An evaluation of the time required to obtain complete sedimentation of fixed algal particles prior to enumeration

Abstract

Studies were made to investigate the minimum time that should be allowed for settling of fixed, freshwater phytoplankton prior to enumeration. Results using a 16 cm vertical column at 20°C indicated that to obtain complete sedimentation the sample should be allowed to settle for a minimum period of 48 h (8 cm day^-1) when small diatoms are absent, and for at least 96 h (4 cm day^-1) when they are present and to be counted. Green algae settled faster than diatoms. Blue-green algae were absent from all samples in this study.