Influence of darkness on pigments of Tetraselmis indica (Chlorodendrophyceae, Chlorophyta)

Publication date: Available online 28 June 2018
Source:Journal of Photochemistry and Photobiology B: Biology
Author(s): Sangeeta Mahableshwar Naik, Arga Chandrashekar Anil
In the photic zone, phytoplankton experience diurnal variation in darkness. However, prolonged exposure to aphotic conditions influences their physiological state. Pigment composition is a useful biomarker to decipher cells physiological state and adaptive response to changing environmental conditions. Chlorophyll, a natural pigment is biosynthesised even in darkness and studies have shown such an ability is determined by the genetic characteristics of the organism. The purpose of this study was to examine the influence of darkness on pigments and chlorophyll autofluorescence of Tetraselmis indica. Dark exposure (up to 6 months) had no significant impact on chlorophyll a and b concentration, whereas carotenoids were enhanced. Upon re-illumination pigments gradually recovered to pre-dark phase concentrations. These adaptive survival strategies by altering pigment concentration in response to prolonged darkness is interesting. The absence of loroxanthin and loroxanthin esters in T. indica is reported in a first Tetraselmis species so far. The evaluation of autofluorescence and cellular chlorophyll concentration pointed out that they are not interdependent in this species. Hence, careful consideration of these two factors is needed when either of them is used as a proxy for other. The results obtained encourage a thorough study of pigment analysis, especially when subjected to darkness, to elucidate potential role in the evolution, chemotaxonomy, and survivability of species.