Spatial and temporal bacterioplankton dynamics during destratification of the James River estuary, Virginia, USA

Abstract

Bacterioplankton abundance and production were examined over the course of a destratification event in the lower James River, Virginia, USA. Goals of the study were to determine if destratification would influence temporal patterns of bacterioplankton parameters and relationships between bacterioplankton and other biological and abiological parameters. Mean bacterial abundance grouped over stations did not change over the course of the study, and were characterized by much smaller coefficients of variation than all other planktonic constituents. However, bacterial production measured by 3H-thymidine (3 H-~d r) incorporation decreased significantly from a stratified (324 pg C I-' d-l) to a destratified (187 pg C I-' d-l) hydrography. The importance of bacterial-autotrophic coupling was also suggested from oxygen metabolism experiments, which indicated substrate limitation of bacteria, and the existence of a rapidly utilized photosynthetically produced substrate. Correlative relationships between bacterial parameters with chlorophyll a were significant during stratified hydrography, but diminished or became non-significant during destratified hydrography. Estimates of microzooplankton grazing rates upon bacteria decreased significantly during the onset of destratification. During the stratified hydrography, bacterial parameters displayed highly significant negative correlations to ammonium, however these relationships disappeared during the destratified hydrography. Results of this study indlcate that destratification changes the trophic interactions of bacterla within the microbial loop, however these changes are not necessarily reflected by temporal patterns of bacterial abundance.

Picoplankton and virioplankton abundance and community structure in Pearl River Estuary and Daya Bay, South China

“…This is the first study, to our knowledge, to evaluate the microbial community structure based on flow cytometry characteristics in Daya Bay waters. Heterotrophic prokaryote abundances (14.55, range (3.61-19.56) × 10 5 cells/mL) in Daya Bay are comparable to those reported by Hamasaki et al (1999) for Sagami Bay and lower than those reported by Koepfler et al (1993) for the Chesapeake Bay and Bai et al (2004) for Jiaozhou Bay, while prokaryote abundance measured in the Pearl River Estuary were within the range recorded in several previous studies (Zhou et al, 2011;Yuan et al, 2011;Zhang et al, 2013). Jellett et al (1996) suggested that the percent contribution of HNA cells to the microbial community (%HNA) could be used as an active cell index.…”

Spatial and temporal variations of picoplankton in three contrasting periods in the Pearl River Estuary, South China

“…However, in some studies, maximal values of bacterial abundance have been detected in the midestuary (Ducklow et al, 1999) or in lower estuarine regions (Koepfler et al, 1993). Coffin and Sharp (1987) stated that the location of bacterial abundance maxima within the estuary was a function of substrate availability i.e.…”