EGU 2014 - Poster

Connecting Terrestrial and Marine Carbon: The Missing Link. Smeaton, 1 1 C *,Austin, W.E.N , Davies, 1 A.L & Howe, 2 J.A 1 School of Geography & Geoscience, University of St-Andrews, Fife, Scotland KY16 9AL 2Dunstaffnage Marine Laboratory, Scottish Association for Marine Science, Oban, Argyll PA37 1QA, Scotland, UK *Corresponding Author: cs244@st-andrews.ac.uk 1. Introduction 3. Background The poster aims to introduce some initial ideas and concepts from my research project (starting October 2013) which aims to create a carbon inventory for sea lochs on the west coast of Scotland. The project sets out to address some of the main questions that are required to fill the gaps in our knowledge and allow a better understanding of carbon in the coastal environment. Here we intend on establishing a first order carbon inventory of a sea lo h’s (fjord) sediment for the Holocene. Additionally we will conducted a holistic “our e to “i k study of carbon, linking terrestrial carbon sources to the marine sink (sea loch). There is currently a disparity in carbon research, deep ocean and terrestrial carbon are both intensely researched areas within both a Scottish and global context. Terrestrial carbon has been the focus of intense research over a number of years with the latest research estimating that there is 1620Mt (Chapman et al,2009) of carbon within Scottish peatlands. This combined with the organo-mineral and mineral soils 754 and 498 Mt (Bradley et al. 2005) respectively means that the estimated total carbon stock in Scottish soils is 2872 Mt. In comparison carbon research at the coastal interface between the marine and terrestrial realms is sparse 2. Research Questions How much carbon is held within a Sea loch ? Where does this carbon come from ? What is the depositional history of the sediment/carbon ? What impact have we had on these processes ? 4. Research Site The focus of this project will be on the west coast of Scotland. The west coast is an ideal location because the region contains multiple types of coastal environment with minimal human disturbance. The study will focus on sea lochs these provide a restricted exchange environment ideal for this type of study. The initial research will be conducted within Loch Sunart (Fig.1), Loch Sunart is the largest of the “ ottish “ea Lo h’s stret hi g k ith a a i u depth of 9 . The lo h’s ai tri utar is the Ri er Strontian which supplies approximately 500000m3 of water per year, this is also one of the main transport routes for terrestrial carbon . The Loch and the surrounding area has many anthropogenic pressures (forestry, aquaculture & renewable energy) which makes it ideal to examine the anthropogenic impact on the local carbon cycle. 5. Creating a Carbon Inventory The creation of a carbon inventory will involve both geophysical and biogeochemical techniques. The data collected during geophysical survey's carried out by Baltzer et al. (2010) and Bates et al. (2004) on Loch Sunart will be used to create a 3D representation of the sediment. The seismic survey (Baltzer et al. 2010) produced a number of cross sections of the loch (Fig.2). This project will stitch the seismic cross sections together to create a 3D seismic model of Loch Sunart, this will allow the quantification of sediment within Loch Sunart. Initially the 3D model will only map the bedrock and the surface sediments which will give us the total sediment but over time we will model the separate sediment horizons allowing the depositional history of the carbon to analysed in greater detail. Figure.1 Research Site, Loch Sunart C:N Ratios – Core GC023 To determine the quantity of carbon held in the sediment samples have been extracted, currently we have 85 grab samples (Fig.3) and 5 cores (Fig.4) retrieved using a gravity corer. The samples will be analysed using a bulk elemental analyser linked to a mass spectrometer this will produce C:N ratios and δ13C values. The C:N ratios will allow the total carbon to be quantified this combined with the 3D seismic model will allow the first order carbon inventory to be created. Additionally a basic chronology has been developed through 14C dating which we hope to expand upon. Analysis of the cores is currently underway, with core GC023 producing the first results(Fig.5). ± 0 1.753.5 7 10.5 14 Kilometers Figure.3 Location of 85 Grab Samples Figure.4. Gravity Core Location and Core Stratigraphy Figure.2 Seismic Cross Section of Loch Sunart 6.0 “our e to “ink: Fingerprinting The Car on The “our e to “i k resear h ai s to li k the ar o held i the lo h’s sedi e t to differe t ar o pools i Loch “u art’s catchment and the marine environment. A network of water samplers & sediment traps will deployed throughout the catchment with the aim of collecting particulate matter lost from the soil. In addition to the fluvial samples soil samples will be taken from “u art’s catchment each of these samples will be used to fi gerpri t the differe t ar o pools ithi the at h e t . “i ilarl sedi e t traps ill e pla ed i the Lo h, this i o ju tio ith the gra sa ples ill agai fi gerpri t the differe t ari e ar o pools (algae, aquaculture, etc.) The samples will be analysed to determine the C:N ratio , δ13C value, magnetic susceptibility and particle size disturbance. The data collect from this analysis will be compared to data collect from the sediment cores . Using specialist statistical analysis such as an end member mixing model (Fig.6) we will be able to insolate the different carbon pools and identify the source of the carbon. When combined with 14C dating the changes in the quantity and source of the carbon reaching the loch can be examined over the Holocene . Soil Carbon Pool 1 Soil Carbon Pool 2 7. References Marine Carbon Pool Fluvial Carbon Pool Figure 5. C:N Ratios for Core GC023 Baltzer, A., Bates, R., Mokeddem, Z., Clet-Pellerin, M., Walter-Simonnet, A.-V., Bonnot-Courtois, C. &Austin, W. E. N(2010), Using seismic facies and pollen analyses to evaluate climatically driven change in a Scottish sea loch (fjord) over the last 20 ka, Geological Society, London, Special Publications,344, 355-369. Loch Sediment Carbon Pool Bates, C. R., Moore, C. G., Harries, D. B., Austin,W. & Lyndon, A. R. 2004. Broad scale mapping of sub- littoral habitats in Loch Sunart, Scotland. Scottish Natural Heritage, Commissioned Report No. 006 (ROAME No. F01AA401C) Bradley, R.I., Milne, R., Bell, J., Lilly, A., Jordan, C. & Higgins, A. (2005). A soil carbon and land use database for the United King- dom. Soil Use and Management, 21, 363–369. Chapman, S.J., Bell, J., Donnelly, D. & Lilly, A,(2009), Carbon Stocks in Scottish Peatland, Soil Use and Management, 25, 105- 112. Soil Carbon Pool 3 Degens,E. T., Kempe,S.& Richey, J.E. (1991). Summary: biogeochemistry of major world rivers. In: Degens, E. T., Kempe,S. & Richey, J. E. (eds) Biogeochemis- try of Major World River. Wiley, Chichester, 323–348. Figure. 6 Conceptual Model for End Member Mixing Model Spitzy,A.&Ittekkot,V. (1991). Dissolved and particulate organic matter in rivers. In: Mantoura, R. F. C. Ocean Margin Processes in Global Change. Physical, Chemical, and Earth Sciences Research Report 9. John Wiley & Sons, Chichester, 5–17.