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Past and future ocean productivity: Using ancient extinction crises to inform how we respond to today’s threats

  • Full or part time
  • Application Deadline
    Monday, January 06, 2020
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

The World’s ocean ecosystems may change fundamentally in the next few centuries due to the severe threats posed by present-day human activities which together are changing natural systems like never before. The Intergovernmental Panel for Climate Change modelling of future oceans predicts that a variety of extreme environmental and ecological changes will occur if we continue on our current trajectory. These changes include an imminent “productivity crisis” due to changes in the availability of the essential nutrient nitrogen (N) discharged from agricultural practices, wastewater treatment, fossil fuel and biomass combustion. Nitrogen drives eutrophication – the over-fertilization the oceans – and changes patterns of global marine primary productivity (Fig. 1), causing proliferation of harmful algal blooms and the depletion of ocean oxygen. The dramatic increases in N discharges since pre-industrial times have altered the balance of the marine fixed-N inventory and will drive future primary productivity changes as global populations, and so demand for resources, continue to grow. Confounding factors associated with climate change are likely to fundamentally change the amount and types of primary and secondary productivity in continental-margin ecosystems (e.g. more bacteria, less fish). These synergistic stresses are predicted to dramatically reduce already diminished biodiversity with catastrophic results for marine ecosystems and the services they provide to humans (e.g., fisheries, coastal protection). Such changes will also destabilise the carbon cycle, with major, unpredictable implications for atmospheric CO2 and global warming (dead biomass is sequestered as carbon in the oceans, reducing the amount in the atmosphere). Of great concern is that we do not know how, and over what time, ecosystems will respond to change, as current models are inadequate.

Earth history records numerous examples of N-cycle perturbations that probably occurred – and had impacts persisting over timescales that were orders of magnitudes longer (millions not thousands of years) than those predicted for the present-day oceans. These ancient crises are associated with the greatest mass extinctions, suggesting a causal link between these phenomena. Models for the modern oceans might hugely underestimate the temporal, spatial, and ecological scales of the impending crisis.

There is a clear mismatch between the forecasts for the future and ancient ocean: it has been suggested that atmospheric N fixation will relieve N limitation in modern oceans, stimulating primary production that in turn sequesters carbon into the oceans, buffering rising atmospheric CO2 concentrations. In contrast, runaway greenhouse conditions have occurred multiple times in deep time (e.g. Early Triassic, 250 million years ago) and were associated with changes in ocean upwelling patterns along continental margins, a reduction in marine productivity and a deepening of the nutricline, reducing the rate of delivery of nutrients to the photic zone, suppressing biodiversity and carbon burial. In order to predict the impact of nutrient changing dynamics on the future oceans, and the global climate they regulate we need to understand the long-term interactions between global warming, productivity, and the global C and N cycles. If the events of the past do play out in the modern oceans, the impending “productivity crisis” will be the greatest threat to life on Earth.

This project will evaluate the causes and consequences of past N-driven productivity crises in the geological record, and determine their links to multiple marine mass extinction events through novel and standard geochemical and palaeontological methods. The data will inform predictions about the Earth’s future.

Funding Notes

Eligible for funding under the NERC Panorama DTP (stipend and UK/EU fees for 3.5 years)

View Website

1) Contact the supervisor of your chosen project to register your interest. Please note that you can only apply for 1 project within the DTP.

2) Apply online - View Website

The programme code is ‘NERC PANORAMA DTP’. Section 10 request information about the research area - you should input the title of the project that you wish to be considered for and the supervisors’ names.

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