Current systems crucial to life on earth

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A crucial system of currents that takes 1,000 years to circulate the globe is being impacted by increasing ocean temperatures and will have a profound effect on the world’s climate if it further slows or shuts down altogether, by triggering more atmospheric temperature extremes.

Professor Nicole Jones, a physical oceanographer from The University of Western Australia, explained the meridional overturning circulation as part of the Western Australian Marine Science Institution’s Thinking Blue school outreach program.

“Cold and salty water forms in the Labrador Sea, between Canada and Greenland, as well as in the Weddell and Ross Seas, close to Antarctica, and then it descends into the deepest depths of the ocean and circulates around the ocean before coming back up to the surface closer to the equator,” Professor Jones said.

“It takes a millennium to transport the water from the surface, down to the bottom of the ocean and back to the surface again.”

She said the ocean system was crucial to many processes including transporting gases from the atmosphere down into the deep sea.

“This helps to regulate the amount of carbon dioxide in the atmosphere and also supplies oxygen to the deep ocean,” Professor Jones said.

“It also traps heat so plays a strong role in modulating what is happening in the atmosphere.”

But climate change is impacting the system.

“With climate change, water at the Poles is becoming fresher and also warmer and so it is not going to be able to sink to the same deep depths and that will weaken the return currents such as the Gulfstream,” Professor Jones said.

“So, it’s not only the cold currents that get weakened it’s the warmer currents at the surface.”

Professor Jones said measuring the circulation was challenging but there was evidence it was slowing. She said if it shut down, there would be dramatic atmospheric temperature decreases across Europe. In the southern hemisphere temperatures would be expected to increase.

Professor Jones’ presentation also covered sea level changes and climate change.

The presentation can be found here.

Noisy oceans and the threats to the biggest animals on Earth

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Blue whales feast on several tonnes of krill a day, accumulate earwax that can be used to determine their age and the species of cetaceans, which are the biggest animals to have ever lived on Earth, have tongues that weigh as much as an elephant.

The fascinating facts were outlined during a presentation by Curtin University PhD candidate Brodie Elsdon as part of the Western Australian Marine Science Institution’s Thinking Blue outreach program.

Ms Elsdon said while the world’s population of humpback whales had recovered well since most countries stopped whaling, blue whales remained endangered globally.

Her presentation, ‘Talking Whales in a Noisy Ocean’ covered her research on whale sounds and song and the noises that pose threats to the animals including shipping.

“We can distinguish between species just by listening to the unique sounds they produce,” Ms Elsdon said.

Her research involves analysing recordings of pygmy blue whales captured from deep-sea areas and canyons around Western Australia, some reaching depths of 4,000 meters.

She then analyses the data using spectrograms, and specialised acoustic algorithms to identify the species’ unique low-frequency, high-intensity vocalisations, which are on the edge of the human hearing threshold.

“By listening to whales sing, vocalise and communicate in a noisy ocean we can identify patterns in their presence and their exposure to threats. It helps us identify the timing and the important locations the whales go, which can play a part in informing improved protection for this iconic, ‘data-deficient’ species.”  – Brodie Elsdon

“We know the Perth Canyon is an important feeding area for pygmy blue whales, but it has seen an increase in shipping traffic.”

Ms Elsdon said the ocean soundscape comprised noises caused by animals (biophony), humans (anthropogenic) and noise from the environment (geophony) including wind, rain and breaking sea ice.

“Whales live in an acoustic world and rely on sound for just about every aspect of their life including communicating, finding a mate, hunting for food and navigating,” Ms Elsdon said.

“Unfortunately, they are under increasing pressure from marine industries, habitat degradation and prey depletion.”

Ms Elsdon said her surveys revealed that the Western Australian community places significant value on whales and their conservation. She emphasized this value should be considered in a more holistic approach to managing natural assets, such as pygmy blue whales.

“These marine giants hold immense environmental value through the ecosystem services they provide us and they possess incredible socio-cultural and economic significance.”

“Whales are celebrated in many cultures and societies around the world, and they play a crucial role in maintaining marine ecosystem balance,” Ms Elsdon said.

She told students the ‘blue whale poo’ provided vital nutrients for phytoplankton to grow, which in turn produced about half the world’s oxygen.

Brodie Elsdon is based at Curtin University’s Centre for Marine Science and Technology (CMST).

