Rivers and Coasts

Projects

Supervisors: Dr Steven Palmer  (email: s.j.palmer@exeter.ac.uk) and Dr Matteo Vacchi (email: M.Vacchi@exeter.ac.uk)

Project Description

The scientific issue

Erosion of the UK coastline presents major management issues given high coastal population densities, the high value of coastal land and its intensity and diversity of use. For example, during the winter of 2013/2014 a succession of major storms caused widespread damage to coasts throughout England, causing major transport interruptions such as the 2-month closure of the train line at Dawlish, damage to coastal infrastructure and beach depletion.

The UK Regional Coastal Groups develop Shoreline Management Plans to assist with coastal management, but the forecasts of future coastline position are currently over-simplistic and do not capture processes of Coastal Change. This project aims to make improved estimates of rates and processes of coastal change, with particular emphasis on coastal cliffs, with a view to develop better understanding of the links between environmental conditions and coastal erosion events.

The research

The successful student will use LiDAR and airborne imagery from the Channel Coast Observatory and Environment Agency to quantify the spatial and temporal variations in rates and patterns of erosion at selected sections of UK coastline. Supplementary datasets such as rainfall observations and wave buoy & tide gauge records will be used to characterise the prevailing sea conditions preceding individual erosion events, in order to investigate environmental drivers of coastal erosion. The student needs to have strong GIS and numerical skills, and at least a basic understanding of Coastal systems.

References

Young, A. P., & Ashford, S. A. (2006). Application of airborne LIDAR for seacliff volumetric change and beach-sediment budget contributions. Journal of Coastal Research, 307-318.

Masselink, G., Scott, T., Poate, T., Russell, P., Davidson, M., & Conley, D. (2016). The extreme 2013/2014 winter storms: hydrodynamic forcing and coastal response along the southwest coast of England. Earth Surface Processes and Landforms, 41(3), 378-391.

 

Supervisors: Richard Brazier  (email: r.e.brazier@exeter.ac.uk) and Alan Puttock (email: a.k.puttock@exeter.ac.uk)

Project Description

Hunted to extinction in the UK, some 400 years ago. The Eurasian Beaver - Castor fiber is now making a comeback. Yet, very little research has been undertaken to understand the impacts that this iconic species might have, particularly within the context of the intensively managed landscape that the UK now comprises. This project will fill this important knowledge gap, providing outcomes that will underpin both high-level policy relating to the reintroduction of beaver in the UK and practical management of the species as populations expand over coming years.

The scientific issue

Beavers have been shown to deliver positive environmental benefits in terms of both flow attenuation and water quality. Proof of concept results (Puttock et al., 2017), have shown that at a site containing a sequence of 13 beaver dam and pond structures, surface water leaving the site contained 3 times less suspended sediment, 0.7 times less nitrogen and 5 times less phosphate, compared to water entering the site (draining from an agriculturally dominated catchment. These results suggest beaver reintroduction could play an important beneficial role in water resource management. However, such benefits have yet been shown to manifest at catchment scales and across a wide range of lowland landscapes. It is critical therefore, that research level understanding of the impact of beavers on water quality is built and this MRes project will fulfill that objective.

The research

The project will be closely integrated with research being undertaken by the supervisors across a range of field sites in South West England where beavers have recently been introduced. The successful candidate will investigate whether the impacts of beaver reintroduction, particularly the building of dams has a significant impact upon downstream water quality.

The successful student will be required to undertake a wide range of both field and laboratory based work. Primarily this will involve the regular collection and analysis of water samples (through both stormflow and baseflow conditions) and macroinvertebrate samples, at in-stream sampling locations entering and leaving beaver impacted sites. Water quality samples will be analysed for a suite of variables including: suspended sediment, nitrogen, phosphorus, dissolved organic carbon and pH. Combined information gained from this analysis will provide detailed understanding of the impact beavers can have upon both biological and chemical water quality. Furthermore, the student will have the opportunity to work closely with stakeholder organisations ensuring this research is highly impactful and directly contributes to understanding the role beavers may play in the provision of multiple ecosystem services.

References

Puttock et al. 2015. Aerial photography collected with a multirotor drone reveals impact of Eurasian beaver reintroduction on ecosystem structure. Journal of Unmanned Vehicle Systems : 150429143447007. DOI: 10.1139/juvs-2015-0005

Puttock et al. 2017. Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands. Science of The Total Environment 576: 430–443.DOI: 10.1016/j.scitotenv.2016.10.122

 

Supervisors:  Dr. Dunia H. Urrego (email: d.urrego@exeter.ac.uk) and Dr Barend van Maanen.

