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Philip Heraud - One of the best experts on this subject based on the ideXlab platform.

  • Effects of nitrogen source and UV radiation on the growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Journal of photochemistry and photobiology. B Biology, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    Abstract Cultures of the marine diatoms Phaeodactylum tricornutum and Chaetoceros muelleri were grown in f/2 medium supplied with either nitrate (N-Nt), ammonium (N-Am) or urea (N-Ur) as the nitrogen (N) source at the same final N concentration (0.88 mM). Exponential growth phase cultures of the two diatoms were exposed to four different light regimes for 2 days: (UVAR) PAR (60 μmol quanta m −2  s −1 ) plus 8.22 W m −2 (unweighted) UVAR; (high UVBR) PAR (60 μmol quanta m −2  s −1 ) plus 1.04 W m −2 (unweighted) UVBR plus 13.73 W m −2 (unweighted) UVAR; (low UVBR) PAR (60 μmol quanta m −2  s −1 ) plus 0.19 W m −2 (unweighted) UVBR plus 2.76 W m −2 (unweighted) UVAR and (PAR) PAR (60 μmol quanta m −2  s −1 ) alone (control). No significant effects of N source on the growth rates of the two diatoms were detected. The maximum effective quantum yield of PSII, ΦPSII e-max , and the initial slope of the light curve, α , of P. tricornutum and C. muelleri were all inhibited, whereas I k was somewhat increased, as a consequence of 2 days of exposure to all the UVR treatments. Multiple factor ANOVA revealed that all the major fatty acids, both in P. tricornutum and C. muelleri, were influenced more strongly by N source than by UVR. The composition of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) in P. tricornutum and C. muelleri exhibited almost the same pattern of variation with N source and UVR. The maximum value of SFA was found in the N-Am treatment, that of MUFA in the N-Nt treatment and for PUFA in the N-Ur treatment irrespective of the UV radiation. On the other hand, the impact of UVR resulted in an increase of PUFA and a reduction of SFA both in P. tricornutum and C. muelleri under all N sources.

  • Effect of UV radiation on growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Phycologia, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    Abstract The effect of UV radiation on growth, the maximal effective quantum yield of photosystem II (Fv/Fm), the photosynthetic parameters α, ETRmax and Ik, and the fatty acid composition of two diatoms, Phaeodactylum tricornutum and Chaetoceros muelleri, were examined in batch cultures. The cultures were grown at 18 ± 1°C with a 16 : 8 light : dark cycle under three different light regimes: photosynthetically active radiation (PAR) only (60 μmol photons · m−2 · s−1); PAR + UVA radiation (UVAR) [PAR (60μmol photons · m−2 · s−1) plus 8.22 Wm−2 UVAR] and PAR + UVAR + UVB radiation (UVBR) [PAR (60 μmol photons · m−2 · s−1) plus 13.73 Wm−2 UVAR plus 1.04 Wm−2 UVBR]. The cell density, the Fv/Fm and α values of P. tricornutum and C. muelleri were all inhibited as a consequence of PAR + UVAR + UVBR exposure during the experimental period; on the other hand, ETRmax and Ik were somewhat enhanced under this exposure regime. The P. tricornutum samples were harvested at midexponential growth phase while C. muelleri ...

  • Changes in growth, chlorophyll fluorescence and fatty acid composition with culture age in batch cultures of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Botanica Marina, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    In this study, we investigated changes with culture age in growth rate, FPSIIe-max (the maximal effective quantum yield of PSII,sFv/Fm), the photosynthetic parameters a, rETRmax and Ik, fatty acid composition and macromolecular content (via IR spectroscopy) in batch cultures of Phaeodactylum tricornutum and Chaetoceros muelleri. FPSIIe-max, and the initial slope of the photosynthesis vs. light curve (a) in the two diatoms exhibited almost the same pattern of variation over the experimental period, first increasing slightly to a maximum value, then decreasing with increasing culture age. There was also a significant decrease, with increasing culture age, in the parameters rETRmax and Ik in both diatoms. FT-IR spectra of P. tricornutum and C. muelleri all showed changes over the growth period. The bands attributed to lipids (CH stretching between 3000 cm-1 and 2800 cm-1 along with the ester CsO 1740 cm -1 ) in both diatoms showed the same tendency, increasing with increasing culture age over the entire growth period, consistent with the onset of major nutrient (P) limitation. Changes with culture age were also found in the fatty acid composition. P. tricornutum showed a marked increase in the levels of 16:1 n-7 and 18:1 n-9 and a marked decrease in the levels of 16:3 n-4 and 20:5 n-3 with increasing culture age. There was a slight variation in the fatty acid composition of C. muelleri related to culture age, with the largest increase shown by 16:0 and the largest decrease by 16:3 n-4.

