63. 



Particularly relevant to this are some findings by Grigg 

 (1965) concerning the specificity of substrate type and 

 texture requirements of the black coral Anthi-patharia grandis. 

 In studying the distribution of this organism he concluded 

 that larval individuals of this coral settle only on substrates 

 that have some CaCO on their surface. Small irregularities 

 or depressions on the surface of the rock were also found to 

 be important in determining larval settlement success. Hard 

 corals also initially settle on hard substrates, subsequently 

 some species break off and lie on the surface of sediment. 

 As a result, if increased sedimentation coats the hard sub- 

 strates with even a fine layer of loose material, and if this 

 is not removed by currents, the settling success of coral 

 larvae could be substantially altered. 



A comparison of the filter-feeding populations found in 

 the three canyons surveyed elucidates some of the problems that 

 may be encountered as a result of resource development. 

 Baltimore Canyon has a relatively high sediment load in its 

 water column and not much exposed hard substrate when compared 

 to Lydonia or Oceanographer Canyons. As a result Baltimore 

 Canyon's population of filter-feeders is sparse and not very 

 diverse. Additionally, dead parts or complete colonies of some 

 coral such as Pavagorgia arborea were frequently noted in this 

 canyon. This mortality could well be the result of a high 

 sedimentation rate causing fouling of these colonies. Another 



