Understanding the effects of environmental parameters on endosymbiotic relationship in cnidarians

Coral reef ecosystems constitute habitats of exceptional biodiversity. Their ecological success in costal ecosystem is owed to their endosymbiotic relation with unicellular dinoflagellate algae belonging to the Symbiodinium genus. Coral reefs are declining worldwide due to coral bleaching associated with global climate change. Corals present a diverse range of Symbiodinium communities, which depend to a great extent on ecological conditions, including depth below the sea surface. While the ecology of coral reefs has been extensively studied, the factors affecting this critical endosymbiosis are less well understood. Like stony corals, anemones have symbiotic Symbiodinium species and constitute experimentally tractable models to investigate aspects of the cnidarian-dinoflagellate symbiosis. Anemones can inhabit different depths from the sea surface, possibly by altering their association with Symbiodinium type. To date, however, few studies have investigated the ecophysiology and genetic diversity of Symbiodinium in anemones. This project aims to study the natural depth distribution of anemone Symbiodinium. This will enable us to understand how cnidarians acclimatize to different depths by changing their association with Symbiodinium clades.

Research methodology

Sea anemone samples (Anemonia viridis, and Aiptasia couchii) will be collected from different depths. Environmental parameters (spectral irradiance, water temperature, salinity, oxygen saturation, chlorophyll fluorescence, and light intensity (photosynthetic active radiation) will be recorded at the collection site depths. Tissue samples will be processed to measure the Symbiodinium densities using a LUNA automated cell counter. Symbiodinium species will be identified by genotyping by PCR amplifying the ribosomal internal transcribed spacer 2 region (ITS2). We will carry out field experiments whereby the vertical distribution of anemones will be manipulated. That will let us observe whether altering the anemone depth can influence the Symbiodinium composition and density.

Training

I) Field collection and measurement of physico-chemical parameters in situ.

II) Construction and maintenance of experimental aquaria and animal husbandry.

II) Molecular biology tools and bioinformatics.

III) Advanced microscopy.

IV) Experimental design, data analysis, critical thinking, scientific writing.