A groundbreaking environmental DNA (eDNA) technology is expected to transform the monitoring of marine life in the Southern Ocean, providing an advanced approach for detecting non-native species in the waters near Antarctica. Significant knowledge gaps in one of Earth’s most sensitive marine ecosystems are anticipated to be closed by this development.

In 2019, a research expedition of 3,000 nautical miles from Hobart to the Davis research station was conducted aboard the former Australian icebreaker Aurora Australis. During the voyage, 138 seawater samples were collected by scientists to analyze the eDNA, which is made up of genetic material shed by marine organisms into the environment through skin, scales, eggs, and other biological substances. The aim was to identify the zooplankton species present in these waters at the time.

The comparison of eDNA analysis with data collected using a continuous plankton recorder (CPR) was explained by Dr. Leonie Suter, a molecular geneticist with the Australian Antarctic Division. The CPR is an instrument that is towed behind the ship, capturing zooplankton between two sheets of silk for physical examination.

“Animals captured by the CPR are examined under a microscope for identification,” Dr. Suter explained. The CPR has been used for decades to monitor zooplankton diversity in the Southern Ocean, providing an invaluable long-term dataset. However, this method is most effective for robust organisms like crustaceans, as delicate or gelatinous species are often damaged during collection, making their identification challenging.

A crucial advantage is presented by eDNA technology. “Most organisms present in the environment can be identified with eDNA, even if only a fragment is available—such as a small part of a cell, faeces, eggs, or larvae,” Dr. Suter noted.

The objective of the research was to determine whether eDNA could supplement the existing zooplankton dataset with meaningful insights. The research was led by Georgia Nester, previously of Curtin University and now with the Mindaroo Foundation. A greater range of species was detected by eDNA compared to the CPR, including species in sea ice, which the CPR cannot access.

“Using eDNA, 68 zooplankton species were identified, compared to 32 species found using CPR tows,” Dr. Nester explained. “Interestingly, only 12 species were detected by both methods, with most of these being crustaceans such as krill and copepods.”

The findings highlighted that both eDNA and CPR methods have distinct strengths and limitations, and the combined use of both methods could offer a more comprehensive picture of zooplankton diversity. “A broader understanding and more complete view of the ecosystem can be gained by using both methods,” Dr. Suter explained. “For instance, if some gelatinous organisms cope better with rising ocean temperatures, focusing only on crustaceans would lead to missing these shifts.”

Beyond long-term ecological monitoring, eDNA has shown great potential for assessing marine biosecurity risks. During the 2019 expedition, 16 non-native or potentially invasive species were detected by eDNA. “Most of these species were found closer to Tasmania, where they are already known to be present,” Dr. Nester said. “However, some species were also observed when we entered the sea ice zone, likely due to organisms being scraped off the ship’s hull.”

The potential for marine introductions through biofouling, where organisms attach themselves to ship hulls, has been recognized as a significant risk. While most eDNA detections were minimal, and some may represent non-viable DNA or dead organisms, the findings emphasize the importance of strong biosecurity measures. A biofouling management plan has been implemented on Australia’s new icebreaker, RSV Nuyina, which complies with International Maritime Organization biofouling guidelines to minimize the risk of transporting invasive species to Antarctica. “The highest biosecurity standards for the Australian Antarctic Program are ensured,” said Kirsten Leggett, Environmental Manager at the Australian Antarctic Division.

The vulnerability of Antarctic ecosystems to invasive species was emphasized by Dr. Suter, who suggested improved detection methods be developed. “eDNA-based approaches show significant promise for enhancing the rapid detection of non-native species, enabling timely intervention,” she added.

A more detailed view of the Southern Ocean ecosystem is expected to be achieved by combining eDNA analysis with CPR surveys and biophysical data. This integration will help scientists better understand how environmental changes impact marine life. The findings of this research have been published in Science of the Total Environment.

Detecting native and invasive species accurately is considered crucial for mitigating the impacts of climate change and human activities on Antarctic marine ecosystems. This research is seen as a major step forward in the effort to safeguard one of the world’s most pristine and fragile environments by leveraging cutting-edge DNA technology.

DNA, or deoxyribonucleic acid, is the genetic material present in the cells of all living organisms. It is continuously shed into the environment in various ways—through skin, scales, faeces, and more—forming a complex “environmental DNA” (eDNA) that represents the organisms in that environment.