Project description

The scientific issue

Urban growth and climate change impacts are posing serious pressure on mangrove forests worldwide. Mangroves are therefore rapidly disappearing and important ecosystem services may be lost. Ecosystem services provided by mangroves include breeding grounds for fisheries and food security, coastal protection and wave dissipation, and carbon storage. Therefore, mangrove conservation and restoration can be important parts of the solution for reducing risks to coastal communities and preserving ecosystem services.

Seen as a first line of defense against sea level rise, salinization, and subsidence, restoration of key coastal ecosystem such as mangroves is now actively promoted through Blue Carbon initiatives. Yet, much remains to be done in assessing the ecological baselines for mangrove ecosystems to identify sustainable restoration goals that maximize ecosystem resilience.

The research

The aim of this Master’s by research project is to determine ecological baselines for mangrove ecosystems and to discern what processes control mangrove carbon sequestration in tropical coastal ecosystems. This project offers an exciting opportunity to conduct a research project using sediment cores collected from the Magdalena River Delta in Colombia. The Magdalena is the largest river in Colombia and it is within the top 10 in world for sediment supply. Sediment cores have been collected from two contrasting lagoons in the Delta and are kept in the Geography cold storage. One lagoon is neighbouring the city of Barranquilla and is highly degraded, while mangroves in the other lagoon are flourishing. The project would be interdisciplinary and could combine coastal geomorphology, ecology, palynology and geochemistry. Laboratory analysis may include organic carbon quantification, sedimentology, 210Pb analyses, palynology and charcoal analysis. There is also a possibility to conduct fieldwork in Colombia and collect data on carbon decomposition. The research project can also be developed to fit the student’s interests.

References

Alongi, D.M., 2012. Carbon sequestration in mangrove forests. Carbon management, 3(3), pp.313-322.

Mcleod, E., Chmura, G.L., Bouillon, S., Salm, R., Björk, M., Duarte, C.M., Lovelock, C.E., Schlesinger, W.H. & Silliman, B.R. 2011. A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2. Frontiers in Ecology and the Environment, 9(10), pp.552-560.

van Maanen, B., Coco, G., & Bryan, K. R. 2015. On the ecogeomorphological feedbacks that control tidal channel network evolution in a sandy mangrove setting. Proc. R. Soc. A, 471(2180), 20150115.

Supervisors:   Dr Rob Barnett (email: r.barnett@exeter.ac.uk); Dr Angela Gallego-Sala (University of Exeter); Prof Pascal Bernatchez (University of Quebec at Rimouski); Prof Dan Charman (University of Exeter)

Project description

The scientific issue

The rate of global mean sea level rise has increased from 2.4 ± 0.2 mm yr-1 in 1993 to 2.9 ± 0.3 mm yr-1 in 2014 (Watson et al., 2015; Chen et al., 2017) and sea level will continue to rise into the future, regardless of current emissions targets (Nicholls et al., 2018). Rising global sea levels have major economic and societal impacts. However, the pattern of sea-level rise across the globe is not uniform. Spatial and temporal differences arise from patterns and fingerprints of geophysical processes that influence relative, volumetric and dynamic changes in the oceans (Milne et al., 2009). This means that some coastal locations are experiencing higher than global average rates of sea-level rise and are more vulnerable than others to future changes.

The east coast of Canada is an exciting region to study relative sea-level changes due to the large influence that glacial-isostatic adjustment has on sea-level trends. Ablation of the North American (Laurentide) Ice Sheet during the Holocene has resulted in land uplift towards inland Canada and subsidence at eastern locations along the North Atlantic seaboard. Before regional projections of future sea-level rise can be accurately predicted in eastern Canada, a better understanding of the processes that drive local- (e.g., sediment dynamics), regional- (e.g., vertical land motion and ocean-mass redistribution) and global- (e.g., ocean volume changes) scale sea-level changes is necessary (Barnett et al., 2019).

