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PhD Dissertation Defense - Till Röthig

Start Date: April 13, 2017
End Date: April 13, 2017

ADVISOR: Professor Christian Voolstra
TITLE: Osmoregulation in the Coral Holobiont
DATE: Thursday, April 13, 2017
TIME: 10:00 - 11:00 a.m.
LOCATION: Lecture Hall Level 0 · between Buildings 2 & 3 (Auditorium 0215)

Coral reefs are economically and ecologically important but under considerable decline. The framework builders in coral reefs are scleractinian corals, which comprise so-called holobionts consisting of the cnidarian animal host, its algal symbionts from the genus Symbiodinium, and a complex array of associated microbes (bacteria, fungi, and viruses among others). Corals are commonly considered stenohaline osmoconformers, possessing only limited capabilities to adjust to salinity changes but studies addressing mechanisms underlying salinity adjustment are lacking.

In order to gain insight into omso-adjustive processes in the coral holobiont, this PhD project devised a series of experiments assessing the short- and long-term response of coral holobionts in situ and ex situ and Symbiodinium in vitro and in hospite to salinity changes. The results indicate an acclimatization of coral and Symbiodinium to increased salinity, and changes in the bacterial microbiome that align with the acclimatization of the coral holobiont. Further, potential osmolytes were identified and their potential role in the adjustment of the coral holobiont to changed salinities are discussed. The results indicate that all main compartments of the holobiont (i.e. coral host, Symbiodinium, and bacterial community) contribute to the osmotic adjustment. Further, this project indicates that salinity is a confounding factor in coral health and may be considered to assess coral resilience in future studies. 

Till studied biology at the University of Cologne (GER) and afterwards specialized in marine biology at the University of Bremen (GER). He focused on marine zoological ecology and conducted his MSc on coral resilience to environmental stress at the Australian Institute of Marine Science (AIMS). Till joined KAUST in 2012 were he continued his research focused on coral holobiont resilience to environmental stressors. In his projects he employed ecological, molecular, and metabolomic methods to address the response of coral holobionts to environmental changes.