The End of the Line
The R/V Oscar Dyson pulled into Dutch Harbor, Alaska on May 9 after a hectic few final days! We made it to the mooring site with only minimal ice present, and our NOAA colleagues successfully recovered and re-deployed two moorings that will stay out for much of the rest of the year. Carol, Bill, Scott, Peter, and Dan definitely seemed to relax after those operations were done, that is until the frenzy of packing began.
We sampled at two sites near the mooring, and there was a very strong concentration of phytoplankton actually below the surface in these more open ocean waters. The FlowCAM captured many different species of beautiful diatoms at these sites. One of the other instruments we had on the ship uses Advanced Laser Fluorescence (ALF) to measure multiple aspects of the phytoplankton community. The ALF instrument, which was developed by our LDEO colleague Alexander Chekalyukis and is currently being commercially developed by WetLabs, uses photosynthetic pigments, including chlorophyll, to determine which groups of phytoplankton are abundant. Two lasers “excite” these pigments, and the light that the pigments give off in return is measured. As I mentioned in a previous post, pigments other than chlorophyll are also involved in photosynthesis, giving rise to beautiful leaf color changes in the northeast region of the United States each fall. Different groups of phytoplankton (e.g. diatoms v. Phaeocystis) contain different suites of these “accessory” pigments. The ALF instrument looks at a full range of accessory pigments and can tell us which groups are dominant in a sample or along vast distances in the ocean. Since different groups of phytoplankton can be better or worse food items for other marine critters and may have different implications for carbon cycling and general productivity in the Bering Sea, understanding when and where groups differ helps us understand the potential effects on entire ecosystems.
Most of the equipment and techniques I have described in this blog so far have been ones that we put into the ocean or take with us onto a ship for analyses on site. An exciting area of oceanography that has made huge gains in the last few decades is Remote Sensing, which uses sensors mounted on spacecraft to study the Earth. Since the 1970s, the National Aeronautics and Space Administration (NASA), which also funded our project in the Bering Sea, has included specialized sensors on satellites that can measure ocean color. Ocean color is affected by the scattering of light as it interacts with particles in the ocean, and phytoplankton are one of the most dominant particles that determines ocean color. It is therefore possible to measure the amount of phytoplankton and even what size groups are dominant in the ocean using satellites orbiting the Earth in space!
Eurico D’Sa, an oceanographer from Louisiana State University (LSU), and Charlie Sibley, also from LSU joined us on the Oscar Dyson to measure the optical properties of the waters, namely to figure out what particles and dissolved substances in the water could be affecting how sensors in space see the ocean. Their measurements allow for better refinement of the calculations necessary to convert from ocean color to actual chlorophyll and phytoplankton measurements. Of course, satellites can only collect useful data when the skies are clear (which was not common during our expedition), but this work nonetheless makes it possible to remain in our offices and laboratories while studying the phytoplankton of the Bering Sea.
Our NOAA, University of Alaska, and LSU colleagues are mostly home with their families, friends, and dogs at this point, while Bill Floering remains on the Oscar Dyson to attempt recovery of two moorings even further out than the one we reached on those last days of the cruise. Kali and I enjoyed some time exploring the Museum of the Aleutians and spotting some of the many bald eagles that call Dutch Harbor home before beginning our long journeys back. Kali returned directly to New York, while I visited with family and Ms. Stauffer’s 4th Grade Class at Rawlings Elementary in Pinellas Park, Florida. We are now starting to sift through the hundreds of samples and a hard-drive worth of data we shipped back, unpacking our eleven boxes of gear, and re-packing perhaps even more for an upcoming cruise off the coast of Brazil.
Research cruises have the potential to feel like isolated and exhausting endeavors, but with cruise-mates like Kali, Carol, Bill, Scott, Peter, Morgan, Chrissy, Dan, Eurico, and Charlie the time sped by and new friends and colleagues were gained. We also completed the giant puzzle! The deck and survey crew of the Oscar Dyson helped us probe the depths of the Bering Sea with sophisticated instruments, while the engineers kept the ship running smoothly and our bunks nice and warm. The officers on the bridge ensured our safety when Bering Sea storms threatened, and the stewards kept the delicious meals coming and the dessert shelf stocked with pie. Thanks to everyone who helped make our cruise aboard the R/V Oscar Dyson such a success!