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Moro D., I. M. Grze et al. (2012). "Abundance and diversity of wild
bees along gradients of heavy metal pollution." <u>Journal of
Applied Ecology</u> <b>49</b>(1): 118-125.<br><br>
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<dd><x-tab> </x-tab>1.Wild
bees are one of the most important groups of pollinators in the temperate
zone. Therefore, population declines have potentially negative impacts
for both crop and wildflower pollination. Although heavy metal pollution
is recognized to be a problem affecting large parts of the European
Union, we currently lack insights into the effects of heavy metals on
wild bees. <br>
<dd>2.We investigated whether heavy metal pollution is a potential threat
to wild bee communities by comparing (i) species number, (ii) diversity
and (iii) abundance as well as (iv) natural mortality of emerging bees
along two independent gradients of heavy metal pollution, one at Olkusz
(OLK), Poland and the other at Avonmouth (AVO), UK. We used standardized
nesting traps to measure species richness and abundance of wild bees, and
we recorded the heavy metal concentration in pollen collected by the red
mason bee Osmia rufa as a measure of pollution. <br>
<dd>3.The concentration of cadmium, lead and zinc in pollen collected by
bees ranged from a background level in unpolluted sites [OLK: 1 43 99(mg;
AVO: 0 42 56(mg, respectively] to a high level on sites in the vicinity
of the OLK and AVO smelters [OLK: 6 277 440(mg; AVO: 9 356 592(mg,
respectively]. <br>
<dd>4.We found that with increasing heavy metal concentration, there was
a steady decrease in the number, diversity and abundance of solitary,
wild bees. In the most polluted sites, traps were empty or contained
single occupants, whereas in unpolluted sites, the nesting traps
collected from 4 to 5 species represented by up to ten individuals.
Moreover, the proportion of dead individuals of the solitary bee
Megachile ligniseca increased along the heavy metal pollution gradient at
OLK from 0in uncontaminated sites to 0in sites with a high concentration
of pollution. <br>
<dd>5.Synthesis and applications. Our findings highlight the negative
relationship between heavy metal pollution and populations of wild bees
and suggest that increasing wild bee richness in highly contaminated
areas will require special conservation strategies. These may include
creating suitable nesting sites and sowing a mixture of flowering plants
as well as installing artificial nests with wild bee cocoons in polluted
areas. Applying protection plans to wild pollinating bee communities in
heavy metal-contaminated areas will contribute to integrated land
rehabilitation to minimize the impact of pollution on the
environment.<br><br>
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