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Edge of the Lake Seminar Series
Brown, next green, then yellow water:
Sudden death in planktonic cyanobacteria (blue-green algae)
Open to the Public
Tuesday, August 12, 2003
12:00 – 1:00 p.m.
UW-Green Bay campus, Mary Ann Cofrin Hall, Room 206
(For a map, please see www.uwgb.edu/maps )
Department of Microbial Ecology, KNAW-NIOO Centre for Limnology, Nieuwersluis, The Netherlands
The plankton in the shallow, eutrophic Lake Loosdrecht (The Netherlands) is predominated by cyanobacteria (‘blue-green algae'). Interactions between the cyanobacteria and heterotrophic micro-organisms are studied by using experimental systems in the laboratory that mimic the natural water column. In these systems the cyanobacterial growth is controlled by setting the incident light, temperature and nutrient supply. An experiment was conducted to reveal which micro-organisms benefit from release of photosynthetic products by the cyanobacteria as stimulated by high light. After two weeks of vigorous growth of the cyanobacteria their population suddenly collapsed. Electron microscopy showed that the collapse probably has been due to a viral outbreak The phenomenon appeared to be reproducible independent of the season in which lake water was collected. Similar viral outbreak did not occur in the lake, therefore factors must exist that control the viruses in the natural system but apparently the control was lost in the laboratory experiments. Some observations made on shallow, eutrophic lakes elsewhere indicate that the controlling factors may fail to check viral attack on cyanobacteria in natural water bodies as well. These instances are very rare, therefore only the monitoring of many lakes may reveal the conditions for viral collapse of the cyanobacteria. Because growth and mortality of the cyanobacteria induce marked change in water color, the advent of satellite sensors combining high spectral and spatial resolution makes such monitoring feasible.
For more information contact Kim McKeefry, (920) 465-2798 or email Vicky Harris.
Co-sponsored by the University of Wisconsin Sea Grant Institute
and the Green Bay Metropolitan Sewage District
© University of Wisconsin Sea Grant Institute
all audio, images and video used with permissionlast updated 24 June 2002
http://www.seagrant.wisc.edu/communications/news_releases/2003/EdgeofLake--Bluegreenalgae1.html
