BLOOM AND DOOM 

U.S. coasts regularly face algae assaults in the summer, but this year's invasions are worse than usual, potentially wreaking havoc in ecosystems that can't handle the stress. Researchers recently confirmed the Gulf of Mexico's dead zone will break its all-time size record this summer, and as the Washington Post now reports, an "alarming" dead zone in the Chesapeake Bay — the country's largest estuary — is also on a record-breaking pace.

Dead zones are triggered by excess nutrients in the water, which feed giant "blooms" of algae that eat the nutrients and then die. As these dead algae sink underwater, they in turn become a feast for other microbes, which deplete the water's oxygen levels while devouring the algae. This problem has grown in recent decades as U.S. rivers carry more nutrient runoff — ranging from lawn fertilizers to hog manure — and rivers that pass through farming regions are often especially nutrient-rich. That's true for several rivers flowing into the Gulf of Mexico, namely the Mississippi, that have been swollen this year by above-normal rainfall and snowmelt. It's also true for the Potomac and Susquehanna rivers, which have helped this year's Chesapeake Bay dead zone cover about one-third of the bay, according to the Post. It stretched out for 83 miles when it was last measured in June, but has since expanded beyond the Potomac and into Virginia, the Post reports.

[skipwords]That's bad news for an already-struggling ecosystem, biologists tell the Post, since dead zones are even deadlier for animals like oysters and crabs that can't easily swim to more hospitable waters. Scientists aren't sure exactly how many fish flee dead zones and how many suffocate, but even the stress of swimming long distances for a breath can be taxing, experts say. "We know it's not good habitat for fish," says Bruce Michael of the Maryland Department of Natural Resources. "If there's not good habitat, they're stressed and they won't reproduce. They're more susceptible to disease and won't eat. We want them to eat a lot of food and reproduce and grow."[/skipwords]

(Sources: Washington Post, Associated Press, MNN)

BRIEF RELIEF 

Last week's oppressive U.S. heat wave is fading, but warmth-weary Americans won't get much of a break before another one starts scorching the country again, USA Today reports. Heat will begin building over the Northern Plains and Ohio Valley around midweek, Weather Channel meteorologist Mark Ressler tells USA Today, and while it may not reach the balmy extremes of last week, it could pile more misery onto what has already been a brutally hot summer in much of North America.

This July is on track to become one of the five hottest months in U.S. history, according to Weather Underground forecaster Jeff Masters, and AccuWeather's Meghan Evans points out the month has already been historically hot for several cities across the Plains, Midwest and Eastern Seaboard. In Oklahoma City, for example, there have only been three days so far this July when the high temperature was less than 100 degrees Fahrenheit. Dallas has seen only one day this month — July 1 — with a high below 100, which has put the Texas city more than 6 degrees above its normal temperature for the month. Last week's severe heat also set new records in a variety of cities, USA Today reports, including Newark, N.J. (108 degrees), Washington, D.C. (105) and Hartford, Conn. (103), on Friday. Baltimore (106) came within one degree of a record high, and New York City's Central Park (104) fell just two degrees short.

More than a dozen deaths were blamed on the heat wave last week, which was made even more dangerous by high humidity and nighttime temperatures that didn't cool off as much as normal. A cold front pushing across the Plains could offer temporary relief this week, AccuWeather reports, but it's expected to stall over Kansas. With afternoon heat-index values projected to reach 115 across the Plains in coming days, experts recommend staying indoors as much as possible, drinking plenty of water, and wearing light, loose-fitting clothes.

(Sources: USA Today, AccuWeather)

TOXIC THAW 

Besides fueling heat waves and storms at lower latitudes, rising global temperatures are famously causing even more dramatic changes in the Arctic. And according to a new study, melting Arctic sea ice may be doing more than killing polar bears, raising sea levels and reducing the Earth's reflectivity — the dwindling ice is also releasing toxic pesticides that have been frozen there for decades, the study's authors report. 

Known as the "dirty dozen," the group of 12 persistent organic pollutants (POPs) were widely used as pesticides before being outlawed in 2001. They're composed of "extremely tough molecules that take decades to break down in nature," the AFP reports, and they also bioaccumulate, which means they build up as they move higher through the food chain, making them even more dangerous to larger, meat-eating species. They're also insoluble in water, a trait that allows them to easily be transmitted among soil, water and air as temperatures change. The new study, published in the journal Nature Climate Change, detected a long-term drop in primary emissions of these chemicals — it focused on DDT, HCH and cis-chlordane — but also used computer models to see a rise in "secondary emissions" as they escape from melting Arctic ice. 

"A wide range of POPs have been remobilized into the Arctic atmosphere over the past two decades as a result of climate change," the study's authors write. As a result, they add, ongoing warming in the Arctic "could undermine global efforts to reduce environmental and human exposure to these toxic chemicals." As pollution expert Jordi Dachs tells the AFP, "The remobilization of pollutants generated by our grandparents ... are unwanted witnesses to our environmental past that now seem to be 'coming in from the cold.'"

(Source: Agence France-Presse)

OZONE DEFENSE 

Within weeks or even days, U.S. officials are expected to issue a new crackdown on ozone pollution, NPR and McClatchy Newspapers report, a move that's welcomed by public-health advocates but despised by many industry groups. The EPA's new ozone rules would revamp those set by President George W. Bush, whose administration disregarded its own scientific advisers to set the national ozone standard at 75 parts per billion.

Scientists have argued for years that the 75 ppb standard is too high, and the EPA has now proposed reducing it to between 60 and 70 ppb. If the White House signs off on that proposal, it would mean more orange and red air-quality alerts for many communities around the country, NPR points out. But according to New York University's George Thurston, a professor of environmental medicine, the current ozone standards mislead people into thinking the air is healthy when it really isn't. "There are areas of the country that thought their air was safe, but now we can see that there are adverse health effects, significant adverse health effects: hospital admissions, increased risk of death," Thurston tells NPR. Hot days like the U.S. has recently experienced make ozone pollution even worse, since the heat evaporates more toxic hydrocarbons into the air, where the sun's ultraviolet rays cook them — along with other airborne pollutants — to create smog.

Health advocates say the new EPA rules have been a long time coming. "The air ought to be safe enough for people to be able to go outside any time, and we shouldn't have to hide inside our homes on high-pollution days," Thurston says. "And that's really what these standards are all about, trying to make it so that our air is safe to breathe." Some industry groups and economists, however, say the rules would hurt economic growth — and possibly even public health. "When families have less money available, that takes on the kinds of food they can purchase, the kinds of medicine, the heath care they can seek," argues MIT economist Michael Greenstone. "And in its own way, those costs are a very important feature [of] public health, just as cleaner air is."

(Sources: NPR, McClatchy Newspapers)

THIS DAY IN HISTORY

Construction begins on Japan's Fukushima Daiichi nuclear plant, U.S. Senate nixes the Kyoto Protocol, and more.

Russell McLendon

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Photo (algae bloom in Chesapeake Bay tributary): Maryland DNR

Photo (sun shining through wildfire smoke): Bruce McKay/Flickr

Photo (Arctic sea ice): U.S. Pacific Marine Environmental Laboratory

Photo (sun shining through smog): U.S. EPA

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