MEASUREMENT OF FILAMENTOUS CYANOBACTERIA BY IMAGE-ANALYSIS

A method of image analysis is described for measuring total filament l engths of cyanobacteria collected on membrane filters from samples of natural populations or cultures. Images of autofluorescent filaments v iewed by epifluorescence microscopy were transferred to a computer scr een by using a high resolution television camera and an image integrat or to enhance sensitivity. The digitised images, saved as 0.4 Mbyte bi tmap computer files, were analysed with an image analysis program. An evaluation is made of procedures for determining the total length of f ilaments from the detected area or perimeter of their skeletonised ima ges. Methods are described for correcting errors arising from the orie ntation, crossing and overlapping of filaments.