We left Punta Arenas on Thanksgiving Day, but have only been doing our science stations for the past 3 days. Things are going fairly well so far; we're catching zooplankton (salps and krill primarily) in our net tows which is great as we've got animals to do our experiments onboard the ship. However, we have had to skip (or move the location) a few of our planned stations. As we headed towards one station last night, the Captain came down and suggested that I may want to consider moving our station location a bit south (towards the north side of King George Island) as he was starting to see swells that were ~ 28 ft high. So we did that and it's worked out pretty well.
Alarm --- fire drill time!
OK, back from the fire drill. Roughly once a week, the ship will ring the alarm bells unannounced and while the crew goes to their prepared stations and duties (depending on which alarm bell signal was heard), the scientists all muster in the lounge. You have to bring your life jacket and survival suit (and it's a good idea to bring a jacket and hat as well) and we take attendance and make sure the science party is accounted for. Sometimes, if there is a super-great chief scientist onboard, he'll even bring a chocolate bar that gets passed around!
Now that the drill is over, it's back to the science. We haven't really talked about what we're doing on this trip so I'll try to explain that now. In the Antarctic ecosystem, krill are the primary food source for all of the larger animals that exist down here (like whales, seals, penguins, and other sea birds). Unlike other oceanic ecosystems which have many different types of animals, almost all the energy in the Antarctic food web passes through krill at some point.
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| Antarctic krill, Euphausia superba, are crustaceans that can live up to 7 years and as adults are around 5 cm (2 inches) in length. |
In some places or times in Antarctica, you can find very high abundances of another zooplankton, namely the salp (Salpa thompsonii). These animals are gelatinouus (sort of like jellyfish) and are mostly transparent in the water except for their gut which is usually a dark red or brown color. Salps often occur in long chains of animals all connected to each other, or sometimes you'll find solitary (and larger) salps as well. Salps and krill are believed to be in competition for phytoplankton resources (i.e. they compete for the same food) and in some years you find lots of krill and in other years you find lots of salps. The salps are less nutritionally valuable to predators so if you have lots of salps and less krill, that may have a negative impact on the birds and mammals that feed on krill. One hypothesis is that as the climate changes (and the Antarctic peninsula is warming at a much more rapid rate than the earth as a whole), we may see decreases in how much sea ice forms each winter which is believed to be a better environment or conditions for salps than for krill. So some people think we may be seeing a shift in the abundance of salps down here.
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| Salps are kept in a cold room in aerated aquaria. In this tow, we caught lots of small (1 cm length) salps but also a couple of very large salps (~ 10 cm in length). Amazingly some of the salps were still in their chain form despite being brought up in the IKMT net! |
In order to measure how many salps or krill there are in any area, you have to count the animals in the ocean. If you use a net to capture these animals, it can be difficult to count how many salps there were as they are very fragile and can get destroyed by the net tow collection process. We're doing fairly shallow and short net tows so the animals that we bring up are in good shape for our experiments.
One of our goals on this trip is to assess the utility of using acoustic echosounders (which are scientific instruments similar to fish finders you see on most boats) to measure the presence or abundance of salps. Since we're sending out acoustic waves, we don't damage the animals in the process and we can cover a lot more area using a boat with an echosounder than if we are only using net tows. We can use acoustics to survey krill fairly well in this environment, but we'd like to be able to do the same thing for salps. In addition to collecting acoustic data during our survey, we're measuring various properties (size, shape, animal body properties) of the salps we catch to see if we can use that information to better interpret our acoustic survey data. It's a pretty complicated process, but the overall goal of our project is to improve our ability to remotely measure the abundance of salps in this region and then to see if there are changes in salp abundance either spatially, over time, or correlated with other environmental parameters. And if we can measure how many salps there are and if that's changing in space or time, then that can give us insight into how the presence of salps might affect the Antarctic ecosystem and the larger animals that live in these waters.
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| This is not one of the normal krill predators you would find in Antarctica. For the record, krill don't really taste like anything, mostly salt-water. They are full of omega-3 compounds so you can find Krill Oil dietary supplements in many health food stores next to the fish oil section. |
We'll try to provide some more pictures of the actual experiments in the next couple of days. We're just excited to have lots of animals onboard the boat so we can do our projects.
-Joe
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