A Comparison of the Daphnids Ceriodaphnia dubia and Daphnia ambigua for Their Utilization in Routine Toxicity Testing in the Southeastern United States

Abstract

U.S. regulatory agencies commonly require effluent toxicity testing with Ceriodaphnia dubia--a practice that has led to the criticism that this species and test protocol often does not reflect local taxa or site-specific conditions. Using an indigenous test species may produce a more realistic model of local effects and may minimize test endpoint variance due to regional differences in water quality. This study addressed the substitution of C. dubia with Daphnia ambigua for toxicity testing in the southeastern United States. This investigation determined that D. ambigua could be laboratory cultured with only minimal changes to established regulatory protocol and that the life-cycle characteristics of this species were conducive to traditional acute and chronic aquatic toxicity test methods used with other daphnids. Acute toxicity tests showed that D. ambigua was less sensitive to some toxicants (sodium chloride, copper sulfate, and sodium lauryl sulfate) but more sensitive to others (chlorpyrifos). Chronic tests with copper sulfate and sodium chloride resulted in lower EC50S for D. ambigua reproduction with both compounds. When exposed to low-alkalinity, low-pH stream waters typical of many southeastern United States watersheds, C. dubia demonstrated a significant reproductive depression in two of three streams tested, whereas D. ambigua experienced no chronic effect. These results suggest that D. ambigua may serve as a suitable surrogate for C. dubia as an toxicity indicator species in these types of receiving streams.

Observed and predicted reproduction of Ceriodaphnia dubia exposed to chloride, sulfate, and bicarbonate

“…Chloride IC50 values for C. dubia were similar to those determined elsewhere in low-hardness water [10] and in moderate-hardness water [9,11]. The IC50 value for SO 4 2À determined in moderate-hardness water was close to that determined by Soucek [27], who also tested Na 2 SO 4 in a similar water formulation.…”

Effects of road salts on the composition of seasonal pond communities: can the use of road salts enhance mosquito recruitment?

“…We found cladocerans and copepods to be the most sensitive taxa to salts, with copepods being slightly more tolerant than cladocerans. Both taxa were rare or absent in pools with mean concentrations [1,200 mg L -1 , and were more sensitive to concentrations of salts in outdoor mesocosms relative to laboratory tests with NaCl (e.g., Harmon et al 2003;Sarma et al 2006). Based on field surveys, Hart et al (1991) reported that cladocerans are rarely found in natural habitats in Australia with salinities [1,000 mg L -1 , which is consistent with our findings.…”

Implications of water hardness in ecotoxicological assessments for water quality regulatory purposes: a case study with the aquatic snail Biomphalaria glabrata (Say, 1818)

“…In soft water (under 20 mg/L CaCO 3 ) the survival and reproduction of snails were poor. With the microcrustacean Ceriodaphnia dubia, Harmon et al (2003) observed a significant reduction in reproduction when the organisms cultured in moderately hard water were exposed to low hardness waters from streams in South Carolina, USA. The effects of hardness and alkalinity on the reproduction of C. dubia in cultivation water and in tests with water samples were evaluated by Lasier et al (2006).…”