Lakes at high latitudes represent a range of biotic complexity imposed by strong abiotic limitations that are differentially ameliorated by biogeographic factors between the northern and southern latitudes. However, the communities in these lakes are simpler than those typically found in more temperate environments and represent a range of declining biocomplexity as conditions approach the limits to life in these extreme environments. This includes the relative importance of keystone predators and higher trophic levels (e.g., fish and birds) as well as the benthic-pelagic coupling in structuring the food webs. This chapter uses examples and case studies to explore food web interactions between microbial and classic food webs, the importance of autochthonous versus allochthonous carbon, and the implications of a changing climate.