Humans have touched nearly every part of this planet, and the effects are being felt by other species. The human impact on oceans is something some marine mammals are having a hard time dealing with, new research has shown. As marine mammals evolved, they lost a protein that mammals living on land use as a defense against neurotoxins. That has made some ocean dwellers susceptible to the neurotoxic effect of a common synthetic pesticide. The researchers, reporting in Science, call for us to keep a closer watch over waterways so we can truly understand how pesticides and agricultural chemicals are disrupting the health of whales, seals, dolphins, and other oceanic mammals. Knowing more about this protein can also shed light on human biology.
"We need to determine if marine mammals are, indeed, at an elevated risk of serious neurological damage from these pesticides because they biologically lack the ability to break them down, or if they've somehow adapted to avoid such damage in an as-yet-undiscovered way," explained senior author Nathan L. Clark, Ph.D., an associate professor in Pitt's Department of Computational and Systems Biology, and the Pittsburgh Center for Evolutionary Biology and Medicine. "Either way, this is the kind of serendipitous finding that results from curiosity-driven scientific research. It is helping us to understand what our genes are doing and the impact the environment can have on them."
It’s been established that as marine creatures evolved they lost some genes, causing a change in some bodily functions, such as smelling or tasting. Clark worked with his postdoctoral researcher Wynn K. Meyer, the lead author of this study, to find more genes that are retained by land-dwellers and lost from mammals of the sea.
Paraoxonase 1 (PON1) is a gene identified in their study, matching a pattern that indicated its function was kept by animals on land, and lost from ocean animals. The PON1 gene encodes for a protein that functions to reduce cellular damage caused by oxygen atoms that are unstable; it also protects against organophosphates. Those chemicals work to disrupt neurological function; insects lack PON1 and are killed by the substance.
Colleagues from the U.S. Geological Survey's Wetland and Aquatic Research Center were able to get marine mammal blood samples from all over the world. They worked with Clark’s team to see how organophosphates impacted these blood samples.
The scientists observed that the pesticide doesn’t break down as it would in land mammals, leaving the marine mammals poisoned by the organophosphates. The team wanted to learn how this important gene was jettisoned.
"The big question is, why did they lose function at PON1 in the first place?" queried Meyer. "It's hard to tell whether it was no longer necessary or whether it was preventing them from adapting to a marine environment. We know that ancient marine environments didn't have organophosphate pesticides, so we think the loss might instead be related to PON1's role in responding to the extreme oxidative stress generated by long periods of diving and rapid resurfacing. If we can figure out why these species don't have functional PON1, we might learn more about the function of PON1 in human health, while also uncovering potential clues to help protect marine mammals most at risk."
The scientists want to pursue this research to determine how run-off from agriculture, specifically organophosphates that drain into manatee habitats in Florida, affects marine mammal physiology. The researchers want to monitor the habitats as run-off is occurring, rather than using old samples. It could tell us a lot about our own future.
"Marine mammals, such as manatees or bottlenose dolphins, are sentinel species - the canary in the coal mine," added Clark. "If you follow their health, it will tell you a lot about potential environmental issues that could eventually affect humans."
Learn more about how environmental pollutants are negatively impacting other mammals from the video.