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

• Changes in energy flow or nutrient cycling:
o Increased or decreased respiration or biomass
o Increased or decreased turnover/cycling of nutrients
• Changes in community structure:
o Reduced species abundance (i.e., the total number of individuals of a species within
a given area or community)
o Reduced species richness (i.e., the number of different species present in
a community)
o Reduced species diversity (i.e., a measure of both species abundance and species
richness)
Investigators have evaluated the effects of Pb on aquatic communities through microcosm
and mesocosm studies in natural aquatic systems. Field studies in the general literature have
focused on natural systems that were affected by metal stress from various anthropogenic
sources. In most of those natural systems, the sources evaluated were from direct mining waste
inputs, rather than atmospheric deposition, of Pb. Studies published since the 1986 Lead AQCD
(U.S. Environmental Protection Agency, 1986a) that describe the effects of Pb on natural aquatic
ecosystems are presented below and summarized in Table AX7-2.5.2. Studies included here
evaluated the effects of Pb on watersheds, landscapes, aquatic ecosystems, aquatic communities,
biodiversity, lakes, rivers, streams, estuaries, wetlands, and species interaction.
Aquatic Microcosm Studies
The examination of simulated aquatic ecosystems (i.e., microcosms) provides limited
information on the effects of pollutants on natural systems. Microcosm studies typically focus
on only a few aspects of the natural system and do not incorporate all of the ecological,
chemical, or biological interactions. Nevertheless, a few microcosm studies have been
conducted that indicate potential effects of Pb on the community structure of aquatic ecosystems.
Fernandez-Leborans and Antonio-García (1988) evaluated the effect of Pb on a natural
community of freshwater protozoans in simulated aquatic ecosystems and found a reduction in
the abundance and composition of protozoan species with increasing Pb concentrations (0.05 to
1.0 mg/L) compared to controls. Studies with marine protozoan communities in laboratory
microcosms indicated that waterborne Pb exposure reduced protozoan abundance, biomass, and
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