Strangled Waters: First Wave

On a balmy day in June 1955, George Anderson took his sailboat out on Lake Washington, the long stretch of fresh water that separates Seattle from its eastern suburbs. Anderson had recently finished his doctoral research on phytoplankton, and knew the lake well. The water that day looked odd; he noticed a strange brown tinge. So he collected a sample in an empty beer bottle and brought it back to the University of Washington lab where he worked with his mentor, W.T. Edmondson, the ranking authority on the lake. Under the microscope, Anderson and Edmondson found a life form they’d never seen before. It grew in long, narrow chains, striated with lines that separated one cell from the next. They thought this might be a species infamous among limnologists, the cyanobacterium Oscillatoria rubescens. (Cyanobacteria, popularly known as blue-green algae, are in fact distinct from and far more ancient than algae. They appeared more than 3 billion years ago, when the planet was inhabited only by microbes, and were the first organisms to evolve photosynthesis. Their proliferation and release of great volumes of oxygen profoundly changed the chemical makeup of Earth’s atmosphere, making the evolution of complex life possible.) The researchers needed to be sure, so they sent a sample off to an expert, who confirmed their suspicions. O. rubescens signaled deteriorating conditions in Lake Washington. To Edmondson, it also meant an unprecedented opportunity to track the impacts of nutrient overload. O. rubescens had been the harbinger of drastic change in a number of western European lakes. The best-known case was that of Lake Zurich in Switzerland. Fed by Alpine glaciers, Lake Zurich was, until the late 1800s, an expanse of blue known for its abundant populations of whitefish and lake trout, which thrive in deep water. The lake is made up of two basins separated by a narrow passage. In the late nineteenth century towns at the edge of the lower basin, the Untersee, abandoned privies for flush toilets, and began to release their raw sewage into the lake.

Genus Oscillatoria Vaucher (Cyanoprokaryota) in Maldah District, West Bengal, India

Genus Oscillatoria Vaucher is the ubiquitous Cyanoprokaryote, growing in almost all habitats in fresh-water ecosystem like bils, dighis, lakes, ponds, wetlands, and marine water system like - salt marshes and pans, estuaries, brackish waters and ocean. It also occurs on inter-tidal rocks, snow and even in cold lakes underneath 5 m of ice pack as well as in thermal springs. During systematic investigations recorded altogether 25 species, 4 variety and 2 forms from Maldah District viz. Oscillatoria acuta Bürhl and Biswas, Oscillatoria agardhii Gomont, Oscillatoria amoena (Kütz.) Gomont, Oscillatoria amphibia C.Agardh ex Gomont, Oscillatoria amphigranulata Goor, Oscillatoria angusta Koppe, Oscillatoria chalybea G.Mertens ex Gomont, Oscillatoria formosa Bory ex Gomont, Oscillatoria formosa f. loktakensis Brühl and Biswas, Oscillatoria geitleriana Elenkin, Oscillatoria geminata Menegh. ex. Gomont, Oscillatoria limnetica Lemmerm., Oscillatoria limosa C.Agardh ex Gomont, Oscillatoria minnesotensis Tilden, Oscillatoria okenii C.Agardh ex Gomont, Oscillatoria ornata var. crassa C.B.Rao, Oscillatoria perornata f. attenuata Skuja, Oscillatoria princeps Vaucher ex Gomont, Oscillatoria prolifica Gomont, Oscillatoria proteus Skuja, Oscillatoria pseudogeminata var. unigranulata Biswas, Oscillatoria quadripunctulata Brühl and Biswas, Oscillatoria raoi DeToni, Oscillatoria redekei Goor, Oscillatoria rubescens DC. ex Gomont, Oscillatoria splendida Grev. ex Gomont, Oscillatoria subbrevis Schmidle, Oscillatoria tenuis C.Agardh ex Gomont, Oscillatoria tenuis var. natans Gomont, Oscillatoria tenuis var. tergestina Rabenh. ex Gomont and Oscillatoria willei N.L.Gardner. However, Oscillatoria subbrevis Schmidle, Oscillatoria tenuis C.Agardh ex Gomont are the most common species followed by Oscillatoria amphigranulata Goor, Oscillatoria acuta Bürhl and Biswas, Oscillatoria amphibia C.Agardh ex Gomont, Oscillatoria amphigranulata Goor in water bodies of Malda District. Oscillatoria redekei Goor is reported new from India.

Light as a selective factor in the distribution of phytoplankton species

Cyanobacteria are most often the dominant group of organisms in the phytoplankton of eutrophied freshwater lakes. In the first section the distribution of cyanobacterial populations in the Netherlands was described in relation to depth, chlorophyll concentration and average light climate. Long term dominance in shallow lakes was mainly caused by Oscillatoria like organisms. Microcystis was found to be dominant in deeper lakes. Although the dominance of Oscillatoria was closely related with high chlorophyll concentrations, the relation between the Oscillatoria dominance and the average underwater light climate was not clear. A good explanation could not be given. In the second section the dominance of Oscillatoria was followed during the restoration of three lakes. Here it was found that in two shallow lakes of different depth Oscillatoria disappeared from the epilimnion at a Zeu/Zm value of 0.4. This is in good agreement with competition experiments done in the laboratory. The stratified population of Oscillatoria rubescens disappeared from the metalimnion at a Zeu/Zm ratio of 1.2. This fitted also with the physiological information.