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MISSION DISPATCH - DAY 1 Today's Weather - images courtesy of NOAA & RSMAS Dispatch by Dr. Karla Parsons-Hubbard 
July 24, 2001 Today, we collected experiments that were placed in the Gulf of Mexico in 1993. These experiments consist of clams, snails, sea urchins, crabs, and wood placed on the sea floor in mesh bags, and we are studying how these animals become fossils. Of course, fossilization takes thousands of years, and most organisms never become preserved at all. In fact, our experiments are designed to reveal what happens to destroy the hard parts of plants and animals before they can become fossils. On today's submersible dive, we brought up only one of the five kinds of wood and seeds that we put down in 1993 - the black walnuts appear to be very resistant to the marine organisms that eat wood and the hard outer coats of seeds. The types of wood that got destroyed were: white pine, redwood, parana pine, oak, and magnolia. Anne Raymond, of Texas A&M University, is a member of the SSETI team studying wood fossilization. Dr. Raymond tells us that the animals that destroy wood are ship worms and gribbles. 
Ship worms are actually clams that burrow into the wood and live
in calcium carbonate tubes, which they secrete. Gribbles are small marine
animals related to terrestrial pill bugs or 'roly-polys' which make shallow
tunnels in the surface of wood.
Once the wood has been tunnelled and colonized by ship worms and gribbles, brittle stars and polychaete worms also move in. They hide in the crevasses - but do not eat wood. Wood and other land plant fossils are relatively common in marine evironments prior to the end of the Triassic Period 220 million years ago. Ship worms first appear in the Jurassic Period, which follows the Triassic. The evolution of ship worms may play a role in the abscence of wood from the marine fossil record after the Triassic. 
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