Last Tuesday (October 24th), we spent the day doing CTD (conductivity-temperature-depth) casts to collect bottom water at 600 m depth. We did a total of 8 casts – 6 solely dedicated to collecting water to fill 5L, 20L and 50L carboys and twenty-five 5-gallon buckets that we would be using to store the adult coral samples of Flabellum impensum we would be collecting later in the week. We did two additional casts for Maggie’s capstone project where she was collecting water samples from 10 different depths to determine the nutrient profile for phosphate, nitrate and nitrite as well as preserving the phytoplankton community from water collected at the surface and at the chlorophyll max. On the last cast, Jay preserved some water to do a carbonate chemistry analysis, which would tell us something about ocean acidification at Station AA (the location where we would be collecting the corals).
The CTD has 24 Niskin bottles and each one holds 12L of water. You prep the CTD by cocking the niskin bottles so that they are open before the CTD goes overboard. Once the CTD is overboard, it slowly descends to the deepest depth that needs to be sampled and then as it is brought back up, the Niskin bottles are fired at certain depths where water needs to be collected.
Wednesday arrived with absolutely perfect conditions for trawling – calm seas, little to no wind, some ice but not enough to prevent us from putting the net overboard, and sun! We even caught a glimpse of the mountains on Smith Island (the second highest mountains in the South Shetland Islands). The Marine Technicians helped get the net ready – making sure that the net wasn’t tangled, that the floats were at the top and the chain at the bottom.
The anticipation amongst the team was tangible – everyone was anxious for a good tow. In the past, Dr. Waller has had some tows where they’ve only gotten a single coral polyp and others where they’ve gotten more than 50. We were all hopeful that it would be on the higher end of the range.
From the net leaving the deck until it’s return was about three hours. We hit bottom around 600 m. When the net was coming back up, we all got on our sorting gear (bibs, steel-toe boots, etc.) and headed out to the deck to meet the net. Once the net was on board, the sorting frenzy began. Everyone pitched in – the marine techs and other scientists on board. The end result was over 100 corals and very little bycatch - just a few skates, an octopus, some sea stars, brittle stars, sea urchins, sea cucumber, anemones, a fish, and isopods.
On Thursday, we woke up early to see the Neumayer Straight, an extremely narrow passage and absolutely beautiful with sheer mountains on either side of the ship. Shortly thereafter, we arrived at Palmer Station and the unloading process began. Everyone was working to get the cargo off so fresh foods could be unpacked and we could have access to our aquarium tanks and other equipment. The crew worked late into the night and as soon as the tanks were unloaded, we got to work. Jay set out to put together the four aquaria for the experimental treatments while Dr. Waller, Maggie and I setup to start dissecting the adult corals we had collected the day before. We dissected into the wee hours of the morning (3:30 am) and got 832 larvae from 20 female adults – enough for the experiment! It was a rewarding and exhausting experience.