Whale and seal bones cover the coast of Antarctica – but their age can be difficult to measure.
© Robert Harding Video/ Shutterstock
How ancient whale bones could help to restore the Antarctic
When humans started exploiting the rich waters around the Antarctic, they dramatically altered a once pristine environment.
Over a century on after people arrived in Antarctica, researchers are now using the Natural History Museum’s collections of whale and seal bones to help to repair the damage. By finding out what’s changed, they can piece together the steps needed to restore it.
The waters surrounding Antarctica are some of the richest in the world.
Nutrients bubbling up from the deep sea provide the beginnings of extraordinarily rich ecosystems, feeding vast meadows of ice algae and billion-strong swarms of krill. Once upon a time, this incredibly huge concentration of food meant that the Southern Ocean teemed with life.
Huge colonies of elephant seals and fur seals would breed on the Subantarctic islands, their colonies stretching along the beaches as far as the eye can see. Penguins would have roamed the Antarctic continent in mighty flocks, before diving into the oceans to pursue fish, squid and krill.
These Antarctic residents would have been joined each summer by a host of migratory species which had travelled thousands of kilometres to take advantage of the overabundance of food. The squawks of seabirds would have rung out across the waves as they competed with dolphins, whales and other animals all fighting to get their fill.
But in 1904, that all changed.
These boilers once powered a whaling station at Deception Island – but have now fallen silent.
© James Scourse
The remains of old whaling ships litter islands around the Antarctic.
© nwdph/ Shutterstock
The founding of the Grytviken whaling station marked the first major permanent presence of humans in the Antarctic, with many more stations opening in the years that followed. This gave way to large-scale fishing and whaling which transformed the Southern Ocean from an untouched wilderness to a global centre for industry.
Over the next 70 years, the numbers of whales and seals were decimated to feed the demand for oil and pelts. While a ban on whaling in the 1980s allowed some species to recover, others remain at historic lows. Blue whales, for example, are thought to be at just 1% of their historic levels.
Restoring their populations is a vital part of tackling many of the greatest threats facing the Earth today, from ecosystem collapse to climate change. Unfortunately, figuring out exactly what Antarctica was like before human influence is uniquely difficult.
The bones of whales and seals that wash up on the rocky shores of Antarctica often come back thousands of years older than they actually are, confounding efforts to understand when different species lived in the Antarctic.
This makes it almost impossible to build up an accurate picture of what these oceans used to look like.
The Antarctic's whaling stations are now all abandoned – but their legacy lives on.
© Robert Harding Video/ Shutterstock
Finding the ‘original’ Antarctica
It’s hard figuring out what the pristine state of the Antarctic was like. While its remoteness makes it tempting to think that not much has changed, that’s not something that can be relied upon.
Widespread exploitation began long before the invention of the equipment scientists use today to track animal populations. This leaves researchers without detailed information about what Antarctica was like before whalers moved in.
While Antarctica might look pristine, its ecosystems have been modified by people for more than a century.
© Christopher Wood/ Shutterstock
Professor James Scourse is a scientist from the University of Exeter who leads an initiative which is trying to change this. His team is attempting to build up a picture of what the oceans used to look like as part of the SEACHANGE European Research Council Synergy project.
“One factor we have to contend with is shifting baseline syndrome,” James says. “This is the idea that when a generation perceives an ecosystem as ‘pristine’ it may in fact be significantly degraded from its former state and not pristine at all.”
“For instance, while we might see the green fields of the UK as being a natural part of the ecosystem, they haven’t always been there. Previous generations would have had woodlands or wildflower meadows and seen these as pristine instead.”
“It’s exactly the same with the oceans. We can’t rely on people’s accounts of what these areas used to be like. We need to know from the animals which were there and the sedimentary records they left behind.”
This is where the bones of marine mammals come in. Their remains can record a whole wealth of information about an animal, from what it ate to where it lived. All that’s needed is an accurate date to start building up a snapshot of a region at a particular moment in time.
In the Antarctic, however, this is much more difficult than it sounds.
The conditions of the Antarctic lend themselves to preservation – making it sometimes hard to know how old things are.
© James Scourse
Carbon dating of bones in Antarctica is often inconclusive, thanks to the impact of the radiocarbon reservoir.
© Angela N Perryman/ Shutterstock
The problem with dating the Antarctic
When scientists date organic matter, such as bones, they typically use a technique called radiocarbon dating. This measures levels of carbon-14, a naturally occurring radioactive form of the element, to work out how old a particular sample is.
Carbon-14 gets into the bones of these animals when they eat something, and it’s generally assumed that their food is the same age as they are. But thanks to a unique phenomenon known as the radiocarbon reservoir, skeletons found in the Antarctic are actually much younger than radiocarbon dating suggests.
Animals living in the Southern Ocean take up carbon-14 from the seawater which makes them appear thousands of years older when carbon dated.
© Fred Hendriks/ Shutterstock
“Water in the ocean can take thousands of years or more to mix evenly, and some parcels of water might not have seen the surface for hundreds of thousands of years,” James explains. “Some of the oldest upwells are around Antarctica where it gets naturally incorporated into the bodies of the animals that live there.”
“This means that when the bones are radiocarbon dated, they appear to be up to thousands of years older than they actually are.”
