Acute toxicity of acidity in larvae and adults of four stream salamander species (Plethodontidae)

High levels of acid deposition have severely affected streamwater chemistry in the southern Appalachians. Plethodontid stream salamanders living in and around headwater streams rely on cutaneous respiration and are highly susceptible to changes in water quality. We examined the sensitivity to low pH conditions in four stream salamanders by monitoring the response to six pH treatments ranging from pH 2.75 to 6.5. To quantify acid tolerance, we determined median lethal concentrations (LC50) in 96-h laboratory bioassays. This is the first study to quantify the level of sensitivity of stream salamanders to acidic conditions, indicating that stream salamanders are acid tolerant compared with many other lotic organisms. We found that acid tolerance is a species-specific trait with intraspecific variation shaped by life stage and body size. Mortality occurred at pH levels less than 4.2. The acid sensitivity of Desmognathus quadramaculatus larvae (LC50 = pH 3.95) was highest compared to sensitivity of Eurycea cirrigera larvae (LC50 = 3.6), Gyrinophilus porphyriticus larvae (LC50 = 3.5), and Pseudotriton ruber larvae (LC50 = 3.5). Larval survival was lower than adult survival in low pH treatments for E. cirrigera (adult LC50 = 3.1) and D. quadramaculatus (adult LC50 = 3.5). Salamanders responded to sublethal exposure to acidity with lethargic movements and decreased swimming speed. These results suggest that episodic acid events that cause streamwater pH to drop near 4.2 may cause mortality or induce sublethal effects, such as slower swimming speed. Because salamander larvae are more sensitive to acidic conditions than adults, we recommend that population monitoring programs extend methodology to include reliable estimates of larval population sizes.     

Short-term toxicity of five oils to four freshwater species

Short-term lethality tests were conducted with five (waste oil, No. 1 fuel oil, No. 2 fuel oil, mixed blend sweet crude oil, Lloydminister crude oil) oils and four freshwater species. The oils were tested as floating layers, emulsions, and as the water-soluble fraction of 10% oil-water mixtures, in static and flow-through tests. The organisms tested were the American flagfish,Jordanella floridae, the fathead minnow,Pimephales promelas, larvae of the wood frog,Rana sylvatica, and larvae of the spotted salamander,Ambystoma maculatum. LC50 values were quite variable depending on a number of influencing factors, including the species tested, the type of oil, differences between batches of the same oil, the form of the oil when added to the test system, the type of test, duration of exposure, and the oil-water contact time.     

Acute toxicity of pure pentachlorophenol and a technical formulation to three species ofDaphnia

The acute toxicity of a technical formulation of pentachlorophenol (PCP) and pure pentachlorophenol to three age classes ofDaphnia magna, and adultD. pulex andD. galeata mendotae was determined by static toxicity tests. The influence of a number of factors on toxicity of PCP was also examined. The 48-hr LC50 estimates for adult daphnids of the three species exposed to pure PCP were 1.78, 4.59 and 0.51 mg/L, respectively, while those for the technical formulation were 2.57, 3.66 and 0.33 mg/L, respectively. There was little difference in toxicity between the technical and pure PCP; however, toxicity of both forms of PCP was influenced by duration of exposure, age (and/or size) and species of test organism and pH of the test solution.Pentachlorophenol caused a toxic response over a very narrow range of concentrations, with the greatest response occurring immediately between 0 and 24 hr. Pure PCP was equally toxic to all age classes ofD. magna but susceptibility to technical PCP decreased with maturation.D. g. mendotae was ten times more sensitive thanD. pulex to PCP. Pure PCP was significantly more toxic toD. magna at pH 5.5 than 7.0 with mean 48-hr LC50 values of 0.082 and 1.78 mg PCP/L, respectively.At 12°C, the toxicity of both forms of PCP toD. g. mendotae andD. pulex did not differ significantly from that at 20°C; however, technical PCP was significantly more toxic toD. magna at 12°C for an exposure duration of 48 hr. There was no effect of test container size (100, 250, 600 and 1,000 mL) on the toxicity of PCP toD. magna at 20°C with the lower pH of 5.5, suggesting that adsorption to glassware was not a factor in availability of PCP to test organisms. Beaker size had no effect on the toxicity of PCP toD. pulex at 20°C with test solutions having a pH of 7.0-8.0.     

