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The effects of ammonium nitrate, ammonium chloride, ammonium sulfate, and sodium nitrate on survival and growth of Pacific treefrog (Pseudacris regilla) and African clawed frog (Xenopus laevis) embryos were determined in static-renewal tests. The 10-day LC50s for the three ammonium compounds for P. regilla ranged from 25.0-32. 4 mg/L NH4 -N. The 10-day sodium nitrate LC50 for P. regilla was 578. 0 mg/L NO3-N. LC50s for X. laevis exposed for 4 or 5 days to the three ammonium compounds ranged from 27.5-60.2 mg/L NH4-N. The sodium nitrate LC50 for X. laevis ranged from 438.4-871.6 mg/L NO3-N. The lowest LOAEL based on length or weight was 6.1 mg/L NH4-N for the two species. The lowest LOAELs for NO3-N were 111.1 mg/L for P. regilla and 56.7 mg/L for X. laevis. Calculated unionized NH3 comprised 0.5-1.8% of measured NH4-N concentrations. Potential harm to amphibian populations could occur if NH4-N and NO3-N in agricultural runoff or drainage impacts sensitive life stages for a sufficiently long period.

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The chronic effects of the herbicide diuron on survival and reproduction of Daphnia pulex, and survival and growth of the amphipod Hyalella azteca, the midge Chironomus tentans, juvenile and embryo/larval fathead minnows, Pimephales promelas, annelid worms, Lumbriculus variegatus, and snails, Physa gyrina, were determined in laboratory static and static-renewal tests. D. pulex 96-h and 7-day LC50 values were 17.9 and 7.1 mg/L; 7-day LOAEL and NOAEL values based on mortality and reproduction were 7.7 and 4.0 mg/L. H. azteca 96-h and 10-day LC50 values were 19.4 and 18.4 mg/L; 10-day LOAEL and NOAEL values based on survival and reduced weight were 15.7 and 7.9 mg/L. C. tentans 10-day LC50 value was 3.3 mg/L; 10-day LOAEL and NOAEL values based on growth were 7.1 and 3.4 mg/L, and 3.4 and 1.9 mg/L based on mortality. Juvenile fathead minnows had a 10-day LC50 of 27.1 mg/L and 10-day LOAEL and NOAEL values based on growth of 3.4 and <3.4 mg/L. The fathead minnow embryo-larval test had a 7-day LC50 value of 11.7 mg/L and 7-day LOAEL and NOAEL values based on reduced growth of 8.3 and 4.2 mg/L. L. variegatus had 10-day LOAEL and NOAEL values based on reduced weight of 3.5 and 1.8 mg/L. P. gyrina had 10-day LOAEL and NOAEL values based on reduced weight of 22.8 and 13.4 mg/L. Laboratory effects concentrations were higher that those found in normal field application situations, except in areas of localized pooling after recent herbicide applications, indicating that there would probably be little harm to these fish and invertebrates from diuron exposure in the field.

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The effects of the insecticides Guthion (technical grade) and Guthion 2S (commercial formulation) on survival and growth of tadpoles of the Pacific treefrog Pseudacris regilla, and larvae of the Northwestern salamander Ambystoma gracile and the spotted salamander Ambystoma maculatum were determined in continuous-flow exposures in the laboratory. Ninety-six-hour LC50 values were >3.6 mg/L for P. regilla with technical grade Guthion and 1.47 mg/L with the formulation Guthion 2S (measured as active ingredient Guthion). Ten-day LOAEL and NOAEL values based on length and weight for P. regilla with Guthion were 3.60 and 0.98 mg/L. LOAEL and NOAEL values based on length and weight for P. regilla with Guthion 2S were 0.17 and 0.07 mg/L. The 96-h LC50 for Guthion 2S was 1.67 and 1.90 mg/L for A. gracile and A. maculatum, respectively. LOAEL and NOAEL values based on length and weight for A. gracile with Guthion 2S were 0.22 and 0.10 mg/L; they were 0.11 and 0.03 mg/L for A. maculatum based on weight. These species are as similar in sensitivity as some fish species but are more tolerant to Guthion than most invertebrates.

