24.9 C
Byron Shire
March 22, 2023

Baleen isotopes tell whale of a tale

Latest News

We all live in a magic submarine…

Several commentators have remarked that, while the mainstream media is locked in furious agreement with the government over AUKUS and the trillion dollar submarines (a guess at the final price tag), social and independent media are telling quite a different tale.

Other News

Election 2023 – Lismore: Part II local and state issues Q&A

We asked all candidates for the seat of Lismore the same set of questions. This is the second round of answers. Their responses are in the order they arrived in our inbox.

Swimmers take plunge for mental health

Swimmers took to Byron Bay pool and swam over 2000 laps to raise money to help improve services to...

A bonanza for developers and land bankers?

The NSW Planning Rezoning Pathways Program will service the current agendas of developers and land bankers throughout Tweed Shire, particularly the State Significant Farmlands of Cudgen Plateau.

Child protection and DCJ workers ‘feeling abandoned’ in Lismore

The failure of the NSW government to support the most vulnerable people in Lismore and the Northern Rivers a year on from the devastating 2022 floods is being called out.

Lismore candidate Vanessa Rosayro

With just a few days until we head to the polls, The Echo asked the candidates for the seat of Lismore one last bunch of questions.

Jeremy Buckingham back to legalise cannabis

Former NSW Greens MLC Jeremy Buckingham is back on the hustings as the lead upper house candidate for the Legalise Cannabis Party in the NSW state election.

Isotopic analysis reveals how baleen whales’ feeding and migration is impacted by climate change. Photo Christopher Michel

Brought to you by Cosmos Magazine and The Echo

Work matching isotope data drawn from whales’ diets to climate records reveals how the climate crisis is affecting the planet’s biggest creatures.

Baleen whales in the southern hemisphere are likely to face challenging conditions as climate change continues, new research from the University of New South Wales suggests.

The study used stable isotope data preserved in whale baleen – a bristly feeding apparatus made of keratin – to unlock information about feeding and migration patterns of humpback whales and southern right whales going back 60 years.

The researchers matched the isotope information with climate data to understand how climate cycles have been affecting the whales over the study period.

Their results indicate that La Niña events, such as the southern hemisphere has been experiencing this summer, can make life much more difficult for whales.

Photo Sonia Friedrich.

What a whale wants, what a whale needs

Both humpback and southern right whales are baleen whales – meaning that instead of teeth, their mouths contain a structure called baleen. It’s made of keratin, the same material as our hair and fingernails, and acts a bit like a tea strainer.

As the whale lunges through the water with an open mouth, the baleen traps its main prey – krill – and filters the water back out.

Baleen whales gave up on teeth, explains Tracey Rogers, a professor in marine ecology at UNSW and senior author on the study. They strain their food with this feathery material, baleen.

Both species of whale spend their summers feeding on large schools of krill in the Southern Ocean around Antarctica. In the southern hemisphere winter, they migrate north to tropical temperate waters to breed.

Whales can’t feed very much on the journey north, so they rely on gorging themselves in Antarctica to build up the reserves that will sustain them during migration.

[Baleen] has really worked for them in the past, because there were these massive predictable schools of prey, in the Southern Ocean, which allowed them to really boom and become enormous, says Rogers.

Southern right whales, Great Australian Bight. Photo Peta North.

How climate change is impacting baleen whales

However, due to human-induced climate change, these schools of krill are getting less reliable – and that’s bad news for the whales.

Krill rely on sea ice for survival in the Southern Ocean, and sea ice is driven by different climates conditions that unfortunately, due to climate change, are becoming more difficult to predict, explains Adelaide Dedden, a PhD student at UNSW and lead author on the study.

Rogers explains that sea ice helps krill survive the dark Antarctic winter, during which their normal prey – photosynthetic phytoplankton – can’t grow due to lack of sunlight.

Instead, the krill will feed on bacteria found on the under-surface of sea ice in winter. They also use brine channels in the ice to hide from predators.

The new study looked at climate data from multiple climate cycles, including the Southern Annular Mode in the Southern Ocean, the Indian Ocean Dipole, and the El Niño Southern Oscillation (ENSO), which includes El Niño and La Niña events. Their findings confirmed earlier evidence that La Niña can negatively impact baleen whales.

After a La Niña event, sea ice is less concentrated in the whales’ Antarctic feeding areas. Less ice means less krill and so less food for the whales.

