Standing stocks and production rates of phytoplankton and abundance of bacteria in the Seto Inland Sea, Japan |
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Authors: | Kuninao Tada Koji Monaka Masakazu Morishita Toshiya Hashimoto |
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Institution: | (1) Faculty of Agriculture, Kagawa University, Miki, 761-0795 Kagawa, Japan;(2) Faculty of Applied Biological Science, Hiroshima University, 739-8528 Higashi-Hiroshima, Japan |
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Abstract: | Standing stocks and production rates of phytoplankton and abundance of bacteria were investigated at 39 stations in the Seto
Inland Sea, Japan during four crulses in October 1993, January, April and June 1994. Primary productivity was measured by
the13C tracer method. Photosynthetic rate varied from 0.41 to 32.1 μgC/1/h with an average value of 4.67 μgC/l/h. Annual primary
production was estimated to be 218 gC/m2/year. Annual primary production in this study was 1.8 times as high as the values which were previously reported at same
area. The reason for the disagreement between our primary production value and previous values is not thought to be due to
the difference of methods used for measuring primary production or the different Chl.a concentrations but to the method of estimating the primary production in the euphotic zone from thein vitro measurements. The distribution of bacterial cells in surface seawater was examined during the same cruises. Bacterial cell
density ranged from 0.32 to 3.4×106 cells/ml. The density was relatively high in the eutrophic regions of Hiroshima Bay and Osaka Bay In addition, a high density
of bacteria was also observed in an area within Suo Nada where Chl.a was relatively low. The disparity between Chla and bacterial density in Suo Nada suggests that bacterial abundance can be controlled by the availability of substrates other
than phytoplankton exudate. |
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Keywords: | Primary production Seto Inland Sea 13C tracer method bacteria |
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