Consultant's Report - Minnesota State Legislature

Table 2. Summary ofLCso values.
Expt Chemical
Pre-fert
LCso
Post-fert
LCso
24-h
LCso
48-h
LCso
72-h
LCso
1
Cutrine 0.001
0.013
(0.006 0.019)
0.008
(0.002 - 0.014)
0.009 0.012
CUS04 - - 0.008 - 0.007
2
3'
Cutrine - - - - -
CUS04
0.004
(0.002 - 0.005)
0.005 - - -
Cutrine 0.002 - - - -
CUS04 - - - - -
Since there was no difference in the toxicity of Cutrine®-Ultra and Cu to postfertilization
stage eggs, we conclude that Cutrine®-Ultra has a mode of toxicity upon
gamete viability or the fertilization physiology other than that associated with Cu
exposure.
Literature TRVs for D. polymorpha are scarce, although Fisher et al. (1994)
determined LCso values for six molluscides and concluded that larvae were more
sensitive than adults to five of the compounds. The only Cu-related D. polymorpha
information that these authors are aware ofis unpublished by McMahon and Tsou (1990)
from a conference proceeding, indicating that 5 mg CulL 100 % mortality of D.
polymOlpha veliger in 24 h in unknown water quality conditions. Based on results from
the current study, such levels of mortality can be achieved at much lower concentrations
ofCu in Lake Ossawinnamakee water.
Results for LC99 data are summarized in Table 3. LC99 values are shown in bold
type, and 95 % confidence limits in parentheses where the model allowed this estimation.
All data are mg CulL.
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