Apr 28, 2019
Large numbers of dugongs, sea snakes and other marine animals disappeared from the UNESCO World Heritage Site Shark Bay, Western Australia, after a heat wave devastated seagrass meadows, according to recently released research. The reasons for the population losses, however, differed among species, according to Rob Nowicki, an FIU alumnus and postdoctoral research fellow at Mote Marine Laboratory. "Essentially we found that, for most species, when you lose the seagrass resources you lose a lot of the animals, but the nature of how they get lost - for instance, whether they starve or leave - and the degree to which you lose them differs by species," Nowicki said. "Dugongs, which have to eat seagrasses, and sea snakes, which use it for foraging and refuge, were really hard hit." The findings offer insight into how some vital ecosystems may change in a warming climate. Nowicki was a Ph.D. student during the 2011 heatwave studying under biological sciences professor Mike Heithaus, now dean of the FIU College of Arts, Sciences, and Education. For more than two decades, Heithaus has led the most detailed study of the ecological role of sharks in Shark Bay collecting extensive data that provided the perfect baseline to assess the impacts of the extreme climate event. "We started the Shark Bay Project in 1997 to understand how pristine ecosystems work and how important big animals are to healthy oceans," Heithaus said. "Twenty-two years later, we are seeing what happens to this once-pristine ecosystem faced with an extreme climate event. Our oceans are under stress from what seems like from all angles and we're finding these heatwaves may push systems into degraded states they struggle to recover from." Previously published research by the team, which also included FIU research specialist Kirk Gastrich, showed Shark Bay's dominant seagrass species, Amphibolis Antarctica, declined and failed to rebound significantly in the few years following the heatwave. In some spots, it was replaced by smaller, tropical Halodule uninervis seagrass - somewhat like replacing a forested canopy with a mowed lawn. The Amphibolis seagrass creates habitat and food, slows down water currents and clarifies the water. With the loss of that particular species of seagrass, those functions were also lost. The team, which also included partners from Deakin University in Australia, Nova Southeastern University in Florida, and the University of Washington, analyzed shark data from some 27,052 hours of catch-and-release fishing across 414 days between 1998 and 2015, including 95 days after the seagrass die-offs. They also analyzed data from 3,375 transect surveys, including 714 after the seagrass die-off, which documented 22,371 animals of multiple species.
Category severe weather
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