Bacterial abundance and production and their relation to primary production in Funka Bay [Japan]
2001
Lee, C.W. (Hokkaido Univ., Sapporo (Japan)) | Kudo, I. | Yanada, M. | Maita, Y.
Abundances of bacteria, phototrophic picoplankton, and heterotrophic and phototrophic nanoflagellates in Funka Bay were measured on five occasions (from June to November) in a water column with a summer thermocline. Nutrient concentrations (nitrate, nitrite, ammonium and phosphate) in the euphotic layer were low whereas chlorophyll-a concentrations fluctuated from 0.3 to 1.2 microgl sup(-1) . Bacterial abundance ranged from 3.lxi0 sup5 to 1.1X10 sup6 cells ml sup(-1), whereas the heterotrophic nanoflagellate (HNF) abundance ranged from 4.2X10 sup2 to 3.5X10 sup3 cells ml sup(-1) . In the euphotic layer, cyanobacterial abundance ranged from 1.3x10 sup4 to 2.9X10 sup5 cells ml sup(-1) . Bacterial abundance correlated significantly with both chlorophyll-a concentration and HNF. Bacterial growth rates in the euphotic layer were estimated using a dilution culture method, and ranged from 0.024 to 0.048h sup(-1) . Bacterial net production ranged from 8.7 to 23.9mg C m sup(-3) d sup(-1). Net primary production measured in this study ranged from 1.1 to 52.5mg Cm sup(-3) d sup(-1) . We found that for the euphotic layer, integrated bacterial net production (460-780 mg Cm sup(-2) d sup (-1)) was higher than integrated net primary production (220-610 mg Cm sup(-2) d sup(-1) )- The disparity between bacterial net production and net primary production allowed us to suggest that primary production may not be adequate to support bacterial carbon demand, and that other sources of organic matter were also used.
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