Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Human Pollution Reaches Underground Cave Ecosystems, New Study Shows

Human Pollution Reaches Underground Cave Ecosystems, New Study Shows
A cave at the Mediterranean Sea in Sicily. ClaraNila / iStock / Getty Images Plus

Not even underground ecosystems are safe from human pollution.

New research published in PLoS ONE May 6 examined how water runoff from the surface impacted the communities of microbes in the Monte Conca cave system in Sicily. The answer? Quite a lot. Potentially human-introduced bacteria made up less than 4 percent of the microbial community during the dry season, but shot up to almost 90 percent during the wet season, after heavy rains.

"Anthropogenic microbial contaminants originating from outside of the cave environment can replace endemic cave communities," the researchers concluded.

The Monte Conca cave system is one of many caves formed by a process called sulfuric acid speleogenesis, by which groundwater containing sulfur dissolves limestone. Communities of microbes within the caves contribute to this process, the researchers explained.

But the study, carried out by a team of microbiologists and geoscientists at the University of South Florida (USF), indicates that bacteria from urban and agricultural areas can enter these unique communities via runoff from surface water, the university press release explained. This happens despite the fact that the Monte Conca system sits below a nature preserve.

To assess the impact of surface-level bacteria on the cave's microbial communities, the researchers compared their composition between the dry and wet seasons.

During the dry season, more than 90 percent of the microbes were sulfur oxidizers. These are bacteria uniquely adapted to use both oxygen from the cave and sulfur from its spring pool. But during the wet season, when large amounts of rainwater enter the cave, the composition radically changed. Escherichia and Lysinibacillus bacteria jumped from 3.7 percent of the microbial community to 89.5 percent. These are fecal and soil bacteria researchers identified as influenced by human activity, including the fecal bacteria Escherichia coli, or E. coli.

Researchers also found evidence of a transition period between the wet and dry seasons in a sample taken when rains were 50 percent of typical wet season levels. During this period, the human-introduced bacteria made up 67.3 percent of the microbes, while sulfur-oxidizing bacteria and nitrogen-fixing bacteria were also present.

More research is needed to understand the impact of these changes on the cave ecosystem itself and on groundwater, lead author Dr. Madison Davis of USF's Department of Cell Biology, Microbiology and Molecular Biology said in the press release.

However, the pollution of caves and the groundwater that springs from them is already a known problem across the U.S., as Scientific American reported in 2009:

Examples abound, including raw sewage flowing into Shalers Brook inside Mammoth Cave National Park in Kentucky, an animal feedlot in eastern Missouri washing waste down sinkholes into Crevice Cave and dirt runoff from logging activity choking Whispering Canyon Cave at Tongass National Forest in Alaska.
"People need to be aware that there's a subterranean ecosystem and that what happens on the surface impacts these unique ecosystems in a very real way," American University in Washington, DC cave expert and biologist David Culver told Scientific American at the time.

Plastic waste is bulldozed at a landfill. Needpix

The plastic recycling model was never economically viable, but oil and gas companies still touted it as a magic solution to waste, selling the American public a lie so the companies could keep pushing new plastic.

Read More Show Less

EcoWatch Daily Newsletter

54% of parents with school-age children expressed concern that their children could fall behind academically, according to a poll conducted over the summer of 2020. Maria Symchych-Navrotska / Getty Images

By Pamela Davis-Kean

With in-person instruction becoming the exception rather than the norm, 54% of parents with school-age children expressed concern that their children could fall behind academically, according to a poll conducted over the summer of 2020. Initial projections from the Northwest Evaluation Association, which conducts research and creates commonly used standardized tests, suggest that these fears are well-grounded, especially for children from low-income families.

Read More Show Less


A teenager reads a school English assignment at home after her school shut down because of the COVID-19 pandemic on March 22, 2020 in Brooklyn, New York. Andrew Lichtenstein / Corbis via Getty Images

The pandemic has affected everyone, but mental health experts warn that youth and teens are suffering disproportionately and that depression and suicide rates are increasing.

Read More Show Less
In an ad released by Republican Voters Against Trump, former coronavirus task force member Olivia Troye roasted the president for his response. Republican Voters Against Trump / YouTube

Yet another former Trump administration staffer has come out with an endorsement for former Vice President Joe Biden, this time in response to President Donald Trump's handling of the coronavirus pandemic.

Read More Show Less
Climate Group

Every September for the past 11 years, non-profit the Climate Group has hosted Climate Week NYC, a chance for business, government, activist and community leaders to come together and discuss solutions to the climate crisis.

Read More Show Less

Support Ecowatch