Sommaruga, R & Conde, D.
AQUATIC MICROBIAL ECOLOGY 1997, Vol 13, Iss 3, pp 241-248
We studied the seasonal variation in the abundance
of metabolically active bacteria (cells with an active electron transport
system based on the INT-reduction method) and the proportion of active
cells in the euphotic zone of a hypertrophic lake with the objective of
determining the main factors related to their dynamics. The annual average
proportion of active cells was similar to 47% and changed from similar
to 17% in winter to 100% in autumn. Both total direct counts (range: 1.5
to 20.4 x 10(6) ml(-1)) and abundance of active cells (range: 0.4 to 6.0
x 10(6) ml(-1)) varied annually by 14-fold and were highly correlated (r
= 0.74, p < 0.001). Bacterial activity, based on [C-14]leucine uptake,
was more strongly correlated with active bacterial abundance (r = 0.83,
p < 0.001) than with total bacterial counts (r = 0.70, p < 0.001).
Water temperature explained similar to 81% of the temporal variability
of active bacterial abundance but only 55% of total bacterial numbers.
Chlorophyll a concentration (range: 99 to 335 mu g l(-1)) was only weakly
correlated to the abundance of active bacteria (r = 0.34, p < 0.05).
Compared with data from other freshwater systems, our results show that
although in this lake the average proportion of active bacteria was higher,
their absolute abundance was lower than in less
enriched systems.
Keywords: INT Method; Bacterial Activity;
Temperature; Bacterivory; Cell-Specific Activity;
Lakes BACTERIAL PRODUCTION; MARINE-BACTERIA;
NATURAL-WATERS; FRESH-WATER; INDIVIDUAL MICROORGANISMS; METABOLIZING BACTERIA;
PROTEIN-SYNTHESIS; AQUATIC SYSTEMS; COMMUNITY; RESERVOIR
