after Smith, 1941). 



attacked in the following order: velvet, grass, 

 wool, and reef. In the Bahamas, the order of 

 attack was different, for the wool sponges 

 were attacked before the grass. 



In British Honduras Spongiophaga was ob- 

 served growing on the surface of eelgrass, 

 Thalassia, with no apparent effect on the health 

 of the plant. 



Between 90 and 95 percent of the commercial 

 sponges were destroyed in most areas of the 

 Caribbean and Gulf. All the velvet sponges 

 were destroyed in the Bahamas, and none has 

 been observed since. Two or three velvet 

 sponges were taken along the west coast of 

 Florida in 1947. In 1938 the sponging grounds 

 in the Gulf along the west coast of Florida 

 north of Tampa were least affected by disease 

 with production falling off by 1940 to about one- 

 third of 1936, 



The 1947-48 Sponge Disease 



In 1947 commercial sponges along the west 

 coast of Florida were again attacked by 

 disease. Immediate investigation by mem- 

 bers of the scientific staff of the Marine 



Laboratory of the University of Miami did not 

 reveal the cause of this destruction of the 

 sponges. No evidence of fungal disease was 

 found, and the oceanographic conditions were 

 generally within the range common to in- 

 shore Gulf of Mexico waters. 



Other Detrimental Effects 



Sponge fishermen claim that a killing off of 

 sponges in shallow water is sometimes as- 

 sociated with the occurrence of the "mallee" 

 (from the Greek "hair"). This mallee is a 

 heavy growth of fine alga which apparently 

 covers the rocky bars during the late spring, 

 the time of occurrence depending on tempera- 

 ture. After a short period of attached growth, 

 the mallee breaks loose and rolls or washes 

 about the bottom, thus making sponging in the 

 area next to impossible. By inference mallee 

 has come to mean any heavy bottom plant 

 growth that finally breaks loose and rolls 

 about the bottom in large mats 2 to 3 feet deep. 

 At times this mat is made up of a "sea grass," 

 Halophila baillonis Large amounts of other sea 

 plants may add to the mass. Certainly a col- 

 lection of this material covering the sponges 

 would be detrimental. The actual cause of the 

 sponge destruction accompanying this condition 

 is unknown. Examination of sponges apparently 

 affected by a malleelike condition in the 

 summer of 1956 did not reveal any fungal 

 disease or other disease organism. The condi- 

 tion was local in extent, affecting a series of 

 rather limited areas in the shallower water 

 just north of Tarpon Springs with serious 

 effects to the sponges. 



Growth experiments by Moore (1910b) and 

 Crawshay (1939) showed a 2-percent mortality 

 of sponges during the winter and a 10-percent 

 mortality in the summer. Total mortality of 

 sponges during the period required to reach a 

 6-inch diameter was estimated at 20-30 per- 

 cent. These percentages represent the expected 

 mortalities in water depth of 6 feet and in 

 protected areas where adverse ecological fac- 

 tors would be expected to be encountered most 

 often. Mortalities in deeper and more open 

 water could be expected to be lower. 



A sudden freshening of the water in local 

 areas has also caused considerable loss of 



48 