The research

This project will research past and ongoing relative sea-level changes in eastern Canada using a multi-proxy palaeo-data approach, with the aim of quantifying the contributions from different processes. The researcher will reconstruct sea-level changes at multiple locations around the Gulf of St Lawrence over recent centuries and millennia by: i) defining modern relationships between sea level and salt-marsh microrganism indicators (e.g., testate amoebae, foraminifera), ii) analysing sedimentary archives for fossil assemblages and applying relationships determined in (i) using a transfer function (see Barlow et al. (2013) for a review of these techniques), and; iii) establishing a chronological framework for new sea-level records by using radionuclide techniques (e.g., 210Pb) at the University of Exeter Radiometry Laboratory, radiocarbon analysis and age-depth modelling. Material for palaeoenvironmental analysis is currently available, although it is likely that there will be the opportunity for fieldwork in eastern Canada and / or an academic research visit to collaborating institutes.

The project has a focus on laboratory work and the researcher will be taught how to prepare and analyse salt-marsh samples for microorganism (e.g., testate amoebae, foraminifera) content. Applicants with (palaeo)ecological experience (e.g., microorganism sample preparation / analysis) are encouraged to express their interest. This project will be run in collaboration with the Laboratoire de dynamique et de gestion intégrée des zones côtières at the University of Quebec at Rimouski.

References

Barlow, N.L.M. et al. 2013. Salt marshes as late Holocene tide gauges. Global and Planetary Change, 106, 90-110.
Barnett, R.L. et al. 2019. Late Holocene sea-level changes in eastern Quebec and potential drivers. Quaternary Science Reviews, 203, 151-169.
Chen, X. et al. 2017. The increasing rate of global mean sea-level rise during 1993-2014. Nature Climate Change, 7, 492-495.
Milne, G.A. et al. 2009. Identifying the causes of sea-level change. Nature Geoscience, 2, 471-478.
Nicholls, R.J. et al. 2018. Stabilization of global temperature at 1.5°C and 2°C: implications for coastal areas. Philosophical Transactions of the Royal Society A. 376, 20160448.
Watson, C.S. et al. 2015. Unabated global mean sea-level rise over the satellite altimeter era. Nature Climate Change. 5, 565-568.

 

Supervisors:   Professor Chris Perry (c.perry@exeter.ac.uk), Dr Mike Salter (M.A.Salter@exeter.ac.uk)

Project description

The scientific issue

Coral reefs support large and diverse communities of marine fish, some of which are known to play important functional roles in these ecosystems. Two particularly well known examples are: i) the role played by surgeonfish, and other herbivorous fish, in regulating algal cover and in helping to maintaining reefs in coral-dominated states; and ii) the impacts from the scraping and excavating actions of feeding parrotfishes, with contributes to erosion of reef surfaces, and the conversion of coral framework to sediment. These functional roles are well known and influence specific aspects of reef ecology or geology. However, on observing a coral reef it is quickly apparent that many other groups of fish also play an important role in the production and reworking of carbonate material. For example, in search of prey, benthic feeders such as the goatfishes constantly sift through surface sediments, rays excavate large feeding pits, and triggerfishes can quickly destroy coral heads. These types of activity were eye-catchingly documented in the tuskfish sequence of the 2017 BBC series “Blue Planet II”. Other examples include fishes that burrow and live within the sediment, fishes that construct piles of rubble as ‘nests’, and even fish that create sand sculptures to attract mates (as illustrated in the 2014 BBC series “Life Story”). Collectively these processes probably exert a major influence on the nature of the accumulating sediment and framework structure of coral reefs, and may strongly influence processes of carbonate and nutrient cycling.

The research

This project aims to develop our understanding of the diverse range of sedimentary, geomorphic and geochemical functional roles that fish play in coral reef, and specifically to start to develop a more complete understanding of these functional roles across habitat types. This is an especially topical issue given the rapidly growing interest in quantifying and assessing species functional roles in reefs as reef ecosystems globally change. To answer these questions requires these interactions to be quantified, but to date there have been few attempts to do this even at the level of individual fish species, let alone for entire communities within habitats. This project will develop and execute video census methodologies to facilitate the classification and quantification of fish interactions with sediments and reef substrates across different habitat types at a field location on the Great Barrier Reef, Australia. Data generated through these video censuses will then be used to develop a model that quantifies different types of fish–sediment interactions, identifies key fish groups, and explores the implications of these interactions at the ecosystem scale.

