Aquatic Ecosystem Variability and Climate Change – A Palaeoecological Perspective - Climate Change Impacts on Freshwater Ecosystems - page 30

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Relative abundance (%) Pb (Bq/g)

Figure 2.7 Changes in diatom composition and 210 Pb concentration in a sediment core
from Elison Lake, Cape Herschel. The 210 Pb increase indicates that the uppermost 5 cm
of the core covers a time span of approximately 100 years. (From Douglas et al . 1994.
Reproduced with permission of The American Association for the Advancement of Science.)

With respect to acidification, climate change influences the acidity status of lakes
primarily through the impact of changing temperature on biogeochemical processes
(e.g. Koinig et al . 1998) and of changing precipitation patterns on catchment
hydrology (Monteith et al . 2001). The clearest palaeolimnological evidence is
provided at sites that either are remote from the effects of acid deposition or have
a relatively high acid-neutralizing capacity. Sommaruga-Wögrath et al . (1997)
showed for such a site in the Austrian Tyrol that changes in diatom-inferred pH in
a core were strongly correlated with instrumental temperature records over recent
decades. Larsen et al . (2006) described a similar response in two Norwegian lakes.
Curtis et al . (2009) used Canonical Correspondence Analysis (CCA) of diatom
records from European mountain lakes to show that air temperature, independently
of acid deposition, explained a significant amount of the variation between diatom
assemblages from early 19th century sediments and the present day, and Simpson
and Anderson (2009) using an Additive Modelling (AM) approach demonstrated
that temperature change was responsible for some of the temporal variation in
diatom assemblages in a core from a lake in North-West Scotland.