Vertical distribution of phaeopigments—I. A simple grazing and photooxidative scheme for small particles

Abstract

The vertical distribution of phaeopigments in the open temperate ocean generally parallels the patterns in the vertical distribution of chlorophyll a. When the euphotic zone is thermally stratified the principal difference between the vertical distribution of chlorophyll and its degradation product is that the concentration of phaeopigment relative to that of chlorophyll increases with depth. We suggest that particles containing phaeopigments are so small that their sinking is not significant in determining their distribution. The suggestion is supported by the particle size distribution; the majority of phaeopigment is in particles < 5 μ in diameter. We also suggest that the distribution of such small particles results from two balancing processes, the production of phaeopigment by the grazing of microzooplankton herbivores and the loss of the pigment by photooxidation.