Project 3: Do phytoplankton parasites affect marine water quality? A pioneering investigation with a focus on a dominant toxin-producing diatom

The hypothesis underpinning this area of research is that parasitism of phytoplankton is an under-estimated driver of marine ecosystem functioning. In a pilot study, we unveiled many unreported parasites infecting pelagic diatoms. A notable example was the toxin producing, dominant diatom bloom forming Pseudo-nitzschia, which was frequently subjected to epidemic outbreaks of an Ectrogella-like oomycete pathogen during the three consecutive years investigated. This diatom undergoes unexplained inter-annual variations in abundance and toxicity, making our observations particularly relevant to the regulatory framework of water quality monitoring in Scotland. This project is investigating experimentally and in silico the biodiversity and ecological impact of the parasites of diatoms, in particular on the abundance and toxicity of Pseudo-nitschzia sp.

Andrea Garvetto has been appointed researcher for this project which is based at the Scottish Association for Marine Science – SAMS. His research will investigate the Pseudo-niztschia pathogen and other phytoplankton parasites using the sampling programmes run by each partner and a combination of bright field and electron microscopy. Single cell PCR of infected cells, followed by 18S/28S rRNA sequencing, will confirm their phylogenetic position and set a basis for development of Fluorescent In-Situ Hybridisation (FISH) probes.

Andrea will collaborate the Laboratoire Micro-organismes: Genomes et Environment at CNRS which is developing similar approaches on chytrid-diatom infections.  To shed light on the ecological impact of diatom infections, Marine Scotland‘s phytoplankton archive will be screened for pathogen loading in order that we can study the possible correlation between pathogen outbreaks, toxic Pseudo-nitzschia events and other environmental data (temperature, salinity, nutrients, full phyto- and zooplankton community data).

With the expert support of Dr Rowena Stern, phytoplankton time series and metagenomic datasets available at SAHFOS will be used to investigate parasites prevalent in the spatially-extensive North-Atlantic/English Channel region. Public marine metagenomic datasets will also be screened for the presence of diatom related pathogens worldwide. This will broaden the geographical and ecological significance of the project. Bringing Pseudo-nitzschia and its pathogens into laboratory culture will also be attempted although this challenging step is not critical to the success of the project.