Evaluation of Methods for Chlorophyll Estimation of Littoral Epilithic Microalgae

Abstract

Knowledge on the abundance of epilithic microalgae is necessary to understand the ecology of grazers properly. But, quantitative sampling of microalgae on the natural rock surface is difficult and is prone to wide variations. In this study, I used natural rock tile (commonly called as "Amakusa touseki") and two types of ceramic tiles of size 10×10 cm as artificial substrata to compare the several methods of extraction of chlorophyll. Among the three types of tiles studied, rock tiles recorded highest concentration of chlorophyll contents. The variation of chlorophyll contents within the rock tile was small and was within the range of chlorophyll contents observed on the natural boulders. In the upper and the middle intertidal zones, chlorophyll contents attained constant values within six weeks. But in the lower zone, due to the growth of macroalgal spores, the chlorophyll contents seldom increased steadily and hence the constant values could not be obtained within the period of observations. Comparison of sampling methods showed that brushing and scraping of rock tile surface were less effective than immersing the substratum directly in the extraction liquid in a polyethylene bag (polyethylene-bag method). Among the two extraction liquids tested, the 90 ethanol gave better extraction of chlorophyll than the 90% acetone. After compiling the whole results obtained, it is concluded that the "Amakusa touseki" rock tile is a good substratum to monitor the chlorophyll contents of epilithic microalgae, and 90% ethanol and polyethylene-bag method is the best suitable method for the extraction of chlorophyll.