Richard J. Geider - One of the best experts on this subject based on the ideXlab platform.

  • growth under varying light and nitrate: phosphate supply ratios and their influence on critical N: P
    2015
    Co-Authors: Nikos Leonardos, Richard J. Geider
    Abstract:

    of elemental and biochemical composition of Chaetoceros muelleri t

  • Responses of elemental and biochemical composition of Chaetoceros muelleri to growth under varying light and nitrate : phosphate supply ratios and their influence on critical N: P
    Limnology and Oceanography, 2004
    Co-Authors: Nikos Leonardos, Richard J. Geider
    Abstract:

    The critical nitrogen-to-phosphorous ratio (N : P) defines the transition between N and P limitation of growth rate and is not a biological constant. To test the effect of environmental conditions on the critical N : P, we cultured the diatom Chaetoceros muelleri in chemostats with inflow nitrate : phosphate ratios ranging from 5 to 90 mol N (mol P) 21 at two photon flux densities (PFDs; 50 and 700 mmol photons m 22 s 21 ). The nitrate : phosphate ratio marking the transition between N and P limitation increased from between 15‐30 mol N : mol P at the high PFD to 45 mol N : mol P at the low PFD. The particulate ratio marking this transition increased from 16‐23 mol N : mol P at low PFD to 35 mol N : mol P at high PFD. Cell phosphorus and RNA contents decreased with increasing N : P ratio up to the critical N : P ratio for each PFD, above which they remained stable. In contrast, cell dry weight, chlorophyll a, C, N, and protein were not influenced by nitrate : phosphate in the inflow medium, although they were influenced by PFD. Total protein per RNA increased with increasing N : P ratio at the low light conditions, suggesting increased ratio of protein synthesis per RNA. Our results showed the effect of PFD, growth rate, or both on the critical N : P ratio. Agreement was found in the assessment of the transition between N and P limitation on the basis of nutrient enrichment bioassays, cellular elemental (N and P) quotas, and cell RNA content. Our results are consistent with theoretical predictions of higher N requirements under low light conditions due to the coupling of the photosynthetic mechanism with N uptake. In contrast, P-rich cellular components, such as RNA, were dependent on P availability rather than light.

  • Effects of nitrate : phosphate supply ratio and irradiance on the C : N : P stoichiometry of Chaetoceros muelleri
    European Journal of Phycology, 2004
    Co-Authors: Nikos Leonardos, Richard J. Geider
    Abstract:

    The ratio of nitrate consumption to phosphate consumption (the draw-down ratio) during phytoplankton growth is often assumed to equal the Redfield ratio of 16 mol N : 1 mol P. As such, both nutrients are expected to be exhausted simultaneously during phytoplankton blooms in ocean waters where upwelling brings nitrate and phosphate to the surface in the Redfield ratio. We examined the extent to which the draw-down ratio can vary from 16 : 1 in batch cultures of Chaetoceros muelleri grown under two irradiances, and initial NO3 −: PO4 3− ratios of 5 and 35 mol N mol P − 1 in the culture media. Cell growth and nutrient concentration were measured together with particulate C, N and P. Exponential phase growth rates of 0.3 day − 1 and 1.8 day − 1 were observed under low and high light, respectively, while initial NO3 −: PO4 3− ratios did not affect growth rates. The NO3 − to PO4 3− draw-down ratio differed significantly from the Redfield ratio, with the ratio increasing with decreasing irradiance and increasing...

