Seaweeds in Cold Seas: Evolution and Carbon Acquisition

Abstract

Much evidence suggests that life originated in hydrothermal habitats, and for much of the time since the origin of cyanobacteria (at least 2.5 Ga ago) and of eukaryotic algae (at least 2.1 Ga ago) the average sea surface and land surface temperatures were higher than they are today. However, there have been at least four significant glacial episodes prior to the Pleistocene glaciations. Two of these (approx. 2.1 and 0.7 Ga ago) may have involved a 'Snowball Earth' with a very great impact on the algae (sensu lato) of the time (cyanobacteria, Chlorophyta and Rhodophyta) and especially those that were adapted to warm habitats. By contrast, it is possible that heterokont, dinophyte and haptophyte phototrophs only evolved after the Carboniferous-Permian ice age (approx. 250 Ma ago) and so did not encounter low (</=5 degrees C) sea surface temperatures until the Antarctic cooled some 15 Ma ago. Despite this, many of the dominant macroalgae in cooler seas today are (heterokont) brown algae, and many laminarians cannot reproduce at temperatures above 18-25 degrees C. By contrast to plants in the aerial environment, photosynthetic structures in water are at essentially the same temperature as the fluid medium. The impact of low temperatures on photosynthesis by marine macrophytes is predicted to favour diffusive CO(2) entry rather than a CO(2)-concentrating mechanism. Some evidence favours this suggestion, but more data are needed.

Loss of Extracellular Superoxide Dismutase Leads to Acute Lung Damage in the Presence of Ambient Air

“…28 At that time, the first photosynthetic organisms, cyanobacteria, became capable of photosynthesis, leading to a sudden increase in oxygen in the oceans and atmosphere. This triggered the development of complex multicellular organisms that depended on oxygen; 29 however, a very complex biology arose as a result of this involving utilization of oxygen and protection against oxygen metabolites.…”

Algal evolution in relation to atmospheric CO 2 : carboxylases, carbon-concentrating mechanisms and carbon oxidation cycles

“…General references on earliest known occurrence of algae: [6][7][8]. References on presence or absence of CO 2 -concentrating mechanisms (CCMs): [9][10][11][12][13][14]. CCM absent in all ?…”

“…All other well-investigated CCMs seem to involve 'normal' carbonic anhydrases, i.e. those catalysing the equilibration of CO 2 and HCO À 3 [11,67,111]: this is the case for 'active CO 2 influx' in cyanobacteria, which involves a carbonic anhydrase in the carboxysome as well as the energized conversion of CO 2 to HCO À 3 at the thylakoid membrane, which is effectively a unidirectional carbonic anhydrase [56].…”

“…Modified from [10]. Further details and references are given in the text and in [10][11][12]101,105,106,110,[112][113][114][115][116][117][118][119][120]. Predicted resource costs of synthesizing and operating a photosynthetic apparatus using a CCM relative to one relying on entry of CO 2 by diffusion [66,[68][69][70][71]73,91,105,121] Pleistocene, they would have had to have survived intervening period(s) of higher CO 2 and higher temperatures.…”

Rewinding the Tape: Selection of Algae Adapted to High Co2 at Current and Pleistocene Levels of Co2

“…Thus, the variability seen in the affinity and regulation of CCMs in microalgae could be partially attributable to neutral variation produced by chance during repeated changes in CO 2 and bicarbonate levels. Examples of both CO 2 -sensitive and CO 2 -insensitive growth have been reported in natural populations of phytoplankton (Hein and Sand-Jensen 1998;Tortell and Morel 2002), as have different CCM regulation strategies, even among phytoplankton with similar biology (Raven et al 2002;Raven 2003;Rost et al 2003). It is clear that historical factors constrain adaptive outcomes over very long timescales in phytoplankton, as can be seen by differences in Rubisco affinities between taxa, in which affinity correlates with atmospheric CO 2 at the epoch when each taxon emerged (Tortell 2000).…”