Blue light effect on growth, light absorption characteristics and photosynthesis of five benthic diatom strains

Bio-optical characteristics and photosynthetic performance of five strains of benthic diatoms belonging to three different species (Nitzschia thermalis Kutzing var. minor Hilse sensu Podzorski, Nitzschia laevis Hust and Navicula incerta Grunow) were examined. The effects of treatments with monochromatic blue light (BL) were also determined. The values of photosynthesis rate at saturating photon fluence rate (PFR) (P-max and ascending initial slope of the P-PFR curves (alpha) ranged from 0.22 to 3.58 mumol O-2 per mg Chl alpha min(-1) and from 0.012 to 0.169 mumol O-2 per mg Chl alpha (mumol photons m(-2) s(-1))(-1) respectively. Onset of light saturation parameter (E-k) ranged from 43 to 12 mumol photons m(-2) s(-1). These values were comparable to those reported from measurements performed with sub-tidal benthic communities. In vivo effective optical cross-section of Chl alpha (alpha* values) was correlated to average cell surface area. Interestingly, alpha* and alpha were also negatively correlated, probably indicating that a higher pigment packaging affects negatively to alpha. The acclimation of the five strains to monochromatic BL for 2 weeks produced a reduction of P-max and alpha although the effective quantum yield of photosystem II (DeltaF/F-m') was not affected. In addition to these changes, chlorophyll alpha increased and alpha* decreased in the five strains. Therefore, it was concludedthat the reduction of alpha* could contribute to the changes in the photosynthetic performance in BL. (C) 2004 Elsevier B.V. All rights reserved.