She completed a marine and environmental science degree at Murdoch University and is co-founder of the Marine Industry Mentoring Network.

You can see the presentation, which includes recordings of different whale species here.

World first as marine mammal experts migrate to Perth for international conference

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Have you ever wondered what a whale thinks, sought to understand a sea lion, pondered a porpoise, or had dolphins dive through your dreamtime? Do you want to know how our finned friends are faring in a changing sea?

For the first time in the international Society for Marine Mammalogy’s 50+ year history, the world’s marine mammal experts will convene in Australia to tackle these issues and more.

Perth will play host, with over 1,300 attendees from 80 nations gathering to discuss the latest innovations and research from around our blue planet.

The conference theme is “Culture and Conservation: Fishing for Change”, shining a light on two key areas; the interplay between marine mammal and human cultures and conservation, and marine mammal interactions with fishing gear, the biggest threat to extinction they face.

“We are thrilled to bring this meeting to Perth, where we’ll workshop how best to blend western science with Traditional Ecological Knowledge, and quantify the winners and losers in the face of human activity in our rivers and seas”, said Dr Krista Nicholson, of the Local Organising Committee.

Scientists will also present findings from the WAMSI Westport Marine Science Program, including on the hearing, movement, and dive behaviour of Australian sea lions, and dolphin whistles in Cockburn Sound.

WAMSI Westport Marine Science Program Theme Leader, Dr Delphine Chabanne, said the conference provided a wonderful opportunity to share some of the research coming out of Cockburn Sound with an international audience.

“The exchange of ideas and experiences at this conference will not only enhance our understanding of marine mammals, but also inspire innovative solutions to the challenges they face in a rapidly changing world,” Dr Delphine Chabanne.

The 25th Biennial Conference on the Biology of Marine Mammals will take place at the Perth Convention and Exhibition Centre from the 11-15 the November 2024.

 

Conference Art by Sarah Humphries

 

 

The varied life of coral reefs: from warm and tropical to arctic depths

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The popular image of coral reefs is colourful life forms, in clear, tropical water. But marine scientist Dr Shannon Dee said some exist in chilly Arctic seas and others thrive in warm, turbid water where there is limited visibility. Finding out more about the many types of coral reefs could improve understanding of reef vulnerabilities and resilience under climate change.

Dr Dee, from Edith Cowan University, gave her presentation ‘Characteristics of coral communities’ as part of WAMSI’s Thinking Blue school outreach program.

The scientist, whose career has included working on a bull shark aid project in Fiji, a tourist vessel in Queensland and with an environmental consultancy, said the ‘Hollywood’ image of coral reefs only represented one element of what were varied ecosystems.

“Coral reefs are architectural and biological masterpieces,” Dr Dee said.

“Corals, which are animals, are critical for biodiversity, they are a source of food and medicine around the world, and coral reefs help with flood protection in low lying coastal areas.”

Dr Dee has undertaken most of her research on turbid reefs. Exmouth Gulf, in Western Australia, was one example of a turbid reef site and an area where fine sediment gets resuspended or flushed on to the reef by tides.

Other coral systems include Arctic and mesophotic (low light) reefs, such as the 350 metre deep Røst Reef in Norway and temperate reefs including those off Perth and WA’s south coast.

Dr Dee said one of the biggest threats to corals globally was from climate change along with disease, pollution, cyclones and the crown of thorns starfish.

“Corals will be stressed when waters rise above their thermal limits. They then start expelling zooxanthellae, the symbiotic photosynthetic algae within them, which then makes the coral turn white.”

Coral polyps are clear but algae within them gives them their colour.

“At this stage the corals are alive but starving, as the algae aids in coral digestion and nutrient take up”

“If this continues the coral will die.”

“Even if corals survive a bleaching event, the skeleton is more fragile, and the coral may be more susceptible to bleaching in the future.”

“Branching corals can be more susceptible to bleaching.”

Dr Dee said turbid reefs were usually covered in slow growing corals which were generally more stress tolerant.

“Some may be more resilient in the future.”

Dr Dee said there were some simple ways everyone could help protect corals: Don’t touch or step on them, use sunscreen that doesn’t contain ingredients that harm corals and eat seafood that is sustainably caught.

Dr Shannon Dee’s presentation: Characteristics of coral communities is available to view on WAMSI’s YouTube channel.