Light absorption of Isochrysis galbana (Prymnesiophyceae) under a day–night cycle with ultraviolet radiation

Abstract

Diel variation in chlorophyll a -specific absorption coefficients, a* ph (λ), m 2 (mg chl a), was examined to study the effect of ultraviolet radiation (UVR) on a* ph (λ) of the prymnesiophycean Isochrysis galbana (Parke). A continuous culture was exposed for 2 wk to a 12 h light:12 h dark cycle of photosynthetically available radiation (PAR) supplemented with UVR. Photosynthetic and photoprotective pigments as well as cell density and diameter were also determined every 2 h for 2 d to confirm the periodicity of a* ph (λ). A distinct diel variation was observed, with maxima toward the end of light periods and minima toward the end of dark periods. The magnitude of diel variation in a* ph (440) and a* ph (676) was 14 and 6.6%, respectively. To reconstruct the absorption coefficient, the absorption efficiency factors Q a (λ), were determined using intracellular chl a concentration, cell diameter, and chl a-specific absorption coefficients after solubilization on Triton X, a* TX (λ). The main source of diel variation for Q a (λ) appears to be a* TX (λ). Diel variation in the absorption ratio of photoprotective pigments to chl a was observed to be more significant than that for the absorption ratio of other photosynthetic pigments to chl a. The diel variations in a* ph (λ) were primarily caused by changes in pigmentation of photoprotective pigments due to UVR.

Carbon to volume relationship of Isochrysis galbana (Prymnesiophyceae) during cell divisions

“…The response of MCD estimated using cell volume and/ or carbon quota showed a hyperbolic relationship when the published experimental data were included (Eppley & Coatsworth 1966, Kohata & Watanabe 1986, Berdalet et al 1992, DuRand & Olson 1998, Varela & Harrison 1999, DuRand et al 2002, Ohi et al 2002, 2003p<0.001;Fig. 6).…”

“…6. Relationship between the magnitude of change during cell division (MCD) for cell volume (closed circles) and carbon quota (open circles) and irradiance in nanophytoplankton, determined using data from Eppley & Coatsworth (1966), Kohata & Watanabe (1986), Kohata & Watanabe (1989), Berdalet et al (1992), DuRand & Olson (1998), Varela & Harrison (1999), DuRand et al (2002), Ohi et al (2002), Ohi et al (2003), and the present study with the fitted curve (solid line).…”

“…Previously published data on maxima and minima in either cell volume or carbon quota during cell divisions of nanophytoplankton were obtained from the following sources: Eppley & Coatsworth (1966), Kohata & Watanabe (1986, Berdalet et al (1992), DuRand & Olson (1998), Varela & Harrison (1999), DuRand et al (2002, and Ohi et al (2002Ohi et al ( , 2003. From these sources, we selected the data giving both the cell volume and carbon quota during cell division: Kohata & Watanabe (1989), DuRand & Olson (1998), Varela & Harrison (1999) and DuRand et al (2002).…”

Spectroradiometric monitoring for open outdoor culturing of algae and cyanobacteria

“…Gao et al [69] noted that the morphology of cyanobacteria can be temperature dependent, with increasing temperature leading to increased tightness of the helical spiral structure. Diurnal cycling of the optical properties is not unique to multicellular cyanobacteria, but has been observed for other species as well [70][71][72][73][74][75][76][77][78][79]. The impact of such effects could be considered when relating optical properties to culture parameters.…”

“…The impact of such effects could be considered when relating optical properties to culture parameters. For example, rather than treating culture absorption spectra as temporally invariant, these spectra could instead incorporate the expected deviations due to diurnal cycling [70,72,[75][76][77][78].…”