Variability in pigment composition and bio-optical characteristics of phytoplankton populations in the Atlantic basin

Understanding sources of variability in the optical properties of phytoplankton and how the properties vary over the global ocean is essential in the development of ocean-colour algorithms to map the distribution of phytoplankton functional groups. Using data from oceanographic cruises covering different biogeochemical biomes and provinces over a broad latitudinal gradient of the Atlantic Basin, this study examined the spatial distribution of phytoplankton diagnostic pigments and absorption coefficients and how they varied with ocean observables (temperature and chlorophyll-a concentration) that can be detected from space. It was found that variation in the chlorophyll a-specific absorption coefficient of phytoplankton at 440 nm, *ℎ(440), was influenced significantly by changes in the proportion of the non-photosynthetic pigment (NPP), whereas pigment indices of cell size showed only a weak correlation with *ℎ(440). There were province- and biome-specific changes in the relationships between both temperature and chlorophyll and *ℎ(440). This suggests that when developing remote-sensing algorithms that use temperature or chlorophyll as a predictor of phytoplankton size structure, the underlying physical oceanographic processes that control the biogeochemistry and ecology of the region should be taken into consideration.