Happy New Year, everyone! The Wormherders are back on the ice!
We began our field season with the necessary (but not exactly pleasant) travel from the United States on the 31st of December. Our field team for the season met once again in Los Angeles, with Diana Wall and Uffe Nielsen flying from Denver, Colorado, Byron Adams from Sacramento, California and Zach Sylvain from Portland, Maine. From LA, it was roughly a 13 hour flight to Auckland, New Zealand and then another hour to Christchurch. Although we left at 11:30pm on December 31st, we didn’t arrive into New Zealand until the 2nd of January because of the International Date Line–a whole day, lost! Fortunately we didn’t have to wait long before heading down to Antarctica, and so late at night on the 3rd, we caught our C17 flight (seen here landing on the ice runway at the end of last field season) down to McMurdo.
Once we had arrived in Antarctica, we spent the morning going through a wide variety of updates about the facilities and responsibilities down here, and then began to set up the lab. The flight had arrived very early in the morning on the 5th (we started our first briefings upon arrival at 5:30am!), and so most of our group opted to take a quick nap before getting to work. What sort of work goes into setting up the lab, you ask? First, many pieces of equipment must be picked up and moved into our empty lab, such as microscopes and a variety of chemicals as well as glassware such as beakers, flasks, and vials. How much glass (and plastic) ware do we need to carry out all the extractions we do while we’re down here? Quite a bit!
On the left is a cart full of plastic falcon tubes that we use to collect the nematodes during extractions (and the caps to the tubes), with a pile of plastic spoons and scoops below–to the right are all of the plastic beakers we need for our extractions, as we mix soil with water in these prior to sieving (more on extractions later!).
After two days of gathering everything we required to start working, we finally were able to begin extracting soil samples in order to see what animals (nematodes, rotifers and tardigrades) we can find. This is the good stuff–taking the soil and running it through all the steps we do in order to see what lives within it is exciting, letting us explore the mystery of where we might find life on this harsh continent. Fortunately, we had many samples from a colleague stored in a freezer waiting for us, so we were able to get to work today without having had to go into the field just yet! Each of us helped in extracting the samples in order to get the animals out and under the microscope. Zach began by weighing out 100g of each soil sample into one of those plastic beakers shown above: we weigh the soil samples so that we can compare each sample to every other sample more easily.
After a sample has been weighed, it gets mixed with water in the plastic beaker, and the water is then poured over two sieves stacked together–this helps strain out some of the soil and rocks and collects liquid with the soil animals on the sieve at the bottom, which has very small holes in it to catch the animals but let most of the water flow through. The sieve is then rinsed over a funnel into one of those small plastic falcon tubes to collect the soil animals (and some residual soil). Here you can see Diana rinsing the sieves between samples, which she is doing in order to prevent one sample from contaminating another: if she didn’t do this, we may end up with animals from one sample being transferred to another, which would provide incorrect data of what lives in each area the samples were collected from.
Samples in the falcon tubes are then passed to someone operating the centrifuge. Here, the samples from the first run of the sieves are checked to make sure the water levels are roughly equal and then are added into the centrifuge four at a time: this first run lasts five minutes, and helps to move all the soil animals down onto a pack of soil. Once this first spin through the centrifuge is complete, all but the very last remnants of water are poured out as waste–the vast majority of soil animals are all tightly packed along with the soil at the bottom, and not in the water in the tube. We then add a solution of water and sugar, mix the soil up into this to re-suspend the nematodes into the solution, and then replace the tubes into the centrifuge for an additional minute. In this last centrifugation, the soil is spun into the bottom of the tubes while the soil animals remain suspended in the sugar solution. Here you can see Byron checking the level of water in the falcon tubes prior to operating the centrifuge:
When the second spin through the centrifuge is complete, the samples are passed back to be sieved once more, this time over a small sieve with an extremely fine mesh. This sieve is then rinsed once more over a new falcon tube, and all of the soil animals are concentrated into this tube for examination under the microscope. In this image, Uffe is looking at a sample under the microscope, where he will count the number of living and dead nematodes from each species present, as well as the number of rotifers, tardigrades and other soil animals.
These numbers will be entered onto a data sheet and then be checked so that we can conduct analyses on our data later. Once we have completed looking at all the samples from a given experiment, the samples will be preserved with formalin and then packaged to be shipped back to the US, along with the unused soil from each sample that wasn’t used in the extractions or for obtaining characteristics of the soil such as soil moisture or nutrient levels (such as carbon, nitrogen and phosphorus).