Dr. Evelyn Keaveney
BA (mod) 2004 (Trinity College Dublin) Zoology;
MSc 2005 (University of York) Zooarchaeology;
PhD 2010 (QUB)
Archaeology and Palaeoecology
School of Geography, Archaeology and Palaeoecology (GAP)
Queen’s University Belfast
Belfast, BT7 1NN
Northern Ireland, UK
+44 (0)28 9097 5295
14C as a tool to trace terrestrial carbon in a complex lake: implications for food-web structure and carbon cycling
Primary production of autochthonous carbon in a highly alkaline lake is partially based on dissolved inorganic carbon (DIC) containing radiocarbon (14C) – free ‘dead’ carbon from the weathering of carbonaceous bedrock. The low 14C activity yields an artificial age offset from the modern atmosphere leading the samples to appear hundreds of years older than their actual modern age. With terrestrial inputs likely to increase, the origin and utilisation of allochthonous carbon in the food-web is in question; is it recent ‘modern’ carbon or from ‘old’ soil carbon stocks.
Carbon and nitrogen Stable Isotope Analysis (SIA) has been used to show utilisation of terrestrial carbon by zooplankton and fish. The differences in the isotopic signatures of terrestrial and aquatic carbon are generally accepted; however SIA only, yields limited information. Natural abundance 14C can help untangle riverine zooplankton food webs. Lough Erne, Northern Ireland, has been chosen for the study for a number of reasons. It is a large lake (109 km2) that is economically important for tourism with specific conservation value associated with a diverse fish stock. It is also an example of an alkaline, humic lake – a globally common lake type. The lake water is coloured by high levels of DOC (>10 mg L-1) including terrestrial carbon from its peat catchment. As the lake is also eutrophic, the food web is potentially based on large allochthonous and autochthonous carbon source. Furthermore the invasive zebra mussel (Dreissena polymorpha) which feeds on phytoplankton, present in the lake since 1994, could be leading to increased reliance on terrestrial carbon by lake organisms. Variation in stable isotope values and 14C activity of components of the freshwater system will determine the origin of carbon – autochthonous, ‘old’ allochthonous or ‘modern’ allochthonous – at the base of the food web: Lake sediments, Dissolved Organic Carbon (DOC), Dissolved Inorganic Carbon (DIC), Particulate Organic Matter (POM), algal species, invertebrate species and fish species will be measured.
14C activity and 13C and 15N values from plant material, zooplankton and fish will determine the contribution of terrestrial carbon to the diet of lake organisms. The proof-of-concept study will provide a new methodology for larger projects examining multiple sites in the future. The results will also prove the value of this new method in freshwater ecology, providing valuable information for conservation of native species in the lake and investigations into carbon cycling and greenhouse gas emissions from aquatic systems.
Keaveney E.M., Reimer P.J. (2012) Understanding the variability in freshwater radiocarbon reservoir offsets: a cautionary tale Journal of Archaeological Science 39 (5), 1306-1316
Keaveney E. M. (2010) ‘Fish bones from Tulsk, Co. Roscommon’ Commercial Report for Discovery Programme.
Keaveney E. M. (2010) ‘Additional Fish Remains from Rothe House’ Commercial Report for Kilkenny Archaeology.
Keaveney, E. M. (2009) ‘Fish bones from Killeen Castle’ in Baker C The Archaeology of Killeen Castle, Co. Meath, Bray: Wordwell Press
Keaveney, E. M. (2008) ‘Fish Remains from Rothe House’ Commercial Report for Kilkenny Archaeology.
Keaveney, E. M. and Parks, R. L. (2006) ‘Fish Remains from Earith Campground, Cambridgeshire’ Reports for the Centre of Human Palaeoecology, University of York
I completed my undergraduate BA (mod) in Zoology in 2004 at Trinity College, Dublin. I became interested in archaeology when I worked on a fish bone assemblage from excavations at Temple Bar in Dublin. I went on to York University in the U.K. to complete an MSc degree in Zooarchaeology where I specialised in fish bone identification. I have completed my PhD at Queen’s University, Belfast. I investigated radiocarbon reservoir offsets from freshwater fishbone in Britain and Ireland in order to calibrate the offset and discovered that the variability seen, while preventing correcting the reservoir offset could be used to investigate utilisation of terrestrial carbon by freshwater fish. I now work in Lower Lough Erne investigating carbon cycling within the lake and terrestrial carbon support of the food web.