Testing the Waters
Could environmental DNA allow scientists to test water for invasive species?
Wildlife Biologist Colleen Kamoroff is seeking a more cost-effective and timely way of determining whether or not an invasive species is present in an aquatic ecosystem. Kamoroff presented her latest research at the Mono Lake Committee on Wednesday, August 23.
Kamoroff told lecture attendees that Yosemite National Park is engaged in a long effort to remove non-native Brown and Brook trout from the 10 percent of high country lakes that are deep enough to not freeze solid during the winter. The fish, which were introduced during the 1800s, are being removed to restore habitat for the native Mountain Yellow-Legged Frog, which is found exclusively in a very small portion of Yosemite’s high lakes.
Kamoroff works for Yosemite National Park, and has participated in many invasive species removal projects in the High Sierra. While doing research for her Masters Degree from the University of Washington, she worked on a crew that removed non-native Brook trout from select high country lakes.
The process of mechanical fish removal is slow, expensive, and labor-intensive. As a graduate student, Kamoroff wondered if there were a better way to determine whether a species is present and alive in a body of water. She eventually began perfecting a method of extracting miscellaneous DNA from a water sample and testing it for the presence of genetic information that matches that of an invasive species or disease. The DNA Kamoroff collects is called eDNA, or environmental DNA, and comes primarily from feces, urine, and pieces of skin deposited by critters, macroscopic and microscopic, in the water column. Kamoroff said it only costs about $50 to process a sample of eDNA. She said the process is relatively inexpensive when compared with other research methods.
To collect the eDNA, Kamoroff filters water from a source she is surveying through a break-bleeding kit. She then removes the filter, which contains particulate matter from the water source, and transports it to a laboratory. In the lab, Kamoroff uses a piece of technology known as a Polymerase Chain Reaction Machine to compare eDNA samples collected from various lakes with DNA from various invasive species believed to be present in those lakes. After a lot of lab work, Kamoroff tested the efficacy of the method in the field by collecting and processing water samples from 30 lakes across Yosemite and Kings Canyon and Sequoia National Parks. She found that eDNA extraction was largely an effective means of detecting the presence of fish. She also determined, following tests in the field, that it is possible to determine whether or not the eDNA collected is from living individuals, as opposed to decaying matter from deceased organisms. This nuance was important in distinguishing between restored lakes, in which no fish were present, versus lakes where restoration was ongoing and there were dead fish present in the water.
