This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP). The GW4+ DTP consists of the Great Western Four alliance of the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus five Research Organisation partners: British Antarctic Survey, British Geological Survey, Centre for Ecology and Hydrology, the Natural History Museum and Plymouth Marine Laboratory. The partnership aims to provide a broad training in earth and environmental sciences, designed to train tomorrow’s leaders in earth and environmental science. For further details about the programme please see http://nercgw4plus.ac.uk/
Whether global warming precipitates a major decline in the ocean’s primary productivity, which supports diverse food webs and drives carbon sequestration, will depend on the ability of marine phytoplankton to adapt to rising temperatures. Unfortunately, we currently understand exceptionally little about whether members of the key groups of marine phytoplankton can adapt quickly enough to keep pace with warming and how the potential for adaptation differs among ecotypes from different regions.
Using experimental evolution, we have recently shown that Thalassiosira pseudonana, one of the most abundant and widely distributed marine diatoms, can rapidly evolve tolerance to levels of warming previously in excess of its thermal optimum. We found that the evolution of elevated thermal tolerance was linked to adjustments in physiological traits that increase in the fraction of metabolic energy available for allocation to growth (i.e. the carbon-use efficiency). Whether the capacity and mechanisms of rapid adaptation to warming are common in other key groups of marine phytoplankton, which span enormous physiological and evolutionary diversity are unknown but are central to predicting how marine primary productivity will respond to 21st century climate warming.
This studentship will undertake research to address these knowledge gaps by understanding whether and how diverse, geographically distributed isolates of the most abundant, ecologically and biogeochemically important phytoplankton groups (e.g. Bacillariophyceae, Prasinophyceae, Prymnesiophyceae, Prochlorococcales, Synechoccales) adapt to warming.
Project Aims and Methods:
The overarching aim is to develop a mechanistic understanding of the processes that set the limits of thermal tolerance and the potential for evolutionary adaptation to future scenarios of warming in marine cyanobacteria. The student will achieve this by addressing the following objectives:
Objective 1. Characterising the limits of thermal tolerance and the physiological basis of acclimation. We will use an array of algal taxa spanning multiple phyla and with strains from different geographic locations that are known to vary in their thermal tolerance to characterize how the temperature dependence of photosynthesis and respiration and the capacity for physiological acclimation (plasticity) set the limits of thermal tolerance in marine cyanobacteria. [The student will have flexibility in which taxa and strains are used and we as a team will collaborate on taxa and strain selection]. We will measure thermal responses of photosynthesis and respiration over acute and acclimation timescales and couple these measurements with population growth rate estimates to quantify how changes in temperature alter metabolic allocation to growth, repair and maintenance. We will then use these data to develop and parameterise models of cellular physiology that capture patterns of resource allocation that constrain the thermal niches of diverse algal taxa and ecotypes.
Objective 2. Characterising rapid evolution of elevated thermal tolerance. In objective 1 the student will have quantified the physiological constraints that determine the upper limits of thermal tolerance achievable via phenotypic plasticity alone and the processes that set these constraints. Here we will determine the capacity for, and mechanisms that underpin, genetic adaptation to supra-optimal temperatures using experimental evolution. We will experimentally evolve the isolates characterised in objective 1 under a range of warming scenarios. We will quantify the potential for adaptation by determining fitness improvements in the selected environments and assess the physiological mechanisms underpinning adaptation.
Objective 3. Infusing rapid evolution into an IPCC-class model of ocean biogeochemistry: implications for future projections of marine primary production. This work package will translate our understanding of rapid adaptation of thermal tolerance into a 3D model of plankton in the world ocean, run under climate change scenarios. We will develop a computationally-efficient model for adaptation of phytoplankton thermal tolerance and insert this into MEDUSA – the marine biogeochemical component of the UK Earth System Model (UK-ESM). We will embed this in a global ocean model to simulate the evolution of the thermal response and its impact on marine ecosystem functioning under IPCC climate change scenarios.