Bioturbational rates and effects in carbonate sand, St John, US Virgin Islands

Clifton, H; Hunter, Ralph

Studied movement of sand pebbles on the sea floor produced by animals in the environment. Study site was Greater Lameshur Bay, St. John. Participation in the Tektite man-in-the-sea experiments provided a unique opportunity to observe bioturbational rates and effects in carbonate sand at depths ranging from about 10-20 m near a coral reef. Experimental studies established the rate at which organisms in this environment modify the surface, disturb the interior of the sediment, and undermine solid objects on the sea floor. Inactive sand ripples are totally destroyed in 2-4 weeks. Lamination in the upper 2 cm is largely obliterated in the same amount of time. Pebbles on the sea floor can be buried in a few days by faunal undermining. The rate and style of bioturbation are strongly controlled by grain size of the substrate: surface modification and pebble burial are most rapid in relatively fine sand, whereas the rate of shallow internal disruption of the sediment may be more rapid in coarser sand. Bioturbation in this environment results largely from activity during daylight hours. A prodigious amount of sediment can be moved vertically or laterally by such activity.

Bioturbational rates and effects in carbonate sand, St John, US Virgin Islands

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