  • impact of iron limitation on the photosynthetic apparatus of the diatom Chaetoceros muelleri bacillariophyceae
    Journal of Phycology, 2001
    Co-Authors: Margaret Davey, Richard J. Geider
    Abstract:

    Iron starvation induced marked increases in flavodoxin abundance and decreases in light-saturated and light-limited photosynthesis rates in the diatom Chaetoceros muelleri. Consistent with the substitution of flavodoxin for ferredoxin as an early response to iron starvation, increases of flavodoxin abundance were observed before declines of cell division rate or chl a specific photosynthesis rates. Changes in the abundance of flavodoxin after the addition of iron to iron-starved cells indicated that flavodoxin was not actively degraded under iron-replete conditions. Greater declines in light-saturated oxygen evolution rates than dark oxygen consumption rates indicated that the mitochondrial electron transfer chain was not affected as greatly by iron starvation as the photosynthetic electron transfer chain. The carbon:nitrogen ratio was unaffected by iron starvation, suggesting that photosynthetic electron transfer was a primary target of iron starvation and that reductions in nitrate assimilation were due to energy limitation (the C:N ratio would be expected to rise under nitrogen-limited but energy-replete conditions). Parallel changes were observed in the maximum light-saturated photosynthesis rate and the light-limited initial slope of the photosynthesis-light curve during iron starvation and recovery. The lowest photosynthesis rates were observed in iron-starved cells and the highest values in iron-replete cells. The light saturation parameter, I k , was not affected by iron starvation, nor was the chl-to-C ratio markedly reduced. These observations were consistent with iron starvation having a similar or greater effect on photochemical charge separation in PSII than on downstream electron transfer steps. Declines of the ratio of variable to maximum fluorescence in iron-starved cells were consistent with PSII being a primary target of iron starvation. The functional cross-section of PSII was affected only marginally (<20%) by iron starvation, with the largest values observed in iron-starved cells. The rate constant for electron transfer calculated from fast repetition rate fluorescence was found to covary with the light-saturated photosynthesis rate; it was lowest in the most severely starved cells.

  • IMPACT OF IRON LIMITATION ON THE PHOTOSYNTHETIC APPARATUS OF THE DIATOM Chaetoceros muelleri (BACILLARIOPHYCEAE)
    Journal of Phycology, 2001
    Co-Authors: Margaret Davey, Richard J. Geider
    Abstract:

    Iron starvation induced marked increases in flavodoxin abundance and decreases in light-saturated and light-limited photosynthesis rates in the diatom Chaetoceros muelleri. Consistent with the substitution of flavodoxin for ferredoxin as an early response to iron starvation, increases of flavodoxin abundance were observed before declines of cell division rate or chl a specific photosynthesis rates. Changes in the abundance of flavodoxin after the addition of iron to iron-starved cells indicated that flavodoxin was not actively degraded under iron-replete conditions. Greater declines in light-saturated oxygen evolution rates than dark oxygen consumption rates indicated that the mitochondrial electron transfer chain was not affected as greatly by iron starvation as the photosynthetic electron transfer chain. The carbon:nitrogen ratio was unaffected by iron starvation, suggesting that photosynthetic electron transfer was a primary target of iron starvation and that reductions in nitrate assimilation were due to energy limitation (the C:N ratio would be expected to rise under nitrogen-limited but energy-replete conditions). Parallel changes were observed in the maximum light-saturated photosynthesis rate and the light-limited initial slope of the photosynthesis-light curve during iron starvation and recovery. The lowest photosynthesis rates were observed in iron-starved cells and the highest values in iron-replete cells. The light saturation parameter, I k , was not affected by iron starvation, nor was the chl-to-C ratio markedly reduced. These observations were consistent with iron starvation having a similar or greater effect on photochemical charge separation in PSII than on downstream electron transfer steps. Declines of the ratio of variable to maximum fluorescence in iron-starved cells were consistent with PSII being a primary target of iron starvation. The functional cross-section of PSII was affected only marginally (

John Beardall - One of the best experts on this subject based on the ideXlab platform.

  • The role of external carbonic anhydrase in photosynthesis during growth of the marine diatom Chaetoceros muelleri
    Journal of phycology, 2017
    Co-Authors: Tamsyne Jade Smith‐harding, John Beardall, James G. Mitchell
    Abstract:

