By Shane Balian
On a sunny day in mid-July, a team of wildlife biologists wades through a waist-deep pond and head-high horsetail with nets in hand, searching for boreal toads in Prince William Sound. They are conducting a survey to determine if deadly pathogens, related to major amphibian die-offs across the globe, are infecting local toads and frogs.
On the Copper River Delta and Prince William Sound, amphibians act as one of many interconnected pieces within the ecosystem. According to Deanna Olson, research ecologist with the U.S. Forest Service, they are prey and predator to many species, and due to their central position in food webs, reliance on land and water and permeable skin, they, “can be a harbinger for environmental degradation.”
Amphibians are also the most threatened vertebrates in the world. Habitat destruction including pollution, climate change and disease are the top three contributing factors to their decline, said Olson.
To make matters worse, amphibians have a low “social capital” or ability to garner political and social support for conservation efforts, Olson said. Without support, amphibians are left more vulnerable to dangers like Chytrid Fungus and Ranavirus, which are deadly amphibian pathogens that have spread to every continent where amphibians are found.
“Globally, both pathogens have had strong negative effects, even devastating effects on a large number of species and populations of amphibians across the board,” said U.S. Forest Service wildlife biologist Brandt Meixell.
Since outbreaks around the world overwhelmed amphibian populations a few decades ago, the disease-causing Chytrid Fungus and Ranavirus have become a cause for concern across the United States. Currently, Alaska appears to sit on the northern extent of these pathogens’ ranges with only a few documented occurrences so far.
“It’s important to monitor these pathogens at their current northernmost distribution limit to catch range expansions to new areas as early as possible,” said Dr. Claire Goodfellow, research associate with Oregon State University.
Both Chytrid Fungus and Ranavirus were detected in Prince William Sound and the Copper River Delta in a previous 2017 study. During July of this year, Goodfellow and Meixell replicated the field surveillance to assess the extent of these pathogens today.
Meixell and Goodfellow traveled by boat, skiff and on foot across Prince William Sound and the Copper River Delta to reach locations with reported amphibian activity.
There, they collected water samples for a scientific process known as eDNA, which can detect pathogens in the environment.
This technique is useful for studying cryptic species, like Alaska’s wood frogs and boreal toads. These species are part of the world’s northernmost amphibian populations, and their patchy distribution makes them difficult to study.
However, with eDNA, finding and capturing toads and frogs is not necessary for environmental detection. These studies use molecular methods to detect the presence of genetic material, left by pathogens and amphibians, from environmental samples.
This technique is becoming increasingly common in Alaska due to a lack of available data and constraints on field sampling.
“Chytrid Fungus is in Alaska, but we don’t really know the extent of the geographic distribution or the prevalence,” Meixell said, “nor do we know what pathogenic effects it may have on our amphibians here.”
With a few hundred liters of pond water and time in a lab, Goodfellow’s results will yield detailed information on the occurrence, distribution and identification of the pathogens. They will also be used to fine-tune a longer-scale surveillance and monitoring approach for the Copper River Delta and Prince William Sound.
With so much still unknown about the potential spread in Alaska, surveillance is necessary to create better informed questions and establish a baseline for assessing change in the future.
Ultimately, eDNA is a valuable first step, but more steps need to be taken to turn the data into effective action. Currently, slowing the spread is the most viable way to combat Ranavirus and Chytrid Fungus.
According to Olson, humans have contributed to the spread by moving amphibians across habitats.
If an amphibian is moved to a new habitat, its skin could be carrying a pathogen that other amphibians have not evolved with, leaving them more susceptible.
“That’s one way we think Ranavirus and Chytrid Fungus have recently come onto our radar,” said Olson, “They are hitch-hiking on introduced species or habitat components to new areas.”
Without knowing how prevalent these pathogens are in Alaska, it is imperative to keep the spread to a minimum.
For the time being, surveillance efforts will continue, but no conclusions can be drawn about the future of Alaska’s amphibians.
Although they may be small and elusive creatures that most Cordovans rarely see, amphibians are a piece of the local ecology. They are some of the most vulnerable, fragile animals in the world, and these toads and frogs could benefit from diligent stewardship by the public.
“We always appreciate reports of local toad and frog sightings, especially of those from locations where they are consistently observed,” said Meixell.
If there is noticeable and consistent amphibian activity observed near Cordova or in Prince William Sound, please report it to the Forest Service office at 612 Second St. or contact Meixell at [email protected].
Shane Balian is a student at the University of Oregon pursuing a degree in journalism. He has been working with the U.S. Forest Service in Cordova for the past six months as a media intern, participating in various Forest Service projects around Cordova, the Copper River Delta and Prince William Sound.
