An invasive species, the quagga mussel, is to blame for a slew of environmental damages in Lake Mead, Nevada, ranging from clogging the Hoover dam’s cooling pipes to starving local fish populations and poisoning the water with concentrated toxins and heavy metals. The mussels are also creating an ideal habitat for deadly cyanobacteria as they consume all other algae varieties.
The quagga mussel and its smaller relative, the zebra mussel, have already invaded the Great Lakes, creating a huge financial toll on the region – in the billions of dollars – but have not been a problem in the West until just recently. The recent appearance of the quagga could be devastating for Lake Mead and other western bodies of water, because the region is the perfect breeding habitat for them. The lake’s temperature is ideal for quagga reproduction – they can lay eggs six times a year there, compared with once or twice a year in the Great Lakes.
Quagga mussels are excellent bioaccumulators, taking up heavy metals and toxins from the water, but when they excrete those chemicals in their waste pellets, the concentrated toxins carpet the bottom of the lake and are consumed by bottom feeding species. Those species concentrate the harmful substances and pass them up the food chain when they in turn are eaten by other fish and birds, and eventually humans.
The quaggas are filter feeders, straining the water for phytoplankton, zooplankton, and algae, and because they don’t eat cyanobacteria, the lakes where the mussels live experience a rise in the population of the deadly algae. Quaggas also lower the ratio of nitrogen to phosphorous in the lakes, which makes an even more ideal habitat for cyanobacteria.
The cyanobacteria can form huge algae ‘blooms’ which create dead zones in bodies of water, releasing cyanotoxins that are deadly to humans and animals. The source of water for Las Vegas Valley, Boulder Basin, is already experiencing a population explosion of cyanobacteria, and the quagga invasion could have devastating effects on the water quality there.
A biologist with the University of Nevada’s School of Community Health, biologist David Wong, says that by 2012, the quagga population will be “an underwater empire vast enough to begin to diminish the water quality” and that as far as potential ecological impact and economic loss, “the quaggas are the worst threat facing Las Vegas”.