Certain fish, such as ostraciontidae (trunkf ishes) and balistidae 

 (trigger fishes) , blow holes in the sand. A Balistes vetula (queen 

 triggerfish) was observed (pers. coram., John van Derwalker 1970) 

 blowing a hole that was later measured as about 40 cm across and 

 15 cm deep. Holes blown in the sand by fish are distinctive in 

 that they have very steep walls. 



Less was ascertained about the effects of organisms that spend 

 their lives within the sand. Mounds that have the form of small 

 volcanoes of sand are highly abundant in certain areas. These 

 mounds are formed by the casting of sand from small burrows that 

 vertically intersect the sandwater interface. The organisms res- 

 ponsible were not identified, but the burrows are similar to those 

 produced by burrowing shrimp (Shinn, 1968, p. 883). Other orga- 

 nisms, such as small gastropods, tend to stir the sand by burrowing 

 horizontally. Some vertebrates such as Ophichthus ophis (spotted 

 snake eel) apparently have the ability to "swim" through the upper- 

 most part of the sediment. Numerous other endofauna, including 

 pelecypods, crustaceans, and worms, undoubtedly contribute greatly 

 to bioturbation of the carbonate sand. 



CONCLUSIONS 



The studies conducted as part of Tektite II have documented the 

 great importance of bioturbation as a geologic process in the 

 semiprotected coral reef environment. The faunal disturbance of 

 sediment has a wide variety of effects. Bioturbation can create 

 or destroy sedimentary structures. It can produce an assemblage 

 of empty pelecypod valves that lie predominantly concave side up, 

 an orientation that contrasts markedly with that produced by waves 

 or currents. This difference in shell orientation provides a use- 

 ful means of interpreting the energy regime under which a fossili- 

 ferous sedimentary rock was deposited. The activity of organisms 

 may control the distribution of sediment on the sea floor, in 

 particular, the aggregations of coarse shells and coral fragments 

 produced by M. pl\imieri and the lateral shifting of sediment at 

 the surface. 



The style and rate of bioturbation depend on environmental factors 

 such as proximity to the reef and substrate . At the canyon mouth 

 site, the substrate is distinctly finer grained than at the other 

 experimental sites, and more organisms live in burrows within the 

 sand. The style of bioturbation by these organisms differs consi- 

 derably from that at the other sites and the rate of sediment 

 modification differs accordingly. A prolific burrowing fauna 

 generate a higher rate of destruction of sedimentary surface struc- 

 tures such as ripple marks but a lower rate of disruption of inter- 

 nal structures. In each of the environments examined, the rate of 



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