Navigating the South Pacific Using DNA
I’ve never been good at navigating. When I come out of the subway I invariably turn the wrong direction, even though I already have my nose buried in Google Maps, and then walk around the block to save face.
The navigation strategy for this cruise, however, is one that is particularly tailored to my strengths: we’re using DNA to guide our trek through the South Pacific.
Each day, water is sampled from the surface ocean down to around 40 meters, and a team of graduate students from Stockholm University extracts the DNA from the microbes within these samples. Then they use a technique called quantitative polymerase chain reaction, or qPCR, which enables them quantify the number of copies of particular genes within a sample. This technique requires pipetting miniscule volumes of liquid into microscopic tubes with razor sharp precision—a challenging feat on land, and one that makes me seasick just thinking about on a moving ship. This qPCR technique is being used to look for hotspots of a particular, newly discovered group of unicellular nitrogen-fixing bacteria called UCYN.
Unlike Trichodesmium, which I can identify in a water sample just by looking, the UCYN group is mysterious and elusive. First off, they’re tiny and unicellular, so even under the microscope they can’t be distinguished from other bacteria. To make matters more complicated, many are thought to live in symbiotic association with larger eurkaryotic microbes. The physiology of these organisms is interesting as well: they’re cyanobacteria, but some are thought to be missing half of the photosynthetic machinery. In short: these critters are weird, but they have a potentially overlooked but critically important role in the marine nitrogen cycle.
For our next long duration stop, we’re on the hunt for a region with particularly high abundance of these organisms. It seems like each station we visit has more and more UCYN bacteria present. Unfortunately, we’ve yet to stop for another extended period because we’re trying to outrun a tropical cyclone.
The outskirts of this are storm catching up to us, and each day the waves seem to be getting stronger and stronger. I’m thankful that I just have to look at the UCYN qPCR data and not generate it myself. I’ve been thinking more and more about the Dramamine stashed in my desk, but that being said, the temperature is still way above freezing and I don’t think I’d trade it for the end of winter in New York City.
From 20 degrees south, 179 degrees east in the South Pacific, Kyle.