Today was a good one. We started out in the lab processing samples from an experiment that we broke down on Saturday. Like all weekends we spent the last one working and putting samples into the freezer and preservatives. It feels great to be making progress towards the end of our project, even though that is still a month and a half away. As we were typing away Rory noticed a lot of people on the ice and pointed them out. Well it turned out to not only be a lot of people but a quite a few people and a group of very lost emperor penguins.
Its rare to see Emperors here as they normally roost during the winter on the far (far!) side of the island at Cape Crozier. Cape Crozier is 55 miles as the penguin waddles from here adding around 100 miles to these penguins journey. There appeared to be quite a bit of dissent among the ranks as they often stopped and grrrred at each other while walking by the station. This group was likely females on their way back to feed the chicks that they hatched over winter.
The rest of the day we spent jumping in the water to finish an experiment. We had noticed that as the light become more abundant during the rapidly approaching summer, diatoms appeared on the sediment surface. Diatoms are plankton (i.e. microscopic plants of the sea) and are a potential food source for animals. We decided to measure how much energy these emerging diatoms were producing by doing an in situ (i.e. underwater) experiment. To measure this we took cores and blacked them out (using some handy electrical tape) and left others clear (replicated at all of our sites, of course). The black cores would let no light in so we knew there was no photosynthesis going on and the clear cores did let light in allowing any plants present to act normally. One black and one clear core were used to collect sediment without disturbing it, and then placed upright overnight on the seafloor. We let them sit there for 24 hours and then measured the amount of oxygen in the cores (we had also measured the oxygen concentration in the water when we set out the experiment yesterday). The difference between the starting oxygen and the ending oxygen of these cores told us how much oxygen was used by the community that we trapped in our cores. Since we know that photosynthesis produces oxygen, the difference between the clear cores and the dark cores tells us how much photosynthetic production is occurring. In other words: Photosynthetic production (measured by O2) = Oxygen produced by photosynthesis – oxygen consumed by the community. The clear cores integrate both the oxygen produced by photosynthesis the amount consumed by the community and the dark cores only measure the amount consumed. Simply by subtracting the amount of oxygen in the dark cores from that in the clear cores to get how much net photosynthetic energy is being produced. The answer? At this time of year the seafloor photosynthetic community is producing ~ 19 mg O2 per square meter. We can use this number (after repeating the experiment a few more times throughout the year) to come up with an estimate of the amount of food benthic (seafloor) production provides for the animals that live in and on the sediment. To put that in perspective, that is about 25% of the daily food used by this community today.
Not everything works as planned though. For example we had issues with sea urchins deciding that they wanted to climb on top of our treatments, knocking them over (this treatment was to measure what was going on in the water – hence no sediment). Not to mention another one deciding that my station marker would make a nice addition to this particular individuals camouflage.
At the end of the dive we took our samples back to the lab to measure the oxygen and saw a nice fish along the way. This is Trematomus bernacchii, one of the fish we often see here, hiding underneath Alcyonium antarcticum, a soft coral.