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Biology

Winter Cruisin’ on the North Atlantic

At the beginning of the month, I spent 5 nights aboard the R/V Endeavor with about 15 other scientists from the University of Rhode Island (GSO), Woods Hole Oceanographic Institution and Wellesley College. We participated in the winter transect for the Northeast US Shelf Long Term Ecological Research (NES LTER) project.

What is the NES LTER?

Since 1980, the National Science Foundation has funded 28 LTER sites around the US and Antarctica, many of which are terrestrial. LTER sites are important because they are studied over long periods of time–some of the sites have been researched for over 30 years! Researching one site over a long period of time and collecting the same measurements enables scientists to understand how processes at a particular site may be changing, either from natural variation or from human influence. The NES LTER is a recently funded marine site examining how planktonic food webs are changing on the Northeast US continental shelf. There are four NES LTER cruises evenly spaced through the year for scientists to study the seasonal and long term changes of food webs.

A phytoplankton bloom! This is Coscinodiscus sp.

Phytoplankton are at the bottom of the marine food web and they fuel the productivity of ocean life; they produce oxygen through photosynthesis. Zooplankton, the next step in the food web, eat phytoplankton and in turn are eaten by various commercially important fish. The Northeast US Shelf is one of the most biologically productive areas in the world. Thus, it is important to understand how physical, chemical and biological processes affect the connectivity of organisms in this region.

What does a “normal” day at sea look like?

Time on a research vessel is very expensive; think about all of the costs that go into running a research ship, such as the food we eat or the fuel needed to power the ship. To be as efficient with our valuable time as possible, we worked 24 hours a day for five days straight. Don’t worry, each scientist is assigned to a 12-hour shift. My shift was noon to midnight, and by the end of the cruise I was sleeping for almost the entirety of my “off-shift.” At the beginning of each day, I had my breakfast (actually lunch) and figured out where we were on our cruise track. Depending on how close we were to the next station, I got suited up in a warm Mustang suit to protect me from the cold waves coming aboard and headed out on deck. We collected water at multiple depths using a CTD Rosette (pictured below) which measures the salinity and temperature of the water. It also contains large bottles, called Niskin bottles that the scientists program to close at various depths in the ocean.

Retrieving the CTD Rosette from the ocean.

As I mentioned earlier, phytoplankton fuel the marine food web. Because phytoplankton photosynthesize, they have chlorophyll-a, a pigment in their cells to help them absorb sunlight. Using a fluorometer attached to the CTD, we measured the fluorescence (light that is re-emitted by chlorophyll) of the water to determine where in the water column the chlorophyll-maximum (chl. max) occurred. The determination of where to sample in the water column (a “water column” is simply a piece of the ocean from surface to depth) is probably one of the most important factors of a research cruise; well besides making sure the Niskin bottles properly close to collect our water!

What specific research took place?

For my lab’s research, we sampled water at three depths within the water column (depending on depth of the chl. max). What this means is that for five days I was a glorified Brita filter and couldn’t be happier because I was in the middle of ocean surrounded by nothing but water.

A view of the lab. Pictured in front are filter funnels used to filter for chlorophyll. In the background you can see all of the equipment necessary to run a research expedition. Photo courtesy of Grace Medley.

I filtered liters and liters of water for chlorophyll and DNA analyses. Just like you and me, phytoplankton also have DNA, the genetic code for how a cell (or body) functions. Filtering water for DNA gives us the “inside look” into what is in the water at various depths across all of the stations. Other work on the cruise involved sampling zooplankton and carrying out experiments to determine how quickly the zooplankton eat the phytoplankton (grazing experiments). Coupling these multiple analyses together over a long period of time will enable us to better assess marine food webs both now and in the future.When there was a break in the action, I went up to the Fly Bridge (the very top of the ship) to appreciate the opportunity I had to work alongside amazing scientists and admire the wonderful world we live in. I’m looking forward to the next cruise!

A view of the stern of the R/V Endeavor. The large tank is for grazing experiments (description in text).

 

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