NERC GW4+ DTP PhD Studentship: Evolution and diversity of novel marine nitrogen-fixing organisms and their impact on global climate

Scientific Background and Significance: Ocean phytoplankton are key in regulating the marine ecosystem and climate. Particularly important are phytoplankton which can fix atmospheric N2 into a bio- available source of nitrogen such as ammonium. Because nitrogen is the dominant limiting nutrient in the ocean, nitrogen fixers are crucial in supporting marine productivity and thus regulating our climate via the uptake and sequestration of atmospheric CO2. Unicellular N2 fixers have been shown to play a key role and within this group new symbiotic species have been discovered [Thompson et al., 2012; Bombar et al., 2014]. Interestingly these micro-organisms have undergone genome reduction as a result of establishing symbiotic associations with unicellular algae hosts. A trend in genome reduction likely reflects adaptation of the host to grow in nutrient-poor environments such as the mid-ocean gyres which are geographically dominant. These findings offer an exciting opportunity to study the evolution of nitrogen fixers and their impact on past and present marine life, global nutrient cycles and climate.

Research Methods and Student’s Role: This project aims to study how genomic differences of newly discovered nitrogen fixers and their closest relatives, and how these differences are reflected into their ecological niches (e.g., coastal versus open ocean). The student will mainly employ comparative analyses using genomic data to determine how genetic differences (e.g., gene structure, gene content) relate to ecological differences, geographical distribution and past climatic events. The student will also have the opportunity to use the already developed MIT-Darwin model [Monteiro et al., 2010] to perform numerical investigations of the diversity and importance of these novel organisms to fuelling life in the ocean. This project stands out for its inter-disciplinary nature, novelty and expert supervisory panel, and is a great opportunity for any students interested in marine biology, evolution and climate.