MEPS 216:31-41 (2001)  -  doi:10.3354/meps216031

ABSTRACT: To determine whether parameters related to hydrography and phytoplankton utilization of nitrogenous nutrients are responsible for the variability in ratios of euphotic zone-integrated bacterial production (BP) to primary production (PP), we measured bacterial production, primary production, new production, regenerated production and environmental variables in the euphotic zone in May 1995 and June 1996 at a frontal region in the Yellow Sea. The BP/PP ratios were highly variable with different hydrodynamic conditions, ranging from 0.03 for mixed waters to 0.40 for stratified waters. The BP/PP ratios were significantly correlated (r² = 0.64, p < 0.01) with water-column stability of the euphotic zone and, to a greater degree, with sea-surface temperature (SST; r² = 0.74, p < 0.001). SST was also closely correlated with water-column stability (r² = 0.91, p < 0.0001). An inverse relationship was found (r² = 0.61, p < 0.01) between BP/PP and Ÿ-ratios, indicating close association of the variability of the BP/PP ratios with the relative utilization of nitrogen by phytoplankton. High BP/PP values were found when the euphotic zone was stratified and phytoplankton mostly depended on ammonium for nitrogen source, and low BP/PP values were found when the euphotic zone was completely mixed and phytoplankton mostly depended on nitrate. Our results suggest that both turbulent mixing and water temperature were underlying physical forces regulating variations in BP/PP ratios in the Yellow Sea. It might be possible to predict energy pathways in the Yellow Sea and, presumably, in other marine environments by remote-sensing of SST and ocean color.

KEY WORDS: Bacterial production/primary production ratio · Water-column stability · Sea-surface temperature · f-ratio · Yellow Sea