The Relative Abundance of Pheophorbide a and Pheophytin a in Temperate Marine Waters

Pheophytin a and pheophorbide a were measured with reverse-phase, high-performance liquid chromatography (HPLC) in samples from Dabob Bay, a temperate fjord in Puget Sound, Washington. Pheopigment diversity was higher than expected in all samples analyzed (water column, sediment trap material, and fecal pellets of Calanus pacificus): two major forms of pheophytin a and three major forms of pheophorbide a were separated and quantified. These pigments were labeled by their relative polarity a1 and a2 in the case of pheophytin and a1, a2, and a3 in the case of pheophorbide, with a1 being the most polar. Pheophytin a1 and pheophorbide a2 had the same chromatographic characteristics as the in vitro forms obtained by acidification of Chl a in acetone and chlorophyllide a in methanol. Pheophorbide a1 was present only in the euphotic zone. Pheophorbide a2 showed a maximum at the depth of the Chl a maximum and was least abundant in sediment traps. Pheophorbide a3 was most abundant below the euphotic zone, in sediment traps, and in C. pacificus fecal pellets. Pheophytin forms showed no clear pattern, although pheophytin a2 was more abundant in laboratory experiments than in field samples. The total mass concentration of pheophorbide forms was four times higher, on average, than that of pheophytin forms (n = 64). Because of their field distributions, the more polar may be the more degraded forms of the chlorophyll molecule.