Whale sharks (Rhincodon typus) eat plankton at the surface.
Ningaloo Reef, Australia it is known for its enchanting turquoise waters and variety of marine life. Home to more than 500 different species of fish, the elusive (and rather massive) whale shark is arguably the face of the entire area as they congregate here annually between April and August each year. It is such an iconic visitor, it is the emblem of Western Australia’s marine life and is protected in Australian waters by both state and federal law! As the largest fish in the world, Rhincodon typus attracts thousands of visitors annually, contributing significantly to the local economy.
But some whale sharks at Ningaloo Reef have developed unusual white patches on their skin. Dr. Mark Mikanprincipal investigator from University of Western AustraliaThe Ocean Institute notes that these patches have raised concerns as they can signal skin conditions and potentially indicate poor health. For a huge animal that lives mostly unseen in open ocean waters, even subtle changes in skin appearance can be a valuable indicator of underlying health problems.
Whale sharks are filter feeders, meaning they eat by sifting small fish, shrimp, and other organisms from the water. this feeding method makes them extremely sensitive to the pollutants we have dumped into the ocean. These pollutants include plastics, as well as organic chemicals such as flame retardants, which can be toxic. As whale sharks swim through polluted waters, they may ingest small particles and toxins, exposing them to the adverse effects of these pollutants over time. Researchers from UWA and Flinders University until he examines the condition of the whale sharks and looks for signs of pollution-related health problems. The project is co-financed by Jock Clough Marine Foundation.
Shale sharks swimming at the surface of the ocean in Western Australia off Ningaloo Reef in April … [+]
“This is probably the most detailed look at whale shark health that anyone has ever attempted,” Meekan said. To get a clearer picture of how pollution affects whale sharks, the researchers collected skin samples and tissue biopsies from the whale sharks and used underwater ultrasound scanners to measure body condition. While ultrasound scans provide information about the whale sharks’ physical condition, skin and tissue samples offer a closer look at what may be going on at the cellular and molecular level. “We took a multidisciplinary approach to measuring the condition of free-swimming species in the wild, which is no small task when you’re dealing with an animal averaging six to seven [meters] body length and swim as fast as you can to collect samples’. According to Meekan, this approach allows for in-depth observation without having to remove the animals from their natural environment. He noted that, fortunately, the whale sharks seemed to tolerate the presence of scientists and the sampling procedures without much fuss, seeing the researchers simply as part of the crowd of fish that often follow them.
Dr. Michael Doane from Flinders University will lead the analysis of the microbiome samples collected, focusing on genomic and biomolecular markers in the shark’s microbial community. “Genomic and biomolecular markers in the whale shark’s microbial community will show whether the white patches are a sign of disease, and if so, provide insight into the cause,” explained Doane. This analysis is necessary because these microbes can provide an early warning system for changes in environmental health, similar to how changes in gut bacteria can indicate human health problems.
Dr. Charlotte BirkmanisDirector of the Jock Clough Marine Foundation and Adjunct Research Fellow at The University of Western Australia Oceans Institute, points out that whale shark health is more than a matter of academic interest. “We need to improve our understanding of the condition and health of our marine ecosystem, including iconic species like sharks,” Birkmanis said. “The Ningaloo Reef is such a unique environment and it’s on our doorstep, so by funding this type of research we can ensure that the animals that inhabit this World Heritage site are here for the long term.” Whale shark tourism also contributes significantly to the economy of the Exmouth areaso this project will help ensure a unique local economy dependent on ecotourism.
Whale sharks watched by tourists off the coast on April 22, 2012 at Ningaloo Reef, West … [+]
As the researchers continue their analysis, they hope any health insights from this work will guide future conservation strategies, both for whale sharks and other filter-feeding species that face similar risks.