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The effects of the herbicide diuron on survival and growth of Pacific treefrog (Pseudacris regilla), bullfrog (Rana catesbeiana), red-legged frog (Rana aurora), and African clawed frog (Xenopus laevis) embryos and tadpoles were determined in static-renewal tests. P. regilla and X. laevis embryos had reduced growth and developed increased deformities in diuron concentrations over 20 mg/L. Hindlimb bud and forelimb development were retarded in R. aurora following 14 days exposure to diuron concentrations of > 7.6 mg/L. Mean 14-day LC50s for P. regilla and X. laevis tadpoles were 15.2 and 11.3 mg/L diuron, respectively. The 21-day LC50 for R. catesbeiana tadpoles was 12.7 mg/L diuron. The 14-day LC50 for R. aurora tadpoles was 22.2 mg/L. The lowest NOAELs calculated in embryo tests were 14.5 mg/L for P. regilla (10 days) and 7.6 mg/L diuron for X. laevis (4 days). The lowest NOAELs calculated in tadpole tests were: P. regilla, 14.5 mg/L (14 days); R. catesbeiana, 7.6 mg/L (21 days); R. aurora, 7.6 mg/L (14 days); and X. laevis, > 29.1 mg/L (14 days). Diuron concentrations having an effect on survival, growth, and malformation in the laboratory were much higher than those found in normal field spray situations; field studies would be needed to determine the hazard to amphibians in areas of localized pooling of recently applied herbicide in the environment.

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Daphnia magna Straus, a common organism used for freshwater sediment toxicity tests, was evaluated to determine its tolerance to salinity and suitability for tests with estuarine water and sediments. Daphnids were exposed for 2 to 21 days to salinity in a variety of water-only tests, in tests with freshwater sediment overlain by salt water, and in tests with estuarine sediments overlain by freshwater. Daphnid age, test length, and temperature seemed to have little effect upon the range of LC50, NOAEL, and LOAEL values. LC50s for all tests ranged from 5.10 to 7.81 g/L, with a mean of 6.6 g/L salinity (measured conductivity 10.0 mS/cm) [corrected]. The mean NOAEL and LOAEL values based on production of young were 4.6 and 6.9 g/L salinity (measured conductivity 7.1 and 10.5 mS/cm) [corrected], respectively. The results indicate that D. magna will survive and reproduce well in water with salinities below 4 g/L and demonstrate the potential usefulness of this organism in monitoring sediment toxicity from both freshwater and estuarine wetland sites.

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Embryos, larval stages (instars I-V), pupal stages, and pharate adults of the caddisfly Clistoronia magnifica (Limnephilidae) were exposed to a range of dissolved oxygen (DO) concentrations (0.9-8.3 mg/L) for 4-88 days in the laboratory. Some embryos suspended growth at low DO, resuming growth and hatch when DO was increased. Embryos and larvae all had 96-h EC50 values (50% mortality at 96 h) of about 2.0 mg/L DO. The statistical Effect and No-Effect Thresholds for larvae exposed through two molts from instars I-III were 1.6 and 2.4 mg/L, respectively. At DO concentrations below 4.6 mg/L, egg hatch, larval development, molting success, time of molting, pupation, and adult emergence were delayed.

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The development of Xenopus laevis (African clawed frog) embryos exposed to the pesticide Guthion (technical grade) and Guthion 2S (commercial formulation) was evaluated in modified Frog Embryo Teratogenesis Assay--Xenopus (FETAX) tests. The embryos were exposed to five or six increasing concentrations of pesticide in 10- and 100-ml exposure volumes of test solution for 96 h. Embryos exposed in 10-ml volumes of Guthion exhibited increased mortality, increased deformation, and decreased size as compared to those exposed in 100-ml volumes. LC50s for embryos exposed in the 10-ml Guthion tests ranged from 6.1 to 6.3 mg/L as compared to 10.6 to 11.9 mg/L for those in the 100-ml tests. The percentage of deformities at 3 mg/L Guthion in test survivors in 10-ml tests ranged from 73 to 89%, while in the 100-ml tests less than 2% were deformed at the same concentration. Mean control embryo lengths at test completion were 8.2 and 10.6 mm, respectively, for 10- and 100-ml tests. The LC50 for embryos in 100 ml Guthion 2S was 1.6 mg/L active ingredient, indicating a much greater toxicity of the commercial formulation. NOAEL (No Observed Adverse Effect Level) values for Guthion and Guthion 2S ranged from 0.48 to 7.96 mg/L, depending upon basis (length, deformity, mortality) and pesticide formulation, and were many times greater than the existing water quality criterion of 0.01 microgram/L.

