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.

Responses of Marine Organisms to Climate Change across Oceans

“…Polar species have the narrowest thermal windows and low energy-demand lifestyles, making them particularly sensitive to relatively small changes in temperature. Tropical species also have relatively narrow thermal windows and some species inhabit the warmest waters globally thus are near physiological temperature tolerance limits (Storch et al, 2014). The thermal range tolerated by a species can vary among life stages, with early stages (e.g., egg and larvae) generally being more sensitive (Pörtner and Peck, 2010).…”

Oxygen- and capacity-limited thermal tolerance: bridging ecology and physiology

“…cellular and molecular levels; Pörtner, 2002). Recently, Storch et al (2014) developed a 'complexity index' to compare the largely different thermal limits found across marine organism domains. They found a relationship between sublethal (and lethal) thermal limits and the number of body and cell Box 1.…”

Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

“…Water with lower O 2 concentrations are effectively dead zones for many higher animals (reviewed in Keeling et al, 2010;Storch et al, 2014). Species are also sensitive to thermal stress (Gattuso et al, 2015) and their sensitivity to hypoxia increases with higher temperatures (Pörtner, 2010).…”