References

Perry C.T., Kench P.S, O’Leary M.J., Morgan K.M., Januchowski-Hartley F (2015) Linking reef ecology to island-building: Parrotfish identified as major producers of island-building sediment in the Maldives. Geology 43: 503-506.
Perry, C.T., Salter, M.A., Harborne, A.R., Crowley, S.F., Jelks H.J., Wilson, R.W., (2011) Fish as major carbonate mud producers and missing components of the tropical carbonate factory. Proceedings of the National Academy of Science 108: 3865-3869
O’Shea et al. (2011) Bioturbation by stingrays at Ningaloo Reef, Western Australia. Marine and Freshwater Research, 63, 189.
Rotjan R.D., Lewis S. M. (2008) Impact of coral predators on tropical reefs. Marine Ecology Progress Series 367: 73–91



 

Supervisors:   Professor Chris Perry (c.perry@exeter.ac.uk), Dr Mike Salter (M.A.Salter@exeter.ac.uk)

Project description

The scientific issue

Recent work at the University of Exeter has established that all marine bony fishes continuously produce and excrete calcium carbonate particles, contributing significantly to carbonate sediment production budgets and to the inorganic carbon cycle. These carbonates precipitate within the fish intestine as a by-product of normal physiological functioning, and to date most studies have focussed on carbonates collected specifically from starved fish as a means of isolating them from dietary items. However, the presence of such items and associated digestive fluids in the gut must influence the precipitating environment, possibly resulting in the production of different types of carbonate to those documented from starved fish. Indeed, emerging data indicate that many fish produce morphologically and compositionally distinct carbonates when given a controlled diet. In many cases these carbonates are thought to be considerably more soluble than corresponding carbonates from starved fish, with major implications for the way in which we understand their roles in the cycling of sediment and inorganic carbon. However, neither case is necessarily a good representation of processes occurring in nature: empty gut vs. unnatural diet, and in both cases potentially elevated stress levels associated with being housed in research aquaria. An important question, relevant to advancing this field of research and resultant carbonate modelling efforts, is thus: what types of carbonate are produced by fishes under natural feeding circumstances, and what is the nature of their role in sediment and inorganic carbon cycles?

The research

This project will aim to answer these questions by building on the growing body of research involving coral reef fishes of the Great Barrier Reef, Australia. Specific research questions will be: 1) what types of carbonate do coral reef fish produce under natural conditions?; 2) how do these carbonates compare with those produced by the same fish when starved?; 3) if transitions in carbonate type are observed, over what timescales do they occur (i.e., do feeding effects persist on the order of hours or days?)?; and 4) is the type of transition influenced by dietary habits (i.e., food items and feeding rate)?. Data collection will involve two core elements. Firstly, fieldwork at a research station on the Great Barrier Reef, Australia, will be conducted to collect sample materials. This element will involve the collection of three or four wild fish species to be temporarily housed in research aquaria. Any material they excrete during the period immediately after their collection, and for several days thereafter, will be sampled in order to track the transition of carbonates from fish being fed (natural diet pre-capture) to starved. Following this fieldwork, characterisation of these carbonate samples will be carried out at the University of Exeter involving scanning electron microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR), among a suite of other analytical techniques. Data generated through this work will then be used to develop new models of fish carbonate production in coral reef systems.

References

Wilson R.W. et al., 2009. Contribution of fish to the marine inorganic carbon cycle: Science, v. 323, p. 359–362, doi:10.1126/science.1157972.
Perry, C.T. et al., 2011. Fish as major carbonate mud producers and missing components of the tropical carbonate factory: Proceedings of the National Academy of Sciences, v. 108, p. 3865–3869, doi:10.1073/pnas.1015895108.
Salter, M.A. et al., 2018. Reef fish carbonate production assessments highlight regional variation in sedimentary significance: Geology, v. 46, p. 699-702, doi:10.1130/G45286.1



 

Supervisors:   Prof. Rolf Aalto (email: rolf.aalto@exeter.ac.uk), Prof. Andrew Nicholas (email: A.P.Nicholas@exeter.ac.uk).

Project description

The scientific issue

The vast majority of organic carbon (Corg) is stored in sedimentary rock compared to atmosphere + biosphere + ocean (by a factor of > 1000x). Large river systems transport and bury huge loads of Corg throughout giant lowland basins that form some of the largest sedimentary deposits on Earth, but the mechanisms and rates of burial over annual to century timescales are poorly constrained. Fluvial processes and fluxes may therefore represent a significant player in Earth’s carbon cycle (Aufdenkampe et al., 2011), especially given rising seas that tend in turn to lead to accelerated sediment and carbon sequestration. Such deposits may be laid down in coordination with ENSO flooding (Aalto et al., 2003), or typhoons that are shifting as climate changes (Darby et al, 2016).

