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With growing concern about the environmental impacts of invasive species to freshwater ecoysystems, the National Park Service has decided to close the pristine waters of Crater Lake National Park to scuba diving.

Some scientists consider Crater Lake to be the most pristine naturally occurring large body of water on the planet. Minor changes in the hydrologic conditions of the lake could permanently affect both purity and clarity. Invasive species are almost impossible to eliminate once they’ve been introduced, at least without massive chemical intervention that would likely have other unwanted consequences.

Read more about invasive species threats to freshwater ecosystems at this Nature Conservancy web page.

Other use of water gear in the lake will also be prohibited until the park service established new rules to minimize the risk of introducing unwanted shellfish or aquatic plants. The park service hopes to lift the closure before the start of the 2013 summer season, and will likely require decontamination procedures like those used for many other freshwater lakes.

“We have seen the devastation to ecosystems and economies caused by the inadvertent introduction of invasive species from Lake Mead to Lake Erie,” said park superintendent Craig Ackerman.”We want to prevent it from happening at Crater Lake rather than deal with the aftermath.

“The increasing popularity of the lake for scuba diving also increases the opportunities for divers and their gear to carry microscopic ‘hitchhikers’ into the water.They may be small, but damage that can be caused by aquatic invasives is enormous and oftentimes irreversible,” Ackerman said.

Aquatic invasive species like quagga mussels, spiny water flea, and viral hemorrhagic septicemia virus cause severe and permanent damage to the habitats they invade by reducing the abundance of native species and altering ecosystem processes. They rank among the most severe threats to biological diversity and are among the leading causes of extinctions.

Aquatic invaders can range from microscopic bacterial and viral pathogens to plants and animals. In their native environments these species are often controlled by interactions with predators, parasites, pathogens, or competitors.

However, when introduced to new environments, like Crater Lake, the same natural checks are often absent, giving invasives an advantage over native species and making them very expensive and difficult, if not impossible, to control.Consequently, focusing on preventing introduction of harmful invasives is key to reducing the risk.

For more information, visit the Aquatic Nuisance Species Task Force website.

Environmental coverage made possible in part by support from Patagonia. For information on Patagonia and its environmental efforts, visit www.patagonia.com. In affiliation with High Country News. Crater Lake photo by Shutterstock