How does cell volume influence the total light absorption efficiency of a mixed population of dinoflagellates with similar cell shapes and pigment compositions?

抄録

In vivo absorption spectra and spectrally reconstructed absorption spectra from HPLC-determined pigment concentrations were obtained and compared for five different mixtures of two dinoflagellates (large cells, Prorocentrum micans and small cells, Prorocentrum minimum) with similar cell shapes and pigment compositions but significant differences in pigment contents and cell volume. Although the large cells contained 4-fold higher chlorophyll a content than the small cells, the observed intracellular chl a contents per unit cell volume (C_i) increased with decreasing cell volume. Exponentially grown cells with the abovementioned characteristics were prepared for use in mixing experiments with 0, 25, 50, 75, and 100% of P. minimum and vice versa for P. micans. The in vivo absorption values determined at nine wavelengths (412, 440, 480, 510, 532, 555, 650, 676, and 700 nm) were significantly associated with the biomass with respect to either cell volume or chl a concentration and were inversely correlated with C_i (p <0.01). The observed package effect [Q*_a (λ)] indicated an overestimation of absorption spectra at all wavelengths by reconstruction. The fractional reduction of pigment absorption due to Q*_a (λ) was wavelength dependent regardless of the mixing ratio of the two populations. The results showed that the product of equivalent spherical diameter and C_i should be considered for quantitative studies of Q*_a (λ) in various chromatic-adapted species in cultures as well as in coastal waters.