Assessment of a new method in protist research: NanoSIMS analysis
Summary
The hypereutrophic Lake Taihu in China was used as a model system for the development of a new
method in protist research. The possibilities and challenges of nanoscale secondary ion mass
spectrometry (NanoSIMS) analysis were assessed for the study of carbon transfer by protists. Lake
samples were incubated with 13C-labelled DIC (13C-NaHCO3) to study the uptake and transfer of carbon
in the Taihu food web. The NanoSIMS 50L instrument (Cameca) was used to measure stable carbon
isotope ratios in protists and the cyanobacteria Microcystis sp. Individual organisms were studied to
assess spatial heterogeneity within the cells. Precipitated crystals interfered with the signal of the
organisms. A way to remove crystals or to prevent crystal formation must be developed in the future.
Regions of interest were identified and analyzed. Significant differences were found between a light
and dark uptake experiment indicating the importance of autotrophs for the food web. 13C/(12C+13C)
values increased over the timepoints of the incubation experiment. The high 13C/(12C+13C) values of
protists indicated autotrophy. Although several challenges in the methodology remain, the NanoSIMS
approach was promising for single-cell analysis of protists.