Rationalizing elemental ratios in unicellular algae

“The N* approach calculates a metric that compares the amount of nitrate in a water mass with that predicted from the remineralization of planktonic material with a characteristic C:N:P ratio of 106:16:1, generally referred to as the Redfield ratio (Redfield 1958; Falkowski 2000; Michaels et al. 2001).”

“Most notably, resource (light or nutrients) acquisition machinery, such as proteins and chlorophyll, is high in N but low in P, whereas growth machinery, such as ribosomal RNA, is high in both N and”

“:P ratios of around 106:16:1, referred to as the Redfield ratio since its original description in the 1930s (Redfield, 1934; Falkowski, 2000; Arrigo, 2005).”

“This distinction between P and N as ultimate and prox- imate limiting factors is therefore far from clear-cut (Falkowski 2000).”

“Experimental evidence suggests that differences in cellular N:P composition between marine eukaryotic phytoplankton is a reflection of the ratio of total cell protein to ribosomal RN”

“It was generally assumed that individual phytoplankton cell lines were immortal unless an external factor (predation, viral infection or sinking into prolonged darkness) caused their death (Kirchman, 1999; Bidle & Falkowski, 2004; Franklin et al., 2006). Recent research has shown that phytoplankton also undergo the ph…”

“Nitrogen and phosphorus are assimilated and removed from the surface ocean at a ratio within about a factor of 2 of the Redfield ratio (Falkowski, 2000; Karl, 2002).”

“…results from differences among algal species in their cellular P uptake rates and specific growth rates and to associated differences in their biochemical composition, particularly in the abundance of RNA, DNA, R E V IE W phospholipids, and polyphosphate (Falkowski 2000, Geider and La Roche 2002).”

“Furthermore, the reliance on Redfield ratios has been questioned by Falkowski (2000) who pointed out that the ratio is far from constant and has been embraced by aquatic ecologists as conveying more information than is warranted.”

“The above considerations raise the issue of the constancy of N/P ratios, and whether Redfield’s (1958) interpretation that the plankton control rather than respond to the oceanic nitrate/phosphate ratio (see Falkowski, 2000) is correct.”

“This congruence between actual surface particulate ratios and linked changes in deep-water ratios led him to propose that marine chemistry reflects a strong biotic influence (see also Falkowski 2000; Sterner and Elser 2002; Sarmiento and Gruber 2006).”

“(2 00 6) elements are typically derived from the ‘Redfield ratio’ dating back to 1934, suggesting amolar ratio of C106N16P1 as described in Falkowski (2000).”

“:P in microalgal biomass assume tightly constrained and predictable values of 106:16:1 by moles, the canonical so-called Redfield ratio, although deviations from it have been observed (Redfield 1934, Redfield 1958, Falkowski 2000, Geider and LaRoche 2002).”

“Since Redfield (1934, 1958) presented this concept of closely linked 15 elemental ratios in the biogeochemical cycles of the ocean, it has served as one of the foundations of biogeochemical researches (Falkowski, 2000; Falkowski and Davis, 2004).”

“Several recent examinations of the metabolic basis of phytoplankton nutrient limitation and oceanic biogeochemistry (for example, Falkowski 2000; Geider and LaRoche 2002; Arrigo 2005) have deepened our understanding of both nutritional demands of phytoplankton, and of several ‘non-Redfield’…”

“…organic molecules largely determines overall cellular stoichiometry (Geider & La Roche 2002), and reflects both the evolutionary history of plankton lineages (Falkowski 2000, Quigg et al. 2003) and physiological adaptation of organisms to environmental conditions (Finkel et al. 2006, Price 2005).”

“…(POC) and dissolved organic material (DOC) equals inorganic nutrients removed from the water in a Redfield atomic ratio (106 C : 16 N : 1 P, Falkowski 2000); and (2) that the total POC and DOC accumulation is 3 × the measured net accumulation of total phyto- and zooplankton (cf. Banse…”

“Any discussion of phytoplankton stoichiometry should start with the work of Alfred Redfield (1934, 1958; Falkowski 2000).”

