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April 11th, 2014 - Laurence M. Gould

Our first sampling from the Laurence M. Gould

by Andrew Klein

Andrew's head

One of the things that we wish to accomplish on this trip is to reoccupy a number of sites at which Chuck Kennicutt, Steve Sweet and other Texas A&M scientists collected following the sinking of the Bahia Pariso. These samples were collected from the Polar Duke from 1989-1991 and are all within a few kilometers of the station.

There are two types of sites we intend to resample. The first are PD samples (PD is short for Polar Duke) and the others are SB sites (SB referring to soft bottom). At each of the PD sites we will only collect enough sediment to analyze for hydrocarbons and a suite of trace metals and do grain size analysis on. At the SB sites, we will collect the top 10 centimeters in order to look at the macroinfauna community structure in addition to the geochemical analysis.

 

Potential Sampling Sites
Potential sites we wish to sample from the Gould

To sample these sites from the LMG we are using a Smith-McIntyre grab sampler. This device has two sides that when hitting the bottom snap together to form a bucket – thus collecting a fairly intact portion of the bottom as long as it is not too rocky. Because the other two science groups on the boat are biologists who need their samples to be brought quickly aboard the station, we have to sample either just as the LMG leaves Palmer Station or like today before the groups collect any samples.

Today we lucked out – because the Drake was so smooth, we made our crossing much faster than anticipated and have a few hours before it gets dark and we begin trawling for zooplankton. Therefore, we were able to collect seven PD samples before the Gould headed out to Palmer Deep for zooplankton collection.

Because our samples were going to be the first collected this trip, Steve and I had to spend some time preparing for our sampling and getting the wet lab ready and because we were early, this occurred a bit earlier than we had anticipated.

Our sampling basically goes something like this – with the help of the wonderful Marine Techs, we put the Smith-McIntyre grab sampler over the aft end of the Gould and lower it to the bottom on a wire. When the feet of the sampler hit bottom, it closes. Then we bring the sample to the surface were a core tube is inserted to extract the required amount of mud which is then extruded into a 250 ml jar for analysis back at Texas A&M University. A small about of the sediment is also put into a whirlpack for grain size analysis.

After the first couple of sites, we became quite adept at both cocking the Smith-McIntyre open for deployment and for collecting the sediment once it was successfully raised from the surface. There were only a couple of deployments that came up with nothing – usually due to a rock keeping the grab sampler from closing completely.

 

Preparing the Smith MacPreparing the Smith-McIntyre for deployment

Smith-McIntyre into the water
The Smith-McIntyre enters the water

 

a bad Smith-McIntyre grabThe Smith-McIntyre after an unsuccesful grab

The bottom was actually fairly fine-grained and it turned out to be a fairly messy process – especially at first when we forgot to use our extruder to remove the sediment from the tube and instead had to blow it out by mouth!

good mudGood sediment in the Smith-McIntyre! Note how the sediment appears mostly intact.

 

Steve and Andrew collecting sediment
Steve and Andrew collecting sediment

While all of this is old hat to Steve, I found this pretty cool as it was the first time I have ever worked on a ship before. It was both cool and successful!