Lab Rats

July 21, 2010
Lat/Lon: 40* 18.006'N / 48*27.9988'W
Air Temp: 23.9*C / 75.02*F
Wind Speed: 15.85 kts
Humidity: 87.1%
Water Temp: 24.71*C / 76.50*F
Salinity: 34.8 psu
Depth: 3835 m

Day 2 of working with 2-shifts of watches. It looks like the CDH Long Core is going to go down today! Hurrah! The gravity core went in on our shift just after 3 am and when it was time to bring it back in the boat we were delighted to see not only large chunks of floating seaweed but a big school of fish - each fish measuring about a foot long. There was lots of activity. Some fish were skittering above the crowd, just at the surface. We figured that we weren't the only ones watching the school...

Today I thought we could move inside the R/V Knorr to start covering all that goes on in the labs.

When each of the cores are brought to the surface and then into the boat, samples of the mud are gathered from each cut segment of the cores. In the picture below you see some of the sampling bags. Preparation for sampling is crucial because it can hold up the entire process of
cutting, capping, sealing and moving the cores if the sampling tools are not ready. Each sample bag is named for the cruise, the leg, the core type, the sampling event and the location of the sample relative to the entire core:

- KNR 197-10 (R/V Knorr Cruise 197, Leg 10)
- CDH 2 (CDH Long Core, Sampling Event #2)
- BOT 2 (bottom of the second section of the core)

I know I mentioned this in an earlier blog entry but it's relevant here too - in the gravity core you'll have about 4 sections of core and in the long core you could end up with up to 26 sections of core. Each segment is about 1.5 meters (~5 feet).

At the top of this blog you see Isabelle Gil, French researcher working in Portugal. Her research is focused on different fossils organisms than those the chief scientist is interested in - however, those she studies, called "diatoms", are found in the very same cores in which Keigwin finds his foraminifera. Gil is pictured at the top sampling the bottom of a segment of the long core. In her hand you can see the labeled sample bag and a spatula. She has to be careful how much mud she scrapes from the core because, if you recall, several centimeters represents hundreds of years - even
over one thousand years depending on the particular site. Gil samples for chief scientist Keigwin and for her own research.

In deep marine environments the size of particles that land on the ocean floor tends to be very small. For this reason, a very fine sieve (63 microns), pictured right, is used to separate forams and diatoms from the fine muds. The fine muds from the samples "washed" on the ship are captured in a bucket and tossed overboard. When the samples are washed at Woods Hole the muds are kept and studied to provide information about settling rates. This gives researchers a better idea of how fast / slow sediments are settling on the bottom. This kind of data is vital because it provides a framework for how much time is associated with a set thickness of sediment. The average rate of seafloor deposition in the North Atlantic is 3-4 cm/year. The North Pacific is significantly less. Check out this image of the thicknesses of ocean floor
sediments. I LOVE maps! And this one is particularly cool! Look carefully at it - find the scale.

Why do you think certain areas have significantly more sediment than others?

The bags pictured left give you an idea of what the mud samples look like before they are washed.

After "washing" the muds, all that is left is the forams and some diatoms, pictured right in filter paper.

They are then dried in the lab oven and poured into carefully labeled
vials. Paola Moffa Sanchez, PhD researcher, is pictured to the right "picking" forams. Marti, Kathryn, Sarah and Isabelle all work with Paola to pick the forams.

Notice that she has a gridded black tray. She has poured the dried sediments from one vial onto the black tray so she can study them. The grids facilitate the process of identifying and counting the forams. Quantity and identity of the foraminifera can tell researchers a great deal about the history of the ocean and climate!

More to follow on R/V Knorr labwork!

No comments:

Post a Comment