Weather Window
After dealing with some very rough sea conditions for the last few days, we found a weather window late yesterday that provided us the opportunity to sample seawater. As you learned in yesterday's journal, sea water can be sampled using the ship's onboard flow-through system, however, large quantities of water from specific depths cannot be sampled in this way. Instead, the RVIB Palmer is equipped with two different rosettes or carousels. These rosettes are essentially large epoxy coated metal cages that can hold equipment for sampling at various depths. The two rosettes used throughout this research cruise hold a CTD instrument and Nisken bottles. Additional sensors like a photosynthetically active radiation (PAR) sensor or sensors for dissolved oxygen levels can be added, if needed. Using this equipment, we were able to collect some water samples from both rosettes as a practice or "shakedown" of the future procedures. Each rosette can weigh more than 1000lbs, so it is important that the Marine Technicians, the crane operators and the scientists complete a few deployments (or casts) before reaching our first incubation station. This type of sampling technique will be used throughout the research cruise, so it was excited to be able to begin sampling.
Marine Technicians Rich Thompson and Holly Martin prepare to deploy or cast the trace metal rosette. The white circular frame holds a CTD instrument and Nisken bottles.
CTD
The CTD instrument is a collection of sensors that transmits data on the conductivity, temperature and depth. You may not be familiar with the term conductivity as it relates to ocean water. The conductivity sensor uses electrical conductivity to measure the salinity of the ocean (in other words, how salty the water is at an given location). The information collected from the CTD can be seen in real-time on the monitor at the ship's CTD station. An electronic technician (ET) can monitor the data collection, identify sensors that are not working properly and alter the speed of the cast from the computer station. Members of the science team are able to view the data collected by the CTD to determine where to sample water.
Electronics technician Barry Bjork and Dr. Bethany Jenkins monitor the real-time data from the first conventional CTD cast. Information about chlorophyll levels, water temperature and salinity can help Dr. Jenkins determine where (what depth) to collect water samples.
Nisken Bottles
Nisken bottles are attached to the rosette and programed to collect water samples at desired depths. Nisken bottles were patented by Shale Nisken in 1966 as improvements on a collection bottle known as the Nansen bottle. The Nisken bottles have caps on each end that are open prior to the cast. The caps are connected to a tensioned or spring-loaded wire that closes both caps when triggered. The trigger can be programed to close all of the caps at once, or have a group of bottles close at one depth while another group of bottles closes at a second depth and so on. This type of sampling can allow for large quantities of water from a specific depth, or to acquire samples at different depths in the same cast to create a profile (to see what changes or similarities are present over different depths at similar times).
Marine Technicians Rich Thompson and Holly Martin watch as Dr. Kristen Buck prepares the Nisken bottles on the trace metal rosette. The CTD instrument is located at the base of the rosette, just below the Nisken bottles.
Two Rosettes
During this research cruise, two different rosettes are used for water sampling. The first is the trace metal rosette (shown in the previous pictures of this journal). The trace metal rosette holds twelve Nisken bottles and is deployed near the trace metal van on the main deck. The cable attached to the rosette is able to lower the rosette to a depth of just over 2500m (~7500ft). The trace metal rosette completed two casts last night, one at 200m (~600ft) and another at 2000m (~6000ft). In case you are wondering, the depth at that location was around 4000m (~12,000ft)! The water from the trace metal bottles is immediately transported to the trace metal van for removal and storage. This is done in order to limit contamination.
The second rosette is referred to as the conventional rosette. Twenty four Nisken bottles hang on this rosette. The conventional rosette is deployed from a dedicated room on the ship known as the Baltic Room. A cargo bay door opens and a large crane moves the rosette out the door and then lowers the rosette into the water. Once the rosette returns and is secured in the Baltic room the science team can empty the Nisken bottles into pre-washed carboys. These carboys can be stored for use with the molecular biology sampling or other uses within the labs.
Cara Pekarcik learns how to empty Nisken bottles from the conventional CTD rosette. These nisken bottles are not removed from the rosette because they do not require trace metal clean techniques. Photo courtesy Maia Theophanis.
Ten liter and twenty liter carboys were filled with water from the first conventional CTD cast. These Nisken bottles collected samples at a depth of 300m (~900ft.). Photo courtesy Maia Theophanis.
The conventional CTD is deployed in the Baltic Room of the Nathaniel B. Palmer. The yellow and black door swings inward to allow a crane to deploy the CTD. Photo courtesy Maia Theophanis.
The Real Deal
Tomorrow, we will reach our first incubation station. This means that we will be at the first desired sampling station for this research cruise. At this station, we will be completing four trace metal casts and a conventional cast to collect water for the incubation studies discussed in a previous journal. Each science team member has been assigned a specific duty during this sampling period. It is important that sampling is done as quickly as possible to help maintain the ambient (natural) temperature of the water to limit heat shock for the microorganisms. It is also important to sample quickly to limit contamination. The goal is to get the incubation bottles filled and begin sampling from the bottles throughout the day. It will be a busy, but exciting day on the RVIB Palmer. Stay tuned for a more detailed description of the process and to find out what it is like to do deck work outside in the Southern Ocean!
Fearless leaders (l to r) Dr. Kristen Buck, Dr. Dreux Chappell and Dr. Bethany Jenkins are prepped for deck work. Working in the Southern Ocean during high seas requires proper gear. Waterproof, warm clothing and safety gear like float coats are required while working on deck.
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