The way climate change interacts with other human changes on environment is well illustrated by the impact of warming on Greats Lakes waters in the US.
Parallel environmental problems – pollution runoff from agriculture, and spread of invasive species, both enhanced and accelerated by warmer temperatures, were vividly on display this past summer across the Great Lakes basin – source of 20 percent of the world’s fresh water.
The problem was exacerbated during 2010, one of the warmest summers in the record globally, and discussed in an article from the Cleveland Plain Dealer.
“Blue-green algae — actually the peptides secreted by certain blue-green algae known as microcystis — is a known neurotoxin, meaning that at high concentrations it can severely damage the nervous system, including the brain. That makes it especially dangerous to small children or those with weak immune systems.
While there are currently no official health standards for microcystin, state officials are posting warnings based on those recommended by the World Health Organization: No more than 20 parts per billion for recreational water and 1 part per billon for drinking water.”
Some smaller, inland lakes in Ohio have blown that standard out of the water, at unimaginably high readings of 2000 ppm.
As the article notes, several species of blue green algae, under conditions not well understood, can produce a toxin deadly to animals and humans.
In one inland Ohio lake, at least 3 dogs have been killed by exposure to blue green algae, and similar deaths have been reported in other great lakes states.
Invasive species compound the problem. The well-known zebra mussels, invaders that hitched their way into the Great Lakes decades ago in the hold of ocean going freighters, can make matters worse, according to Alan Steinman, an aquatic ecologist at Grand Valley State University. In an email, Steinman told me:
“…zebra mussels have been implicated in the growth of Microcystis (and other blue-green algae). The mussels are filter-feeders, and they suck in the algae in the water column, but they don’t like blue-green algae. It could be their chemicals, size, or taste, but they end up spitting them back out as pseudo-feces. The algae in these pellets are still viable, and now coated in a rich nutrient bath from inside the mussels, and do quite well.”
In addition, Steinman and his team have identified species of algae not known in the Great Lakes systems when waters and winters were colder than today.
Cylindrospermopsis raciborskii is an invasive species that has heretofore been observed in tropical and subtropical environments, and is now being found in the Great Lakes region.
In a 2006 paper, Steinman and colleagues wrote that:
“Toxin-producing invasive species are one of the greatest threats to global freshwater resources today.
At least three distinct toxins can be produced by Cylindrospermopsis…. cylindrospermopsin, which targets primarily the liver and kidneys, and anatoxin-a and saxitoxin, which are both neurotoxins.
Because of its potential to produce these toxins and its highly adaptable growth, this genus ranks near the top of the watch list of toxic cyanobacteria for water managers (WHO 1999).”
In a greenhouse world, supplies of fresh water, some say, will become the new oil – a significant issue of national security. Global warming intensifies the impact and severity of other environmental stresses, and makes solving future problems of energy, food, and population more difficult.
