Phytoplankton in extreme environments: importance and consequences of habitat permanency

There is hardly any sunshine exposed surface on this Earth, be it water or terrain, which would not support some biota. Still, many habitats offer harsh conditions requiring specialized physiological adaptations to survive. These environments are referred to as extremes; often inhabited by extremophilic organisms. In this review, characteristic species and assemblage properties of phytoplankton inhabiting extreme environments (especially lakes and pools where planktic life is potentially possible and independently of their origin) in terms of alkalinity, acidity, DOC, salinity, temperature, light and mixing regime will be outlined. Lakes characterized by more than a single extreme are common (e.g. saline + alkaline; acidic + high DOC + high metal content + low light). At the edge of extremes (e.g. pH of 1; salinity over similar to 100-150 g l(-1)) single species with appropriate physiological adaptation are selected and the phytoplankton is often dominated by a single species (monodominant) setting compositional diversity to zero. Under less extreme conditions permanent equilibria may persist; in many cases over several years in contrast to average lakes where equilibria are rare and ephemeral. Food webs depending on extreme phytoplankton are often atypical for example because the microbial loop is of prior importance or because birds are top predators.

Automated summary

The article explores the characteristics of species living in extreme environments and their impact on phytoplankton communities. In extreme environments, specific species adapted to the conditions are selected, leading to a dominance of one species in the phytoplankton community, while under less extreme conditions, a relatively stable equilibrium can be maintained.