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Earth Science Applications Travelogue: Day 4: Wednesday, May 14
May 15, 2014

[image-51]About 9 a.m. EDT (ship operates on EDT regardless of the geographic location) this morning the captain announced over the ship’s intercom that we were nearing the first station. A problem with ship hydraulics delayed sampling about 20 minutes before being resolved by the ship’s engineer. Hard hats and life jackets are required for all science members while on watch or observing sampling on the rear deck, including foul weather gear as needed.

[image-78]We began sampling about 9:30 a.m. EDT today at a site off the LA/MS coast, 28 30.2 N and 089 14.4 W in a moderately heavy thunderstorm. Rain was heavy at times and some lightning, but the seas were calm. Training was provided for the four new science team members including myself on how to prepare and lower nets, clean and store equipment after deployment and processing of samples. To secure some of the gear it was necessary for me to learn to tie a Bowlin knot, which is an old and simple knot, used to form a fixed loop at the end of a rope.

Three types of nets and a conductivity, temperature and depth (CTD) instrument are being deployed. An S10 net is first deployed at depths from surface to 10 meters for approximately a 10-minute standard tow. The Bluefin tuna larvae are typically found in the top 20 meters of the water column. Following the S10 the CTD is deployed to gain information on the physical characteristics of the water column including depth, temperature, salinity, oxygen, and chlorophyll, which are useful to validate satellite measurements of surface physical conditions and assess physical habitat suitable for Bluefin larvae. The third step is the deployment of a mini bongo net, which is very fine mesh net (about one half millimeter) capable of capturing zooplankton and microplankton.

[image-94]If Atlantic Bluefin Tuna larvae are thought to be likely present or found in the initial samples, the Multiple Opening and Closing Nets Environmental Sampling System (MOCNESS) is deployed. The MOCNESS deployment is a 45 minute to 1 hour tow with five net sections that allows sampling in 10-meter depth columns of water from 0 to 50 meters.

All samples are tagged at Greenwich Mean Time (GMT), which is aided by a large digital clock in the lab. All the initial samples collected in the S10 net are evaluated in the lab. A sampling of water column conditions with the CTD is done while the initial samples are being analyzed. This takes about 30 minutes. Depending on the sampling results, the mini bongo net and MOCNESS may be deployed or we will move to the next sampling station.

[image-110]No Bluefin tuna larvae at the first four sampling stations today; a few blackfin tuna (like we caught fishing yesterday), scorpion fish, squid, and others. We are working to sample stations from west to east today based on Roffer’s satellite data and the analysis by the chief scientist. Note that the green circles west to east from our current location are proposed sampling locations determined with satellite data by the Roffers team.

Dr. Lamkin indicated that the satellite data helps determine position and surrounding environmental conditions very quickly, which enables the sampling effort to be more efficient.

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Map of sampling station locations.
Map of sampling station locations.
Image Credit: 
Maury Estes
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Deployment of the conductivity, temperature and depth (CTD) instrument.
Deployment of the conductivity, temperature and depth (CTD) instrument.
Image Credit: 
Maury Estes
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Water column samples are examined under a microscope.
Analyzing water column samples.
Image Credit: 
Maury Estes
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Chief scientist John Lamkin explains CTD data analysis.
Chief scientist John Lamkin explains CTD data analysis.
Image Credit: 
Maury Estes
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Page Last Updated: May 15th, 2014
Page Editor: Brooke Boen