Ph.D. Dissertation Defense - Nils Rädecker

Jul 04 2019 02:00 PM - Jul 04 2019 03:00 PM

TITLE: Coral Bleaching – Breakdown of a Nutrient Exchange Symbiosis

ADVISOR: Professor Christian Voolstra

DATE: Thursday, July 04, 2019

TIME: 2 p.m. – 3 p.m.

LOCATION: Building 2 - Level 5 - Room 5209


Abstract: Ocean warming is causing the disruption of the symbiosis between corals and their endosymbiotic algae on a global scale. While the symptoms of the resulting coral bleaching have been extensively characterized, our understanding of the underlying causes remains incomplete. By investigating the physiological and molecular heat stress response of the coral-algae symbiosis prior to the onset of bleaching we were aiming to identify processes involved in symbiotic breakdown. We show that heat stress shifts the metabolism of the coral holobiont from a nitrogen-to a carbon-limited state. The resulting changes in nutrient availability destabilize the mechanisms that ensured nutrient exchange between partners in a stable symbiosis. Thereby, heat stress undermines the ecological benefits of hosting photosynthetic symbionts for the host prior to the expulsion of symbionts. Integrating these findings into our mechanistic understanding of the coral-algae symbiosis will not only improve our understanding of the environmental drivers of bleaching but may also help identify novel approaches for preserving coral resilience in an age of rapidly progressing climate change. 

Bio: Nils obtained his bachelor's and master's degree in marine biology at the University of Bremen, Germany. In his bachelor's thesis, supervised by Prof. Christian Wild, he investigated the role of ocean acidification on microbial nitrogen fixation associated with corals. As a master's student, Nils visited KAUST for the first time in 2014 to conduct his experimental work on the effects of nutrient pollution on nitrogen cycling in Red Sea corals. Convinced by the research environment KAUST had to offer, Nils returned in 2015 to start his Ph.D. under the supervision of Prof. Voolstra. In his Ph.D. work Nils combines physiological and molecular tools to investigate the role of metabolic interactions in the coral holobiont during coral bleaching.