The greening of Iowa waters is not a hopeful sign to environmentalists.
As in years past, many Iowa lakes this summer bloomed a sickly green with algae, some of it toxic, the rest otherwise harmful to the environment.
“It’s always a good algae-growing year in Iowa,” said Iowa State University limnologist John Downing, a nationally recognized expert on the sometimes toxic blooms that are the leading impairment of Iowa waters.
Whether 2013 will prove to be an exceptional algae year remains to be seen, said Downing, who is still analyzing data collected from the more than 130 Iowa lakes he has been studying for the past 13 years.
The two main ingredients for algae growth – water-borne nutrients, primarily phosphorus, and summer heat -- were especially prevalent this year, said Downing.
Those factors likely contributed to the substantial increase in toxic algae advisories at the 39 state park beaches monitored by the Department of Natural Resources, said Stuart Schmitz, an environmental toxicologist with the Iowa Department of Public Health.
Advisories for elevated microcystin, Iowa’s most common algae-produced toxin, nearly doubled this summer at state park beaches, from 14 in 2012 to 24 this year, according to Jason McCurdy, who coordinates the DNR’s state park beach monitoring program.
The number of toxin-affected beaches increased from eight last year to 10 this year, and the number of lakes affected by toxic algae advisories increased from seven last year to nine this year, according to statistics provided by McCurdy.
The toxic algae season also lasted much longer this year, according to Schmitz. In 2012, elevated microcystin levels were recorded in five separate weeks; this year advisories were issued in 10 separate weeks, with an unbroken nine-week string stretching from July 5 to Aug. 20, he said.
When toxin levels reach 20 micrograms per liter, the DNR posts signs advising beach users to stay out of the water. Harmful algae- produced toxins have exceeded the DNR’s safe swimming guidelines for state parks 68 times since 2006.
Schmitz said the health department recorded three cases of reported human illnesses caused by toxic algae this year, bringing to 27 the total of such cases since his department began monitoring them in 2008.
Adverse human health effects, he said, typically include skin irritation or gastrointestinal upset. Such cases are likely under-reported, since many people with symptoms do not seek medical treatment, he said
Schmitz said the department’s data come only from DNR monitoring of beaches at state parks so most of the state’s water is not monitored for algae-produced toxins.
A recent analysis by the National Wildlife Federation found that Iowa is among 21 states that issued health warnings about toxic algae this summer. The warnings covered about 150 locations on lakes, rivers and reservoirs nationwide, said Andy Buchsbaum, director of the federation's Great Lakes office.
While the blue-green algae, which produces the toxin microcystin, has recently drawn increased attention, common, non-toxic algae, which impairs swimming, boating and fishing, is the leading pollutant on the state’s list of impaired lakes.
Of the approximately 90 Iowa lakes and wetlands considered impaired and awaiting a restoration plan, algae is the most common pollutant, affecting 42 of them, according to an analysis of the listing approved this spring by the U.S. Environmental Protection Agency. Bacteria, the second-most common pollutant, was listed as an impairment cause in 24 lakes and wetlands.
Algae is also considered a leading cause of pollution among impaired lakes and wetlands for which the state has formulated a restoration plan.
Apart from its often unpleasant appearance and smell, which discourages recreationists, algae blooms can harm aquatic life by reducing the amount of dissolved oxygen available to them – the precise mechanism responsible for the so-called Gulf of Mexico dead zone.
“Iowa’s lakes have among the highest nitrogen and phosphorus levels in the world, and consequences of this problem, including algae blooms and poor water clarity, have already landed 79 of the state’s top recreational lakes on Iowa’s impaired waters list,” said Susan Heathcote, water programs manager for the Iowa Environmental Council, which has pushed hard for numeric water quality standards at both the federal and state levels.
In addition to the group’s petition for proposed lake standards, rejected Monday by the Iowa Environmental Protection Commission, the group is also a plaintiff in a federal lawsuit that has forced the U.S. Environmental Protection Agency to determine whether to set quantifiable standards and cleanup plans for nitrogen and phosphorus pollution.The Sept. 23 federal court decision does not tell the EPA how to address the problem, only to make a decision on the issue