My name is Tom Theirlynck and in May 2019 I started as a PhD candidate at the University of Amsterdam and Netherlands Institute for Sea Research (NIOZ) , supervised by Prof. Linda Amaral-Zettler and Prof. Gerard Muyzer. I finished my masters’ in Freshwater and Marine Biology at the University of Amsterdam early 2019, where I worked on microbial communities in ecosystems varying from coral reefs to freshwater lakes. The topic of my current PhD project is the floating macroalgal genus Sargassum. Sargassum is well known for its diverse associated communities, sometimes poetically referred to as the “golden floating rainforest of the Atlantic Ocean”. However, over recent years floating Sargassum has started forming unprecedented accumulations on the coasts of the Caribbean that threaten biodiversity. In my PhD research I will focus on the growth causes and comparative (population) genomics of floating Sargassum and their holobiomes to hopefully gain insight in these urgent environmental issues.

Research questions that I will address in my PhD include the following:

• What are the transcriptional and ecophysiological mechanisms of floating Sargassum in response to abiotic changes in the environment?
• Are different populations of holopelagic Sargassum genetically distinct?
• What is the microbial community composition and what are typically affiliated taxa within holopelagic Sargassum?