extreme environments

what is in extreme environment?

• typically defined according to human standards

• extremophiles live in extreme environemnts

  • depending on the textbook: extremophiles are those that require, tolerate, or survive in extreme conditions

extremophiles

organisms that thrive under environmental conditions considered inhospitable to closely related organisms that have not adapted to those conditions, requiring complex adaptations to cope with the associated stressors

characteristics of extreme environments

• lower biodiversity

• simplified food webs

• lower productivity

molecular adaptations to extremes

• DNA- stabilized against high temperature by more binding proteins, more CG pairs

• RNA- more extensive regions of base pairing in areas that need to hold conformation

• membranes- higher temperatures increase saturation, branching and length

• proteins- more β sheets and α helix, hydrophobic core, more stabilizing bonds

• salt- water is limiting. complex animals pump out salt, halophilic bacteria & archaea are isotonic with water

• lack of water- similar to salt. organisms in temporary habitats must be able to withstand desiccation

saline lakes

• form because they are closed basins, evaporation balances with inputs. many lakes on earth are saline

• chemistry dependent upon watershed

• limitation by O2 may be important because solubility decreases with increased salinity

• brine shrimp can be important consumers, will not coexist with fish

hot springs

• thermophilic- heat loving organisms

• bacteria and archaea only inhabit highest temps

• chemistry variable from very acidic to basic

• acid springs dominated by sulfide; sulfur oxidizing bacteria common

cold habitats

• arctic habitats

• organisms inhabit ice and snow

• snow algae color snow pink (produces caratenoids)

• arctic lakes can be ice-free for only a month or two

• Antarctic lakes always have an ice cover

temporary waters and small pools

• can be categorized by permanency

• generally lack fish, larger pools can be important for large crustacea and amphibian breeding

• prairie potholes important for waterfowl

• small pools in plants etc. form unique habitats (important for mosquito larvae)

• some vernal pools (e.g. california) have high numbers of endemic species

• these animals must be able to cope with the water source dissapearing

ultra-oligotrophic habitats

• very low nutrients can be stressful

• if carbonate is low enough, mollusks cannot survive

• organisms grow slowly

deep surface habitats

• all inhabited by microbes as long as liquid water exists

• nematodes found in depths up to 3600m

• fungi are rare, bacteria and archaea most common, protozoa top predators

• active microbes found in waters isolated for 1200 years

water surface layer

• neuston- microbes at surface

• pleuston- microorganisms at surface

• unique chemical and biological habitat

• extreme, high light & UV

• Vela capria use chemical that lowers water tension to move up to 10 cm/s

why study extreme environments?

• biotechnology

• conservation

  • greater risk

  • parallels for human-induced extremes