CORVALLIS, Ore. — Scientists from the U.S. Geological Survey and Washington State University have discovered that endangered Chinook salmon can be detected accurately from DNA they release into the environment. The results are part of a special issue of the journal Biological Conservation on use of environmental DNA to inform conservation and management of aquatic species.
The special issue contains eleven papers that move the detection of aquatic species using eDNA from concept to practice and include a thorough examination of the potential benefits, limitations and biases of applying eDNA methods to research and monitoring of animals.
“The papers in this special edition demonstrate that eDNA techniques are beginning to realize their potential contribution to the field of conservation biology worldwide,” said Caren Goldberg, Assistant Professor at Washington State University and lead editor of the special issue.
DNA, or deoxyribonucleic acid, is the hereditary material that contains the biological instructions to build and maintain all life forms; eDNA is the DNA that animals release into the environment through normal biological processes from sources such as feces, mucous, skin, hair, and carcasses. Research and monitoring of rare, endangered, and invasive species can be done by analyzing eDNA in water samples.
A paper included in the special issue by USGS ecologists Matthew Laramie and David Pilliod, and Goldberg, looked at the potential for eDNA analysis to improve detection of Chinook salmon in the Upper Columbia River in Washington, USA and British Columbia, Canada. This is the first time eDNA methods have been used to monitor North American salmon populations. The successful project also picked up evidence of Chinook in areas where they have not been previously observed.
“The results from this study indicate that eDNA detection methods are an effective way to determine the distribution of Chinook across a large area and can potentially be used to document the arrival of migratory species, like Pacific salmon, or colonization of streams following habitat restoration or reintroduction efforts,” said Laramie.
Spring Chinook of the Upper Columbia River are among the most imperiled North American salmon and are currently listed as endangered under the Endangered Species Act. Laramie has been working with the Confederated Tribes of the Colville Reservation Fisheries Program in the use of eDNA to document the success of reintroduction of Spring Chinook into the Okanogan Basin of the Upper Columbia River.
The papers of the special issue focus on techniques for analyzing eDNA samples, eDNA production and degradation in the environment and the laboratory, and practical applications of eDNA techniques in detecting and managing endangered fish and amphibians.
The co-editors, Goldberg, Pilliod, and WSU researcher Katherine Strickler, open the special issue with an overview on the state of eDNA science, a field developed from the studies of micro-organisms in environmental samples and DNA collected from ancient specimens such as mummified tissues or preserved plant remains.
“Incorporating eDNA methods into survey and monitoring programs will take time, but dedicated professionals around the world are rapidly advancing these methods closer to this goal,” said Goldberg.
Strickler, Goldberg, and WSU Assistant Professor Alexander Fremier authored a paper which quantified the effects of ultraviolet radiation, temperature, and pH on eDNA degradation in aquatic systems. Using eDNA from bullfrog tadpoles, the scientists determined that DNA broke down faster in warmer temperatures and higher levels of Ultraviolet-B light.
“We need to better understand how long DNA can be detected in water under different conditions. Our work will help improve sampling strategies for eDNA monitoring of sensitive and invasive species,” said Strickler.
“These papers lead the way in advancing eDNA sample collection, processing, analysis, and interpretation,” said Pilliod, “eDNA methods have great promise for detecting aquatic species of concern and may be particularly useful when animals occur in low numbers or when there are regulatory restrictions on the use of more invasive survey techniques.”
For the first time, scientists have developed a detailed explanation of how white-nose syndrome (WNS) is killing millions of bats in North America, according to a new study by the U.S. Geological Survey and the University of Wisconsin. The scientists created a model for how the disease progresses from initial infection to death in bats during hibernation.
“This model is exciting for us, because we now have a framework for understanding how the disease functions within a bat,” said University of Wisconsin and USGS National Wildlife Health Center scientist Michelle Verant, the lead author of the study. “The mechanisms detailed in this model will be critical for properly timed and effective disease mitigation strategies.”
Scientists hypothesized that WNS, caused by the fungus Pseudogymnoascus destructans, makes bats die by increasing the amount of energy they use during winter hibernation. Bats must carefully ration their energy supply during this time to survive without eating until spring. If they use up their limited energy reserves too quickly, they can die.
The USGS tested the energy depletion hypothesis by measuring the amounts of energy used by infected and healthy bats hibernating under similar conditions. They found that bats with WNS used twice as much energy as healthy bats during hibernation and had potentially life-threatening physiologic imbalances that could inhibit normal body functions.
Scientists also found that these effects started before there was severe damage to the wings of the bats and before the disease caused increased activity levels in the hibernating bats.
“Clinical signs are not the start of the disease — they likely reflect more advanced disease stages,” Verant said. “This finding is important because much of our attention previously was directed toward what we now know to be bats in later stages of the disease, when we observe visible fungal infections and behavioral changes.”
Key findings of the study include:
- Bats infected with P. destructans had higher proportions of lean tissue to fat mass at the end of the experiment compared to the non-infected bats. This finding means that bats with WNS used twice as much fat as healthy control bats over the same hibernation period. The amount of energy they used was also higher than what is expected for normal healthy hibernating little brown bats.
- Bats with mild wing damage had elevated levels of dissolved carbon dioxide in their blood resulting in acidification and pH imbalances throughout their bodies. They also had high potassium levels, which can inhibit normal heart function.
The study, “White-nose syndrome initiates a cascade of physiologic disturbances in the hibernating bat host,” is published in BMC Physiology. Learn more about WNS, ongoing research and actions that are being taken here:
- USGS National Wildlife Health Center, WNS page
- USGS Fort Collins Science Center, WNS page
- University of Wisconsin-Madison