Ge. Schultz et H. Ducklow, Changes in bacterioplankton metabolic capabilities along a salinity gradient in the York River estuary, Virginia, USA, AQUAT MIC E, 22(2), 2000, pp. 163-174
Changes in metabolic capabilities of bacterial communities along the estuar
ine salinity gradient may affect the extent of organic matter processing an
d bacterial growth and accumulation during transit through the system; As p
art of a larger study of estuarine microbial processes, we attempted to qua
ntify differences in bacterial community structure using Biolog plates. Bio
log GN plates (Biolog, Inc., Hayward, CA, USA) were used to determine diffe
rences in bacterioplankton community metabolic potential. Biolog GN micropl
ates are 96-well microtiter plates in which each well contains an individua
l carbon source as well the redox dye tetrazolium violet. As bacteria grow
and oxidize each substrate, a purple color is formed that can be quantified
spectrophotometrically. The resultant patterns are a function of the origi
nal community inoculated into the sample wells. Samples were taken weekly f
rom May 1997 through May 1998 at a fixed location. Samples were also collec
ted bi-monthly from July 1997 through May 1998 at 6 stations located along
the salinity gradient. Principal component analysis shows clear differences
in the patterns of community metabolic capabilities along the salinity gra
dient. Bacterial communities were separated by both temperature and salinit
y. Rates of color development mimicked the pattern of a strong landward gra
dient in specific growth rates. Biolog analysis is shown to be a powerful t
ool for identifying shifts in bacterial community composition in space and
time, and provides a useful guide for deeper analysis of bulk property data
.