This document describes a spectrophotometric method for determining the chlorophyll-a content corrected for phaeopigments as a measure of the amount of phytoplankton for all types of surface water including marine water. The determination limit is usually 2 µg/l to 5 µg/l and is calculated by each laboratory individually. It can be as low as 0,5 µg/l using 2 l of sample (or even more) and a 50 mm cuvette.
NOTE In some measurement programs like marine studies on time series data and ecological status/classification no correction for phaeopigments is used and acidification is omitted, e.g. as recommended by OSPAR.