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Allochtonous input and trophic level heterogeneity: impact on an aquatic food web
Author(s) -
Lövgren J.,
Reinikainen M.,
Persson L.
Publication year - 2006
Publication title -
oikos
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.672
H-Index - 179
eISSN - 1600-0706
pISSN - 0030-1299
DOI - 10.1111/j.2006.0030-1299.13737.x
Subject(s) - periphyton , phytoplankton , daphnia pulex , food web , biology , trophic level , primary producers , ecology , mesocosm , scenedesmus , algae , zooplankton , plankton , daphnia , nutrient
The impact of food web complexity in open and closed food webs was explored experimentally under controlled laboratory conditions. We used an aquatic model community consisting of two forms of primary producers, phytoplankton ( Scenedesmus obtusiuscusculus ) and periphyton ( Nitzschia perminuta ) and two types of consumers, Daphnia pulex feeding on phytoplankton and Chydorous sphaericus feeding on both periphyton and phytoplankton. Three different food webs all having the phytoplankton and periphyton, but having either one of the consumers or both were set up. These food webs were studied in an open and closed treatment. In the open treatment, phytoplankton was continuously flowing through the aquaria whereas in the closed system all the phytoplankton was delivered at the start of the experiment. D. pulex had a positive effect on the density of C. sphaericus in both the open and closed treatments. In the open treatment C. sphaericus increased to very high numbers and was able to depress phytoplankton and thereby negatively affect D. pulex . Our study shows that the explicit handling of the population dynamics of both grazers allowed us to show how a compensatory increase in one primary producer due to increased grazing on another primary producer creates a negative feedback between consumers: C. sphaericus increased and negatively affected D. pulex .