Contrast autochthonous and allochthonous food webs. Which type would be expected to dominate in a clear lake? Solution Contrast autochthonous and allochthonous food webs: The allochthonous food webs are associated with high inputs of organic matter to obtain carbon from surface catchment or ground water catchment where amount o flight is lower & low primary production. This food webs forms among heterotrophic ecosystems mainly in dystrophic lakes Autochthonous food webs are mainly associate with production of organic carbon from photosynthesis inside the clear lake, in which higher carbon generated mainly in eutrophic lakes where high light incidence across the clear lake.