Bacterial biomass and production rates in the Gulf Stream front regions

Abstract

3H-Thymidine incorporation rate, bacterial total count and mean bacterial cell volume were measured at eight depths throughout the euphotic zone at 10 stations in Gulf Stream water and front regions in October 1985. Highest rates of bacterial biomass and production were found in the surface layers of entrained shelf water and in the mixing zones between shelf water and Gulf Stream water. High variability in bacterial production and in biomass related to layers of different water masses was observed in the front regions. Thymidine incorporation rate varied between 3 and 300 pmol l −1 day −1 (mean = 30, S. D. = 50, N = 76). Bacterial total count varied between 3.6 × 10 7 and 2.3 × 10 9 cells l −1 (mean = 6.8 × 10 8, S. D. = 4.4 × 10 Su8, N =76). Bacterial mean cell volume varied between 0.01 and 0.11 μm 3 (mean 0.056, S. D. = 0.024, N = 75). Thymidine incorporation rate was positively correlated with bacterial total count, but not correlated with temperature and mean bacterial cell volume.