“…ribosomal RNA constitutes the major pool, but also free nucleotides and phospholipids), while N is mainly used in proteins but is also needed for nucleic acids and key components of the photosynthetic machinery such as chlorophyll (Falkowski 2000, Geider & La Roche 2002, and references therein).”

“As human activity is thought to have increased N and P loads to coastal waters by different proportions (Falkowski, 2000; Conley et al., 2009), resultant changes in the N”

“Disentangling the relative importance of the influence of these and other mechanisms on the biogeography of algal stoichiometry is challenging because the mechanisms encompass multiple time-scales (ecological to evolutionary) and levels of biological organization (subcellular to ecosystems) (Falkowski, 2000).”

“Today, marine biologists question a strict, linear correlation between nitrogen utilisation and carbon uptake (e.g. Falkowski, 2000; Sorensen and Siegel, 2001; Geider and LaRoche, 2002), and biogeochemical models with constant C:N and C”

“As Paul Falkowski has so eloquently stated “the elemental stoichiometry that we call the Redfield ratio is a result of nested processes that have a molecular foundation but are coupled to biogeochemical processes on large spatial and long temporal scales” (Falkowski, 2000).”

“Indeed, the slow response timescales of some diazotrophs may ultimately render such experiments unfeasible (19, 20).”

“However, Falkowski (2000) suggests that we are still far from achieving that level of understanding and predictability.”

“" Certain fundamental limits on elemental composition in organisms are set by phosphate requirements for nucleotides, nucleic acids and membranes, the nitrogen requirements of proteins and varying iron requirements as a factor in specific enzymes of metabolism (Falkowski, 2000).”

“Nutrient and nutrient-silicate ratios are indicators of the trophic status of water courses, and a typical N:P ratio of a system in balance is expected to be near 16 (Redfield, 1958; Falkowski, 2000 ).”

“:P ratio in phytoplankton (16N:1P; Redfield 1958, Falkowski 2000, Falkowski and Davis 2004).”

“At the primary producer level, many of these effects are well understood, framed largely in the concepts of Leibig’s law of the minimum and Redfield stoichiometry (reviewed by [8 ,9,10 ]).”

“Thus, the assumed C:N:P ratio is the Redfield ratio (106:16:1; average in marine environment) for macroalgae, phytoplankton, zooplankton and non-living organic matter (Atkinson and Smith, 1983; Falkowski, 2000 ).”

“In several oligotrophic parts of the oceans, low iron availability may impede nitrogen fixation, thus preventing the dominance of nitrogen-fixing cyanobacteria ( Falkowski, 2000 ).”

“:P ratios in green algae with cellulose walls (Falkowski 2000) could partially explain the high ratios at low loading rates and the decrease at higher loading rates where filamentous cyanobacteria and diatoms were common turf algae.”

“…in the northern hemisphere are P-limited (Hutchinson, 1971; Turner et al., 2003), there is a mounting evidence that, based on the Redfield ratios of nutrient concentrations, an N-limitation may be more common than the previously suspected one (Bedford, Walbridge & Aldous, 1999; Falkowski, 2000).”

“…by a more comprehensive view that also assigns an important role to silica and to trace elements, and which takes into account changes in the controlling factors at different spatial and temporal scales (Tyrrell 1999, Falkowski 2000, Pahlow & Riebesell 2000, Tréguer & Pondaven 2000, Karl 2002).”

“Redfield (1934, 1958) surmised that the matching stoichiometric proportions of C, N, and P in surface ocean seston, compared to changes in ratios of dissolved elements in deep water, meant that the chemistry of the ocean had a biological basis (Falkowski 2000).”

“This approach, however, may be a poor measure of nutrient limitation for several reasons: (1) analytically determined dissolved inorganic nitrogen and SRP may deviate from ‘‘true’’ nutrient concentrations and do not necessarily reflect the bioavailable fractions (Baldwin 1998; Benitez-Nelson 2000), (2) nutrient requir…”

“The ratio of C–N in phytoplankton is constrained to a fairly narrow range (Falkowski, 2000) near the Redfield ratio (Redfield et al.”

