Distribution of phytoplankton pigments in the North Pacific Ocean in relation to physical and optical variability

Abstract

To investigate phytoplankton distributions in the North Pacific Ocean, samples of suspended particulate material were collected from the upper 300 m during two cruises in 1985 for detailed analysis of algal pigments by high-performance liquid chromatography (HPLC). Transpacific Leg I along 24°N in April and May, crossed three prominent hydrographic features: the California Coastal Current, the North Pacific Central Gyre and Kuroshio Current. Transpacific Leg II, along 47°N in August and September, crossed the Kuroshio extension, the Subarctic Gyre and the North Pacific Current. Individual pigments were partitioned vertically in the water column, showing distinct spatial patterns across the Pacific Ocean which reflected the large-scale circulation. Vertical distributions of phytoplankton pigments displayed consistent patterns over spatial scales of thousands of kilometers. In near-surface, nitrate-rich waters, fucoxanthin was the dominant carotenoid. In nitrate-poor surface waters, zeaxanthin was the dominant carotenoid at the surface, and 19′-hexanoyloxyfucoxanthin and chlorophyll b concentrations were elevated near the base of the euphotic zone. Phacopigment concentrations greater than a few tens of nanograms per liter were never encountered. Based on Principal Component Analysis, station clustered into three general pigment categories which followed specific hydrographic characteristics of oligotrophic, highly productive and transitional regions.