Lw. Hali et al., INFLUENCE OF SALINITY ON ATRAZINE TOXICITY TO A CHESAPEAKE BAY COPEPOD (EURYTEMORA-AFFINIS) AND FISH (CYPRINODON-VARIEGATUS), Estuaries, 17(1B), 1994, pp. 181-186
The objective of this study was to determine the influence of a range
of salinities (5 parts per thousand, 15 parts per thousand, and 25 par
ts per thousand) on the acute toxicity of atrazine to nauplii of the c
opepod Eurytemora affinis and larvae of the sheepshead minnow, Cyprino
don variegatus. Ninety-six-hour LC50 values for the copepod were 0.5 m
g l-1, 2.6 mg l-1, and 13.2 mg l-1 at salinities of 5 parts per thousa
nd, 15 parts per thousand, and 25 parts per thousand, respectively. A
comparison of LC50 values between adjacent salinities showed a statist
ical difference between 15 parts per thousand and 25 parts per thousan
d, but not between 5 parts per thousand and 15 parts per thousand. Atr
azine was more toxic to E. affinis at the lowest salinity. The 96-h LC
50s for the sheepshead minnow were 16.2 mg l-1, 2.3 mg l-1, and 2.0 mg
l-1 at salinities of 5 parts per thousand, 15 parts per thousand, and
25 parts per thousand, respectively. There was a statistical differen
ce between LC50 values at 5 parts per thousand and 15 parts per thousa
nd but not between 15 parts per thousand and 25 parts per thousand. In
contrast to E. affinis results, atrazine was more toxic to C. variega
tus at the highest salinity. The toxicity data from these species sugg
est that development of estuarine water quality criteria is warranted.