Comparison of east and west chlorophyll a standing stock and oceanic habitat along the Transition Domain of the North Pacific

• Published in: Journal of Plankton Research
• Main Authors: Shiomoto, Akihiro, Hashimoto, Shinji
• Format: Text
• Language: English
• Published: Oxford University Press 2000
• Subjects: ORIGINAL ARTICLES; Pacific; Subarctic
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/22/1/1; https://doi.org/10.1093/plankt/22.1.1

Chlorophyll (Chl) a was measured every 10 m from 0 to 150 m in the Transition Domain (TD), located between 37 and 45°N, and from 160°E to 160°W, in May and June (Leg 1) and in June and July (Leg 2), 1993–96. Total Chl a standing stocks integrated from 0 to 150 m were mostly within the range of 20 and 50 mg m–2. High standing stocks (>50 mg m–2) were generally observed westof 180°, with the exception of the sporadic high values at the easternmost station. The total Chl a standing stock tended to be higher in the western TD (160°E–172°30′E) than in the central (175°E–175°W) and eastern (170°W–160°W) TD on Leg 1, but the same result was not observed on Leg 2. It was likely that large phytoplankton (2–10 and >10 μm fractions) contributed to the high total Chl a standing stock. We suggest that the high total Chl a standing stock on Leg 1, in late spring and early summer, reflects the contribution of the spring bloom in the subarctic region of the northwestern Pacific Ocean. The distribution of total Chl a standing stock on Leg 2 was scarcely affected by the spring phytoplankton bloom, suggesting that total Chl a standing stock is basically nearly uniform in the TD in spring and summer. Moreover, year-to-year variation in the total Chl a standing stock was observed in the western TD on Leg 1, suggesting that phytoplankton productivity and/or the timing of the main period of the bloom exhibits interannual variations.