    Carbon dioxide concentrating mechanisms (CCMs) act to improve the supply of CO2 at the active site of ribulose-1,5-bisphosphate carboxylase/oxygenase. There is substantial evidence that in some microalgal species CCMs involve an external carbonic anhydrase (CAext ) and that CAext activity is induced by low CO2 concentrations in the growth medium. However, much of this work has been conducted on cells adapted to air-equilibrium concentrations of CO2 , rather than to changing CO2 conditions caused by growing microalgal populations. We investigated the role of CAext in inorganic carbon (Ci ) acquisition and photosynthesis at three sampling points during the growth cycle of the cosmopolitan marine diatom Chaetoceros muelleri. We observed that CAext activity increased with decreasing Ci , particularly CO2 , concentration, supporting the idea that CAext is modulated by external CO2 concentration. Additionally, we found that the contribution of CAext activity to carbon acquisition for photosynthesis varies over time, increasing between the first and second sampling points before decreasing at the last sampling point, where external pH was high. Lastly, decreases in maximum quantum yield of photosystem II (Fv /Fm ), chlorophyll, maximum relative electron transport rate, light harvesting efficiency (α) and maximum rates of Ci - saturated photosynthesis (Vmax ) were observed over time. Despite this decrease in photosynthetic capacity an up-regulation of CCM activity, indicated by a decreasing half-saturation constant for CO2 (K0.5 CO2 ), occurred over time. The flexibility of the CCM during the course of growth in C. muelleri may contribute to the reported dominance and persistence of this species in phytoplankton blooms.

  • Differential responses of growth and photosynthesis in the marine diatom Chaetoceros muelleri to CO2 and light availability
    Phycologia, 2011
    Co-Authors: Sven Soren Ihnken, Simon Charles Roberts, John Beardall
    Abstract:

    Abstract Ihnken S., Roberts S. and Beardall J. 2011. Differential responses of growth and photosynthesis in the marine diatom Chaetoceros muelleri to CO2 and light availability. Phycologia 50: 182–193. DOI: 10.2216/10-11.1 This study investigated the impact of photon flux and elevated CO2 concentrations on growth and photosynthetic electron transport on the marine diatom Chaetoceros muelleri and looked for evidence for the presence of a CO2-concentrating mechanism (CCM). pH drift experiments clearly showed that C. muelleri has the capacity to use bicarbonate to acquire inorganic carbon through one or multiple CCMs. The final pH achieved in unbuffered cultures was not changed by light intensity, even under very low photon flux, implying a low energy demand of bicarbonate use via a CCM. In short-term pH drift experiments, only treatment with the carbonic anhydrase inhibitor ethoxyzolamide (EZ) slowed down the rise in pH considerably. EZ was also the only inhibitor that altered the final pH attained, althoug...

  • Effects of nitrogen source and UV radiation on the growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Journal of photochemistry and photobiology. B Biology, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    Abstract Cultures of the marine diatoms Phaeodactylum tricornutum and Chaetoceros muelleri were grown in f/2 medium supplied with either nitrate (N-Nt), ammonium (N-Am) or urea (N-Ur) as the nitrogen (N) source at the same final N concentration (0.88 mM). Exponential growth phase cultures of the two diatoms were exposed to four different light regimes for 2 days: (UVAR) PAR (60 μmol quanta m −2  s −1 ) plus 8.22 W m −2 (unweighted) UVAR; (high UVBR) PAR (60 μmol quanta m −2  s −1 ) plus 1.04 W m −2 (unweighted) UVBR plus 13.73 W m −2 (unweighted) UVAR; (low UVBR) PAR (60 μmol quanta m −2  s −1 ) plus 0.19 W m −2 (unweighted) UVBR plus 2.76 W m −2 (unweighted) UVAR and (PAR) PAR (60 μmol quanta m −2  s −1 ) alone (control). No significant effects of N source on the growth rates of the two diatoms were detected. The maximum effective quantum yield of PSII, ΦPSII e-max , and the initial slope of the light curve, α , of P. tricornutum and C. muelleri were all inhibited, whereas I k was somewhat increased, as a consequence of 2 days of exposure to all the UVR treatments. Multiple factor ANOVA revealed that all the major fatty acids, both in P. tricornutum and C. muelleri, were influenced more strongly by N source than by UVR. The composition of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) in P. tricornutum and C. muelleri exhibited almost the same pattern of variation with N source and UVR. The maximum value of SFA was found in the N-Am treatment, that of MUFA in the N-Nt treatment and for PUFA in the N-Ur treatment irrespective of the UV radiation. On the other hand, the impact of UVR resulted in an increase of PUFA and a reduction of SFA both in P. tricornutum and C. muelleri under all N sources.

