Dl. Kirchman et al., BIOMASS AND PRODUCTION OF HETEROTROPHIC BACTERIOPLANKTON IN THE OCEANIC SUB-ARCTIC PACIFIC, Deep-sea research. Part 1. Oceanographic research papers, 40(5), 1993, pp. 967-988
As part of the Subarctic Pacific Ecosystem Research (SUPER) program, w
e measured the abundance and biomass production of heterotrophic bacte
rioplankton in the subarctic Pacific and compared these parameters wit
h those of phytoplankton during four cruises in 1987 and 1988. Bacteri
al biomass was about equal to phytoplankton biomass during all cruises
. Based on rates of bacterial biomass production and assuming a growth
efficiency of 50%, we estimate that heterotrophic bacteria consumed 1
0% (June 1987) to 24% (August 1988) of primary production in the eupho
tic zone. These percentages are low compared with other aquatic ecosys
tems, apparently due to low bacterial growth rates (<0.1 day-1) in the
subarctic Pacific. In contrast, phytoplankton growth rates were much
higher (0.1-0.8 day-1). Bacterial growth rates were limited by the sup
ply of dissolved organic matter and temperature. Even with these low g
rowth rates, however, bacterial biomass and rates of biomass productio
n increased by 2-5-fold in May and August 1988, changes that were not
obviously related to corresponding changes in phytoplankton biomass no
r primary production. Heterotrophic bacterioplankton constitutes a lar
ge reservoir of carbon and nitrogen that needs to be considered in mod
elling ecosystem dynamics of the subarctic Pacific.