Benthic organisms play an important role in lake food webs. I explored several questions related to this theme.;The relative importance of benthic and pelagic pathways for supporting fishes can be estimated using stable isotope ratios of carbon and nitrogen. This requires information about the isotope ratios of food web baselines, usually represented by zoobenthos and zooplankton. I described variability in carbon and nitrogen isotope ratios of zoobenthos and zooplankton over 23 years. A simulation model showed that error, but not bias, in fish trophic niche estimates increases substantially in long-term studies when researchers do not have complete baseline data available.;Production of zoobenthos is supported by organic matter originally fixed by primary producers in either benthic, pelagic, or terrestrial habitats. Using a whole-lake 13C addition experiment, I estimated resource use by the predominant macroinvertebrates in a 26-ha lake. Chironomids and odonates derived between 17 and 75% of their carbon from current autochthonous (in-lake) primary production. The remainder (25-83%) of their carbon derived from the detrital pool, including both allochthonous terrestrial organic matter and old autochthonous primary production from previous years.
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