Our colleagues have shown humpbacks are leaner – a sign they’re experiencing poor feeding conditions – and have a higher chance of stranding in the years following La Niña events, says Rogers.

The study found that whales migrating up the east coast of Australia were particularly vulnerable, while whales based off the continent’s west coast seemed to fare better during La Niña periods. That’s probably because ENSO impacts the Pacific Ocean more strongly than the Indian Ocean.

It’s a poignant issue, all the more so because humpback whales have only recently been removed from Australia’s threatened species list, as their populations have slowly recovered since bans on commercial whaling were enacted in the 1960s.

But they do still face probably one of the biggest threats of all, which is climate change, Dedden says.

A whale shortly after it beached at Casuarina. Photo courtesy National Park & Wildlife Service.

Isotope insights

The researchers gained their insights into the whales’ feeding and migration by analysing stable isotopes preserved in the whales’ baleen.

These isotopes come from the whales’ diet and are integrated into their tissues, including baleen.

It’s basically a form of natural tagging, Dedden says. Stable isotopes within marine consumers like baleen whales reflect the isotope signals of the prey that they eat, and they can also tell you [about the] general region that they feed in.

The baleen continues to grow throughout the whale’s life. Dedden says that a baleen ‘plate’ about one metre long contains isotopes from about four years of the whale’s life.

Carbon isotopes can tell scientists where the whales were feeding, because waters around Australia and Antarctica contain markedly different carbon levels.

Carbon varies latitudinally, so you see lower carbon levels in Antarctic regions and higher carbon values as you get closer to temperate and tropical regions, Dedden explains.

Nitrogen, meanwhile, can indicate when and how much whales have been feeding or fasting. That’s because heavier nitrogen isotopes tend to accumulate up the food chain.

When krill are feeding on the algae and bacteria in the environment, they take in the stable isotope signatures from the algae, says Rogers.

They excrete lighter stable isotopes and hold the heavier elements in their body tissues. Then the whale comes along and eats that krill and it does the same thing.

When humpback whales are fasting on their migrations, they actually begin to break down their own bodies to get energy, which leads to even higher nitrogen isotope values.

They’re essentially eating themselves when they’re fasting, Dedden says.

A humpback whale breaching. Photo Wild About Whales

What does the future hold for whales – and us?

Dedden says that climate change is likely to impact other predators who rely on krill, like certain seal species. However, the whales are particularly vulnerable due to their migratory behaviour, which requires them to build up reserves within a relatively short feeding period.

She hopes that this clear evidence linking the whales’ feeding patterns to climate cycles in the past may help to predict how they will fare under different future climate scenarios.

For Rogers, the results are just another reason to add to the list of why we need to work to limit further climate change. She points to the stress that increased La Niña events have put on humans as well, referencing the recent floods in eastern Australia.

It’s all driven by the oceans being too warm and the atmosphere being too warm so there’s more heat for us and more moisture being held in the atmosphere,she says.

In actually doing something for the whales, we’re doing something for ourselves.

This article was originally published on Cosmos Magazine and was written by Matilda Handsley-Davis. Matilda is a science writer at Cosmos. She holds a Bachelor of Arts and a Bachelor of Science (Honours) from the University of Adelaide.

Published by The Echo in conjunction with Cosmos Magazine.

Support The Echo

Keeping the community together and the community voice loud and clear is what The Echo is about. More than ever we need your help to keep this voice alive and thriving in the community.

Like all businesses we are struggling to keep food on the table of all our local and hard working journalists, artists, sales, delivery and drudges who keep the news coming out to you both in the newspaper and online. If you can spare a few dollars a week – or maybe more – we would appreciate all the support you are able to give to keep the voice of independent, local journalism alive.



Please enter your comment!
Please enter your name here

Could Tweed Hospital see the first patient cannabis consumption room?

Marc Selan of the Legalise Cannabis Party is keen to keep the old Tweed Hospital open and says he would like to see the first patient cannabis consumption room at that site. 

Voting guide to preferencing in the NSW lower house

The NSW election, to be held on Saturday March 25, uses optional preferencing in both houses of parliament.

Homeless koala house hunting in Manly

As the trees continue to fall at the hands of the NSW government's Forestry Corporation in Yarret State Forest Blinky the koala has had to abandon his home.

Residents of Cabbage Tree Island want to go home

Anger and frustration at not being able to go home saw a group of residents reclaim their properties yesterday on Cabbage Tree Island.