05, n = 12, Table 1). In contrast, viral abundances were always lower in the oligotrophic Lake Annecy. Table 1 Physicochemical and biological characteristics of the sampling sites (2 m depth) Parameters LA1 LA2
LB1 LB2 Sampling date 26/03/2007 10/07/2007 02/04/2007 17/07/2007 Temperature °C 6.2 19.6 7.5 20.4 DO mg l-1 10.5 9.7 11.7 10 TOC mg l-1 1.7 2.2 2.1 2.5 NO3 mg l-1 0.2 0.1 0.5 0.2 NH4 μg l-1 2.0 1.0 6.0 4.0 PO4 μg l-1 2.0 3.0 4.0 2.0 P total μg l-1 7.0 6.0 21.0 6.0 Chla μg l-1 0.7 2.7 1.2 0.7 Cyanobacteria 104 cell ml-1 9.0 ± 0.5 15.0 ± 1.1 2.0 ± 0.1 12.0 ± 0.8 Het. Bacteria 105 cell ml-1 24.4 ± 0.3 12.3 ± 0.4 35.0 ± 1.2 25.2 ± 2.0 Viruses 107 part ml-1 3.7 ± 0.1 5.1 ± 0.4 8.3 ± 0.3 15.3 ± 0.7 HNF 102 cell ml-1 7.5 selleck compound ± 1.3 6.9 ± 0.6 2.6 ± 1.3 3.9 ± 1.5 PNF 102 cell ml-1 4.9 ± 1.3 18.0 ± 3.1 1.4 ± 0.2 2.9 ± 0.5 DO, dissolved oxygen; Chl a, Chlorophyll a; TOC, total organic carbon; NO3, nitrate; NH4, ammonium; P total, total phosphorus; Het.
Bacteria, heterotrophic bacteria; HNF, heterotrophic nanoflagellates; PNF, pigmented nanoflagellates. LA1, March sampling in Lake Annecy; LA2, July sampling in Lake Annecy; LB1, April sampling in Lake Bourget; LB2, July sampling in Lake Bourget. Values are means ± standard deviation of results from triplicate measurements. selleckchem Conditions in experimental bottles – Effect of filtration The < 5-μm prefiltration removed a relatively small fraction of both LY2606368 HNF and PNF (less than 20%), whereas the < 1.6-μm filtration removed, as expected, all of them (Table 2). At the start of the experiments, in VF (Viruses+Bacteria+Flagellates) and VFA (Viruses+Bacteria+Flagellates+Autotrophs)
treatments, HNF abundances varied between 2.5 × 102 cell ml-1 (LB) and 6.5 × 102 cell ml-1 (LA), PNF between 1.1 × 102 cell ml-1 (LB) and 14.4 × 102 cell ml-1 (LA), and picocyanobacteria between 0.7 × 104 cell ml-1 (LB) and 11.2 × 104 cell ml-1 L-gulonolactone oxidase (LA) corresponding to 52 to 72% of in situ abundances. Comparatively, a small fraction of the picocyanobacterial community passed through the < 1.6-μm filter and only 0.1 and 0.8 × 104 cell ml-1 were recorded in treatment V (only bacteria and viruses), i.e. 1 to 5% of in situ abundance (Tables 1 and 2). In contrast, filtration through 1.6 μm resulted in a small loss of bacterial and viral abundances (less than 14% and 20%, respectively) whereas after 5-μm filtration, loss never exceeded 4% for heterotrophic bacteria and 13% for viruses. At the beginning of the incubation, heterotrophic bacteria and viral abundances, in the four treatments of all experiments varied between 9.4 × 105 and 33.5 × 105 cell ml-1 and between 2.9 × 107 and 13.4 × 107 virus ml-1, respectively (Figure 1).