KNAW Repository

Methodology of light response curves: application of chlorophyll fluorescence to microphytobenthic biofilms

Herlory, O. and Richard, P. and Blanchard, G.F. (2007) Methodology of light response curves: application of chlorophyll fluorescence to microphytobenthic biofilms. Marine Biology, 153, 91-101. ISSN 0025-3162.

[img]PDF - Published Version
Restricted to KNAW only

752Kb

Official URL: http://dx.doi.org/10.1007/s00227-007-0787-9

Abstract

The light response curve methodology for microphytobenthic biofilms was studied by comparing the two most usual approaches used in pulse amplitude modulated (PAM) fluorometry. The non-sequential light curve (N-SLC) method is characterized by independent measures of the photosynthetic activity across a light gradient whereas the rapid light curve (RLC) method consists of successive measures on the same sample exposed to a stepwise increase of light intensities. Experiments were carried out on experimental microphytobenthic biofilms prepared from natural assemblages and acclimated to dark conditions. In preliminary experiments, N-SLCs were constructed from fluorescence induction curves performed at 12 different photon flux densities (PFDs). A minimum of 50 s of illumination was necessary to reach a stable light response curve; shorter illumination times resulted in underestimating the physiological parameters (α the light utilization coefficient in light-limited conditions and rETRmax the maximum rate of photosynthesis efficiency) of the light response curve. For the comparison between N-SLCs and RLCs, the same time of illumination (50 s) was used for each light step of RLCs so that N-SLCs differed from RLCs only by the way the amount of light was delivered, i.e., a light dose accumulation for RLC. The experimental results showed the difference between the two photobiological response curves. In the lower range of PFDs, RLCs exhibited a larger value of α; in this light-limited part of the response curve the incremental increase of PFDs limited the development of NPQ and resulted in a better optimization of electron transport rate for RLC. In the higher range of PFDs, the trend was reversed and the RLC showed a lower value of rETRmax than the N-SLC did; this is attributed to the light dose accumulation which likely led to a more efficient dispersion of energy, as illustrated by a higher non-photochemical quenching (NPQ). In conclusion, these results confirm that parameters derived from both methods differ in their value and do not bear the same physiological information.

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:4664
Deposited On:16 Sep 2009 02:00
Last Modified:24 Apr 2012 16:47

Repository Staff Only: item control page