Simulated In Situ Measurements of Primary Production in Japanese Waters

Katsumi Yokouchi^*, Atsushi Tsuda2, Akira Kuwata3, Hiromi Kasai4, Tadafumi Ichikawa5, Yuichi Hirota5, Kumiko Adachi6, Ichio Asanuma7 and Hiroshi Ishida8

1Seikai National Fisheries Research Institute, Fisheries Research Agency, 1551-8 Taira-machi, Nagasaki 851-2213, Japan

2Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Tokyo 164-8639, Japan 3Tohoku National Fisheries Research Institute, Fisheries Research Agency, 3-27-5 Shinhama-cho, Shiogama, Miyagi 985-0001, Japan

4Hokkaido National Fisheries Research Institute, Fisheries Research Agency, 116 Katsuragoi, Kushiro, Hokkaido 085-0802, Japan

5National Research Institute of Fisheries Science, Fisheries Research Agency, 6-1-21 Sanbashidori, Kochi 780-8010, Japan

6National Research Institute of Fisheries Engineering, Fisheries Research Agency, Ebidai, Hasaki, Kashima 314-0421, Japan

7Frontier Research Promotion Department, JAMSTEC, 2173-25 Showa, Kanazawa, Yokohama, Kanagawa 236-0001, Japan

8General Environmental Technos Co., Ltd., 1-3-5 Ando-cho, Chuo-ku, Osaka 541-0052, Japan

Abstract

In the global carbon cycle and related mapping based on satellite imagery program (GCMAPS), daily primary production, integrated over the euphotic zone (IPP), was measured around Japan for the validation of algorithms to estimate primary productivity derived from satellite observations. A total of 176 measurements were made by simulated in situ deck-incubations and a small number of in situ incubations, with inoculation of stable isotope 13C-bicarbonate, essentially according to the JGOFS protocol. IPP ranged from 30 mgC/m2/day

*Corresponding author.

E-mail address: [email protected] (K. Yokouchi).

Elsevier Oceanography Series 73 65

Edited by H. Kawahata and Y. Awaya ISBN: 0-444-52948-9

© Elsevier B.V. All rights reserved.

in March in Oyashio-transition waters (subarctic) to 3,980 mgC/m2/day in May in continental shelf waters of the East China Sea (ECS, subtropic Case II). IPP varied seasonally in Oyashio-transition waters, with high values from April to August, and very low values from September to March. In contrast, seasonal variations in IPP in other areas were not marked, with a slight increase in May in Kuroshio waters (subtropic) and Tosa Bay (subtropic inshore), and in both May and August in ECS continental shelf waters. We estimated annual primary production (gC/m2/year) to be 340 in ECS continental shelf waters, 280 in Tosa Bay, 200 in Oyashio-transition waters, and 110 in Kuroshio waters. Maximum primary production per unit of chlorophyll a (Ppt) tended to increase with temperature where sea surface temperature (SST) was between 0 and 30°C, but varied largely above about 16°C in the subtropics including Kuroshio waters, Tosa Bay, and ECS continental shelf waters. The water-column light-utilization efficiency index increased as photosynthetically available radiation (PAR) on the surface decreased in Oyashio-transition waters, Kuroshio waters, and ECS continental shelf waters. We propose preliminary empirical relationships for estimating IPP from standing stock of chlorophyll a (IPP) and surface PAR (integrated over a day), for these three waters around Japan.

Keywords: primary production; simulated in situ method; 13C-spiked incubations; seasonal variations; validation

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