The World of Sharks Podcast

How will climate change impact sharks?

Show notes

For the last episode of the season, we're joined by fish physiologists Dr Jodie Rummer and Carolyn Wheeler to talk about a VERY topical and much-asked-about subject: climate change, and its impact on sharks. Carolyn and Jodie study the effects of climate stressors and other human-driven issues on fish, including sharks and rays, in tropical waters, and we talk about their pretty sobering findings. On the way, we meet Edna, the epaulette shark, visit some picturesque shark nurseries in French Polynesia and learn what it's like to observe coral bleaching in real-time.

Of course, no Whole Tooth episode would be complete without a quick dive into the beautiful waters of our guests' most memorable ocean experiences [6.04 – 9.29]. We meet some prehistoric, six-foot-long fish for Carolyn's, whereas Jodie takes us swimming with tiger sharks in Tahiti.

We start our discussion by breaking down the concept of climate change. Jodie talks us through some terminology, including ocean acidification, deoxygenation and warming [9.41 – 15.17]. We discuss how the changes we're experiencing today are different from natural climate fluctuations, as human activity is causing the rate of these changes to accelerate dramatically [15.24 – 17.11]. Carolyn also adds that an important thing to remember about sharks is that they have long generation times, so although they have survived through climate changes in the past, they will find it harder to cope with the more rapid changes we are seeing now [17.12-17.38].

We take a slight detour to meet Jodie and Carolyn's study species, starting with the fantastic epaulette shark [18.28 – 20.41]. We learn that they are an egg-laying species, only found on the Great Barrier Reef, with some fascinating adaptations that allow them to cope with pretty tricky conditions. One includes being able to live without oxygen for four hours! Because epaulettes are relatively easy to study under lab conditions and can exist right at the edge of what sharks can tolerate, they are known as a 'bio-indicator' – if they're in trouble, it's highly likely other shark species will be too [20.44 – 23.47]. Jodie also tells us about the reef sharks she works with in French Polynesia, specifically newborns and juveniles, and why she has chosen that specific life stage [23.55 – 28.30]. Returning to our main subject, we move on to talk about the impacts of ocean acidification and warming on the species Jodie and Carolyn study [28.43 – 42.07]. Their findings are pretty sobering – at just a few degrees warmer, there are several knock-on effects on shark reproduction and juvenile survival. For example, epaulette shark hatchlings are smaller and were born hungrier, suggesting they are using up essential reserves quicker and hunting for food earlier, making them vulnerable to predation. Equally, adult epaulettes lay less often and lay more empty egg-cases. Similarly, in juvenile and newborn reef sharks, individuals subjected to high temperatures in the lab cannot cope with additional stressors – which is worrying, as life for a baby shark isn't easy under normal conditions.

Jodie also tells us of her experience diving the Great Barrier Reef in 2016 and seeing a coral bleaching event in real-time [42.45-48.08]. We discuss how climate change is knocking on our doorstep – we are seeing its effects now, all over the world. The time to act is now. With that in mind, Carolyn acknowledges that while it can be a depressing and scary thought, we as individuals hold so much power to enact change, and we can use our voice to fight for more robust climate policies [49.00 – 49.30]. We end our episode by talking about the need for hope, outreach, and science communication. Here, we learn about Edna, the epaulette shark, the new icon of the Great Barrier Reef!

About our guests

Carolyn Wheeler

Originally from New York state, Carolyn found her passion for fish biology during her undergraduate honours research at the University of New England. There she conducted physiological research on sturgeon and a variety of species of sharks and skates. Carolyn is currently a co-tutelle PhD candidate between the School for the Environment at the University of Massachusetts Boston and the ARC Centre of Excellence for Coral Reef Studies at James Cook University jointly supervised by Drs. John Mandelman and Jodie Rummer. Carolyn spent the first half of her PhD working with the Anderson Cabot Center for Ocean Life at the New England Aquarium in Boston studying the effects of temperature on the development and physiological performance of epaulette shark embryos and hatchlings. She was awarded a graduate fellowship through the American Australian Association and a small grant from SOSF to continue her research at JCU assessing the impacts of thermal stress on reproduction in adult epaulette sharks.

Instagram: @wheel_house23. Twitter: @Wheel_House23


Dr Jodie Rummer

Dr. Rummer is currently an Associate Professor at the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies at James Cook University. Over the course of her career, Jodie has researched fish buoyancy, exercise, and is a leading authority on the evolution of oxygen transport and how performance is maintained during stress. Today, Jodie’s team continues to combine ecology, evolution, and physiology to address issues important to conservation, such as the effects of climate change and other human-caused problems on coral reef fishes, sharks, and rays and the potential for adaptation.

Dr. Rummer has an array of accolades and has been awarded for her research as well as her capacity to communicate and connect her findings to broad and diverse audiences. In 2015, she received the highly prestigious UNESCO-L’Oréal Women in Science Fellowship for Australia and New Zealand and gave a TEDx talk, “Athletes of the Great Barrier Reef”.In 2016, Jodie was named one of Australia’s top 5 scientists under the age of 40 by the Australian Broadcasting Corporation (ABC) and Radio National (RN) and was awarded the Society for Experimental Biology’s President’s Medal. Jodie has published 62 peer-reviewed journal articles and 6 book chapters and has presented her work at more than 100 professional conferences and public events. She also uses social media to communicate scientific findings, highlight fellow scientists’ success stories and achievements, and to advocate for issues related to women in science, gender balance, and diversity in STEM.

Twitter: @physiologyfish. Instagram: @rummerjodie. Website: | Watch Jodie’s TED Talk here

Photo © Donna Larcom
Photo © Donna Larcom