DAVIS, Calif. -- Weighing in on the ecological debate about how best to
control human-induced algae growth in naturally clear lakes, University
of California, Davis, researchers have made a bottom-line discovery.
Tinkering with food webs may not help restore most lakes to their previous
clarity. This is because in most cases the upper levels of a lake's food
web cannot exert enough influence to control the algae feeding on polluting
nutrients coming into the lake.
Instead, limiting the supply of nutrients in a lake appears to be a stronger
mechanism for controlling algae blooms, according to a meta-analysis of
eight lake studies involving 11 experiments in Canada, Czechslovakia, Norway
and the United States, said Michael Brett, a staff research associate in
the UC Davis environmental studies division.
Brett and UC Davis professor Charles Goldman, director of the UC Davis Castle
Lake and Lake Tahoe research groups, published the results of the analysis
in the Jan. 17 issue of the weekly journal Science.
The analysis also casts doubt on a popular model of how energy moves through
food webs in general and of how many plants and animals can be found at
each level of the web. The way energy moves through food webs plays a key
role in determining fisheries production in lakes and oceans.
In most lakes around the world, the most common pollutants causing murky
water are actually nutrients that fuel the growth and number of tiny plants
at the bottom of the food chain. Limnologists have long recognized that
nitrogen (typically from sewage and fertilizer) and phosphorus (from nearby
construction or logging) feed the tiny marine plants known more commonly
as algae.
Algae thrive on these pollutants. The quantity of algae directly determines
water clarity. In a process called eutrophication, algae can deplete oxygen,
killing fish, and severe algae blooms can water to sm
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Contact: Carol Morton
ccmorton@ucdavis.edu
916-752-7704
University of California - Davis
17-Jan-1997