Tahoe’s invasive aquatic animals under a microscope

Andrea Schreier, an adjunct associate professor at UC Davis and director of the Genomic Variation Lab at the university, goes in the field for research. (Image: Provided)

DNA isn’t just a human trait associated with health-family issues or solving crimes. Scientists are also using it to better understand animals. They call it eDNA for environmental DNA.

“We can collect it from water or soil. It can come in different forms, so, skin cells and hair from humans, but when you think about fish or other wildlife, their mucous, feces or urine or gametes all have DNA,” explained Andrea Schreier during a recent talk hosted by the Tahoe Environmental Research Center.

Schreier is an adjunct associate professor at UC Davis and director of the Genomic Variation Lab at the university.

“We can learn what species are present at that location where you are sampling. We can do that because each species has unique DNA sequences that are not shared with any other species. We call these DNA barcodes,” Schreier said.

(DNA stands for deoxyribonucleic acid.)

She calls eDNA “exciting new technology.”

“You could take a sample at a location and ask what species live here? Do communities change over time in space? So you could sample in one location at different seasons of the year to see if different species are present at different times or you could sample say along the length of a stream to see if the organisms at different points in the stream are different or if they’re the same,” Schreier said in explaining what answers could be forthcoming. “What is a species eating? So you can collect poop samples from the environment or swab parts of an animal’s body to see what they have been eating. Has an invasive species entered an area?”

Schreier points to how eDNA collection is not invasive and isn’t stressful compared to when samples are taken after animals are trapped. This newer method can be more reliable than trail cameras, while at the same time costing less money. She admits it comes with flaws. Scat from a predator reveals another animal’s presence, but it doesn’t mean the prey was ever actually where the feces was located.

Researchers are also extracting eDNA through footprints. Spider webs have been used to discover critters in the area besides the arachnids.

In murky water where it’s impossible to see what all is living below the surface eDNA techniques can be revealing.

South Lake Tahoe native Grace Rosburg Francot is leading an eDNA study at Lake Tahoe. (Image: Provided)

Grace Rosburg Francot, who was born and raised in South Lake Tahoe, is a doctorate student of Schreier’s doing a fellowship at TERC. Francot and others are trying to determine the best ways to sample eDNA of the various invasive species at Lake Tahoe. This includes plants, fish, invertebrates and amphibians.

Francot was not at the talk because she just became a mom.

Lake Tahoe no longer mixes every year, which means some eDNA can be trapped at the bottom of this 1,645-foot deep body of water.

“So, we want to know if we take a water sample from the surface, can we detect things that live in deeper water or do we have to grab a sample of the deeper water to detect some invasive species that live down there?” Schreier said.

The study’s focus area will be marinas and boat launches because that is usually where invasive species are introduced.

On TERC’s boat Francot will be able to take samples mid-lake and deeper with a specialized apparatus. Sediment samples may have a story to tell as well.

Once the eDNA is extracted a PCR, or polymerase chain reaction, is used that can give a “snapshot of all of the species in an area.”

This process will also be able to detect if there are species in the lake previously unknown to scientists.

Note: A version of this story first appeared in the Tahoe Mountain News.