| Summary: | Eutrophication of lakes can lead to dominance by cyanobacteria, which are hardly used by
zooplankton due to their low nutrition value. However, sedimented cyanobacterial detritus
may be a useful source for benthic invertebrates. We studied the
Microcystis-derived nitrogen incorporation in benthic invertebrates in
Lake Taihu using stable isotopic nitrogen (15N) as a tracer. The δ15N of all
organisms increased significantly with time after addition of the labeled
Microcystis detritus. δ15N values of POM and periphyton peaked
earlier than for benthic invertebrates, and the maximum levels were also higher than
bivalves, snails and worms (Limnodrilus spp.). Among benthic
invertebrates, Radix swinhoei peaked later than other invertebrates, but
the maximum level and the excess 15N of the last sampling day were higher. At the end of the
experiment, approximately 70% of the added 15N was retained in the benthic food web, while only a
small fraction (less than 1%) of the added detritus 15N occurred in the pelagic food
web. Our results suggest that nitrogen from cyanobacteria can be incorporated more in
benthic than pelagic food webs and cyanobacterial blooms may contribute to the development
of benthic animals.
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