GULF OF MEXICO 

 Table 1. — Geographical distribution of alcyonarians known from the Gulf of Mexico — Continued 



281 



This table has been compiled from the literature 

 and from collections in the U. S. National Museum, 

 including unpublished records from the Albatross, 

 Fish Hawk, and Pelican expeditions. Published 

 locality records within the Gulf of Mexico as 

 defined above have been located for 72 species; 

 records of only 9 species from Gulf localities exclu- 

 sive of the lower Florida Keys and Tortugas have 

 been found. Another 19 species have been added 

 by records m the collections of the U. S. National 

 Museum, bringing the total number of species to 

 91. These species represent 18 families in 4 of the 

 6 known orders. 



Although little is known of the physiology of 

 the alcyonarians, it is clear that bottom condi- 

 tions, temperature, salinity, available oxygen, 

 and sedimentation play important parts in limit- 

 ing their distribution. Limits of tolerance are 

 apparently quite narrow but not equally so for all 

 factors. A solid substrate providing satisfactory 

 conditions for the attachment of larvae is almost 

 universally required among all alcyonarian groups 

 excepting the pennatulids. A very few gorgona- 

 cean species are able to live unattached, and 

 a number, especially of the families Chrysogorgi- 

 idae and Isididae, can adapt themselves to live 



on either hard or soft bottom. The few gorgonian 

 species which have been investigated in regard to 

 temperature tolerance (L. R. Cary, Papers from 

 the Dept. of Marine Biology, Carnegie Institu- 

 tion of Washington, v. 12, No. 9, 1918) can with- 

 stand from 5° to 9° C. (approximately) above the 

 average maximum surface temperature of the area 

 (at the Tortugas, about 29° C), but it is unlikely 

 that colonies would establish or thrive outside of 

 a rather limited temperature range. In the 

 absence of experimental evidence, it is impossible 

 to state the limits of the salinity and oxygen 

 variation which the alcyonarians can tolerate. 

 A few species can live in situations where the 

 salinity is occasionallj' somewhat reduced, but 

 most, including the West Indian reef-dwelling 

 forms, are never found where appreciable dilution 

 regularly occurs. Certain species are limited to 

 outer reef situations, and oxygen may be the 

 critical factor in such cases. As a rule, alcy- 

 onarians are not found in continuously muddy 

 waters, but some can tolerate very muddy con- 

 ditions for short periods. 



The reef areas of the Tortugas and lower Florida 

 Keys support a typically West Indian gorgonian 

 assemblage. The predominant families are the 



