by Carl R. Froede Jr

The bioturbation of sediments by trace makers is often perceived by naturalists as a process requiring extensive periods of time. Little experimental work has been conducted to either support or refute such a concept. However, recent laboratory analysis indicates that the bioturbation of marine sediments can occur within short periods of time.

Bioturbation experiments

Marine worms, bivalves (clams), arthropods (shrimp and crabs), and echinoderms (sea urchins and brittle stars) are just some of the many animals that live on or in marine sediments (figures 1 and 2). The study of traces created in sediment is identified as ichnology (Gk ichnos = trace).1

Recently, an investigation was conducted to determine the rate that select bivalves, arthropods, and echinoderms could bioturbate marine sediments. The animals were collected from tidal flats and shallow subtidal sediments from the Ogeechee estuary, Georgia (U.S.A).2 They were placed into glass aquaria filled with alternating layers of sand and heavy minerals with each layer being approximately 5 to 10 mm thick.2 Examination of the rate of bioturbation occurred at 1, 6, 24, 72 and 144 hour intervals by collecting X-ray images of the aquaria sidewalls.2

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