Sorting sea pigs from sea spiders: How we collect, sort and preserve seafloor species

Reporting from the RSV Nuyina, SAEF field assistants Jesselyn Brown and Joshua Lesicar explain how the team collects, sorts and preserves seafloor species and how the data stored in their DNA could contribute to research for perpetuity.

Sorting and preservation

Our process begins with the retrieval of the trawl net onto the back deck, where our team of scientists sort through the payload, collecting fish and benthic invertebrates into buckets. In the images above, you can see our team suited up and sorting through the recent catch!

From the back deck to the lab, each bucket’s contents are sieved and sorted into broader taxonomic groups, like crustaceans or echinoderms, and then further separated by order, family, and individual species where possible. Some of the animals we’ve collected so far include feather stars, sea spiders, urchins, scale worms, and the ship favourite, sea pigs! In one of our more recent trawls, we’ve even had a small sounder of sea piglets, which you can see in the image below!

Specimens are then cleaned with paint brushes to museum standards and photographed with a unique identification number. Tissue from the specimens is sampled for future DNA extraction.  The animals are then preserved whole in either ethanol or formalin in their respective containers. All steps of this process are carefully recorded by a scribe and each retrieval usually yields over 100 individuals, usually with varieties from most phyla!

Research contribution

The Southern Ocean off East Antarctica and the Denman Glacier is a poorly sampled region. Considering that the Denman Glacier is one of the fastest receding glaciers in this region, the data, samples and specimens being collected will significantly contribute to present research and future understanding. Records of species presence and subsequent biodiversity will serve as a baseline for understanding community composition and population dynamics. The morphological preservation of organisms in formalin will preserve physical characteristics, enabling the identification of new traits and likely new species. Additionally, subsamples taken from each individual will provide genetic information that has versatile uses, including investigation of connectivity between populations, changing population sizes over time, deep evolutionary relationships, and a range of evolutionary processes. 

Long term value

Although the immediate impact of these specimens will be significant, their long-term preservation enables them to be included in future studies for years to come. Our technology and research methods have vastly improved over time, and in recent years, genetic research and technology have taken off at a rapid rate of improvement and refinement. 

If we look to the future in 20, or even 10 years from now, advances in technology are likely to enable us to unlock even more secrets from their DNA, that we simply can’t reach with our current toolset. These animals could help us unlock mysteries of the past and present simultaneously as well. The species we are finding have been present in this habitat for millions of years, and have experienced and survived extreme changes in climate and environment. Understanding their past is a key resource providing insight into how climate change will affect not only Antarctica’s environmental future, but ours as well.

The Denman Marine Voyage is a collaboration between the Australian Antarctic Division (AAD), the Australian Centre for Excellence in Antarctic Science (ACEAS), the Australian Antarctic Program Partnership (AAPP) and Securing Antarctica’s Environmental Future (SAEF). The SAEF team includes scientists from James Cook University, Geoscience Australia, the University of Adelaide, CSIRO, and the University of Colorado Boulder.