Rebuilding and comparing pyramids of numbers (Elton) and energy (Lindeman) with selected global δN data.

Widespread omnivory in aquatic food webs has been recognized to compromise interpretation of Lindeman's 'pyramid of energy' wherein organism biomass is constrained into rigidly delineated trophic levels. A compilation of global, pre-1997 stable nitrogen isotope data for aquatic food webs produced vertical energy profiles that were ataxonomic and therefore similar to Elton's 'pyramid of numbers' which he believed to be based on size-structured feeding relationships. Further, the present secondary-analysis confirms findings from other recent data compilations in suggesting that aquatic animals in real food webs are rarely found above the fifth or sixth broadly based trophic category. Therefore, δN analysis of food webs permits a reconciliation between theoreticians and empiricists by assuming a middle position in estimates made of the vertical length of food webs. [ABSTRACT FROM AUTHOR]