  • Effect of UV radiation on growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Phycologia, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    Abstract The effect of UV radiation on growth, the maximal effective quantum yield of photosystem II (Fv/Fm), the photosynthetic parameters α, ETRmax and Ik, and the fatty acid composition of two diatoms, Phaeodactylum tricornutum and Chaetoceros muelleri, were examined in batch cultures. The cultures were grown at 18 ± 1°C with a 16 : 8 light : dark cycle under three different light regimes: photosynthetically active radiation (PAR) only (60 μmol photons · m−2 · s−1); PAR + UVA radiation (UVAR) [PAR (60μmol photons · m−2 · s−1) plus 8.22 Wm−2 UVAR] and PAR + UVAR + UVB radiation (UVBR) [PAR (60 μmol photons · m−2 · s−1) plus 13.73 Wm−2 UVAR plus 1.04 Wm−2 UVBR]. The cell density, the Fv/Fm and α values of P. tricornutum and C. muelleri were all inhibited as a consequence of PAR + UVAR + UVBR exposure during the experimental period; on the other hand, ETRmax and Ik were somewhat enhanced under this exposure regime. The P. tricornutum samples were harvested at midexponential growth phase while C. muelleri ...

  • Changes in growth, chlorophyll fluorescence and fatty acid composition with culture age in batch cultures of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Botanica Marina, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    In this study, we investigated changes with culture age in growth rate, FPSIIe-max (the maximal effective quantum yield of PSII,sFv/Fm), the photosynthetic parameters a, rETRmax and Ik, fatty acid composition and macromolecular content (via IR spectroscopy) in batch cultures of Phaeodactylum tricornutum and Chaetoceros muelleri. FPSIIe-max, and the initial slope of the photosynthesis vs. light curve (a) in the two diatoms exhibited almost the same pattern of variation over the experimental period, first increasing slightly to a maximum value, then decreasing with increasing culture age. There was also a significant decrease, with increasing culture age, in the parameters rETRmax and Ik in both diatoms. FT-IR spectra of P. tricornutum and C. muelleri all showed changes over the growth period. The bands attributed to lipids (CH stretching between 3000 cm-1 and 2800 cm-1 along with the ester CsO 1740 cm -1 ) in both diatoms showed the same tendency, increasing with increasing culture age over the entire growth period, consistent with the onset of major nutrient (P) limitation. Changes with culture age were also found in the fatty acid composition. P. tricornutum showed a marked increase in the levels of 16:1 n-7 and 18:1 n-9 and a marked decrease in the levels of 16:3 n-4 and 20:5 n-3 with increasing culture age. There was a slight variation in the fatty acid composition of C. muelleri related to culture age, with the largest increase shown by 16:0 and the largest decrease by 16:3 n-4.

Ying Liang - One of the best experts on this subject based on the ideXlab platform.

  • Effects of nitrogen source and UV radiation on the growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Journal of photochemistry and photobiology. B Biology, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    Abstract Cultures of the marine diatoms Phaeodactylum tricornutum and Chaetoceros muelleri were grown in f/2 medium supplied with either nitrate (N-Nt), ammonium (N-Am) or urea (N-Ur) as the nitrogen (N) source at the same final N concentration (0.88 mM). Exponential growth phase cultures of the two diatoms were exposed to four different light regimes for 2 days: (UVAR) PAR (60 μmol quanta m −2  s −1 ) plus 8.22 W m −2 (unweighted) UVAR; (high UVBR) PAR (60 μmol quanta m −2  s −1 ) plus 1.04 W m −2 (unweighted) UVBR plus 13.73 W m −2 (unweighted) UVAR; (low UVBR) PAR (60 μmol quanta m −2  s −1 ) plus 0.19 W m −2 (unweighted) UVBR plus 2.76 W m −2 (unweighted) UVAR and (PAR) PAR (60 μmol quanta m −2  s −1 ) alone (control). No significant effects of N source on the growth rates of the two diatoms were detected. The maximum effective quantum yield of PSII, ΦPSII e-max , and the initial slope of the light curve, α , of P. tricornutum and C. muelleri were all inhibited, whereas I k was somewhat increased, as a consequence of 2 days of exposure to all the UVR treatments. Multiple factor ANOVA revealed that all the major fatty acids, both in P. tricornutum and C. muelleri, were influenced more strongly by N source than by UVR. The composition of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) in P. tricornutum and C. muelleri exhibited almost the same pattern of variation with N source and UVR. The maximum value of SFA was found in the N-Am treatment, that of MUFA in the N-Nt treatment and for PUFA in the N-Ur treatment irrespective of the UV radiation. On the other hand, the impact of UVR resulted in an increase of PUFA and a reduction of SFA both in P. tricornutum and C. muelleri under all N sources.

