Quantum-enabled nano-scale rheology of the microbial seawater environment

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Despite appearances, a single drop of seawater is teeming with life. Even more surprising perhaps, is that this microscopic life has a huge influence on both the oceans and our climate. Microorganisms such as phytoplankton and bacteria interact with each other in complex ways that ultimately determine both productivity (how much algae is available at the base of the food web, leading to differences in fish populations and fisheries) and carbon storage in the deep ocean (helping to mitigate climate change). Over the past few decades we have come to realise that these microorganisms live in a world that is patchy - that is their food sources and predators are not spread evenly, even at scales of around 100 micrometres (1/10 of a mm). This microscale patchiness is strongly determined by the way nutrients and other chemicals move at smaller, even nanometric scales.We have recently developed a novel quantum sensing scheme that, when combined with a specific class of fluorescent molecules, can sense nano-scale viscosity in water-environments, therefore outclassing previous classical techniques that can only operate at the micro-scale or at very high viscosities. We aim to further improve our recent demonstration of this technique by optimising the photon sources and also the sensors for the detection of photon pairs.Therefore, by using a range of cutting-edge quantum sensing techniques we will be able to obtain a clear idea of what the nanoscale and microscale environment looks like to a microbe. We will take advantage of new methods to measure viscosity at small scales, microfluidic devices that now allow us to study behavioural responses of individual microbes and of populations in the lab, and novel theory to demonstrate the existence of these processes in real life. Our aim is to consolidate a new field of quantum-enabled nanorheology and to then use this to reveal the 'hidden' impact of small-scale differences in viscosity on the interactions between marine microorganisms and ultimately ocean and climate dynamics. The results generated by this project will improve our understanding of marine microbial interactions in localised areas, but will also help inform global biogeochemical and climate models that rely on accurate estimates of microbial productivity.