DIEL PATTERNS IN LIGHT ABSORPTION AND ABSORPTION EFFICIENCY FACTORS OFISOCHRYSIS GALBANA(PRYMNESIOPHYCEAE)¹

Abstract

The chl a specific absorption coefficients [ a * ( ), m 2 и mg chl a Ϫ 1 ] were examined in chemostat culture of the Prymnesiophyceae Isochrysis galbana (Parke) under a 12:12-h light:dark cycle at low light (75 mol photons и m Ϫ 2 и s Ϫ 1 ) and high light (500 mol photons и m Ϫ 2 и s Ϫ 1 ) conditions. Other associated measurements such as pigment composition, cell density, and diameter as the measure of cell size were also made at the two light regimes every 2 h for 2 days to confirm the periodicity. A distinct diel variability was observed for the a * ( ) with maxima near dawn and minima near dusk. The magnitude of diel variation in a * (440) was 15% at low light and 22% at high light. Pronounced diel patterns were observed for cell size with minima near dawn and maxima near dusk. The magnitude of diel variation in cell size was 9.3% at low light and 21% at high light. The absorption efficiency factors [ Q a (440)] were determined by reconstruction using intracellular concentrations of pigments and cell size. The Q a (440) also showed a distinct diel variability, with minima near dawn and maxima near dusk. The diel variation in a * ( ) and Q a ( ) was primarily caused by changes in cell size due to growth, although there was some influence from diel variations in the intracellular pigment concentrations. The results presented here indicated that diel variation in a * ( ) was an important component of the optical characterization of phytoplankton.

Packaging of mycosporine-like amino acids in dinoflagellates

“…In vivo light absorption is highly variable, being affected mostly by photoacclimation (Stramski & Morel 1990), nutrient status (Sosik & Mitchell 1995) and cell size (Ohi et al 2002). UV radiation is also absorbed by phytoplankton and can cause damage to several metabolic pathways (Vincent & Neale 2000).…”

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).…”

“…For the experiments on carbon quota to cell volume relationships regulated by cell division, we chose the Prymnesiophyte Isochrysis galbana as a model species because it is classified as an open-ocean eukaryotic nanophytoplankter based on its size and the division pattern of its cells (Nelson & Brand 1979, Ohi et al 2002. We measured cell volume and cell carbon quota under a 12/12 h light/dark cycle for 48 hours at three light intensities.…”