Tuesday, January 12, 2010
The A Team
Pffff…a loud noise startles me as I am preparing to lower an instrument into the water that measures conductivity, temperature and depth. About thirty feet to my left I see a smooth black surface with a large blowhole disappearing beneath the waves, and then a humped back rises behind.
A humpback whale visited me and my partner Amanda yesterday as we collected water samples in our zodiac boat. It circled and showed itself twice more in the next minute. It was very special to be near such a large animal, but it was also disconcerting because it was probably twice the length of our boat! At one point it looked as though it was coming straight toward us (although it was actually moving directly away) and my mind flashed to the story of the whaling ship Essex that was rammed and sunk by a sperm whale in the South Pacific. Of course that was very different, but it didn’t seem so far fetched when we were out in our little inflatable boat. It was certainly a wildlife encounter that I will never forget.
The A Team, my partner Amanda and I, collects water samples twice weekly from two different sites, at five different depths: 50m, 25m, 10m, 5m and the surface. “Station E” is about two miles from shore and “Station B” is just off of a point near Palmer Station. When we go boating, we wear so much clothing that Amanda calls herself the Michelin man and it certainly seems so. Between the long underwear, fleece pants, fleece jacket, possibly a vest, rubber fisherman’s bibs, hat, balaclava, heavy Sorrel boots and our bulky orange “float coats,” the world beyond our bodies begins to seem far away. We also have a complicated glove system: there are leather work gloves that are good for dexterity but not waterproof, there are the lined rubber gloves that do not allow for a huge range of motion, and there are thin wool liner gloves, best for fine motor tasks but not good for cold protection. Then some of our fieldwork requires that we wear latex gloves, but latex gloves alone would probably lead to frostbite so we wear thin polypropylene or wool liner gloves underneath XL latex gloves. Quite a bit to think about!
For safety purposes, we also bring a drybag filled with extra clothing, and food in case we are stranded on an island due to bad weather. In addition there are marked emergency caches on many of the islands within the boating limits, containing food, tents and stoves. I am glad that the weather has been good so far!!
But back to work: once we arrive at our sample collection station, we attach cylinders with open ends to a cable that we lower into the water with a winch, and then we can close the ends of all of the bottles simultaneously. Once we pull the bottles back up, we take water samples for dissolved organic carbon and for ammonium concentrations. We take the rest of the water back to the lab and take more of it to count the density of bacterial cells using a flow cytometer.
In addition, we take small amounts of seawater and add a radioactively tagged amino acid to some and a radioactively tagged nucleotide to others. The significance of the amino acid (leucine) is that the bacteria use it to make proteins, so the rate at which they uptake it tells us about how fast they are growing. The bacteria use the nucleotide (thyamine) to make DNA, so their rate of thyamine uptake tells us about how fast they are dividing. We allow the bacteria in the water to take up the leucine for a specified amount of time and then we kill them, likewise with the thyamine. We remove all the seawater leaving just the bacterial cells. When we measure the radioactivity in the bacteria we can calculate how fast they took up the tagged leucine and thyamine that we gave them.
The significance of this is that from the rates of protein and DNA synthesis, one can model the rate of overall carbon uptake. Since bacterial are the recyclers of the ocean (and the land), they are a crucial link in the carbon cycle. If their abundance changes or if the timing of their annual bloom shifts, there could be major implications for carbon cycling and storage in the ocean. The West Antarctic Peninsula is a great place to study the effects of climate change on microbial ecology because this marine ecosystem is one of the most productive on the planet, AND temperatures are warming faster here than anywhere else on earth. I have arrived at ground zero for climate change and I’m holding a pipette!!