title: Climate sensitivity across marine domains of life: limits to evolutionary adaptation shape species interactions.
abstract: Organisms in all domains, Archaea, Bacteria, and Eukarya will respond to climate change with differential vulnerabilities resulting in shifts in species distribution, coexistence, and interactions. The identification of unifying principles of organism functioning across all domains would facilitate a cause and effect understanding of such changes and their implications for ecosystem shifts. For example, the functional specialization of all organisms in limited temperature ranges leads us to ask for unifying functional reasons. Organisms also specialize in either anoxic or various oxygen ranges, with animals and plants depending on high oxygen levels. Here, we identify thermal ranges, heat limits of growth, and critically low (hypoxic) oxygen concentrations as proxies of tolerance in a meta-analysis of data available for marine organisms, with special reference to domain-specific limits. For an explanation of the patterns and differences observed, we define and quantify a proxy for organismic complexity across species from all domains. Rising complexity causes heat (and hypoxia) tolerances to decrease from Archaea to Bacteria to uni- and then multicellular Eukarya. Within and across domains, taxon-specific tolerance limits likely reflect ultimate evolutionary limits of its species to acclimatization and adaptation. We hypothesize that rising taxon-specific complexities in structure and function constrain organisms to narrower environmental ranges. Low complexity as in Archaea and some Bacteria provide life options in extreme environments. In the warmest oceans, temperature maxima reach and will surpass the permanent limits to the existence of multicellular animals, plants and unicellular phytoplankter. Smaller, less complex unicellular Eukarya, Bacteria, and Archaea will thus benefit and predominate even more in a future, warmer, and hypoxic ocean.
authors.affiliation: Department of Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Center for Polar- and Marine Research, Bremerhaven, 27570, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Storch
authors.forename: Lena
authors.initials: L
authors.lastname: Menzel
authors.forename: Stephan
authors.initials: S
authors.lastname: Frickenhaus
authors.forename: Hans-O
authors.initials: HO
authors.lastname: Pörtner
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000222:Adaptation, Physiological; D059001:Aquatic Organisms; D001105:Archaea; D001419:Bacteria; D005075:Biological Evolution; D057231:Climate Change; D017753:Ecosystem; D056890:Eukaryota; D006358:Hot Temperature; D009792:Oceans and Seas; D010100:Oxygen / Q000378:metabolism
chemical_list: D010100:Oxygen
keywords: Archaea; Bacteria; Eukarya; adaptation; complexity of organisms; domains of life; evolution; hypoxia tolerance; oxygen and capacity limited thermal tolerance; thermal tolerance