Stuck in the mud: suspended sediments as a key issue for survival of chrysomonad flagellates

Abstract

The effect of suspended fine sediments on chrysomonad flagellates was investigated for 'Spumella-like' flagellates in laboratory studies and exemplarily for a flagellate community (with a focus on chrysomonads) originating from the oligomesotrophic Lake Mondsee, Austria, using different clay minerals and silicate beads. In the community experiment, the abundances of Spumella-like flagellates decreased significantly after introduction of suspended clays, but on the community level suspended clays did not negatively affect flagellate abundance. In order to understand this taxonspecific response, the influence of different clay characteristics, specifically of particle concentration and size, was investigated for Spumella-like flagellates in laboratory studies. We used ultramicrobacteria, i.e. typical bacterioplankton of Lake Mondsee, as food. For comparison we also investigated growth rates of the Spumella-like flagellates feeding on the large bacterium Listonella pelagia. These experiments confirmed that at bacterial abundances realized in oligotrophic and mesotrophic lakes, the flagellates are severely food limited. The presence of suspended sediments generally decreased the growth at any food concentration tested. This decrease was reflected in shifts of the growth kinetic parameters, i.e. in a positive correlation between the half-saturation constant and the threshold food concentration and a negative correlation between the maximal growth rate and the suspended sediment concentration. The clearance rates strongly decreased when small and large particles were present, but were only slightly affected for intermediate-sized particles. We assume that small particles in the size range of ingestible bacteria interfere with the feeding process and cause lower clearance rates, while intermediate-sized particles may serve as substrate for the attachment of flagellates and to subsequently optimize their clearance rates.

Single bacterial strain capable of significant contribution to carbon cycling in the surface ocean

“…4C). This suggests that preferential feeding of protists on a single morphotype may be prey density threshold-dependent, as has been observed in some freshwater heterotrophic nanoflagellages when feeding exclusively on large bacteria (44). However, even preferred prey populations have been shown to survive and persist during sustained grazing, albeit at low levels, during tight coupling between predator and prey populations (45).…”

Unusual behaviour of phototrophic picoplankton in turbid waters

“…The filtration rate of the rotifer Brachionus calyciflorus and the growth rate of the ciliate Strobilidium gyrans was also supressed by suspended particles at a concentration of 50 mg l -1 or 100 mg l -1 , respectively [63,64]. Pfandl and Boenigk [65] studied the effect of suspended particles (up to 10 mg l -1 ) on colourless chrysomonad flagellates. It has been found, that small suspended particles in the size range of ingestible bacteria interfere with the feeding process of flagellates and cause lower clearance rates [65,66].…”

“…Pfandl and Boenigk [65] studied the effect of suspended particles (up to 10 mg l -1 ) on colourless chrysomonad flagellates. It has been found, that small suspended particles in the size range of ingestible bacteria interfere with the feeding process of flagellates and cause lower clearance rates [65,66]. …”

Protistan Grazing on Marine Bacterioplankton

“…on large and small bacteria, plotted as bacterial abundance (a) or as bacterial biovolume (b). Data are compiled from Boenigk et al (2006) and Pfandl and Boenigk (2006). The large bacterial strain was Listonella pelagia CB5 (mean volume 0.38 mm 3 ) and the small bacterial strain was Polynucleobacter sp.…”