This post includes an explanation of the Virginia Institute of Marine Science teams work on this cruise and a summary of their two weeks of work in Barrow, Alaska. The next post will feature Kendra Turk-Kubo, a research specialist at the University of California Santa Cruz, who collaborates closely with the VIMS team. Scroll to the bottom to read an update on our overall cruise – we are halfway through!
Take a deep breath. Most of what you just inhaled is nitrogen. Nitrogen gas makes up 78% of our atmosphere. The reason we don’t feel it is because it’s inert, or nonreactive. But we need nitrogen to survive – it’s in the protein we eat and, along with carbon, is one of the most prominent elements in our bodies. In order for us to use the nitrogen gas that makes up most of the atmosphere, a tiny bacteria had to do the work of changing it around. That change is called nitrogen fixation.
Nitrogen fixation isn’t only key to us; it’s key to regulating life on this planet. It happens in the air, the ground, and it happens in the ocean.
The Virginia Institute of Marine Science (VIMS) team is here to measure nitrogen fixation. It was previously thought that nitrogen fixers only existed in warm waters, but the VIMS team and others have found it happening in the cold waters of the Arctic. Scientists have become more and more aware that nitrogen fixation is happening in places we didn’t realize. We don’t yet know if thats because we just didn’t see it before, if improved science has helped our ability to detect it, or if climate change is the main cause and has enhanced the process or changed nitrogen fixers’ range. The VIMS team wants to find out what bacteria is doing the nitrogen fixation here, how quickly it’s happening, how much of it is being done, and how this may impact the the nitrogen cycle globally.
When it comes time to do their science, the VIMS team rightly calls themselves a well oiled machine. Rachel Sipler, lead scientist on the project, Deborah Bronk, co-principal investigator, and Jenna Spackeen, who recently completed her Ph.D. dissertation, have worked together for seven years. Brianna Stanley joined the lab last year. Zane Norton has spent the summer with the lab as an intern. They move around each other in the analytical lab calling out bottle names and numbers, speaking in a foreign science language like teammates calling out plays. The lab is decorated with tropical touches the team brings with them to decorate their polar work spaces (they’ve also spent significant time working in Antarctica). They don’t operate on 8am to 8pm or noon to midnight shifts like the other teams on the ship; they do their water collections and filtrations en masse. This is because they want to observe the water that just came out of the ocean as quickly as they can, and because part of their process involves a 24 hour incubation period.
When the ship gets on station – that is, a place where we’ll collect data – some or all of the VIMS team gathers in the computer room for the CTD cast. The CTD is lowered to collect water at different depths. There is some jockeying involved among the scientists about who will get which bottle at what depth, which is duly noted on a clipboard and restated once the CTD is brought back onboard. Then the VIMS team fill their differently labelled bottles with water from the CTD. Some of this water goes with Brianna Stanley into the main lab to use as a sort of “blank” to compare against their other “injected” samples.
The rest of the water is taken to the analytical lab to be injected with nitrogen gas or different liquids. Rachel Sipler injects the nitrogen gas from a gas canister into some of the bottles. The rest of the team puts a slew of different liquids into the other bottles – ammonium, nitrate, urea, amino acids, glutamic acid, lucine, thymidine, and creatine. The idea is to see what the tiny micro-organisms in these bottles of water do with the materials given to them. Once filled, these bottles are moved to the incubation tanks on the back deck.
The 24 hour incubation period is used so the micro-organisms have a chance to use the low levels of nutrients that have just been injected into the water around them. The bottles are put into different bags that correspond to the depths at which they were collected – more transparent bags for water collected at shallower depths, darker bags for water collected at deeper depths. This is done in order to mimic the micro-organisms’ natural conditions. The key is to make them think that nothing has changed since they were taken from the CTD.
When the 24 hour period is over, the VIMS team brings the bottles into the analytical lab for filtering. This means they pour the water from the bottles into funnels that pass through different sized filters (3 micron and 0.3 micron). What’s left on the filters tells them how fast each nitrogen source is being used. The water that passes through the filters gives them an idea of how the nitrogen sources are processed – this is called the filtrate. The team stores the filters and the filtrate to take back home to their lab in Virginia.
Who’s doing the fixing?
Kendra Turk-Kubo, a research specialist at the University of California Santa Cruz in John Zehr’s lab, plays an important role in helping the VIMS team decide when and where to sample. She does DNA analysis for a gene that indicates the ability to do nitrogen fixation. If she finds it, this signals the VIMS team to pay more attention to that location. She also collects other samples that will be taken back to the Zehr lab in Santa Cruz. Her work will be featured more exclusively in the next blog post.
Two Weeks in Barrow
Before this cruise began, the Sipler team spent two weeks collecting data in the coastal waters from Prudhoe Bay to Wainwright, Alaska aboard the Research Vessel Ukpik. When they were off the 50 foot vessel, their home base was Barrow, Alaska at the Barrow Arctic Research Center. The team consisted of Rachel Sipler, Deborah Bronk, Brianna Stanley, Zane Norton and Sue McIninch from VIMS, Katie Harding and Britt Henke from UCSC and Miguel Goñi from OSU.
The goal of the coastal small boat operations was to sample regions close to the coast and within Alaskan Rivers too shallow to sample using the Sikuliaq. The team wasn’t able to get close enough to shore last year to see riverine signals. A key part of their hypothesis is that some groups of nitrogen fixers need the carbon that is transported by rivers to give them the energy needed for nitrogen fixation. They also hypothesize that the bacteria that fix nitrogen near rivers may be different from those found in deeper/ offshore Arctic waters.
Cruise Update: Halfway Point
We are halfway through our two week cruise. The SuperSucker successfully finished its 24 hour run on the DBO 4 line tonight. In the early hours of Monday, August 14, we began our next big run of CTDs and multi-coring on the Hannah Shoal line. We are scheduled to finish this run at 19:00 tonight.