had a greater impact on algae growth than the top-down processes.
"Both played a role, but nutrients had a bigger impact on algal biomass,"
The science meta-analysis paper by Brett and Goldman also casts doubt upon
the universal nature of a popular model developed by Lauri Oksanen, a theoretical
ecologist at the University of Umeå in northern Sweden. The model
predicts that food webs will respond to increased growth at the plant level,
such as algae, in different ways depending upon the number of levels in
the food web.
In the experiments summarized in the UC Davis analysis in Science, the response
of phytoplankton and zooplankton to adding nutrients was not related to
the number of trophic levels in the system, Brett said. In food webs with
two levels (plants and herbivores), Oksanen's model predicts that increased
plant production will fuel growth of herbivores to the extent that the plant
eaters munch all the extra food, resulting in no net gain at the plant level.
In food webs with three levels (plants, herbivores and predators), Oksanen's
model predicts that increased plant production will result in more predators
and plants, but fewer herbivores, because the predators will eat all the
extra herbivores, allowing the plants to grow and thrive.
The UC Davis researchers found opposite results from the model predictions
for the two-level food webs. "The crux of the model is that the number
of levels determines how energy moves through the food web, and we found
the response was not related to the number of trophic levels," Brett
Some of the most important unanswered questions in food web ecology still
remain, according to Brett and Goldman. What determines how fast and how
much energy moves through food webs? How can lakes or oceans with similar
algae production vary so dramatically in fisheries production?
Contact: Carol Morton
University of California - Davis 17-Jan-1997Page: 1 2 3 4 Related biology news :1
. Ecological science for a crowded planet2
. Ecological success?3
. Ecological Society of America 88th annual meeting4
. Ecological effects of climate change include human epidemics5
. Ecological significance of tool-use in the woodpecker finch Cactospiza pallida6
. Ecological risks of GMOs come in unexpected ways, model shows7
. Energy departments Idaho lab teams with Russia to establish Ecological Biotrade facility8
. Ecological trends of food availability yield clues to Americans weight problem9
. The Geometry of Ecological Interactions: Simplifying Spatial Complexity10
. Ecological Society of America and the British Ecological Society to meet11
. Colorado State scientist is Ecological Society of America president