Understanding the effects of environmental parameters on endosymbiotic relationship in cnidarians

Scientific background

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.

Person specification

Students with a background in molecular and/or cellular biology, marine biology or aquatic biology should consider applying. An interest in evolution and coral endosymbiosis is essential.

References:

Gong, S., et al. (2018). Flexible Symbiotic Associations of Symbiodinium with Five Typical Coral Species in Tropical and Subtropical Reef Regions of the Northern South China Sea. Frontiers in Microbiology 9(2485).

Ziegler, M., et al. (2017). Biogeography and molecular diversity of coral symbionts in the genus Symbiodinium around the Arabian Peninsula. Journal of biogeography 44(3): 674-686.

Boulotte, N. M., et al. (2016). Exploring the Symbiodinium rare biosphere provides evidence for symbiont switching in reef-building corals. The Isme Journal 10: 2693.

Modepalli, V., et al. (2018). The methyltransferase HEN1 is required in Nematostella vectensis for microRNA and piRNA stability as well as larval metamorphosis. PLoS Genet 14(8): e1007590.

Columbus-Shenkar, Y. Y., et al. (2018). Dynamics of venom composition across a complex life cycle. Elife 7.