Simultaneous quantum yield measurements of carbon uptake and oxygen evolution in microalgal cultures - Fig 6

<p><b>(A) Chlorophyll a specific oxygen evolution, and (B) carbon uptake rates, as a function of light intensities measured with the pHOS-MIMS system at 0 and 24 at the start and end of the 24 hours low-to-high light acclimation.</b> Error bars are standard deviations for n = 3; for values with no error bar shown, the standard deviation was smaller than the symbol in the figure. The initial slopes (μmole carbon or oxygen mg^-1 Chla h^-1 [μmole quanta m^-2 s^-1]-1) of the fitted curves were determined using equations developed by Jassby and Platt [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199125#pone.0199125.ref035" target="_blank">35</a>] with values as follows: 2.17 for oxygen evolution at 0 hour; 1.46 for oxygen evolution at 24 hours; 2.12 for carbon uptake at 0 hour; 2.36 for carbon uptake at hour 24 hours.</p

Alkalinity calibration constants and results.

<p>Alkalinity calibration constants and results.</p

The pHOS apparatus for pH calibration, measurement and data logging.

<p>The configuration of nodes on the Arduino UNO controller was simplified to highlight the circuit connections. To improve the precision of pH measurement, the Arduino micro-controller must be plugged in with an independent power supply to avoid reference voltage fluctuation when powered only by the USB connection.</p

P vs. E parameters with data fitted using equations from Platt et al. [22], with sensitivity test results.

<p>P vs. E parameters with data fitted using equations from Platt et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199125#pone.0199125.ref022" target="_blank">22</a>], with sensitivity test results.</p

t-scores of pHOS and MIMS measurements as a function of Chla concentration.

<p>The critical value (CV = 1.943) for 95% confidence in replicates is marked with a dashed line. For Chla > 1.5 μg mL^-1 replicated measurements are not significantly different.</p

Carbon uptake rates vs. irradiance (n = 3) using pHOS.

<p>The estimated net carbon growth rate for a separate culture validation experiment at 110 μmole quanta m^-2 s^-1 is indicated by the closed square and the corresponding interpolation from the pHOS data at the same irradiance is shown in the inverted triangle (n = 6). Carbon uptake rates determined from these two approaches are not significantly different from each other (p > 0.05).</p

Integration of pHOS and MIMS system with the ALG instruments.

<p>The dashed line shows the size and shape of an ALG instruments bioreactor control unit in the background.</p

Physiological parameters measured at 0 and 24 hours during the low-to-high light acclimation (n = 3 for all samples).

<p>Physiological parameters measured at 0 and 24 hours during the low-to-high light acclimation (n = 3 for all samples).</p

Simultaneous quantum yield measurements of carbon uptake and oxygen evolution in microalgal cultures - Fig 8

<p><b>Observations during the 24 hours low-to-high light acclimation of (A) Maximal observed quantum yield for net photosynthesis, (B) the corresponding light intensities where maximal net quantum yield was observed, (C) Photosynthetic quotient of P</b>_<b>max</b>. All data points were determined from a P vs. E curve fitted to the mean of 3 replicates; see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199125#pone.0199125.g006" target="_blank">Fig 6</a> for typical statistics for the replicates that were fitted.</p

Empirical determination of PAR light attenuation within the ALG instruments measurement cuvette as a function of OD₇₅₀.

<p>For OD₇₅₀ less than 0.35 the effect of culture density has less than 10% reduction of PAR.</p