Day 4 (84) The DSL-120 sonar mapping of South Chamorro Seamount continued through the night. I arrived on watch at 0345 to watch the recording of the last segment of the last transect. Originally, there were 9 parallel transects plotted on the chart to map the seamount. We got good data from 5 of those transects. That involved 3 lowerings of the DSL-120 and 54 hours total time including lowering and retrieving the DSL-120. There just wasn’t enough time to map every transect but the data is good and Akel, the sonar/ ROV data specialist, is putting together a bathymetric map. Hopefully, future side-scan sonar surveys will be completed in a single lowering so more data can be collected in a shorter time.

When the DSL-120 was safely secured on deck, we collected one of the 3 transponders that had been used to help navigate the site. The other 2 were left in place because we will return to South Chamorro near the end of this expedition. We then headed north to Celestial Seamount. We will do core sampling and side-scan sonar. It will take over 20 hours to reach the seamount but the work on the ship doesn’t stop.

While underway, we are using the multibeam sonar on the hull of the ship that can map the deep sea floor from the surface. The information received doesn’t have the high resolution of the DSL-120 but we can still get new information about this segment of the sea floor.

Charlie told me that this ship takes the following things into considerations before dumping or incinerating: 1) the laws of the U.S., 2) health issues and, 3) safety.

The U.S. laws of trash disposal at sea are posted on the ship. By international law no plastic may be thrown into the ocean. Plastic does not decompose. Sea animals are killed when they become entangled in it. Some sea animals mistake it as food and are killed when it lodges in their digestive systems. By U.S. law, nothing may be thrown overboard unless you are more than 3 miles from shore. From 3 miles to 12 miles, it is permissible to throw paper, rags, glass, crockery, metal and food but the pieces must be one inch or smaller. From 12 miles to 25 miles you can throw trash overboard except plastic and dunnage. Dunnage is the term for lining and packing materials that float. Past 25 miles, all trash, except plastic, may be disposed of by throwing it overboard.

Health issues include rats, cockroaches and flies. The ship tries to recycle as much as possible but saving bags of aluminum cans for weeks can contribute to the presence of pests. Often the cans must be thrown overboard due to fruit fly population explosions. Fortunately rats and cockroaches are not a problem on this ship which is kept really clean. Garbage, steel cans, other metal and glass are also thrown overboard.

Safety means they don’t incinerate things that are a danger for the operator like aerosol cans and batteries. There are special trash cans for these and other items that are taken back to shore for disposal. The ash from the incinerator is also taken back to shore.

Science Summary - Day 4, March 26

By Patricia Fryer

Science Objectives, Day 4:

The fourth day of the cruise, March 26, after completing the DSL120 survey of the summit of South Chamorro Seamount at about 11AM local time, will be spent transiting to the next seamount that we will be surveying. The transit will take about 17 hours and we will collect both EM300 and Hydrosweep bathymetry data on the way north. The lines will complete portions of older surveys where the previously collected tracks left gaps in the bathymetry coverage. We will actually arrive at about 7 AM tomorrow morning and do a gravity core before deploying transponders for the next DSL120 survey at the summit of Celestial Seamount.

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