For Love of Lakes

Blue-Green Nemesis

· · 125 · · Blue-Green Nemesis Everythinghasindirecteffectsandinterconnectedfunctions,soif youalteroneprocess,youareboundtodisturbathousandother processesyoudidnotevenknowexisted. NANCY LANGSTON Today, August 28, marks the one-year anniversary of my epiphany visit to Diamond Lake. Curiosity has brought me back. Has the lake’s condition changed since my mind-shaking visit? From the landing the lake appears much as it did then, a sea of blue-green algae run riot, as dominating and repulsive as before. As then, lake bottom disappears from view in shin-deep water. Detestable though blue-greens are in such crushing numbers, I admit to grudging respect and intense curiosity about any living being that can so overwhelm a space. Who are these creatures and what enables them to become so dominant? Before I launch the canoe to learn what may have happened elsewhere in “their” lake and its bays in my absence, I must tell a story. I must tell a story about what I have learned about these blue-greens. Together with their sidekick accomplice, the paradoxical element phosphorus, they make a remarkable and fascinating tale. Hearing this know-the-enemy story will help explain just what Diamond Lake and other pea-soupish lakes are up against. mindscapes· · 126 · · • • • MystudentsandIhaveexaminedblue-greensunderamicroscope.Wehave seen them as colonies of round or box-shaped cells, some in small clusters encased in transparent sheaths, others as bluish necklaces, twisted spirals, evenstraightfilamentsofcellslinedupendtoendlikearowofbricks.Ihave seen some form rubbery nodular colonies as large as golf balls. Blue-greens, once considered a kind of algae, have been discovered not tobealgaeatall,butamoreprimitiveformoflifewithanimpressivehistory of transforming things here on earth. Technically, they are known as cyanobacteria (cyano means blue in Greek), though force of habit leads many people to continue to call them blue-green algae. By whatever name, they are the oldest life forms known. Long before the Age of Dinosaurs there was the Age of Cyanobacteria, when for 2 billion years these simple organisms alone inhabited our planet. The earliest ones apparently released much oxygen into our atmosphere, making earth inhabitable by creatures like us. Later in earth’s history the blue-greens helped transform dead plants into Mostlytoosmalltobeseenbythenakedeye,blue-greenalgae(cyanobacteria)can overrunalakerichinphosphorus. · · 127 · · earth’scrudeoil.Theythrivetodayinlakes,inhotsprings,hotdeserts,polar deserts, glaciers, and even the saline lakes and ice sheets of Antarctica. In places they multiply to reach the incredible density of 400,000 cells in a single drop of water. I grudgingly tip my hat to them. Reproductive success boils down to obtaining enough food and avoiding being eaten long enough to have babies. Blue-greens are devilishly good at both. Waterfleas and other microscopic animals comb lakes in search of food the size of algae and cyanobacteria. Many cyanobacteria, unlike most algae, produce toxic chemicals to ward off such predators. Perversely, cyanobacteria toxins are more poisonous to wildlife, farm animals, and humans than to aquatic life. Deaths result when animals drink in cyanobacteria in great numbers or eat cyanobacterial scum from the water surface. Animal deaths caused by cyanotoxins are reported from many states and provinces, with cattle, pigs, horses, dogs, chickens, and turkeys appearing most frequently in these reports. But cats, squirrels, fox, hawks, skunks, mink, snakes, frogs, salamanders, wild geese and ducks, gulls, songbirds, even honeybees and, in South Africa, three rhinoceroses have succumbed to the toxins of the giant-slayer cyanobacteria. A local veterinarian described the death of a dog from blue-green algae poisoning here on Diamond Lake as gruesome. Thistypeofcyanobacteriumcanproduce deadlytoxinsthatareabletokillmany kindsofanimalsandsickenpeople. blue-green nemesis mindscapes· · 128 · · Experts long believed few cyanobacteria species produced toxins, did so infrequently, and the overall risk was minimal. That changed years ago when Brazilian hospital patients became ill. Some people ultimately died, andalltheillnessesanddeathsweretraceabletocyanobacterialtoxinsfrom acontaminatedwatersupply.Illnessduetoliverdamageisamorecommon risk to people than death. Thankfully, not all cyanobacteria blooms on lakes are toxic. In one small triumph against these miniscule giant-killers, several fish speciesaroundtheworldhavedevelopedimmunitytothetoxinsandgobble up cyanobacteria like gourmands feasting on New England clam chowder. Paradoxically,somecyanobacteriaspecieshavealonghistoryashuman food and have been sold as a health food in America. Health officials worry because some of the cyanobacteria used for this purpose are obtained from natural blooms in lakes and, unless subjected to complex tests to verify their safety, could present considerable risk to those who eat it. I am puzzled. Cyanobacteria are noted for causing repulsive tastes and odors in water supplies that typically put people off. Either processing destroys the sensory warnings or natural food aficionados judge that if it tastes bad it must be good. Despite their nasty poisons, however, blue-greens could never achieve the astronomical...