As a result, scientists need specimens taken at a defined point in time. This is where the mammal collections at the Natural History Museum, cared for by Principal Curator Richard Sabin, can help.
The marine mammal collection has thousands of whale and seal skeletons from the 1500s to the modern day, including many from the oceans around Antarctica. Because a significant number of these animals were originally caught live, it means the bones can be precisely linked to a specific time and location.
“There really is no other way of doing this work without material of known age,” James says. “It’s also a real privilege to work with historic specimens collected by famous expeditions, such as the Ross expeditions on the HMS Erebus and HMS Terror of the early 1840s, which adds an exciting cultural dimension to our research.”
The whale bones at the Natural History Museum can be used to help reconstruct past conditions in the Antarctic.
© The Trustees of the Natual History Museum, London
Boning up on the Antarctic
Sampling the whale and seal bones from the collections was the job of Dr Anna Genelt-Yanovskaya and Dr Evgeny Genelt-Yanovskiy. Using small drills and other handheld tools, the pair took pieces of the bones to reveal more about the lives of the animals they came from.
In order to best protect the irreplaceable specimens, each incision was carefully planned.
“Every specimen here is historically important, so we don’t want to take too many samples,” Anna says. “The oldest specimen is a leopard seal from the first land expedition to Antarctica led by Sir James Clark Ross, which is almost 200 years old.”
“We try to take samples from areas of the bone that will allow us to perform as many analyses as possible, while using as little as we can so that future researchers will have enough material to work with.”
As well as the precision needed to take the samples, the bones also threw up other unexpected challenges when they were sent to the University of York for the next stage of analysis.
“Normally, the bone samples would be placed in acid and within a couple of days we could extract collagen from them,” Evgeny says. “However, it’s different with these old specimens, which can take up to a month or more to yield enough collagen for us to use.”
“This was anticipated, but we kept calling up our colleagues in York to check how it was going. We just had to keep waiting until the process was finally complete.”
The marine mammal collections cared for by the Natural History Museum span more than 500 years of history.
© Anna and Evgeny Genelt-Yanovskiy
The sampling process is discussed with curators ahead of time.
© Anna and Evgeny Genelt-Yanovskiy
What can whale bones reveal about the past?
Once the team had enough tissue from the bones, they could start analysing them. Anna and Evgeny are particularly interested in the forms of certain elements known as stable isotopes, which can reveal where the whales and seals were living during their lifetime.
“We’re specifically interested in the stable isotopes of carbon and nitrogen in the bones,” Anna explains. “By knowing the biology of a particular species, we can interpret their geochemistry to find out where these whales and dolphins were living more than a century ago.”
Krill are one of the dominant food sources in the Southern Ocean
© Tarpan/ Shutterstock
“Carbon isotopes, for example, provide information about whether these whales and seals were feeding close to or far from the land. They also tell us about how deep an animal is feeding.”
“Nitrogen isotopes tell us a lot about the diet of species,” Evgeny adds. “Antarctic environments are less enriched in nitrogen, so if there is more of it in the bone then the animal was living further away from the continent.”
In parallel to the work taking place on the mammal bones, another team of researchers are investigating cores of Antarctic sediment. The shells, microfossils and eDNA contained within these samples expand the scope of the project’s window into the past to look at the entire ecosystem.
This has allowed the researchers to develop an unprecedented picture of how the Southern Ocean has changed in the past 200 years.
Whales are now returning to the Antarctic waters they used to live in, but recovery is a slow process.
© Bill Perry/ Shutterstock
Revealing a changing Antarctic
While the team’s research is ongoing, they’ve already made some fascinating discoveries.
One of the most surprising came after the team analysed three blue whale skeletons, taken from within just a few kilometres of each other at the southern tip of South America. The scientists expected the specimens to have a similar isotope composition, but the differences between these skeletons were greater than between any other specimens analysed in the entire dataset.
The team suspects this mean they came from two different populations, one in the Pacific and one in the Antarctic, which used to overlap in the past. This all changed with the arrival of humans.
The team have found that leopard seals eat much more krill than expected.
© Angela N Perryman/ Shutterstock
“Our early data suggests that whales and seals changed their foraging behaviour in response to our actions,” James says. “The isotope data suggests they started moving into the deeper waters further offshore as human impacts increased, probably to avoid being captured.”
“This is also evident in the sedimentary eDNA, which allows us to see which whales and seals were living in Antarctic waters at a particular time. We’re seeing clear changes in biodiversity.”
The research is also revealing surprising new insights about living animals, which might help to better protect them.
“We’ve known that leopard seals have a varied diet for some time, but our data suggests they’re further down the food chain than had been assumed,” James says. “They’re eating much more krill and plankton than we expected, and that’s stayed pretty constant across the period of time we were investigating.”
The team’s findings in the Antarctic are just one part of the wider SEACHANGE initiative, which is also investigating how humans have changed the waters around northern Iceland and the North Sea across thousands of years.
“By better understanding how we’ve affected the oceans, from prehistory to today, we can see the full extent of our impact on the planet,” James says. “This gives us a better starting point to return these ecosystems to a more natural state.”
“We hope that this will mean that marine protected areas won’t just protect the status quo, which reflects a damaged ecosystem, but instead will be able to reflect the historic diversity of the area. This will allow us to implement projects that move the ecosystem back towards its pristine state.”
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