CTD rosette instrument being deployed off the fantail of the Wecoma.

Teacher Logbook - R/V Wecoma

Missy Holzer 's Sealog:
CTD Cruise Day 4
Weather at 1630 hours PDT: Cloudy skies with winds of 15 knots from the Northwest. Barometric pressure is 1021.2 mb, and the temperature is 58 degrees Fahrenheit. Ocean swells are 4-5 feet out of the Northwest.

So what happens to those water samples from the Nisken bottles on the CTD? Yesterday you heard about the "fish" that we have deploying and recovering from the R/V Wecoma. Today we will explore what happens after the fish has been recovered as well as what occurs in the chemistry lab on board the ship.

Once the fish has been recovered from either a tow-yo or a cast a number of water samples are taken from some of the bottles. The chemist, Dr. Joe Resing, determines which bottles he wants samples from while watching the monitor that shows the nepholometer (light scattering detector) readings. In areas where there is a high amount of scattering there is the potential for higher quantities of hydrothermal activity, and thus warrant sampling. Now starts the challenge of doing chemistry out at sea! Some of the sampling requires that extreme care be taken so that no air gets in the sample while it is being withdrawn from the Nisken bottle. This is a little bit of a challenge when the ship is rocking in a few different directions, and the water samples ( retrieved from deep in the water column) are roughly 2 degrees Celsius!

Some of the chemistry is completed while at sea, while other samples are carefully prepped for analysis back in the NOAA lab. All the materials and instruments needed to setup the chemistry lab on board had to be shipped from the NOAA lab and unpacked. The lab now looks as if it's been in operation for a long time and is complete with instrumentation to perform various qualitative and quantitative analysis on the water samples. Dr. Resing is looking for evidence of volcanic gases and particulates that are present in trace amounts in the water samples, and from this he can make a relative determination of how long ago an eruption occurred. When a hydrothermal plume is present, the pH of the water goes down, and the quantity of particulate iron and sulfur go up. Chemist Geoff Lebon carefully preps samples for x-ray fluorescence spectroscopy back at the NOAA lab where he will identify and detect the concentration of the particulates in the water. It's amazing that his work can also determine the depth at which the hydrothermal activity occurred based on the various elements attached to the iron particulates in the water!

Dr. Resing says that by completing a bit of chemistry on board, the magmatic state of the undersea volcano can identified and further studied while out at sea. He continues by saying that whether it's an exploratory cruise looking for new hydrothermal activity or a repeated cruise that's continuing to build a long term data set, "advance prep is the key" to doing chemistry out at sea. It's imperative that materials be on hand so that as much prep and analysis out at sea can be done as possible. He feels that one of the challenges of this type of work while at sea is the working with different staff sizes: a smaller staff needs to well organized, while a larger staff can work with a greater amount of equipment. Dr. Resing mentioned that one of the positives about working out at sea is the amount of time he has - 16 hours a day - to accomplish his goals for the cruise.

We will be anticipating the findings of Dr. Resing and his hard working staff as we continue our cruise in the Axial volcano area.