ACCUMULATION OF A PHEOPHORBIDE-A-LIKE PIGMENT IN SEDIMENT TRAPS DURING LATE STAGES OF A SPRING BLOOM - A PRODUCT OF DYING ALGAE

We examined the concentration and composition of pigments in material collected in a sediment trap array that collected samples over 14 sequ ential 4-d periods covering a spring bloom which was dominated by diat oms. Pyropheophorbide a, a chlorophyll a derivative known to be produc ed by copepod grazing, accumulated in traps in similar amounts through out the bloom period. A second more polar a-type pheophorbide accumula ted only during late stages of the bloom, in amounts comparable with t hose of chlorophyll a (+ isomers) and higher than those of pyropheopho rbide a. This pheophorbide was spectrally and chromatographically very similar to a pheophorbide a-like pigment that has been attributed els ewhere to dying Phaeocystis. Previously, pheopigments in the water col umn and in sediment traps have been considered products of zooplankton grazing, but dead or dying phytoplankton may contribute significantly to both pools.