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Wetlands and Aquatic Research Center - Florida
Cruise Log: 8/08/2009
One of the things we cannot capture on video is the small animals that live in the mud and sand on the ocean floor. For that we need specialized equipment. Dr. Amanda Demopoulos of the U.S. Geological Survey uses Push Cores to sample the sediment. These tubes come in a variety of sizes and are used to help answer different questions about both the chemistry and organisms found in the sediments.
The Push Cores use a fairly straightforward and long-standing design. A rigid plastic tube, open on the bottom, is topped with a T-handle and stopper. The tube is carried in a plastic container, called a quiver (like the ones used in archery). The submersible pilot uses the robotic arm to lift the Push Core and place it vertically into the seafloor, then to push it in until the tube fills with sediment. Usually the mud or sand makes a good seal, and the sub pilot can gently lift the Push Core up and place it back into the quiver. The seal in the bottom of the quiver holds the sample until the submersible returns to the surface.
Using Push Cores in extremely deep environments makes for some unusual challenges. One is that the tube can collapse under the great water pressure, In order to prevent this, each tube has a tiny vent in the top, created by a small strand of monofilament which is automatically removed when the Push Core is deployed.
After the sample is brought to the surface, Dr. Demopoulos sorts through the sediment, a very muddy and tedious process. She preserves the animals for identification back in the lab. She collected two samples during the morning sub dive in addition to some sponges, Bamboo Corals and Lophelia fragments. She has set up the Push Cores on the submersible so Dr. Cheryl Morrison (USGS) and Liz Baird (NCMNS) can try to bring back additional material in the afternoon dive. This year Dr. Demopoulos is collecting and comparing samples from the Atlantic and the Gulf of Mexico. This will greatly enhance our knowledge of the community ecology of the habitat.
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