13C/12C fractionation by marine diatoms

Abstract

ABSTRACT. The '"C/C distributions in plants record the integrated pattern of photosynthetic carbon acquisition. Most planktonic marine algae arc. small, relatively rare and hard to separate from background particles, so that very few investigat~ons have used 6 ' "~ to study algal photosynthesis in the sea. Diatoms are perhaps the best studied group among the marine microalgae, and this review summarizes current knowledge of effects of temperature, salinity, pH, growth rate and CO2 conccntrations on diatom 6I3C. External CO, concentrations have the strongest effect demonstrated thus far on 13C/''C distributions and Isotope fractionation, with the largest isotopic discriminations found in high CO2 conditions. Both models and culture studies suggest that 6°C values record the balance between algal growth demand versus supply of inorganic carbon In seawater, and that carbon isotope studies can be used to probe the diversity of algal carbon acquisition strategi.es in the sea.

Marine mammals and the community structure of the Estuary and Gulf of St Lawrence, Canada: evidence from stable isotope analysis

“…Although this makes C a less reliable index of trophic position, it is still useful to the study of diet through its use as a tracer of sources of primary productivity. Primary producers vary in their isotopic C signatures according to their origin (terrestrial or aquatic), C pool used and concentration (CO 2 in air, dissolved CO 2 or HCO 3 -in water), prevailing C pathways (C 3 vs C 4 plants), and the condition of the surrounding environment (well mixed or stagnant) (Smith & Epstein 1971, Osmond et al 1981, France 1995, Fry 1996. These properties assist in discriminating between animals which obtain their resources from terrestrial versus aquatic, benthic versus pelagic or inshore versus offshore environments (Ramsay & Hobson 1991, Smith et al 1996, Page 1997.…”

Sharp differences in the δ13C values of organic matter and carbonate encrustations but not in ambient water DIC between two morphologically distinct charophytes

“…On the other hand, the cited authors provide a value of -27.2% as the average d 13 C value of 13 C-depleted plants, similar to our results for C. globularis. Thus, the difference in the d 13 C values for organic matter between C. tomentosa and C. globularis is similar to that between 13 Cenriched C 4 plants, with d 13 C values ranging from -16 to -10%, and C 3 plants, with d 13 C values ranging from -32 to -22% (e.g., O'Leary et al, 1992;Hayes, 1993;Fry, 1996 and reference therein). Because both studied Chara species are members of the same genus and exhibit similar physiological photosynthetic patterns, the aforementioned comparisons point to the possible risk of misinterpreting the carbon source in palaeoecological studies.…”

“…Because both studied Chara species are members of the same genus and exhibit similar physiological photosynthetic patterns, the aforementioned comparisons point to the possible risk of misinterpreting the carbon source in palaeoecological studies. In terrestrial plants, the differing d 13 C values of organic matter are the result of the photosynthetic pathways used for CO 2 fixation and the isotopic signature of the atmospheric CO 2 used for photosynthesis (Fry, 1996 and references therein; Mendonça et al, 2013). In C 3 plants, large fractionation associated with the enzyme ribulose bisphosphate carboxylase/oxygenase (Rubisco), which catalyses the first step in CO 2 fixation, are observed (e.g., O'Leary et al, 1992;Hayes, 1993;Fry, 1996 and reference therein).…”

“…In terrestrial plants, the differing d 13 C values of organic matter are the result of the photosynthetic pathways used for CO 2 fixation and the isotopic signature of the atmospheric CO 2 used for photosynthesis (Fry, 1996 and references therein; Mendonça et al, 2013). In C 3 plants, large fractionation associated with the enzyme ribulose bisphosphate carboxylase/oxygenase (Rubisco), which catalyses the first step in CO 2 fixation, are observed (e.g., O'Leary et al, 1992;Hayes, 1993;Fry, 1996 and reference therein). During photosynthetic carbon fixation in the C 4 pathway, phosphoenolpyruvate carboxylase catalyses the first carbon fixation step, which is associated with a smaller carbon isotope fractionation compared to that of Rubisco (e.g., O'Leary et al, 1992;Hayes, 1993).…”

“…The d 13 C values of CO 2 are 12% lower than those of HCO 3 -at 0°C and 8.4% lower at 30°C (Mook et al, 1974). For this reason, Fry (1996) assumed that under isotopic equilibrium the cells using CO 2 should have d 13 C values 8-12% lower than cells using HCO 3 -. Thus, the d 13 C values of ambient DIC depend not only on the character of a lake but also on the variable in time and space, temperature, and the pH-dependent proportions of CO 2 , HCO 3 -and CO 3 2- (Smith & Walker, 1980;Zhang et al, 1995).…”