Climate-driven reductions in dissolved oxygen (DO) of the global ocean interior (ocean deoxygenation) is leading to expansion of permanent oxygen minimum zones (OMZ) that comprise about 7% of ocean volume. Impacts on marine animal distributions and abundance may be particularly significant for high-oxygen-demand top predators, such as warm-bodied tunas and sharks, by reducing habitat volumes as OMZs expand (habitat compression) and concentrating fish further in surface waters where they become more vulnerable to fisheries. But predictions of how exploited oceanic fish actually respond to OMZ expansions are not based on mechanistic understandings, principally because direct measurements of oxygen tolerances and associated metabolic costs have not been determined. OCEAN DEOXYFISH will bring about a step change in understanding of OMZ impacts on oceanic ecology by applying our existing expertise in animal movement studies and by developing new biologging technologies and in situ physiology for measuring oxygen tolerances and metabolism directly in free-living fish. This will enable major unknowns to be addressed concerning how oceanic fish respond physiologically and behaviourally to hypoxia, the role of OMZs in upper-trophic-level ecology, how oceanic fish habitats change with predicted OMZ expansion, and whether this will increase fish vulnerability to fishing gear. We will achieve objectives through linked field, experimental and modelling studies. By focusing on key processes underlying fish responses to DO in situ, new modelling approaches will establish effects of future warming and OMZ shoaling on fish niches and determine how these shift distributions and alter capture risk by fisheries. The project represents a discipline-spanning approach linking physiology to ecology and oceanography, with wide-ranging outcomes for understanding global biotic responses to warming and ocean deoxygenation with direct relevance to sustainable fisheries and species conservation.

SEACELLS addresses fundamental questions in phytoplankton biology from cellular to population scales. Our recent studies of phytoplankton, primitive photosynthetic marine protists that play important roles in ocean biogeochemical cycles, are providing exciting new information on the roles and evolution of membrane transport, cell signalling and metabolic regulation. The research builds on a number of recent findings, including the discovery of cell membrane properties that were thought to be typical of animal cells but now must be considered to be of much more ancient origin. The proposed 5-year programme brings together single cell biophysics, imaging and state of the art molecular biology with in situ studies of natural oceanic phytoplankton populations, focussing principally on two significant groups, the diatoms and coccolithophores. A major aim is to gain critical mechanistic understanding of membrane transport, cellular regulation and key physiological processes at the single cell level along with information on the microenvironment that surrounds cells. This will be used in conjunction with modelling studies to determine how phytoplankton cells regulate their immediate environment and how this in turn interacts with metabolic activity. In order to understand how the physiological properties of single cells in the laboratory translate to behaviour of natural populations we will examine cell physiological properties in natural populations. Knowledge of cell- to-cell variability will provide insights into the plasticity of populations and their responses to changing ocean conditions. Underpinning this is the transfer of single cell technology developed in the laboratory to ship-board platforms. SEACELLS presents a discipline-spanning approach, providing opportunities for cross-fertilization of knowledge and ideas from molecular biology through cell biophysics to in situ oceanography with wide reaching outcomes.

Marine planktonic fungi (mycoplankton) have been largely ignored compared to other plankton groups, such as phytoplankton, especially the roles that they fulfil in marine ecosystems. My research has shown that mycoplankton are a major structural and functional component of coastal ecosystems that have been almost completely overlooked. I have shown that mycoplankton are a substantial proportion of plankton biomass and that saprotrophic mycoplankton are active in coastal ecosystems. Mycoplankton are also a major plankton group in the open ocean and dominate on marine snow particles. These studies demonstrate that fungi have potential roles in the marine carbon cycle including the biological carbon pump. The absence of fungi within a general view of the structure and function of the marine carbon cycle, including a lack of mechanistic understanding of saprotroph functional biology and ecology, represent major knowledge gaps in our understanding of marine ecosystems that must urgently be addressed. MYCO-CARB will address these knowledge gaps through an innovative programme of research. Research cruises at established marine observatories will make an unprecedented assessment of active mycoplankton diversity and abundance across a range of ecosystems; from surface coastal waters to the deep open ocean. Innovative approaches, including molecular ecology tools and ecosystem modelling, will establish the impact of fungal saprotrophs on the marine carbon cycle. A culture collection will be developed, informed by the field-based surveys of natural assemblages to produce ecologically-relevant model fungi. Complementary culture-dependent and -independent systems biology methodologies will determine the underpinning biological machinery of saprotrophic marine mycoplankton. Through the MYCO-CARB research programme, I will open the marine fungal ‘black box’, revealing marine mycoplankton functional biology and ecology, and establishing their roles in the marine carbon cycle.