The ocean supports a great diversity of life and ecosystems – UNESCO Ocean Literacy Principle 5
It’s been a very busy start to CAPSTAN voyage 2. With 18 students on board we departed Hobart on Monday. Just about 48 hours later, we arrived at our study area- the Bonney Upwelling zone along the eastern edge of the Great Australian Bight! The seas have been favourable with waves decreasing from 5-6 meters the first day to near flat this evening. And the first 12 hours of sampling have been spectacular!
As part of a CAPSTAN voyage, we try to give students with as much equipment as possible, with overlap in the sample processing between geophysics, sedimentology, chemistry, and biology when possible. Some of the equipment we’re deploying this trip includes:
- CTD Rosette: I’ve talked about the CTD in many from-the-ship posts, but a quick refresher. CTD stands for Conductivity, Temperature, and Depth but often these powerful instruments have additional sensors. In the case of the CTD for this voyage, we also get real-time readouts of dissolved oxygen and chlorophyll. The CTD itself sits at the bottom of a cylindrical frame, surrounded by Niskin bottles.
- Niskin bottle: specialised device for collecting water from a specific depth. With spring loaded closures on both ends, this bottle is lowered through the water column open allowing water to freely pass through (if it was closed, the increasing pressure would make the bottle implode). As the rosette is brought back up, bottles are ‘fired’ with the click of a button from the operations room to snap the ends close and trap the water from that depth.
- Grab sample: sediment sampling device that takes a ‘box’ full of surface sediments
- Kasten core: large steel ‘straw’ that is penetrated into the sediments using gravity to collect a longer sediment record
- Vertical drop camera: the name kind of says it all
- Bongo Nets: two side by side plankton nets – from the top the two frames kind of look like bongo drums
We started our sampling mid-morning when we arrived at our 1800 m site. First in the water was the CTD (Conductivity, Temperature, Depth), followed closely by two vertical plankton hauls using the 1/2 meter bongo nets. From the Niskin bottles attached to the CTD, we can measure dissolved oxygen, temperature, salinity, and nutrients. The CTD goes first largely to help inform the plankton sampling. For plankton, we’re interested in both the photic zone (top 100 m or so) but also the depth where chlorophyll reaches a maximum- which is identified by the CTD! After all the plankton were on board, the kasten core went in! The sub-bottom profiles from our geophysics team looked perfect for a core deployment!
From the first deployment the day flew by in a blur of sample collection, analyses, and seals. I’ve never seen so many seals on a single research voyage. A few appeared early in the day and stayed right with us- coming close whenever we put gear in or took gear out of the water. By sunset we had several seals regularly doing acrobatics off the stern- great entertainment while waiting for an instrument to be recovered!
Inside, the plankton group identified and counted the species present. They caught lots of copepods (even some that had visible pink fat) and a very tiny jellyfish. They also learned that taking photos with a cell phone down the microscope is definitely a skill!
The sediment team logged the nearly 2.5 meters of sediment recovered – with everyone observing noting the smell of hydrogen sulfide coming from the freshly collected mud. They carefully cleaned the surface of the core once the corer’s top was removed (the process of the corer penetrating the sediments can smear the outer most edge- this is then scraped off with spatulas) then photographed the entire core and began sub-sampling.
We ended the day at our 500 meter site with another CTD, plankton tows, two grab samples, and the vertical camera drop! We were greeted by even more seals and a double rainbow around sunset. Many of us made a (short) movie night out of the camera drop, making popcorn as we watched the live footage. A seal checked us out right as the camera started down then we saw lots of squid (scared the ink right out of them) as the camera descended. Can’t wait for day 2 of sampling!