Copyright The Oceanographic Society of Japan. Size-Fractionated Chlorophyll a Concentration and Primary Production in the Okhotsk Sea in October and November 1993, with Special Reference to the Influence of Dichothermal Water

• Main Author: Akihiro Shiomoto
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Okhotsk; okhotsk sea
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.469.7206; http://svr4.terrapub.co.jp/journals/JO/pdf/5306/53060601.pdf

Size-fractionated chlorophyll a (Chla) and primary production at the surface were measured in the southern part of the Okhotsk Sea in the late autumn (October) and early winter (November) 1993. The small-sized phytoplankton (<2 and 2–10 µm fraction) ac-counted for more than 70 % of the total in both seasons. The Chla concentration of large-sized phytoplankton (10–200 µm fraction) increased from the late autumn to the early winter, and the plankton production tended to increase. The average Chla concentration was about six times greater and the production about twice as great in the early winter than in the late autumn. The contribution of the large-sized phytoplankton to Chla concentration and primary production tended to increase in the early winter; the plankton accounted for about 20 % of total Chla concentration and primary production. The increase in nutrient concentrations caused by mixing of the surface water and dicho-thermal water, which contains abundant nutrient concentrations, contributed to the in-crease of Chla concentration and production of the large-sized phytoplankton. It is likely, however, that the bloom of the large-sized phytoplankton is not established until spring, probably because of the large respiratory loss and drift-ice covering the surface layer. Keywords: ⋅Okhotsk Sea, ⋅dichothermal water, ⋅ chlorophyll a, ⋅primary production, ⋅nutrient. 1.