The impacts of storms on coastal marine biogeochemistry and ecosystems

Introduction:

Coastal seas and the life they support are directly influenced by river inputs from land. These inputs carry freshwater that effect currents and density stratification, and nutrients that supports phytoplankton growth. Riverine inputs are subject to intense variations, particularly arising from extreme precipitation events, e.g. storms, but very little is known about how these events impact coastal ecosystems (but see, e.g., Voynova et al 2017). The frequency and intensity of extreme precipitation events is increasing (Thompson et al 2017) and projected to increase into the future under global warming (IPCC, 2013). At the same time, the coastal marine environment is increasingly exploited for food production through fisheries and aquaculture. Near coastal populations are rapidly increasing and becoming more reliant on these resources. Hence, understanding the impacts of storm events on coastal hydrodynamics and biogeochemistry, and the consequences for the marine ecosystems is vital. As an example of potential impacts, the combination of a sudden, intense, input of nutrients and freshwater might lead to increased stratification and strong phytoplankton growth. This increases the risk of Eutrophication, an undesirable disturbance to the marine ecosystem by accelerated algal growth (e.g. Gowen et al 2008). In contrast, accompanying strong winds may disperse effects further off shore, and increased sediment and organic material may inhibit production by reducing light availability in the water column. Repeated storm events over many seasons may then have cumulative effects that alters the character of the regional ecosystem. Hence, the impact of storms on coastal marine ecosystems arise from the interplay of many competing processes, so understanding their effects requires an integrative approach, such as numerical modelling.

Project Summary:

This project will use a combination of hydrodynamic-ecosystem model experiments and observational analysis to explore the effects of storm events on coastal biogeochemistry and the consequences for shelf sea ecosystems. It builds on the model systems developed in the Shelf Seas Biogeochemistry Research Programme (Butenschon et al 2016; Graham et al 2017) and the Land-ocean carbon Transfer project (locate.ac.uk). It will consider both the effects of individual events and how they accumulate over seasons and years, in the context of changing storm frequency and intensity. It will investigate how storms control near coastal physical processes of transport, dispersion and stratification and how these effects drive the biogeochemistry and ecosystem. The geographic focus will initially be the west UK coast, specifically the Celtic Sea and Eastern Irish Sea. These are regions where there have been both intense (the Shelf Seas Biogeochemistry Programme) and sustained (the Liverpool Bay Coastal Observatory) observational effort over recent years, which this project will draw on.

The aim is to use these case studies to develop understanding that is applicable to other coastal regions around the world, particularly
where vulnerability to disruption to coastal ecosystems is most acute (Barange et al 2014). This will build on the NOC’s new National Capability programme in Official Development Assistance, which has a focus on East Africa and South East Asia.

Objectives:

1. Characterise the coastal hydrodynamic response to case study UK storm events
2. Explore the biogeochemical and ecosystem response to the hydrodynamics, focusing on nutrient
cycling and phytoplankton growth.
3. Explore how multiple storm events shape that season’s pattern of phytoplankton growth and their
effects on subsequent years
4. Translate this understanding into an East African or South East Asia case study and explore the
wider implications.

Work plan:

1. Literature review, familiarisation with modelling and data analysis approaches
2. Identifying and characterising storm event case studies, gathering meteorological and terrestrial
forcing data, e.g. from Met Office and CEH.
3. Model experiments and process based analysis: identifying cause and effect
4. Translation to ODA case study and a desk study on wider effects.
5. Output and dissemination: presentation at international conferences and publication.

In addition to the DTP training, the student will receive training in coastal physical and biogeochemical oceanography and modelling approaches. The project would be ideal for a student interested in crossdisciplinary oceanography, with a background in physical, chemical or biological science. Strong numeracy skills and computational literacy are required