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T9
Algal records of carbon flux in Arctic lake sediments, Disko Island, west Greenland
M.A. Stevenson 1 *, S. McGowan 1 , E.J. Pearson 2 , G.E. Swann 1 and E. J. Whiteford 3
1 School of Geography, University of Nottingham, University Park, Nottingham
2 School of Geography, Politics and Sociology, Newcastle University, Newcastle-upon-Tyne
3 Department of Geography, Loughborough University, Loughborough
Studies suggest the Arctic is rapidly warming and vegetation may be expanding at high
latitudes (Sturm et al., 2001). Lakes process carbon at the landscape scale and may act
as net sources or sinks (Williamson et al., 2009). As Arctic lakes process high amounts of
carbon per unit area (Anderson et al., 2009) it is important to identify and decouple when
past conditions over the Holocene promoted carbon release or sequestration. Sediment
cores have been taken from three lake on Disko Island, west Greenland at elevations from
299 m.a.s.l to 575 m.a.s.l, all above the marine limit which is between 60 and 90 m.a.s.l.
(Ingólfsson et al., 1990). Here, we present an algal pigment record for lake Disko 2 (575
m.a.s.l.) situated in an upland, primarily fellfield terrain with limited terrestrial vegetation.
High-performance liquid chromatography (HPLC) has been used to separate and quantify
chlorophylls and carotenoids over the Holocene. We hypothesise that during warm
periods such as the Holocene Thermal Maximum (HTM) and Medieval Warm Period
(MWP), expansion of shrub tundra may increase dissolved organic carbon (DOC) input
stimulating lake mixotrophy and switching the lake from net-autotrophic to netheterotrophic
production (inferred by increases in alloxanthin pigment). Alternatively,
during cool periods such as the Little Ice Age (LIA) terrestrial inputs and DOC may have
been reduced, causing a switch to lake net autotrophy. However, decreasing DOC may
also act to limit autotrophic production due to potential algal sensitivity to UVR (Leavitt et
al., 2003). We found fluctuations in the sedimentary pigment records are likely to be
contemporaneous with key climate periods over the Holocene including the LIA, HTM and
MWP. 14 C dating on terrestrial plant macrofossils is currently in progress at three points in
the core (funded by the QRA). Based on fluctuations in the (LOI 550ºC) organic matter
profile we expect the core to span the entire Holocene. Once dated, cores will be used to
estimate carbon accumulation rates for the Disko Island region over the Holocene.
Planned future analyses include lipid biomarkers (n-alkanes, n-alkenes, n-alkanoic acids)
at key periods to confirm the source origins of organic carbon and δ 13 C of bulk organic
matter to identify changes in autotrophic productivity.
Keywords: pigments; paleolimnology; Arctic; Disko Island; DOC; Holocene.
Anderson, N.J. et al. (2009). Global Change Biology, 15, 2590-2598.
Ingólfsson, Ó. et al. (1990). Boreas, 19, 297-311.
Leavitt, P.R. et al. (2003). Limnology and Oceanography, 48, 2062-2069.
Sturm, M. et al. (2001). Nature, 411, 546-547.
Williamson, C.E. et al. (2009). Science, 323, 887-888.