The research

This project will develop understanding of carbon deposition in river sediment by measuring carbon concentrations for a large set of previously dated cores collected across 1000s of kilometers of floodplains in the Amazon, the lower Mekong, Papua New Guinea, the Danube, and elsewhere. With all project cores already in cold storage at Exeter and necessary lab equipment available to students, research can be focused and efficient in terms of producing datasets of lasting and likely global significance. Previous measurement of similar samples has led to important insights, such as the observation that the island of Papua New Guinea exports more sediment-associated carbon to the ocean than the entire Amazon basin (Alin et al., 2008).

This project will appeal to students who like to measure things, and work in a research lab environment. Unlike models or statistical fits that may be replaced by new advances, good field measurements are eternally valuable. Therefore, it is anticipated that the laboratory focused work proposed here may provide data that leads to novel insights into the significant role of river floodplain deposits may play in modulating Earth’s carbon cycle.

References

R Aalto, L Maurice-Bourgoin, T Dunne, DR Montgomery, CA Nittrouer, JL Guyot, 2003, Episodic sediment accumulation on Amazonian flood plains influenced by El Nino/Southern Oscillation, Nature, 425, 493-407.
 
SR Alin, R Aalto, MA Goni, JE Richey, WE Dietrich, 2008, Biogeochemical characterization of carbon sources in the Strickland and Fly rivers, Papua New Guinea, JGR Earth Surface, 113, F1.
 
AK Aufdenkampe, E Mayorga, PA Raymond, JM Melack, SC Doney, SR Alin, RE Aalto, K Yoo, 2011, Riverine coupling of biogeochemical cycles between land, oceans, and atmosphere, Frontiers in Ecology and the Environment, 9, 1, 53-60.
 
SE Darby, CR Hackney, J Leyland, M Kummu, H Lauri, DR Parsons, JL Best, AP Nicholas, R Aalto, 2016, Fluvial sediment supply to a mega-delta reduced by shifting tropical-cyclone activity, Nature, 539, 276.





 

Supervisors:   Prof. Rolf Aalto (email: rolf.aalto@exeter.ac.uk), Prof. Andrew Nicholas (email: A.P.Nicholas@exeter.ac.uk).

Project description

The scientific issue

Much successful research has been published analyzing planform change of meandering and braided rivers in response to various forcings. However, generally lacking from these analyses are good topographic data to quantify variations in river valley slope and provide documentation of vertical infilling – both essential metrics for understanding driving energy gradients and volumetric responses of the systems for conveying and distributing water and sediment. The problem is that 1) high accuracy field survey data are rare, 2) previous spaceborne sensors presented challenges for accuracy and resolution, and 3) most large floodplains have significant vegetation coverage, making it difficult to determine bare earth elevations.

The new TanDEM-X instrument offers a way forwards, with lower resolution data (~90m) recently released for most of the Earth. Our recent work with the high-resolution (~12.5m) product has developed a promising means to identify and remove trees using various remote sensing techniques and machine learning – with the ultimate result of producing bare earth DEMs that check well against locations we have field data. We have also applied these same approaches using research-grade SRTM (~30m) and find the resulting product is suitable for comparison to the TanDEM-X data collected ~16 years later. Therefore, there are opportunities for comparing and differencing these two datasets.

The research

We have field survey data and have identified various locations that can be used to test these approaches, and would like to involve a student in their further development. After refining the techniques for an apt study area, the student would then focus on quantifying slopes that drive river flow, and the bar/floodplain infill for a particular study river. The ultimate goal will be producing generic findings about the 3D functioning of large river systems that are suitable for publication in a prominent journal.

This project will mainly use ArcGIS and Matlab, and will appeal to students who like working with cutting-edge DEM analysis and considering topographic controls/expressions of large river morphodynamics. We can provide access to research data, specialist software, fast data storage suitable for GIS, plus there may be an opportunity for the student to assist with a survey of river bank and floodplain topography along the Mekong River in Vietnam.

References

Wilson R.W. et al., 2009. Contribution of fish to the marine inorganic carbon cycle: Science, v. 323, p. 359–362, doi:10.1126/science.1157972.
Perry, C.T. et al., 2011. Fish as major carbonate mud producers and missing components of the tropical carbonate factory: Proceedings of the National Academy of Sciences, v. 108, p. 3865–3869, doi:10.1073/pnas.1015895108.
Salter, M.A. et al., 2018. Reef fish carbonate production assessments highlight regional variation in sedimentary significance: Geology, v. 46, p. 699-702, doi:10.1130/G45286.1