Four decades of ocean records spark concern

James Cook University’s Dr Scott Heron co-authored the study, led by Cornell University in the US and published today in the prestigious journal Proceedings of the Royal Society B.

Dr Heron said the researchers examined oceanic infectious disease reports from 1970 to 2013.

“We looked at the records of corals, urchins, seals, lobster, fish, molluscs, sharks and whales, seagrass and turtles,” he said.

Dr Heron said corals and urchins have seen an increase in disease reports over the past four decades.

“For corals, the increase was correlated with rising ocean temperature associated with global warming,” he said.

Dr Heron said for other organisms, such as sharks, rays and other types of fish, there has been a decrease in disease reports.

“This is not necessarily good news though, as it’s likely related to dramatic, human-induced population declines in these organisms such as those caused by overfishing.”

Lead author, Cornell University’s Dr Allison Tracy, said disease increases and decreases are both bad news as changes in disease levels warned something was changing in the oceans.

“All of the changes in the ocean are from anthropogenic causes – from what we’ve been able to measure – and they are manifesting in long-term increases and decreases in sickness,” she said.

Senior author Professor Drew Harvell from Cornell said the paper provides a solid baseline for measuring disease from 1970 to 2013.

“But these years precede the big heat waves we’ve seen in 2015, 2016 and 2019 that are expected to have triggered more outbreaks. Those data will take a few more years to be published,” she said.

Dr Heron said the period since 2000 has been one of intense anthropogenically-driven change.

“We’re continuing to learn about the impacts humans are having on nature.  Reduced disease in fish might at first seem a good thing, but if the reason for that is overfishing then it really isn’t good at all.  And where global warming is increasing disease, like in corals, we’re at risk of even greater ecological impacts than we might have otherwise been expecting.”

Dr Heron said there is an urgent need to act on the causes of human-induced climate change.

Researchers: Allison M. Tracy, Madeline Pielmeier, Reyn M. Yoshioka and C. Drew Harvell of Cornell University’ and Scott F. Heron of James Cook University.

The research was funded by a US National Science Foundation Ecology and Evolution of Marine Infectious Diseases grant.