Monday, December 21, 2009
Review of the Dynamic Great Lakes by Barbara Spring
U.S. Water News - Peter Wild
Are dinosaurs cruising the benthic depths of the Great Lakes even while we go about our daily tasks? Not exactly. Yet sturgeon, fish weighing up to 300 pounds and similarly plated with armor,are nosing around down there. Occasionally you can see the monsters appear, making their spawning runs up rivers and surfacing like submarines in the pools beneath waterfalls... The five Great Lakes, holding nearly twenty percent of the earth's fresh water, are quite young. Gouged out by glaciers, they assumed their present shapes a mere 3,000 years ago. For that, they are a dynamic shifting system, still changing and exhibiting surprising differences. Lake Ontario, for example, the easternmost, although smallest of the bodies, holds more water than Lake Erie, its shallower nearby sister. Here's a handy primer for all such things, from the interaction of phytoplankton and calcium carbonate that gives a white cast to these inland oceans come August and helps clean the water to the charming ice volcanoes spouting chilly "lava" in the winter.
This is intriguing stuff for adults, but the straightforward presentation also lends itself to use in schools, beginning about the sixth grade and up. And yes, we get the latest news on the zebra mussel, the tube nose goby, and other threats to the natural scheme of things. Also good news; how since the banning of DDT in the 1970's, the bald eagles have come back.