—Introduction of lake trout Salvelinus namaycush into a system can add a trophic level, potentially affecting organisms at lower trophic levels. Similar to many lakes and reservoirs in the western United States, lake trout were introduced into Yellowstone Lake, Wyoming. Previous studies showed that lake trout reduced the population and altered the size structure of native Yellowstone cutthroat ...

Models of the effects of disturbance on ecological communities have largely considered communities of competing species at a single trophic level. In contrast, most real communities have multiple interacting trophic levels. I explored several versions of simple single- and multitrophic models to determine whether predictions of the intermediate disturbance hypothesis (IDH), derived from conside...

Aquaculture policy often promotes production of low-trophic level species for sustainable industry growth. Yet, the application trophic concept to aquaculture is complex, and its value assessing sustainability further complicated by continual reformulation feeds. The majority fed farmed fish invertebrate are produced using human-made compound feeds that can differ markedly from diet same in wil...

Models of biomass size spectra assume that organisms with higher body mass feed at higher trophic levels, but explicit empirical tests of this pattern are rare. We used nitrogen stable isotopes (δ15N) as an index of the trophic level in a benthic fish and invertebrate size-spectrum, and demonstrated that body mass was positively and significantly related to trophic level. This pattern was consi...

The consequences of biodiversity loss for ecosystem functioning and ecosystem services have aroused considerable interest during the past decade. Recent work has focused mainly on the impact of species diversity within single trophic levels, both experimentally and theoretically. Experiments have usually showed increased plant biomass and productivity with increasing plant diversity. Changes in...

We tested whether standing autotrophic (unicellular algal) biomass is sensitive to variation in initial consumer (nondecomposer, heterotrophic protistan) diversity in experimental microbial microcosms. Our results showed a strong, negative relationship between autotrophic biomass and consumer species richness. Additional microcosm experiments showed that this relationship was due largely to the...

Factors constraining the structure of food webs can be investigated by comparing classes of ecosystems. We find that pelagic ecosystems, those based on one-celled primary producers, have longer food chains than terrestrial ecosystems. Yet pelagic ecosystems have lower primary productivity, contrary to the hypothesis that greater energy flows permit higher trophic levels. We hypothesize that lon...