J. Iriberri et al., CHANNELING OF BACTERIOPLANKTONIC PRODUCTION TOWARD PHAGOTROPHIC FLAGELLATES AND CILIATES UNDER DIFFERENT SEASONAL CONDITIONS IN A RIVER, Microbial ecology, 26(2), 1993, pp. 111-124
The objective of this study was to analyze the flux of biomass through
the communities of bacteria and phagotrophic protists in the cold and
warm conditions occurring seasonally in Butron River. Bacterial and h
eterotrophic protistan (flagellate and ciliate) abundance was determin
ed by epifluorescence direct counts; protistan grazing on planktonic b
acteria was measured from fluorescently labeled bacteria uptake rates;
and the estimate of bacterial secondary production was obtained from
[H-3]thymidine incorporation rates. The abundance of bacterial, flagel
late, and ciliate communities was similar during cold and warm situati
ons. However, we observed that estimates of dynamic parameters, i.e.,
secondary bacterial production and protistan grazing, in both situatio
ns were noticeably different. In the warm situation, grazing rates of
flagellates and ciliates (bacteria per protist per hour) were, respect
ively, 7 times and 18 times higher than those determined in the cold s
ituation, and the grazing rates of the protistan communities (bacteria
per protists present in 1 ml of water per hour) increased up to 5 tim
es in the case of flagellates and 42 times in the case of ciliates. Es
timates of bacterial secondary production were also higher during the
warm situation, showing a ninefold increase. The percentage of bacteri
al production preyed upon by flagellates or ciliates was not significa
ntly different between the two conditions. These results showed that i
n the different conditions of a system, the flux of biomass between th
e trophic levels may be quite different although this process may not
be reflected in the abundance of each community of bacteria, flagellat
es, and ciliates.