horn, and chitin. The arrangement of spongin into a fibrous network is responsible for the 
commercial sponges properties of compressibility, resiliency and ability to absorb large 
quantities of water. 
The sheepswool sponge ( Hippiospongia lachne) is considered to be the highest quality 
commercial sponge found in the western Atlantic. It is the most valuable species, representing 
75% of the dollar value of sponges collected in Florida and 87.9% in Monroe County during 
1976. The yellow sponge ( Spongia barbara) is elastic and resilient and is harder than the 
sheepswool, harsher to the touch, less absorbent, less retentive of water, and less durable. 
Yellow sponges accounted for 14.7% of the dollar value of sponges collected in Florida and 
6.3% in Monroe County in 1976. Grass sponges collected off the west coast of Florida differ 
considerably from those taken in the Keys. The grass sponges of the Florida Keys, Bahamas 
Islands, and Cuba, Spongia graminea , vary in form and general appearance, but generally grow 
in a rounded, more compact form with a flat or concave top that is perforated by a number of 
oscules up to 0.65 cm in diameter. Large numbers of these sponges are collected in Biscayne 
Bay but the market value of these sponges is the lowest of all the commercial species. 
The commercial sponges apparently cannot tolerate salinities much below oceanic levels. 
Temperature has been shown to be an important factor affecting sponges. Commercial sponges 
appear to have a tolerance range from 10° C to 35° C. Sponges, due to their sessile nature, are 
dependent upon water currents to bring food, dissolved oxygen, disperse larvae, and to carry 
away wastes. The availability of clean, hard substrate for the sponge larvae to settle upon is 
extremely important since larvae are smothered by sediments. Only a small percentage of the 
large areas defined as the Florida sponge grounds actually support sponge populations due to the 
scarcity of rock outcroppings. 
During 1938 - 1939, populations of commercial sponges throughout the western Atlantic were 
decimated by disease. The disease first appeared in the Bahama Islands and rapidly spread 
throughout the West Indies and the Gulf of Mexico. The progress of the mortality was recorded 
in a detailed manner and transmission of the disease was attributed to water currents. This 
disease has been attributed to the fungus Spongiophaga communis. In British Honduras, 
Spongiophaga was observed growing on the surface of turtle grass, Thalassia, with no apparent 
ill effect. As reported in 1978, a sponger in the Key West area reported that he continually 
found a small number of sponges affected by the fungus. Exactly why the blight has not 
triggered mass mortalities, as it has been reported to do in the past, is not understood. 
During 1947 - 1948, a disease affecting the commercial sponges along the west coast of 
Florida was reported. Investigation of this phenomenon by members of the Marine Laboratory, 
University of Miami, did not reveal the cause of this sponge mortality. No evidence of fungal 
disease was found. Mortality of sponges due to the outbreak of red tide has been noted. Sponge 
fishermen have reported that sponges in shallow water are occasionally killed off by a 
phenomenon they call "mallee". This "mallee* is a heavy growth of fine algae that usually 
smothers sponges. 
Recently, sponge dieoffs were observed in 1992, apparently related to microalgal blooms, with 
a time lag of 5-7 days. The region affected was mid-Bay to the southeast, adjacent to the Keys 
(Brown and Ortner, 1994). The population of juvenile Caribbean spiny lobster may have been 
impacted by the sponge die-off as sponges are a primary shelter for these animals (Childress 
and Herrnkind, 1994). 
6.6. Mangrove dieoffs 
The information in this section was found in Hanlon et at. (1975). A thorough discussion of 
mangrove forest ecology can be found in Odum et at. (1982). 
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