IAP2-22-347

Scotland’s salt marshes in a changing climate

Salt marshes are coastal habitats that support biodiversity and provide a range of critical climate adaptation and mitigation services. In Scotland, salt marshes occur in a variety of landscape settings, behind sandy barriers, within sea lochs, and in estuaries. It is largely unknown whether the response to climate change of marsh habitat in Scotland differs between these settings and what the main drivers for change are in different landscapes. This knowledge gap needs to be filled to be able to mitigate against the threats to the salt marshes in a changing climate. The PhD candidate will assess which processes currently determine the habitat characteristics at the lower and upper elevational limits of salt marsh in the three landscape settings. This will be achieved through hydrological data collection using novel low-cost data loggers, botanical, microfossil and geomorphic surveys in addition to GIS and statistical modelling. The candidate will develop a conceptual approach to understand the role of short and long-term variability of hydrological forcing from local to landscape scale for the future trajectories of salt marsh habitats in Scotland. This studentship was developed in partnership with NatureScot.

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Image Captions

Scottish salt marsh

Methodology

This is a fieldwork-based PhD with sites across Scotland in which the candidate will acquire hydrological, botanical, soil science, remote sensing and statistical modelling skills to assess which processes determine the current extent of salt marsh plant communities in contrasting geomorphic landscape settings. The candidate will use and further develop the low-cost Mini Buoys (Balke et al. 2021) and survey equipment to assess tidal and fluvial hydrological constraints on marsh habitats. These hydrological data will be linked to variations in salinity and sedimentation across the sites, two key drivers that determine how saltmarshes will respond to changing external forcing. The continuous deployment of the Mini Buoys will allow the student to assess and model hydrological seasonality effects linked to local weather conditions. The gathered local information on the relative importance of fluvial and tidal input that regulate salinity, inundation and sedimentation characteristics will then be upscaled for Scotland and changes predicted into the future. The project will also include re-analyses of tide gauge data for ecologically relevant high-water levels and the incorporation of available climate change scenarios. Past response of different kinds of Scottish salt marshes (back-barrier, loch-head and estuarine) to 20th Century relative sea-level (RSL) rise will be assessed using microfossil- and sediment-based RSL reconstruction methods. These will include sediment sampling, microscope-based microfossil analysis (either diatoms or foraminifera) and dating methods such as 210Pb and 14C.

Project Timeline

Year 1

3 field sites for each landscape context (estuarine, back barrier, loch-head) will be set up with hydrological monitoring equipment to continuously monitor tidal and freshwater input for two years. Permanent vegetation plots will be set up across the sites.

Year 2

Hydrological monitoring continues while detailed botanical surveys will be carried out. Sediment samples will be collected and analysed for recent RSL reconstructions. Vegetation surveys will be compared to past survey data from across Scotland. The student will complete a 3-month internship with NatureScot to develop a GIS based tool assessing current impediments to salt marsh resilience in a changing climate (e.g. anthropogenic changes to local hydrology, seaward or landward barriers).

Year 3

Field data collection will be complete and the student will begin to develop a statistical model linking local seasonal variability to ecological, tidal and fluvial hydrological response in contrasting salt marsh sites. The gathered data from past response, current processes and future scenarios will be synthesised to create a conceptual model of marsh dynamics in contrasting landscape settings.

Year 3.5

Final write-up phase. The student will be encouraged to attend international conferences.

Training
& Skills

This PhD will equip the candidate with a wide range of interdisciplinary hydrological and ecological field skills. The candidate will be trained in utilizing R language for statistical and spatial modelling throughout the PhD and will benefit from training courses as part of the University of Glasgow, College of Science and Engineering graduate school. The student will be trained in sediment and microfossil analysis for RSL reconstruction at Durham University during the studentship. During the internship at NatureScot, the student will benefit from in-house training opportunities and seminars.

References & further reading

Balke, T. , Vovides, A. , Schwarz, C., Chmura, G. L., Ladd, C. and Basyuni, M. (2021) Monitoring tidal hydrology in coastal wetlands with the Mini Buoy: applications for mangrove restoration. Hydrology and Earth System Sciences, 25, pp. 1229-1244. (doi: 10.5194/hess-25-1229-2021)

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