314
A. Gnamus and M. Horvat
From the bars in Fig. 5, Hg transfer and transformation rates in different
trophic levels of the food web may be established and comparisons of the prey vs.
predator tissue mercury concentrations can be made (herbivores vs. carnivores).
In the specific case of the Idrija region, where a strong local Hg pollution
pattern is expressed, roe deer as large terrestrial herbivorous mammals proved to
be very efficient bioindicators of Hg contamination. As discovered from our
investigation, roe deer reflect locally enhanced Hg contamination in the Idrija
area more distinctively compared to their raptors. Despite the fact that the two
selected predator species prey on roe deer primarily and are directly above roe
deer in the food web, the data on Hg concentrations in selected tissues of lynx
and wolves from the wider Idrija area show some deviations from the expected
prey-to-predator pollutant magnification (see Fig. 5a: herbivores vs. carnivores).
The main reason for the unsuitability of large carnivorous predator species for
monitoring the specific Hg pollution pattern in the Idrija region, compared to
their prey, appears to be their large territorial range. As established before (see
also Figs.3a,b), the Hg pollution in the Idrija area is strongly influenced by specific
geographical relief and is spatially restricted. The individual territory of the lynx
or the wolf is usually much larger than the individual herbivore's foraging area. It
is also substantially larger than the heavily contaminated region in the Idrija area.
Thus, individuals of the predator species only seldom plunder the most exposed
prey (roe deer) and rarely contact the heavily affected area itself. Therefore, the
results obtained from the chosen predator species in the Idrija area do not follow
the general prey-to-predator relationship ratios for Hg concentrations which
should be expressed in more static food webs in the area. However, the
characteristic prey-to-predator pollutant magnification was observed in unpolluted areas of Slovenia affected by the moderate global Hg pollution only, since
territorial distribution of the pollutant in these areas was less influenced by
geographical or other factors (see Fig. 5b: Herbivores vs. Carnivores).
The specific accumulation and distribution patterns in animals at different
trophic levels of the food webs will be revealed through further studies including
other animals from the studied areas. Also, the importance of mercury transfer to
the higher links in terrestrial food webs of the contaminated areas and man will
be elucidated.
5
Conclusions and Recommendation
• A semi-millenium of anthropogenic cinnabar ore processing in Idrija has
caused severe contamination of the natural compartments and biota in the
area. Mercury concentration levels in environmental and biological samples
from the Idrija area mostly greatly exceed the maximal allowed concentrations set by the Steering Committee for the Protection and Management of
the Environment and Natural Habitats (CDPE) for European soil resources,
A. Gnamus and M. Horvat
From the bars in Fig. 5, Hg transfer and transformation rates in different
trophic levels of the food web may be established and comparisons of the prey vs.
predator tissue mercury concentrations can be made (herbivores vs. carnivores).
In the specific case of the Idrija region, where a strong local Hg pollution
pattern is expressed, roe deer as large terrestrial herbivorous mammals proved to
be very efficient bioindicators of Hg contamination. As discovered from our
investigation, roe deer reflect locally enhanced Hg contamination in the Idrija
area more distinctively compared to their raptors. Despite the fact that the two
selected predator species prey on roe deer primarily and are directly above roe
deer in the food web, the data on Hg concentrations in selected tissues of lynx
and wolves from the wider Idrija area show some deviations from the expected
prey-to-predator pollutant magnification (see Fig. 5a: herbivores vs. carnivores).
The main reason for the unsuitability of large carnivorous predator species for
monitoring the specific Hg pollution pattern in the Idrija region, compared to
their prey, appears to be their large territorial range. As established before (see
also Figs.3a,b), the Hg pollution in the Idrija area is strongly influenced by specific
geographical relief and is spatially restricted. The individual territory of the lynx
or the wolf is usually much larger than the individual herbivore's foraging area. It
is also substantially larger than the heavily contaminated region in the Idrija area.
Thus, individuals of the predator species only seldom plunder the most exposed
prey (roe deer) and rarely contact the heavily affected area itself. Therefore, the
results obtained from the chosen predator species in the Idrija area do not follow
the general prey-to-predator relationship ratios for Hg concentrations which
should be expressed in more static food webs in the area. However, the
characteristic prey-to-predator pollutant magnification was observed in unpolluted areas of Slovenia affected by the moderate global Hg pollution only, since
territorial distribution of the pollutant in these areas was less influenced by
geographical or other factors (see Fig. 5b: Herbivores vs. Carnivores).
The specific accumulation and distribution patterns in animals at different
trophic levels of the food webs will be revealed through further studies including
other animals from the studied areas. Also, the importance of mercury transfer to
the higher links in terrestrial food webs of the contaminated areas and man will
be elucidated.
5
Conclusions and Recommendation
• A semi-millenium of anthropogenic cinnabar ore processing in Idrija has
caused severe contamination of the natural compartments and biota in the
area. Mercury concentration levels in environmental and biological samples
from the Idrija area mostly greatly exceed the maximal allowed concentrations set by the Steering Committee for the Protection and Management of
the Environment and Natural Habitats (CDPE) for European soil resources,