Abstract
ABSTRACTWe investigated the predation of nano-protozoa (size fraction < 16 μm) on bacteria in four regions of Lake Taihu, China using the dilution method. The results showed that the growth rate of bacteria in the Meiliang Bay, Gonghu Bay, Dapu River mouth, and Lake Center was 0.613 ± 0.024 d−1, 1.015 ± 0.074 d−1, 1.324 ± 0.052 d−1, and 0.924 ± 0.034 d−1, respectively. The predation rate of nano-protozoa on bacteria at these sites was 0.733 ± 0.061 d−1, 1.245 ± 0.096 d−1, 1.930 ± 0.039 d−1, and 1.040 ± 0.025 d−1, respectively. The growth rate at the Dapu River mouth was significantly higher than that at Lake Center and Meiliang Bay, and that at Gonghu Bay was significantly higher than that at Meiliang Bay. The predation rate was significantly higher at the Dapu river mouth than in the other three regions, and the predation rate at Gonghu Bay was significantly higher than in Meiliang Bay. Wind-induced waves, nutrient levels and algal blooms may explain these variations of the nano-protozoa predation rate in Lake Taihu. Our results also indicated that the mean predation rate in Lake Taihu was higher than those of other freshwater, or marine water environments.
Highlights
In many environments, protozoan predation of bacteria is of great biological and ecological importance
The results showed that the growth rate of bacteria in the Meiliang Bay, Gonghu Bay, Dapu River mouth, and Lake Center was 0.613 § 0.024 d¡1, 1.015 § 0.074 d¡1, 1.324 § 0.052 d¡1, and 0.924 § 0.034 d¡1, respectively
The predation rate was significantly higher at the Dapu river mouth than in the other three regions, and the predation rate at Gonghu Bay was significantly higher than in Meiliang Bay
Summary
Protozoan predation of bacteria is of great biological and ecological importance (deLeo and Baveye 1997). Metazoan and protozoan predation regulates bacterial biomass and community structure (Langenheder and Ju€rgens 2001). Predation pressure affected bacterial abundance, diversity, and size–structure distribution (Corno et al 2008). Microcosm experiments have shown that metazoan and protozoan grazers impact the distribution of bacterial biomass (Ju€rgens and Arndt 1997). Zooplankton grazing on bacteria has received increasing attention, such studies have focused on lakes and experimental microcosms, rather than the spatial variations of predation within lakes that differ in trophic status and humic content. Lake Taihu, a large shallow eutrophic lake in China, has four distinct regions characterized by significant differences in their environmental conditions (Qin et al 2007). Gonghu Bay in the northeast is the macrophyte-dominated region, characterized by submersed vegetation, clear water, and diverse communities of fishes and invertebrates.
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