PHOENIX — Fish-killing algae that first showed up in Phoenix a year ago have spread to lakes throughout the metropolitan area and have proven to be stubborn and sneaky.
Golden algae have infected at least 14 public and private lakes in the state, according to Eric Swanson, manager of the Arizona Game and Fish Department's urban fisheries program.
"It appears to be spreading to more lakes," he said. "We're just trying to find the right magic pill, the right dosage (of algaecides) to knock this back, but it is a very elusive organism that is increasingly frustrating to us. One drop of water can harbor thousands of those organisms."
The algae not only grow quickly, but can kill a number of fish before they can be detected by the naked eye when the water turns the color of tea.
And even when lake water is sprayed with algaecides, the golden algae form a cyst to protect themselves, fall to the bottom of the lake and wait until conditions are more favorable to resurface and bloom.
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"Once you have it, you are going to always have it," said Bob Revolinski, an aquatic biologist with Water Resource Management.
Lakes that are infected include the large Apache, Canyon and Saguaro lakes, and some urban lakes including Alvord Lake in south Phoenix, Cortez Lake in north Phoenix, Water Ranch Lake in Gilbert and Desert West Lake in west Phoenix.
The algae have not been found in Tempe Town Lake.
The algae were first confirmed about a year ago in Saguaro Lake and Water Ranch Lake after a number of fish died.
More lakes could be infected, but getting information on private lakes, such as those in subdivisions, is difficult because homeowners associations are reluctant to share that information for fear of hurting property values, Swanson said.
The algae are not harmful to humans, officials say, but they secrete a toxin that causes certain fish to suffocate.
There doesn't appear to be any immediate danger of the algae wiping out fish in the state. But they are forcing lake managers to be especially vigilant and homeowners associations to pay extra for tests and treatments to keep fish alive in their lakes.
"You only have to have somebody lose $30,000 worth of fish to realize it's so quick. It happens so fast. We have all got caught," said Ralph Moody, owner of Chandler-based Lake Maintenance Service.
Scientists believe that ducks and other birds, or perhaps even fishing poles, are spreading the algae. It only takes a drop, which can contain as many as 2,000 cells of golden algae, to contaminate an entire lake.
Testing and treatments are tricky. One part of a lake can test positive and another part negative.
And managers have to be careful with algaecide; overdoing it could kill the good algae that will eventually crowd out the golden algae.
Last fall, the Game and Fish Department surveyed the numbers of fish in Apache, Canyon and Saguaro lakes and concluded that the algal-induced fish kills may not be as severe as first thought, except for smallmouth in Apache Lake.
But because the algae can pop up when least expected, no one is resting easy because the algae can show up between tests or even after a negative test.
Shortly after water at the Lakewood community's two lakes in Ahwatukee Foothills showed negative, Revolinski noticed a bunch of dead fish. The water was so clear he could see 50 feet down. He had the water tested and it suddenly was positive for golden algae.
Revolinki said he has learned one thing for sure: Golden algae are unpredictable.
"We have the basics down on how to keep it in check," he said. "But now and then something will throw you a curve. So many things affect the ecology of a lake. Weather is a big factor."
Fortunately, the peak season for golden algae in the desert is about over. It tends to peak from October to April. Once the water warms up, other algae begin to grow and crowd out the golden algae.
