Fluorescence tracer technique reveals novel energy pathways in aquatic systems

Šimek, K. and Sirová, D. 2019: Fluorescently Labeled Bacteria as a Tracer to Reveal Novel Pathways of Organic Carbon Flow in Aquatic Ecosystems.  J. Vis. Exp. (151), e59903, doi:10.3791/59903

Elucidating trophic interactions, such as predation and its effects, is a frequent task for many researchers in ecology. The study of microbial communities has many limitations, and determining a predator, prey, and predatory rates is often difficult. Presented here is an optimized method based on the addition of fluorescently labelled prey as a tracer, which allows for reliable quantitation of the grazing rates in aquatic predatory eukaryotes and estimation of nutrient transfer to higher trophic levels.

Two examples of estimates of bacterivory rates in bacterivorous ciliate species from quite distinct environments are presented in detail. The first case study was conducted in an epilimnetic environment from the mesotrophic Římov water reservoir in the Czech Republic, which shows grazer and bacterial abundances comparable to most surface freshwater bodies (cf. references in the pdf file). The second case study was conducted in the highly specific environment inside traps of the aquatic carnivorous plant Utricularia reflexa, which hosts extremely high numbers of both grazing mixotrophic ciliates (Tetrahymena utriculariae) and bacterial cells. Calculations of cell-specific grazing rates and bacterial standing stocks in both sample types are shown. A range of ecological interpretations of the results is then discussed, and examples of possible follow-up studies are finally suggested.

The pdf file of the article is available on: Fluorescently Labeled Bacteria as a Tracer to Reveal Novel Pathways of Organic Carbon Flow in Aquatic Ecosystems

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