It’s the little things that count
14 March 2025
Deep inside the icebreaker RSV Nuyina off the coast of East Antarctica, as 9-metre swells and 50-knot gales rage outside, the plankton team is busy collecting tiny creatures with the ‘wet well’.
The wet well is a unique sampling space below the waterline, connected to the ocean by large inlets, two and five metres below the surface, and in the keel.
The inlets feed seawater – and the plankton living near the surface – on to filter tables for collection by researchers.
Despite some bad weather as the Denman Marine Voyage crosses the Antarctic continental shelf, the AAPP ‘pelagic sampling’ team – Luke Brokensha, Pimnara Riengchan, Inessa Corney, and Haiting Zhang, working with AAD aquarist Anton Rocconi – have so far completed ten successful ‘trawls’ using the wet well.
Dr Haiting Zhang, senior plankton technical officer with AAPP, said the wet well enables particularly fragile animals, like salps and jellyfish, to be captured alive and in good condition.
“The samples collected through this innovative method can provide biodiversity data comparable to that from traditional net-towed sampling,” she said.
PhD student Pimnara (Nia) Riengchan is studying free-swimming sea snails, known as shelled pteropods, and how their shells are affected by increasing ocean acidification.
“We’ve been able to collect live pteropods of different types – shelled pteropods with fragile shells, and carnivorous naked pteropods without shells.”
“For the first time, in the aquarium, we documented a four-centimetre-long naked pteropod or carnivorous ‘sea slug’ called Spongiobranchaea sp. feeding on a much smaller shelled pteropod or ‘sea butterfly’ called Limacina retroversa,” said Nia.
Phytoplankton taxonomist Luke Brokensha said that the wet well allows high-quality photo identification records to be made on board.
“Using the wet well sampling system, we have an incredible opportunity to photograph and document zooplankton and phytoplankton in pristine and near perfect condition – straight out of the ocean.”
“This method of sampling allows us to get highly detailed and consistent imagery, which will assist in building a photo ID database of important Southern Ocean species,” he said.
PhD student Inessa Corney plans to run experiments with some of the captured zooplankton to see how their metabolism responds to changing environmental conditions like warming ocean temperatures.
“Zooplankton are the smallest (and tastiest) animals in the Southern Ocean food web. Many of the large animals we know in the region eat zooplankton almost exclusively, or eat an animal that does.”
“Given their importance to the food web, understanding how zooplankton populations respond to warming oceans is vital to understanding the impact of climate change on the entire food web within the region.”
“The wet well provides us with the means to collect live zooplankton in real time for thermal tolerance experiments that will give us more insight into how they could potentially respond to climate change in the future,” said Inessa.
Project lead Assoc Prof Kerrie Swadling, from AAPP at the Institute for Marine and Antarctic Studies, said such innovative research aims to understand the future health of the entire Antarctic marine ecosystem.
“We know almost nothing about any zooplankton in the Southern Ocean other than Antarctic krill.”
“There is a theory that many Southern Ocean species have a very narrow temperature tolerance but in fact we have almost no measurements to support or refute this claim.”
“Will there be winners and losers in response to climate change and what are the ecological ramifications of such shifts for East Antarctica?”
“This voyage will go a long way to answering that question,” she said.
The Denman Marine Voyage is a collaboration between the Australian Antarctic Division (AAD), Securing Antarctica’s Environmental Future (SAEF), the Australian Centre for Excellence in Antarctic Science (ACEAS) and the Australian Antarctic Program Partnership (AAPP).
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