Rise of the Trematodes
As the warming planet continues to cause sea levels to rise, new research suggests rising seas eventually could prove detrimental to human health. John Huntley, an assistant professor of paleobiology in the department of geological sciences at MU, has just published his first paper stemming from research he conducted as a senior visiting fellow of the Institute for Advanced Studies at the University of Bologna, Italy, last summer.
Huntley and colleagues from the University of Bologna and the University of Florida examined core samples taken from the Po River plain in Italy to analyze traces made by parasitic flatworms (trematodes) on the shells of clams and other bivalves. Huntley is studying how those interactions changed through sea-level cycles. He says an interesting finding from previous research projects in Italy and China is that the prevalence of these parasites increased dramatically during sea-level rise. On his most recent trip to Italy, Huntley discovered a connection between sea-level rise and trematode prevalence on a much shorter time scale than previous findings, which documented the changes over thousands of years. His latest research documented this connection on a centennial scale, with pulses of sea-level rise occurring approximately every hundred years, resulting in a corresponding increase in parasitic flatworms.
“What we see in our research is this is happening on a centennial scale—the same could be happening within the time frame of our grandchildren,” Huntley says. “What concerns me is that these environments are going to continue to change in similar and accelerated ways, but we don’t know if the increase in trematode prevalence is due to changes in temperature or nutrient availability or increased habitat area, and there are related parasites that live in freshwater settings.” Huntley says that poses a concern because freshwater habitats are home to the snail hosts of schistisomes, also known as blood flukes, which infect and kill a million people each year globally due to complications from schistosomiasis—the second most prevalent tropical disease in the world behind malaria.
Huntley says his research has found parasitic intrusions linked to sea-level rise in marine settings and now in lagoonal settings, so he believes the same mechanisms may be in play in freshwater settings.
“It could apply to freshwater settings, and as ecosystems on the coasts break down, that’s important because these lagoonal settings are nurseries for a lot of the big fish that come in from the ocean to reproduce and then return to the ocean,” Huntley says. “The health of those ecosystems is important for people who like to eat fish and shellfish, but human disease could change as well.”
Huntley says his National Science Foundation CAREER grant will fund the work of two doctoral students he will supervise this fall, who will continue and expand his research in Italy. The CAREER grant also is funding one of Huntley’s master’s students, who is continuing to conduct research on parasitic traces on shells in China. Huntley says he will use trace element concentrations to serve as proxies for water temperature, nutrient availability, and salinity, and then compare how those proxies line up with the trematode prevalence they have documented. Still, Huntley says it remains a mystery why trematode prevalence increases as sea levels rise, but the consequences could be dramatic.
“We know temperature will continue to increase and water depth will continue to increase, we know humans are flushing all sorts of nutrients into coastal waterways, and we know sea-level rise creates new habitats, so with global change continuing into the future, all of those processes will continue as well,” Huntley says.
As those processes continue into the future, Huntley worries about the impact on marine ecosystems, the food chain, and ultimately, human health and well-being.