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Synthesizing the Science

Science team and ASC staff

Now that we are done, I want to take a few minutes to look over where we went, the fabulous samples we collected along the way, and the work that lies ahead of us. We completed 15 Stations with 17 CTD casts, 18 TM pump deployments, 17 McLane pump casts, 21 Megacore deployments, 14 Gravity cores, 3 JGCs, 3.1 JPCs, and 2 large volume grow out experiments. That amounts to 32.115 m of sediment, 3460 L of water, and millions of particles. We isolated ~162 individual isolates, representing probably 20-30 species of diatom. More importantly, none of this would have happened without all the hard work and support of the ship’s crew and ASC staff. We encountered our share of rough seas and technical problems to truly appreciate the lovely ride that the Palmer provides and expertise and professionalism of its inhabitants. We worked well as a team, and I cannot thank everyone enough for all their effort and support throughout the cruise.

Our shipboard results show us a first order pattern of variation that one would expect. As we headed north from Antarctica, the surface ocean got warmer, saltier, and more nutrient poor. Chlorophyll a and biogenic silica contents and overall particle load were highest around the northern Antarctic Zone/Polar Front (62-64°S). We ran out silicic acid (dSi) around this point while nitrate (NO3-) persisted until the last station.

Many of the diatom species that we observed in the water column were also present in the surface sediments we examined. Because we are interested in how fossil diatoms record surface ocean conditions, we were thrilled to see this. That means that we have some confidence that the water column conditions and, more importantly, particle types that we were sampling may be represented by these groups in the sediment record.

There is not much more we can say from the samples and data we collected shipboard. The real work lies ahead for us. For Colin, the work starts in a day or so, when he arrives in Dunedin to begin his culture experiments. For the URI group, there are frozen samples headed back to the lab for them to start analyzing soon and then refrigerated sediment samples and cores that will arrive in a couple of months at Lamont Doherty Earth Observatory, where we will go and retrieve them. For the UCSB group, the water samples will also arrive by slow boat in a couple of months while their frozen sediments and nutrient samples will arrive quickly and analysis will begin.

Where we were less than successful in recovering core—in particular in the opal belt—we did not get sediment, but we did learn a lot. Many of us aim to return to the opal belt, armed with a new toolkit specifically tuned to core these unforgiving diatom oozes whose secrets we covet.

For now, though, I am happy to see land and looking forward to a drink and some delicious food, shared with my new friends.

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