Comparative toxicity of Corexit® 7664 to the early life stages of four marine species

The toxicity of the oil dispersing agent Corexit^® 7664 was evaluated using the early life stages of four California marine species: the red abalone (Haliotis rufescens), the topsmelt (Atherinops affinis), a mysid (Holmesimysis costata), and the giant kelp (Macrocystis pyrifera). Spiked-exposure, continuous-flow toxicity tests of 48–96 h were performed in triplicate in closed test chambers. Dispersant concentrations were measured by UV spectrophotometry. In terms of median-effect concentration, the order of test sensitivity was Haliotis>Atherinops>Holmesimysis>Macrocystis. NOEC data also showed Haliotis tests to be the most sensitive, with Macrocystis tests having similar values, followed by Atherinops and Holmesimysis tests, respectively. Toxicity of Corexit^® 7664 was compared to that of Corexit^® 9527, and the latter was found to be more toxic to all four species; interspecific rankings were similar for the two agents.     

Acute cadmium toxicity studies upon nine species of aquatic insects.

Continuous-flow bioassays were employed to determine 96-hour median tolerance limits (TLm), for the stonefly, Pteronarcella badia (Hagen) (TLm was 18.0 mg Cd/l) and the mayfly, Ephemerella grandis grandis Eaton (TLm was 28.0 mg Cd/l). Ninety-six hours TLm values for other species of aquatic insects tested were not determined, since these species were relatively insensitive to cadmium.Insects exposed for four days in cadmium-containing water, then placed in tap water, show a linear rate of cadmium loss. This loss may lower or prevent mortality under ideal conditions.     

Comparative toxicity of inorganic contaminants released by placer mining to early life stages of salmonids

The acute toxicities of four trace inorganics associated with placer mining were determined, individually and in environmentally relevant mixtures, to early life stages of Arctic grayling (Thymallus arcticus) from Alaska and Montana, coho salmon (Oncorhynchus kisutch) from Alaska and Washington, and rainbow trout (Oncorhynchus mykiss) from Montana. The descending rank order of toxicity to all species and life stages was copper greater than zinc greater than lead greater than arsenic. For each of the three species, sensitivity to the inorganics was greater in juveniles than in alevins or in swim-up fry. Arctic grayling from Alaska were more sensitive than the other species tested, including Arctic grayling from Montana. For Arctic grayling, sensitivity to all four inorganics was significantly greater in swim-up fry from Alaska than in alevins from Montana, and sensitivity to arsenic and copper was significantly greater in juveniles from Alaska than in juveniles from Montana. In tests with environmentally relevant mixtures (based on ratios of concentrations measured in streams with placer mining) of these four inorganics, copper was identified as the major toxic component because it accounted for greater than or equal to 97% of the summed toxic units of the mixture, and an equitoxic mixture of these inorganics showed less-than-additive toxicity. Total and total recoverable copper concentrations reported in five Alaskan streams with active placer mines were higher than the acutely toxic concentrations, either individually or in mixtures, that the authors found to be acutely toxic to Arctic grayling and coho salmon from Alaska. However, caution should be used when comparing our results obtained in "clear" water to field situations, because speciation and toxicity of these inorganics may be altered in the presence of sediments suspended by placer mining activities.     

Acute toxicity of lake water to fishes

The present study investigates the acute toxicity of Hussainsagar lake water to fishes. In this context, experiments were conducted on three species of fishes (Cyprinus carpio, Tilapia mozambica and Lebistus reticularis), using 5, 10 and 20% volume of Jeedimetla nallah wastewater and were observed for the signs of survival within the specified period of time. The TLm value for 96 hours test period was found to be 17%. Similarly Toxicity studies were carried out on Hussainsagar lake water with dilutions varying from 10-100%. Absence of mortality during 96 hours of test period indicates that there is no acute toxicity of Hussainsagar lake water to fishes.