The evolutionary inheritance of elemental stoichiometry in marine phytoplankton

Abstract

Phytoplankton is a nineteenth century ecological construct for a biologically diverse group of pelagic photoautotrophs that share common metabolic functions but not evolutionary histories. In contrast to terrestrial plants, a major schism occurred in the evolution of the eukaryotic phytoplankton that gave rise to two major plastid superfamilies. The green superfamily appropriated chlorophyll b, whereas the red superfamily uses chlorophyll c as an accessory photosynthetic pigment. Fossil evidence suggests that the green superfamily dominated Palaeozoic oceans. However, after the end-Permian extinction, members of the red superfamily rose to ecological prominence. The processes responsible for this shift are obscure. Here we present an analysis of major nutrients and trace elements in 15 species of marine phytoplankton from the two superfamilies. Our results indicate that there are systematic phylogenetic differences in the two plastid types where macronutrient (carbon:nitrogen:phosphorus) stoichiometries primarily reflect ancestral pre-symbiotic host cell phenotypes, but trace element composition reflects differences in the acquired plastids. The compositional differences between the two plastid superfamilies suggest that changes in ocean redox state strongly influenced the evolution and selection of eukaryotic phytoplankton since the Proterozoic era.

Whole-cell response of the pennate diatom Phaeodactylum tricornutum to iron starvation

“…T he oxidizing conditions of contemporary marine ecosystems result in exceedingly low levels of dissolved Fe (1), and the cellular Fe demand of modern phytoplankton is frequently in excess of Fe availability (1,2). This paradox reflects the likelihood that their biochemical machinery evolved in the Fe-replete, reducing Proterozoic oceans.…”

Effect of different salinities on growth and intra- and extracellular toxicity of four strains of the haptophyte Prymnesium parvum

“…The C:N:P ratios of Prymnesium parvum, grown in nutrient replete media, varied between 80 and 250 C to between 10 and 20 N to 1 P in laboratory studies (Johansson & Granéli 1999, Hagström 2006, Lindehoff et al 2009) and averaged around 80:10:1 in prymnesiophytes during growth (Quigg et al 2003). In our study, P. parvum cells grown at 7 PSU showed a lower C:N:P ratio during exponential stage compared to that at 26 PSU (80:8:1 vs. 100:10:1).…”

“…In our study, P. parvum cells grown at 7 PSU showed a lower C:N:P ratio during exponential stage compared to that at 26 PSU (80:8:1 vs. 100:10:1). This leads to 2 conclusions: (1) the Redfield ratio may not be appropriate to mirror the actual needs for C, N and P in P. parvum (Quigg et al 2003), and (2) salinity influences intracellular C:N:P needs. As strains cultured at 26 PSU showed lower extracellular toxicity, an explanation for the higher C:N:P ratios at 7 PSU could be that cells are accumulating extra P via the uptake of organic material (e.g.…”

Biological system development for GraviSat: A new platform for studying photosynthesis and microalgae in space

“…Algae and cyanobacteria rely on gas exchange with the atmosphere to provide CO 2 and remove excess O 2 generated through photosynthesis. The carbon requirement for green algae and cyanobacteria is extremely high compared to other nutrients (124:16:1 C:N:P) (Quigg et al, 2003). Without CO 2 as an electron acceptor, photosynthetic efficiency decreases; at least for obligate phototrophs, they cannot produce biomass and thus cannot grow.…”