PHEOPIGMENT DISTRIBUTION DURING THE 1990 SPRING BLOOM IN THE NORTHEASTERN ATLANTIC

The temporal and depth distributions of phaeopigments were determined during a spring bloom in the northeastern Atlantic in 1990 using rever se phase high performance liquid chromatography. Phaeopigment were ver y low (<8% by mole relative to chlorophyll a) and two forms of phaeoph orbide and two forms of phaeophytin were separated and quantified. Pha eophorbides were the dominant phaeopigments, accounting for 80% of the total phaeopigment molar concentration, and phaeopigments closely tra cked the variations in chlorophyll a by increasing during the developm ent phase of the bloom and declining in the post bloom stage. Producti on of phaeopigments was found to occur predominantly at night, and the se rates exceeded the rates of phaeopigment destruction during the day . Lower phaeopigment-chlorophyll a ratios were determined for the surf ace waters, suggesting that photodegradation was possibly the primary mechanism of phaeopigment disappearance in the euphotic zone. A compar ison of phaeopigment data and phyto- and zooplankton structure indicat es that greater phaeopigment production and grazing pressure occurred in the development phase when diatoms dominated, while grazing and pha eopigment production declined in the post bloom stage dominated by pry mnesiophytes.