Automated detection and enumeration for toxic algae by solid-phase cytometry and the introduction of a new probe for Prymnesium parvum (Haptophyta: Prymnesiophyceae)

Abstract

Harmful algal blooms have a severe impact on aquaculture and fishery and can be caused by toxic haptophytes and dinoflagellates. Different toxic species, which are not easy to distinguish from their morphologically similar and non-toxic relatives, occur in both groups. Sequencing of the large subunit ribosomal RNA of different strains and taxonomic relatives allowed the design of a probe specific to the toxic Prymnesium parvum spp. For the rapid detection and enumeration of Prymnesium and Alexandrium cells in cultures and environmental samples, respectively, protocols for fluorescence in situ hybridization were adapted for automated detection by a solid-phase cytometer, the ChemScan. This cytometer enables the automated counting of fluorescently labelled cells on a membrane filter and subsequently a microscopic verification of these results by the user, because the motorized stage of the microscope is driven to each positive signal by the computer software to localize that cell on the filter. With this fast detection method, it was possible to detect, enumerate and verify microalgal cells on a filter, with a detection limit of one cell per membrane filter.