Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

diversity at concentrations of 0.02 to 1.0 mg/L Pb (Fernandez-Leborans and Novillo,
1992, 1994).
Austen and McEvoy (1997) studied the effects of Pb on an estuarine meiobenthic
community (mainly nematodes) in a microcosm setting using sediment samples collected
offshore from England. A multivariate analysis of similarities (ANOSIM) test with square root-
transformed data was used to evaluate differences between treatments and controls. Lead was
found to significantly affect species abundance at 1343 mg/kg dw relative to a control at
56 mg/kg dw, but no significant adverse effects were observed at the highest dose tested,
1580 mg/kg dw. The authors did not attempt to explain why the 1580 mg/kg dw dose was not
significant while the 1343 mg/kg dw dose was. None of the Pb exposures were significantly
different than the controls based on separate univariate tests of abundance, richness, and
diversity. There were no other confounding metals in the Pb tests, as the experiments were with
a single metal dose. In one other mesocosm study, the effects of a mixture of metals (Cu, Cd,
Pb, Hg, and Zn) on a salt marsh meiofaunal community were evaluated (Millward et al., 2001).
After 30-days exposure, significant reductions in copepod, gastropod, and bivalve
abundances were observed at the highest Pb exposure concentration, 177 mg/kg dw. Ostracods
and nematodes were not affected. The authors believed that the response of the meiofauna taxa
to metals was in part due to the various feeding strategies in that deposit feeders were most
affected.
Natural Aquatic Ecosystem Studies
Lead stress in aquatic ecosystems has also been evaluated in natural communities.
Studies examining community-scale endpoints, however, are complex, and interpretation can be
confounded by the variability found in natural systems and the presence of multiple stressors.
Natural systems frequently contain multiple metals, making it difficult to attribute observed
adverse effects to single metals. For example, macroinvertebrate communities have been widely
studied with respect to metals contamination and community composition and species richness
(Winner et al., 1980; Chadwick et al., 1986; Clements, 1994). In these studies, multiple metals
are evaluated and correlations between observed community level effects are ascertained. The
results often indicate a correlation between the presence of one or more metals (or total metals)
and the negative effects observed. While, correlation may imply a relationship between two
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