Ms. Callaghan’s Classroom
Jil Callaghan is a 6th grade science teacher at Houck Middle School in Salem, Oregon. She is posting blogs for her students while aboard the Research Vessel Sikuliaq as part of a teacher at sea program through Oregon State University.
We’re Doing CTDs all the time! What are they??
Out here in the Arctic Ocean, the scientists on board are collecting water samples using a piece of equipment we call the CTD. CTD stands for Conductivity (which tells you the salinity or how much salt there is in the water), Temperature, and Depth.
Typically we take water samples from just above the bottom of the ocean, at the level where the graph tells us that there’s the most chlorophyll (based on real time data from the sensors), and just below the surface. So far we have taken samples from 62 locations!
Laurie Juranek from OSU is mainly sampling water from the surface of the ocean for her studies, but she is using some of the water collected during CTDs to compare how conditions are different from what she’s seeing at the surface.
Miguel Goñi from OSU is mapping the abundance of particles and where they came from. Using chemistry, he can tell if those particles came from the land or from the ocean. He’s collecting evidence about the productivity of the ocean. There are tiny, microscopic organisms in the ocean called phytoplankton that, just like plants, use sunlight and carbon dioxide to make their own food (sugar). By looking at the nutrients and the carbon in the water samples, the scientists can figure out what’s going on in the ocean – how much the phytoplankton are growing and dying.
The scientists from VIMS (the Virginia Institute of Marine Science) are looking for organisms that are nitrogen-fixers. That means that the organism takes nitrogen (N2 gas) out of the water and can use it for food. Not many organisms can do this because N2 has a triple bond between the nitrogen atoms, which makes them hard to break apart. By breaking apart N2, nitrogen fixers allow nitrogen to be available to other marine organisms; it’s a way to get new nitrogen into the ocean. The VIMS team is also looking at how much algae, phytoplankton (microscopic marine plants), and nutrients there are in different parts of the ocean at different depths.
CTD casts are a big part of what we are doing on this research cruise, along with getting sediment samples from the ocean floor using our multi-core and dragging an instrument we call the “super sucker” that sucks in seawater from various depths as the ship is moving. In order to do a CTD or multi-core, the ship has to come to a stop. When we use the super sucker, we tow it behind the ship and so the ship has to be moving. Although we’re using different instruments to collect data, the CTD has been the most common method. We’ve done about 40 CTDs so far!
See Ms. Callaghan’s other posts here.