East Antarctic Expedition Scientists Focus on Predators of Krill—A Critical Food Web Component

Data will contribute to updating ecosystem-based fishery management for the Southern Ocean

East Antarctic Expedition Scientists Focus on Predators of Krill—A Critical Food Web Component
Humpback whales
Scientists in East Antarctica have been researching top predators such as this humpback whale mother and calf—and krill, the keystone prey species they depend on.
Alamy Stock Photo

This is the second instalment of the series, “Krill Chronicles From East Antarctica,” documenting the scientists onboard the research vessel Investigator and their experiences.

When we last checked in with the team of Australian Antarctic Division (AAD) scientists onboard the research vessel Investigator, they were just set to launch from Hobart en route to East Antarctica. 

Their focus: to collect data on the region’s Antarctic krill to better estimate the total amount of the krill present, and to better understand interactions between krill and the species that depend on them as their primary food source, as part of an effort to sustainably develop a potential krill fishery in the region. 

The 20 scientists on board have been tasked with focusing their research on five areas: krill biology, acoustics, predator observations, biological oceanography and genetics.

Kym Reeve and Nat Kelly lead the predators observation team—Reeve aboard the ship, and Kelly remotely from Hobart.

Reeve, who says she knew by the age of 8 that her future was in marine science, is a zoology graduate from the University of Queensland with a Ph.D. in marine mammal science from the University of Sydney. Her first trip to Antarctica as part of an AAD research team was to track blue whales in 2015.

Kelly has more than 20 years’ experience as a statistician, and specializes in methods for animal abundance and distribution, with a particular focus on whales and krill in the Southern Ocean. Her Ph.D., bachelor of science degree in mathematics and statistics, and bachelor’s degree in forest science all come from the University of Melbourne. And her research has been delivered to the International Whaling Commission and the Commission for the Conservation of Antarctic Marine Living Resources.  

The two were joined in answering questions about the expedition by Jeremy Bird and Derek Hamer, who are collecting data on bird predators; Maria Isabel Garcia Rojas, Angus Henderson and Joshua Smith, who are assisting with whale observations; and Brian Miller, who is handling marine mammal acoustics. This interview has been edited for clarity and length.

Kym Reeve
Kym Reeve
Courtesy of AAD
Nat Kelly
Nat Kelly
Courtesy of AAD Simon Payne

Q: Which predators are you observing on the expedition?

Nat Kelly: The onboard team is collecting information on the distribution and density in the survey area in East Antarctica of air-breathing animals such as penguins, flying seabirds, seals, and whales.

Q: What’s the importance of krill to these animals? 

Kym Reeve: Antarctic krill is a key prey species for many of these animals, including baleen whales, crabeater seals, and bird species like Adélie penguins, snow petrels and southern fulmars. And several predators, like killer whales and leopard seals, consume species that are themselves dependent on krill as a food source. So directly or indirectly, krill are a vital component in the food chains of most, if not all, of the air-breathing animals the team is on the lookout for.

Antarctic petrel
Antarctic krill is a key prey species for many Southern Ocean animals such as seabirds, including iconic Adélie penguins, southern fulmars and the Antarctic petrel, above, flying near the RV Investigator.
CSIRO MNF

Q: In addition to observing the predators, you’re also recording noises made by predators. Why is this information important to have?

Brian Miller: It gives us a more complete understanding of which species are in the survey area, and also what they’re doing. Visual observation of marine mammals in the Southern Ocean only provides us with part of the picture of how many animals are present in the study area; many marine mammals spend a large portion of their time underwater, and some are so rare that random chance may not bring them within a few kilometres from the ship, which is as far as visual observers can see. And we’re able to make recordings at night, in fog, or during whiteouts—conditions where visual observations aren’t possible.

Q: What’s an example of a species that is easier to track by sound than by sight?

Brian Miller: Antarctic blue whales and sperm whales frequently make loud calls while underwater, and these sounds can often be detected from much farther away than these animals can typically be seen. By recording underwater sounds, we’re able to monitor and detect distinctive sounds from at least 13 different species of marine mammals, including blue, fin, sei, humpback, southern right, minke, sperm, killer and pilot whales, as well as Weddell, Ross, crabeater, and leopard seals.

penguins
Both krill and their predators, such as these emperor penguins, are experiencing the effects of climate change on the Southern Ocean.
Laurent Ballesta Andromède Oceanology

Q: What do we know about how the predators you’re studying are affected by climate change?

Nat Kelly: The impact of climate change on Southern Ocean ecosystems is at the forefront of our minds. Both empirical studies and modelling tell us that climate change is altering the physical environment of the Southern Ocean (circulation, water temperatures and melting of ice sheets, and atmospheric processes) and biochemistry of the water. These changes are thought to perturb the flow of nutrients through food webs and alter the spatial and temporal distribution of animals’ available habitats, such as sea ice—which is a key habitat for krill.

Q: So if the flow of nutrients is affected, and the habitats are affected, what does that actually mean for the animals?

Nat Kelly: The implications of these changes on krill and krill predators—the changes that we’ve observed as well as the ones that have been predicted—are difficult to assess, often due to the sheer scale of the Southern Ocean, and the expense and risk involved of undertaking research here.

Q: Is that true for all of the Southern Ocean?

Nat Kelly: Most of this research has focussed on the southwest Atlantic and the Antarctic Peninsula region, meaning that the impacts of climate change on East Antarctica are even less clear.

Q: Does fisheries management for krill in East Antarctica currently take into account the protection of krill predators? And can the data you’re collecting on this survey be used to protect air-breathing krill predators?

Nat Kelly: The impact of fishing for krill on its predators is a key consideration in the management of that fishery. In setting catch limits for krill, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the governing body responsible for protecting Southern Ocean wildlife, attempts to explicitly account for the needs of krill predators. To do that, CCAMLR needs accurate estimates of the population size, life history, and consumption needs of the various krill predator species.

Q: That’s a lot of data.

Nat Kelly: It’s a gigantic yet vital task, which voyages like the current AAD expedition are attempting to fulfill. A few years ago, AAD scientists studied the likely krill predator needs in East Antarctica and compared their findings to the region’s existing krill catch limits. The study concluded that, given existing—but aging—krill and krill predator data, the CCAMLR krill catch limits were probably conservative enough to provide for krill predators. But East Antarctica will potentially see resumption of a krill fishery there after a number of decades, and CCAMLR will need new data on krill and krill predators to ensure that its catch limits are appropriate.

Q: What drew each of you to Southern Ocean and predator research? And do you have a favourite krill predator—and, if so, why? 

Nat Kelly: Whether the Southern Ocean and its predators amazed us from childhood, or drew our interest only once we had begun our research careers, we can agree that the natural history of the region is unparalleled. The biology of creatures built to survive vast oceans, savage winds, and freezing temperatures is hard to believe. When it comes to Southern Ocean krill predators, I find them diverse and yet equally inspiring.

Jeremy Bird: My favourite are the sparrow-sized storm petrels, which spend most of their lives traversing the ocean. Yet they always find their way across thousands of miles of featureless seas to their same breeding burrow for 20 years or more.

Maria Isabel Garcia: Minke whales, the only baleen whales known to exploit Antarctic resources year-round. Their small size and manoeuvrability allow them to feed on krill hiding and foraging under sea-ice floes.

Joshua Smith: The largest creatures to ever have lived, Antarctic blue whales, which owe their survival to the continued existence of one of the smallest—krill.

Upcoming articles in “Krill Chronicles From East Antarctica” will include profiles of and firsthand experiences from scientists onboard the Investigator, along with other updates on this critical Southern Ocean research expedition.