Nav: Home

Sea turtles struggle years after unexplained die-off

April 04, 2019

COLUMBUS, Ohio - New research is detailing how environmental stressors, including heavy metals, brought on by human activity are harming coastal green sea turtle populations - work that researchers hope will inform conservation efforts going forward.

In a study that appears in the journal Science of the Total Environment, a multidisciplinary group of researchers set about evaluating turtle health, water quality and other factors in the aftermath of a catastrophic mass death of green turtles in Australia.

"We found evidence of heavy metals - particularly cobalt - in sea turtle populations where we also saw signs of illness," said lead author Mark Flint, program head of Zoo and Wildlife Conservation Medicine and Ecosystem Health in the College of Veterinary Medicine at The Ohio State University.

"Though we can't be sure what caused this, there were cyclones and major flooding in this part of Australia two years prior to the start of our study, and that could have drawn out sediment rich in heavy metals that had been lying in rivers and streams benign for the past 50 years," Flint said.

Green turtles, Chelonia mydas, are an endangered species, and one of the largest sea turtles, weighing in at as much as 400 pounds in adulthood. Green turtles are named for the greenish color of their fat, not their shells, and are found mainly in tropical and subtropical waters, according to the World Wide Fund for Nature-Australia (WWF). The WWF provided funding for this research, and led the Rivers to Reef to Turtles project under which it was conducted.

Large populations live, feed and nest on Australia's Great Barrier Reef, favoring the bays and protected shores near the coast and around islands.

The Rivers to Reef to Turtles project, which ran from 2014 to 2017, examined health of green turtles at two northern Queensland bays - Cleveland and Upstart - known to be impacted by urban and agricultural human activities and at a third remote "pristine" area, the Howick Group of islands.

Following up on a high number of turtle deaths in 2012 and 2013 that conservationists were attributing to a "whole kit and caboodle of reasons" including runoff from agriculture, industrial toxins and climate change, the team conducted physical exams and tested the turtles' blood over time, looking for signs of contaminants and illness, Flint said.

They also counted barnacles on the turtles. Flint's previous work has shown that high barnacle counts on turtles' undersides correspond to poor health. The theory behind that? When healthy and feeding normally, a turtle's trips to the sea floor for seagrass meals effectively scrape away barnacles. When the green turtles aren't eating well, the barnacles build up.

"An unhealthy turtle often has trapped air in its shell and is buoyant, meaning it can't dive down for food. It's almost like a balloon," Flint said. "Also, a turtle that can't dive sits on the surface of the water where algae and barnacles can grow better."

In cases where the researchers found dead turtles, they conducted in-depth necropsies.

The research team found elevated levels of an enzyme called creatinine kinase in turtles at Cleveland Bay. That enzyme typically increases after muscle injury or illness. And they found elevated white cell counts in turtles at Upstart Bay. White cells proliferate when an animal is fighting infection.

One in five of the juveniles examined at Cleveland Bay had high barnacle levels (16 or more) and one in 10 of the young turtles at Upstart Bay had excessive barnacle growth. This level of barnacle growth was not seen in any of the turtles at the "pristine" control site.

By the end of the study, the researchers saw some evidence that the population in Cleveland Bay was returning to normal, but the problem still remains for turtles in Upstart Bay.

This multidisciplinary approach is the first effort to look with this depth at this population of turtles and the potential links between environmental toxins and their well-being, Flint said.

The researchers suspect that the unhealthy measures seen in the turtles that live in areas affected by urbanization, farming and industry are connected to contaminants in their ecosystem. In particular, the study team found evidence of heavy metals, primarily cobalt, in the turtles' blood.

Green turtles migrate long distances between feeding grounds and from the beaches on which they hatched. The reptiles are threatened by overharvesting of their eggs, hunting of adults, being caught in fishing gear and loss of nesting beach sites, according to the WWF.

The green turtle is the only "vegetarian" sea turtle, eating mostly seagrass and algae, which relates to its ecological importance. When green turtles graze on seagrass beds, that vegetation remains productive - something the WWF compares to mowing the lawn. The turtles also recycle nutrients they digest, making them available to other animals and plants, which ultimately is important for the survival of invertebrates and fish, some of which people eat.

The monitoring of sea turtle health also is important because with their long lifespans and tendency to stay in one place, they can potentially serve as proxies for the broader environment, Flint said. The trouble is, their physical responses to environmental assaults and disease are slow-moving, complicating conservationists' ability to draw connections between the environment and sickness and death.

This research gives conservationists and marine biologists a baseline understanding of sea turtle health and response to environmental stressors, he said, which will better enable them to assess turtle health after an insult and over time. It will also provide tools to help decision makers develop environmental mitigation strategies, Flint said.
Other researchers who worked on the study were Ian Bell of the Queensland Department of Environment and Heritage Protection, Anne-Fleur Brand of Utrecht University and the University of Queensland and Christine Madden Hof of the WWF.

CONTACT: Mark Flint, 614-292-6166;

Written by Misti Crane, 614-292-5220;

Ohio State University

Related Climate Change Articles:

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.
Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.
Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.
Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.
A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.
Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.
Could climate change cause infertility?
A number of plant and animal species could find it increasingly difficult to reproduce if climate change worsens and global temperatures become more extreme -- a stark warning highlighted by new scientific research.
Predicting climate change
Thomas Crowther, ETH Zurich identifies long-disappeared forests available for restoration across the world.
More Climate Change News and Climate Change Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at