Positive feedback in aquatic ecosystems.

Aquatic ecosystems offer striking examples of how positive feedback can be integral to the dynamics of complex communities. In particular, microorganisms (bacteria and protozoa) introduce a multitude of positive feedback pathways by rapidly recycling nutrients at the very base of many aquatic food webs. The relatively large magnitude of fluxes being shunted through this 'microbial loop' allows an accumulation of nutrients in localized areas, promotes a general build-up of biomass, and acts as a 'life-support system' in harsh environments. In contrast to customary notions which portray positive feedback effects as undesirable, a reassessment indicates that this 'bootstrapping' can often be advantageous for many organisms.