The introduction of a new species can upset an ecosystem’s delicate natural balance. These types of transported species have many names: invasive, nuisance, non-native, non-indigenous, alien, and exotic. But the name doesn't matter – what matters is their impact. Many invasive species cause havoc on their new ecosystem as a result of rapid reproduction, lack of predators in the new habitat, and the ability to take advantage of a wide variety of food sources and habitats. Invasive species also frequently create negative economic impacts through costs of control measures or causing the loss of economically valuable resources.
The tiny invaders known as quagga mussels.
Lakes Mead and Mohave have a particularly troublesome invader: the quagga mussel (dreissena bugensis). These mollusks vary in size – from microscopic to the size of a nickel – and since their arrival, they have had a huge impact on the native habitat, park management, infrastructure and recreation.
Native to the Ukraine, quagga mussels were transported to Canada and the United States in ballast tanks. Ocean vessels use ballast tanks to keep their stability, similar to how one might use a weight to hold down a canopy or a sign. Once in the United States, quagga mussels were moved from river to river and lake to lake by recreational boaters and commercial river boats, often in bilges. It is currently estimated that over 50 million gallons water are being transported and emptied into U.S. waters daily.
Quagga mussels will damage equipment.
Due to the water temperature and clarity in lakes Mead and Mohave, quagga mussels have adapted and can spawn multiple times per year. Quagga mussel larvae get sucked into boat engines and water treatment plants by the billions. As adults, these mussels will cling to nearly anything including rocks, boat hulls, infrastructure and machinery. As their numbers have grown, they have begun to clog the giant intake pipes that draw water from Lake Mead requiring expensive cleaning regimens and repairs.
Humans aren’t the only ones that are troubled by this new invader; other local species are suffering too. Quagga mussels are filter feeders, which means that they suck water into their shells, eat tiny algae and plankton particles suspended in the water, and then push the newly-cleaned water back out. The first problem with this is that they’re outcompeting native filter feeders for food. But an even bigger issue is that the more water quagga mussels filter, the more the water quality and other aspects of the ecosystem - like nitrogen, phosphorus, and oxygen levels – can change. While this might not seem like a problem from a boater’s or swimmer’s perspective, it could affect conditions for other lake species.
Unfortunately, quagga mussels will most likely never leave lakes Mead and Mohave. However, efforts are being made to prevent the introduction of other invasive species to the Lake Mead National Recreation Area. Through the collaboration of the National Park Service, Nevada Department of Wildlife, Bureau of Reclamation, Southern Nevada Water Authority, Arizona Game and Fish Department, and U.S. Fish and Wildlife Service, these agencies have put programs to combat invasive species. This includes ongoing research and the adoption of the "Clean Drain Dry" program.