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Sub-adult African clawed frogs (Xenopus laevis) were fed pentachlorophenol (PCP)-injected mealworms containing 64.8 to 2604 ug of PCP per gram of worm for 27 days. There was no mortality and no significant bioaccumulation of PCP in the frogs. After three weeks, frogs fed 2,604 micrograms/g of PCP ceased eating. The no observed adverse effects level (NOAEL) based on significantly reduced food consumption (PCP-injected mealworms) was 638 micrograms/g. This corresponded to a NOAEL based on PCP intake of about 8 micrograms PCP/g frog/day. A toxicity threshold model estimated that about 800 micrograms/L of waterborne PCP may be a threshold for adverse effects in Xenopus or similar amphibians. Further study is needed to verify threshold estimates.

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Teratogenesis, acute and chronic toxicity, growth and bioconcentration were investigated in various life stages (embryos, tadpoles, juveniles, adults) of the frogs Xenopus laevis (African clawed frog), Rana catesbeiana (bullfrog) and Rana pipiens (leopard frog) exposed to aqueous dieldrin in static-renewal and flow-through systems in a study on the development of wildlife-based water quality criteria. R. catesbeiana was the most sensitive tadpole in acute tests; X. laevis was the most sensitive in embryo-larval and chronic tadpole tests. Tadpole 96-h LC50s ranged from 40.4 to 49.5 micrograms/L dieldrin for X. laevis, from 8.7 to 30.3 micrograms/L for R. catesbeiana and was 71.3 micrograms/L for R. pipiens. The 24-day LC50 for X. laevis tadpoles was 5.5 micrograms/L dieldrin; the 28-day LC50 for R. pipiens tadpoles was 8.3 micrograms/L. Adult R. pipiens had a 28-day LC50 of 53.4 micrograms/L dieldrin. Gross spinal deformities in embryo-larval tests were observed at dieldrin concentrations as low as 1.3 micrograms/L after 10-days exposure to X. laevis and at 25.4 micrograms/L for a 21-day exposure to R. catesbeiana. Mean X. laevis 14 to 21-day LOAEL (Lowest Observed Adverse Effect Level) and NOAEL (No Observed Adverse Effect Level) values for embryo-larval tests (25.5 and 11.0 micrograms/L dieldrin, respectively) were virtually the same as the 21-day single test values obtained for R. catesbeiana (25.1 and 11.0 micrograms/L dieldrin). Mean 14 to 24-day X. laevis LOAEL and NOAEL values for tadpole chronic tests (1.6 and less than 1.4 micrograms/L dieldrin, respectively) were lower than the 28-day single test values obtained for R. pipiens (4.1 and 1.9 micrograms/L, respectively). Tissue dieldrin levels at the LC50, LOAEL and NOAEL in the tadpole acute tests were fairly similar between X. laevis (11, 24 and 7 micrograms/g, respectively) and R. catesbeiana (means of 8.6, 12.0 and 1.2 micrograms/g, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

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Fathead minnows (Pimephales promelas), the worm, Lumbriculus variegatus, and the amphipods Hyalella azteca and Gammarus lacustris were exposed to hexachlorobenzene (HCB) in water with and without a bed of HCB-spiked sediment. Water HCB concentrations were maintained by recirculation through HCB-packed columns. Recirculating HCB-bound particulates and possibly eroded HCB particulates were an added source of HCB in addition to the sediment bed. Significant bioaccumulation of HCB in animal tissues was observed in water-only and water-sediment exposures. The presence of the HCB-spiked sediment did not result in a significant increase in the uptake of HCB by the organisms, but there was a substantial increase in sediment HCB levels over time. Higher tissue HCB levels in aquaria without sediment suggest that the sediment was a more efficient sink for HCB than the organisms.

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