Size spectrum is critically affected by omnivorous and detritivorous feeding in plankton food webs
Start Page
1
Date Issued
2009
Date
2009
Author(s)
Abstract
One of the most important issues in environmental conservation and ecosystem management is to develop good indices for efficiently monitoring ecosystems. Size spectrum is one of the potential candidate indices and has often been used as an index to detecting functional processes in aquatic ecosystems. However, the mechanism for formation of size spectrum is still under debate. Most theoretical models concerning size spectrum assume a linear relationship between log size and trophic level (size-TL relationship). However, this linear size-TL relationship in microbial food webs has not been examined. In this study, we examined the size-TL relationship and structure of size spectrum under different size-TL relationships. To do so, we sampled time series of plankton size spectra from Feb. 2008 to Feb. 2009 in the Feitsui Reservoir and carried out size fractionated stable isotope analyses. We found that the linear size-TL relationship does not always exist in the microbial ecosystem of the Reservoir, possibly due to the following two factors: (1) the extent of energy contribution from microbes and larger phytoplankton to higher trophic levels, and (2) the omnivorous interactions between zooplankton and microbes. The weak size-TL relationship caused the size spectrum to deviate from power-law distribution and intensify the secondary structure in size spectrum.
Subjects
size spectrum
omnivorous feeding
stable isotope
power-law distribution
trophic level
food web
Type
thesis
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