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

1.1 µg/L Cd, 12 µg/L Cu, 55 µg/L Zn, and 3.2 µg/L Pb (all metals were in the form of chlorides).
Avoidance was quantified as time spent in test water, trip time to test water, and number of trips.
Brown trout avoided the 1Η mixture as well as the 0.5Η, 2Η, 4Η, and 10Η mixtures, but not the
0.1Η mixture. Reduced avoidance was observed at higher concentrations (4Η and 10Η). The
authors proposed that the reduced avoidance response was due to impaired perception due to
injury. These responses are typical of other fish species to individual metals of similar
concentrations (Woodward et al., 1995). This study does not conclusively indicate which of the
metals in the mixture may be causing the avoidance response. However, given the neurotoxic
effects of Pb, impaired perception is a likely response of Pb-exposed fish.
When test water was reduced in pH from 8 to 7, 6 to 5, brown trout avoidance increased,
but with no significant difference between metal treatments and controls. However, in the 1Η
metal mixture treatment, brown trout made fewer trips into the test water chamber at the lower
pHs (Woodward et al., 1995). This response may be related to an increased abundance of Pb
cations at lower pH values in the test system.
Scherer and McNicol (1998) investigated the preference-avoidance responses of lake
whitefish (Coregonus clupeaformis) to overlapping gradients of light and Pb. Whitefish were
found to prefer shade in untreated water. Lead concentrations under illumination ranged from
0 to 1000 µg/L, and from 0 to 54,000 µg/L in the shade. Under uniform illumination, Pb was
avoided at concentrations above 10 µg/L, but avoidance behavior lacked a dose-dependent
increase over concentrations ranging from 10 to 1000 µg Pb/L. Avoidance in shaded areas was
strongly suppressed, and whitefish only avoided Pb at concentrations at or above 32,000 µg/L.
Summary of Avoidance Response
In summary, of those aquatic organisms studied, some are quite adept at avoiding Pb in
aquatic systems, while others seem incapable of detecting its presence. Snails have been shown
to be sensitive to Pb and to avoid it at high concentrations. Conversely, anuran (frog and toad)
species lack an avoidance response to the metal. Fish avoidance of many chemical toxicants has
been well established, and it is a dominant sublethal response in polluted waters (Svecevičius,
2001). However, no studies have been located specifically examining avoidance behavior for Pb
in fish. Environmental gradients, such as light and pH, can alter preference-avoidance responses.
AX7-158