  • Effect of UV radiation on growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Phycologia, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    Abstract The effect of UV radiation on growth, the maximal effective quantum yield of photosystem II (Fv/Fm), the photosynthetic parameters α, ETRmax and Ik, and the fatty acid composition of two diatoms, Phaeodactylum tricornutum and Chaetoceros muelleri, were examined in batch cultures. The cultures were grown at 18 ± 1°C with a 16 : 8 light : dark cycle under three different light regimes: photosynthetically active radiation (PAR) only (60 μmol photons · m−2 · s−1); PAR + UVA radiation (UVAR) [PAR (60μmol photons · m−2 · s−1) plus 8.22 Wm−2 UVAR] and PAR + UVAR + UVB radiation (UVBR) [PAR (60 μmol photons · m−2 · s−1) plus 13.73 Wm−2 UVAR plus 1.04 Wm−2 UVBR]. The cell density, the Fv/Fm and α values of P. tricornutum and C. muelleri were all inhibited as a consequence of PAR + UVAR + UVBR exposure during the experimental period; on the other hand, ETRmax and Ik were somewhat enhanced under this exposure regime. The P. tricornutum samples were harvested at midexponential growth phase while C. muelleri ...

  • Changes in growth, chlorophyll fluorescence and fatty acid composition with culture age in batch cultures of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)
    Botanica Marina, 2006
    Co-Authors: Ying Liang, John Beardall, Philip Heraud
    Abstract:

    In this study, we investigated changes with culture age in growth rate, FPSIIe-max (the maximal effective quantum yield of PSII,sFv/Fm), the photosynthetic parameters a, rETRmax and Ik, fatty acid composition and macromolecular content (via IR spectroscopy) in batch cultures of Phaeodactylum tricornutum and Chaetoceros muelleri. FPSIIe-max, and the initial slope of the photosynthesis vs. light curve (a) in the two diatoms exhibited almost the same pattern of variation over the experimental period, first increasing slightly to a maximum value, then decreasing with increasing culture age. There was also a significant decrease, with increasing culture age, in the parameters rETRmax and Ik in both diatoms. FT-IR spectra of P. tricornutum and C. muelleri all showed changes over the growth period. The bands attributed to lipids (CH stretching between 3000 cm-1 and 2800 cm-1 along with the ester CsO 1740 cm -1 ) in both diatoms showed the same tendency, increasing with increasing culture age over the entire growth period, consistent with the onset of major nutrient (P) limitation. Changes with culture age were also found in the fatty acid composition. P. tricornutum showed a marked increase in the levels of 16:1 n-7 and 18:1 n-9 and a marked decrease in the levels of 16:3 n-4 and 20:5 n-3 with increasing culture age. There was a slight variation in the fatty acid composition of C. muelleri related to culture age, with the largest increase shown by 16:0 and the largest decrease by 16:3 n-4.

Aad C. Smaal - One of the best experts on this subject based on the ideXlab platform.

  • Culturing Chaetoceros muelleri using simplified media with different N sources: effects on production and lipid content
    European Journal of Phycology, 2015
    Co-Authors: Isabel Reis Batista, Ainhoa Blanco Garcia, Pim Van Dalen, P. Kamermans, Marc C.j. Verdegem, Aad C. Smaal
    Abstract:

    Land-based bivalve aquaculture depends on large-scale cultures of live microalgae for food. The intensity of large-scale microalgal production is important for cost-effectiveness. Using Walne’s medium as the control, simplified media containing nitrogen, phosphorus, silica, iron, manganese and vitamins were designed to determine the impact of nitrogen source and molar N:P ratio (sodium nitrate, NO3 9:1, ammonium chloride, NH4 9:1 and NH4 25:1) on growth, dry-weight biomass, culture longevity and lipid content of Chaetoceros muelleri, a diatom commonly used in shellfish aquaculture. During the exponential phase (day 6), dry-weight production in simplified media was similar to controls, indicating that this microalga can grow successfully on simplified media and use ammonium as the nitrogen source. The cultures grown on nitrate or ammonium differed in their time-course. Low nitrogen concentration in cultures grown with nitrate caused the collapse of these cultures within 11–13 days, after a short stationary...