A new study detailed the increasing concentrations of mercury and selenium in the Grand Canyon's food chain, affecting its wildlife.

According to The Arizona Daily Sun, researchers at the U.S. Geological Survey (USGS) published a study on these findings in the journal Environmental Toxicity and Chemistry. They gathered samples from six spots around the Colorado River, which cuts right through the Grand Canyon.

"Managing exposure risks in the Grand Canyon will be a challenge, because sources and transport mechanisms of mercury and selenium extend far beyond Grand Canyon boundaries," study lead author David Walters, USGS research ecologist, said in a news release.

They found the levels of mercury and selenium regularly exceeded recommended levels and has been affecting the region's food webs and how the wildlife is reproducing, growing their family trees, and seeing their youth survive to adulthood.

"The good news is that concentrations of mercury in rainbow trout were very low in the popular Glen Canyon sport fishery, and all of the large rainbow trout analyzed from the Grand Canyon were also well below the risk thresholds for humans," study co-author Ted Kennedy, a researchers at the USGS, said in the release. "We also found some surprising patterns of mercury in rainbow trout in the Grand Canyon. Biomagnification usually leads to large fish having higher concentrations of mercury than small fish.

"But we found the opposite pattern, where small, 3-inch rainbow trout in the Grand Canyon had higher concentrations than the larger rainbow trout that anglers target. This inverted pattern likely has something to do with the novel food web structure that has developed in Grand Canyon."