FIU researchers investigate why volcanoes are shark hotspots

Ceylin Arias/Staff Writer

Prior to being asked by the Discovery Channel to work on researching the link between sharks and volcanoes for this year’s Shark Week, an FIU research team was already assessing shark habitats in coral reefs around the world, according to officials.

Dr. Mike Heithaus, marine scientist and dean of the College of Arts, Sciences & Education, said his team was focusing on trying to understand the importance of sharks in ecosystems, the consequences that would transpire if they became extinct and finding ways to conserve them.

“Part of that was we’ve been working with an international group called Global FinPrint that includes other researchers at FIU like Dr. Demian Chapman [who is a molecular ecologist and associate professor at the School of Environment, Arts and Society],” Heithaus said.

According to the group’s’ website, it is the “world’s largest reef shark and ray survey.” Among what they do as a whole includes understanding how these species affect ecosystems near extinction and establish conservation efforts.

Chapman, lead principal investigator, and Heithaus, co-lead principal investigator, along with Dr. Colin Simpfendorfer from James Cook University, Dr. Michelle Heupel and Dr. Aaron MacNeil from the Australian Institute of Marine Science, and Dr. Euan Harvey from Curtin University, have worked on the Global FinPrint survey for two years and have one more year to go.

Since they began, the team was interested in surveying and assessing where sharks are in trouble, where they are doing well and how the research team could prevent them from dying out, according to Heithaus.

It was during one of their research trips to an island near a coral reef, Heithaus said, that they were asked if they were interested in looking into a particular topic for Shark Week–uncovering why volcanoes became hotspots for sharks.

“For us, it was a really exciting opportunity to advance some of the core research we were doing and also highlighting that in a very exciting way for the public,” Heithaus said. “We were able to go out and do more of our work but then also, as you saw in the show, we were able to work in what other researchers are doing.”

University members from the Heithaus Lab partook in this research including Heithaus, Dr. Jeremy Kiszka, a post-doctoral researcher; Kirk Gastrich, a research analyst and Naomi Frances Farabaugh, a biology Ph.D. candidate.

They discovered that the most important reason sharks are attracted to volcanic islands is because they can create habitats.

“If we didn’t have these volcanic features but we had an open ocean, we’d have a few species of sharks out there but not a whole ton of them, but by creating new land that brings nutrients, concentrates lots of food that brings a lot of different sharks and by having that shallow water, it creates spaces where other species that are kind of small can hide from bigger sharks,” Heithaus said.

Farabaugh, who specifically studied the relative diversity of sharks and their behavior such as predator-prey relationships and how sharks have structure-forward communities, said that having healthy oceans and reefs is of economic and ecological importance.

“The ocean is approximately 99 percent of the living space on Earth that support about half of the world’s species. 44 percent of the human population live close to areas and a lot of these population the ocean itself is a very important source for food while a great portion of their oxygen is produced by these plants and as a result, the ocean’s health is important to people everywhere,” Farabaugh said.

Overfishing, depletion of sources and climate change are all ways humans impact the ocean’s habitats. For sharks, specifically 100,000,000 of them are taken from the ocean every year, according to Farabaugh.

Sharks can move in and out of body of waters based on what kind of temperature they want to be in, according to Heithaus and Farabaugh, making it possible for them to behaviorally handle the heat and use that to help them in certain kinds of situations.  

To test the movement among sharks and capture the different types of sharks that roamed, dated remote underwater video was used.

“Even though it hasn’t really been studied around volcanoes, work has been done in other places that has shown that sharks will move between cold and warm water based on rather they are resting, digesting, hunting on prey, etc,” Heithaus said.

Factors studied in this research included temperature of water across a bigger array of space, and the shark’s movement in these temperatures through tags and sensors that monitored their feedings. By conducting scientific experimentations in their lab, researchers were also able to modify temperature of water and measure how much oxygen sharks were consuming. Doing so, they were able to determine how high sharks’ metabolic rate were and how their digestion changed by looking at how quickly their food went into their gut, according to Heithaus.

Their primary research is far from being over, however. Heithaus says that there will be follow ups and additional questions to answer and in terms of the relationship between sharks and volcanoes.

“There’s plenty of things we need to know like how are sharks using magnetic field to navigate to and from islands or using magnetic fields of the Earth to migrate, and how they get used to temperature differences in their environments,”Heithaus said.

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