Does chlorophyllide a reduce reliability of chlorophyll a measurements in marine coastal sediments?

Pigment concentrations (chlorophyll a, chlorophyllide a and pheopigments a) were measured by HPLC and spectrophotometry with acidification on 57 samples collected in different marine coastal sediments, containing autochthonous microphytes, and with various organic matter contents (plant detritus, biodeposits or hydrocarbons). Statistical analysis shows that the spectrophotometry with acidification, as compared to HPLC, gives reliable values for chlorophyll a. Chlorophyllide a concentrations may be considered as negligible. Though spectrophotometric methods are sometimes questioned when applied to sediments they appear to give easy, quick and good estimates of Chl a contents in benthic microphytes for hydrobiological studies in coastal areas.