Abstract
Kamchatka is a remote, isolated and understudied area and is presumed to be pristine. Here we present the first high-resolution palaeolimnological investigation of the recent past. A short core representing the last 250years was taken from Olive-backed Lake situated in central Kamchatka. Lead-210 dating revealed that sediment accumulation has increased at the site since the 1960s and may be related to greater rates of catchment erosion associated with wetter winters in the region. Mercury and spheroidal carbonaceous particle (an unambiguous indicator of fossil fuel combustion) concentrations are low but clearly detectable indicating that both regional and global pollution sources are observed at this site. The recent increase in the flux of mercury is more related to catchment sources and catchment erosion than increases from regional or global sources. The diatom and chironomid populations are stable and do not show any statistically significant changes related to either the low levels of pollution, or to temperature and precipitation changes. The lake is not pristine since anthropogenic contamination has occurred but since there have been no significant effects on the flora and fauna the lake can be considered to be unimpacted. Olive-backed Lake may be a suitable reference site to benchmark the natural variability of a lake ecosystem.
Highlights
In many regions of the world, lakes are more controlled by anthropogenic forcing than by natural drivers (Wilkinson et al, 2014) and it has even been suggested that stratigraphic changes observed in lake sediments such as changes in isotopic or diatom composition could be used to characterise the start of the proposed Anthropocene era (Wolfe et al, 2013; Dean et al, 2014)
Hg fluxes before the 1970s (b 10 ugm−2 yr−1) are similar to the mean Hg fluxes found in lakes from many other remote areas where catchment inputs are negligible (Swain et al, 1992; Yang et al, 2010b e.g. lakes in the Northern Tibetan Plateau have around a flux of about 10 ugm−2 yr−1 Yang et al, 2010a), suggesting that Hg in this area of Kamchatka is mainly derived from a global source
We suggest that the lake is not pristine but that it is unimpacted
Summary
Introduction and aimsIn many regions of the world, lakes are more controlled by anthropogenic forcing than by natural drivers (Wilkinson et al, 2014) and it has even been suggested that stratigraphic changes observed in lake sediments such as changes in isotopic or diatom composition could be used to characterise the start of the proposed Anthropocene era (Wolfe et al, 2013; Dean et al, 2014). While we do not want to enter here into the wider debate of whether a ‘golden spike’ can be defined it is useful to consider the extent to which remote lakes are impacted by human activity and whether any can still be considered ‘pristine’. This is especially true in understudied regions such as much of South America, Africa, South East Asia, the Polar Regions and the Russian Far East. The study of lakes from areas where there are no direct anthropogenic influences in their catchments can help inform the benchmarks of natural variability as well as assessing impacts of global and regional pollution
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