Environmental Engineering Reference
In-Depth Information
one of which is Acarospora (Acharius
1798
; Weber
1962
; Schwab
1986
). Field
observations suggest the rust colour in these lichens reflects rock chemistry
and is usually considered to be of no taxonomic significance (Hawksworth
1973b
). In copper-rich environments, these populations often have a distinct
green colour. This unusual colouration has resulted in copper-accumulating
populations being described as distinct species at least three times (Sampaio
1920
; Clauzade et al.
1982
; Alstrup
1982
). Molecular phylogenetic methods are
helping to unravel species concepts and understand evolution in Acarospora
smaragdula sens. lat, one of the most enigmatic in the European lichen floras
(Crewe et al.
2006
; Wedin et al.
2009
). Modern SEM's and microanalytical (EPMA,
XRD, FTIR) methods were employed to investigate mineralisation in the lichen
cortex of the rust red Acarospora sinopica and paler yellow-orange A. sinopica
f. subochracea sampled from Swedish mines. Results confirmed the distinctive
colours are not simply due to hydrated iron oxides, 'rust', as previously
believed. Analysis suggests mixed sulphide and oxide phases with little crystal-
linity, as well as other elements arising from clay minerals are present (Purvis
et al.
2008a
). Photobiont influences are also to be expected. Species found in
these specialised acidic habitats were found to contain a single photobiont
species, whilst several photobiont species occurred in 'nitrophyte' species
(Douglas et al.
1995
; Beck
1999
).
Lecanora cascadensis (previously misidentified and now called Lecanora sierrae
(Ryan & Nash
1993
) was found associated with rocks containing bornite (Cu
5
FeS
4
)
and other copper minerals at Lights Creek District, Plumas County, California
(Czehura
1977
). Colour differences in thalli were found to correspond well with
copper mineralisation in soil. The intensity and size of the lichen's green
perimeter increased under the influence of copper mineralisation enabling
1000 ppm and greater than 2000 ppm anomalies to be distinguished in soil.
The ash of anomalous green 'L. cascadensis' contained 4% Cu, a concentration
approximately three times that of associated species collected at the same site.
This evidence suggests that L. cascadensis (i.e., Lecanora sierrae) could be a valuable
geobotanical prospecting tool (Czehura
1977
).
Conclusions
As highlighted in this chapter, mapping studies, long-term monitoring and
herbarium samples identify rapid changes in lichen diversity in Britain and
Europe in response to the success of measures to reduce pollutants and socio-
economic factors. This provides further evidence (Purvis et al.
2007a, b
) that
lichen biomonitoring is a fitting tribute to the 25th anniversary of the Conven-
tion on Long-range Transboundary Air Pollution in 1979, stimulated by
the link between sulphur emissions in Europe and acidification of lakes in
Scandinavia, first suspected back in the 1960s. Lichens continue to be highly
effective biological indicators of air pollution effects, though sensitivity to
