Underway Saves the Day

04/02/2026

Research cruises are meticulously organized, drawing on centuries of collective experience, yet they remain subject to countless variables that can — and almost certainly will — shift any existing plan. On GO-SHIP research cruises, the primary method of collecting water samples is the CTD (conductivity, temperature, depth). A successful deployment of the CTD at each station is dependent on the cooperation of weather, sea state, shipboard personnel, computer systems, the proper functioning of the winch, CTD sensors, niskin bottles…the list can go on.

The Southern Ocean is defined by turbulent sea states, meridionally marked by the Roaring Forties, Furious Fifties, and Screaming Sixties. As the Southern Hemisphere transitions toward winter, sea ice advances northward at a surprisingly rapid pace. Storms are also increasing in frequency and intensity. These environmental variables place a strain on our ability to successfully deploy the CTD for casts that can last five or more hours.

Bio-GO-SHIP, the biological sampling mosaic integrated into the GO-SHIP framework since 2022, adds additional layers of complexity to CTD operations. A separate CTD cast, deployed to 1000 m and referred to as a “bio-cast”, is ideally conducted per day around solar noon. This dedicated cast ensures the collection of sufficient surface water for biological measurements. Although shallower than standard GO-SHIP CTD casts, bio-casts are still subject to the same environmental and mechanical constraints.

Amid many predicaments that have hindered A16S from reaching its first CTD station, nearly all lab groups onboard have collected sample water from the underway seawater system during transit. The underway system provides continuous sea surface water to an onboard sink for sample collection. For Bio-GO-SHIP, the underway system serves as a cornerstone for continuous and discrete measurements along any GO-SHIP transect, especially when CTD casts are unavailable.

 During the first six days of A16S, the bio team was able to complete 35 transit stations and preserve 190 individual samples for later analysis. Discrete data collection includes preserved samples for DNA, RNA, particulate organic matter (carbon, nitrogen, and phosphorus), flow cytometry, high performance liquid chromatography (HPLC) pigments, and microplastics. Continuous measurements are also collected using an Imaging FlowCytobot (IFCB) and an optical backscatter sensor (BB3), both set up inline to receive underway seawater.

Now that the A16S team is underway again, bio has doubled the number of individual samples in 5 days and successfully sampled our first CTD station with a view of the snow-capped mountains of South Georgia Island. Everyone on board is looking forward to continued CTD casts, and for the bio-team, bio-casts and more underway data!