“While it is generally accepted that freshwater ecosystems in the northern hemisphere are P-limited (Hutchinson 1971; Turner et al. 2003), there is mounting evidence that, based on Redfield ratios of nutrient concentrations, N-limitation may be more common than previously suspected (Bedford et al. 1999; Falkowski 2000…”

“N:P ratio of particulate organic matter in the ocean is ~16 N:1P by atoms (Falkowski, 2000), yet the coupling between the vertical flux of organic matter and the ratio of the two elements in the soluble inorganic phases as an ‘emergent’ property of the ocean is generally accepted (Lenton & Watson, 2000).”

“(Falkowski, 2000; Redfield, 1958).”

“He suggested that the ratio of nitrates and phosphates in the interior of the ocean was almost identical to their ratio in plankton, because plankton predetermined the chemical composition of the ocean [172].”

“Although the Redfield ratio is a foundation of marine biogeochemistry, modern oceanography recognizes wide diversions from the assumption that the Redfield ratio of N : P 5 16 : 1 is constant through the ocean and among different phytoplankton species (Falkowski 2000).”

“Since the evolutionary pressure for unicellular algae to take a particular C/N ratio, as exerted by processes with shape-dependent physical limits, is equal for all cells, the Redfield ratio may be a result of biological factors alone, as suggested by Falkowski (2000). The variety of unicellular algal shapes is consis…”

“Falkowski PG. 2000.”

“The establishment of the Red fi eld ratio (C ∶ N ∶ P p 106 ∶ 16 ∶ 1) led to a plethora of studies on the ecological and evolutionary significance of the N ∶ P stoichiometry of freshwater and marine phytoplankton (e.g., Falkowski 2000; Flynn 2002; Sterner and Elser 2002; Loladze and Elser 2011).”

“, 2003), or to mechanistically model the stoichiometry of the nested biochemical processes underlying primary production of unicellular algae (Geider et al., 1998; Falkowski, 2000; Pahlow, 2005).”

“of basic biochemical components ( Falkowski, 2000 ), the relatively stable N/P ratio in T. weissflogii might suggest strict control of the biochemical proportions of these elements in the cell, a homeostatic biochemical condition, particularly related to determining when a cell is ready to divide.”

“Much more work is required as species level variation in elemental composition may not simply translate into community or ecosystem level responses as has been demonstrated for Redfield stoichiometry (Falkowski 2000).”

“:P concentrations and supply ratios are relatively stable in the open ocean (Redfield ratio, 16:1) (Redfield 1958, Falkowski 2000), but there is stronger spatial or temporal variability in coastal seas and in oceanic areas influenced by oxygen minimum zones (Karl et al. 1993, Cavender-Bares et al.…”

“On a regional or temporal scale, however, strong deviations of cellular composition from the Redfield ratio were reported (Fraga, 2001; Geider and LaRoche, 2002) and related to the physiological state of cells (Rhee, 1978; Goldman et al., 1979; Falkowski, 2000; Borchard et al., 2011; Franz et al., 2012a), differences…”

“:P) or nutrient status of phytoplankton is of continual interest and importance in limnology and oceanography (Falkowski 2000; Sterner and Elser 2002).”

“…ratios is that total nutrient ratios represent an integrated measure of nutrient availability over longer time scales (Redfield 1934; Kilham 1990; Falkowski 2000), whereas bioassays, such as N and P debt, alkaline phosphatase activity, and PO4 3– turnover time measure deficiency at shorter…”

“This has recently been further extended to include other important elements [63, 64].”

“Although non-Redfield behavior has been identified, for some plankton species (for instance nitrogen fixers) and during eutrophic periods of algal growth, the Redfield Ratio remains an accepted description of the elemental composition of algae in the open ocean (Folkowski, 2000). The selenium content of SASW and STW p…”

“…cellular components, such as proteins and pigments, have their own stoichiometric 97 characteristics and represent significant amounts of the material in plankton cells, changes in their 98 relative proportions strongly influence bulk stoichiometry (Falkowski, 2000; Geider and La Roche, 99 2002).”

“Increase in anthropogenic influences is expected to affect physical and chemical processes in aquatic ecosystems with a consequential effect on water biogeochemistry (Solomon et al., 2007; van de Waal et al., 2010).”