Acute toxicity of fire control chemicals to Daphnia magna (Straus) and Selenastrum capricornutum (Printz).

Acute toxicity tests were conducted exposing Daphnia magna Straus (daphnid) in soft and hard reconstituted waters (hardness 42 and 162 mg/liter as CaCO3, respectively), and Selenastrum capricornutum Printz (algae) in ASTM algal assay medium (hardness 15 mg/liter as CaCO3) to fire retardants Fire-Trol GTS-R, Fire-Trol LCG-R, and Phos-Chek D75-F, and foam suppressants Phos-Check WD-881 and Silv-Ex. The chemicals were slightly toxic to practically harmless to daphnids and moderately toxic to algae. Water quality did not consistently alter the toxicity of the test chemicals to daphnids. The most toxic chemical to daphnids was Silv-Ex (48-hr EC50 7 mg/liter in soft and hard waters), whereas the least toxic chemical to daphnids was Fire-Trol LCG-R (48-hr EC50 848 mg/liter in soft water, 813 mg/liter in hard water). The most toxic chemical to algae was Fire-Trol LCG-R (96-hr IC50 10 mg/liter), and the least toxic chemical was Phos-Chek D75-F (96-hr IC50 79 mg/liter). Un-ionized ammonia concentrations near the EC50 or IC50 value in tests with the Fire-Trol compounds were frequently equal to or above reported LC50 un-ionized ammonia concentrations. Un-ionized ammonia concentrations in tests with Phos-Chek D75-F were low, thus other toxic components present in the compounds probably contributed to the toxicity. When compared to the daphnids tested in ASTM soft water, the Fire-Trol compounds were most toxic to algae, whereas Phos-Chek D75-F and the foam suppressants were most toxic to daphnids. The results of these tests are comparable to those obtained from research conducted in other laboratories with the same species and similar chemicals. Accidental entry of fire-fighting chemicals into aquatic environments could adversely affect algae and aquatic invertebrates, thus disrupting ecosystem function.

Isotopic tracking of change in diet and habitat use in african elephants.

The carbon, nitrogen, and strontium isotope compositions of elephants in Amboseli Park, Kenya, were measured to examine changes in diet and habitat use since the 1960s. Carbon isotope ratios, which reflect the photosynthetic pathway of food plants, record a shift in diet from trees and shrubs to grass. Strontium isotope ratios, which reflect the geologic age of bedrock, document the concentration of elephants within the park. The high isotopic variability produced by behavioral and ecological shifts, if it is representative of other East African elephant populations, may complicate the use of isotopes as indicators of the source region of ivory.

The effects of selenium on the distribution of mercury in the organs of the black bullhead (Ictalurus melas).

Following i.p. mercuric chloride injections, the mercury was deposited primarily in the kidneys. Simultaneous selenium injections prevented mercury induced osmoregulatory failure even though selenium strongly promoted the movement of mercury to the kidneys and its deposition in an approximate 1:1 mercuric selenite ratio. Whole-body retention of mercury was not altered by simultaneous subcutaneous injections of sodium selenite.

Selenium prevents mercuric chloride induced acute osmoregulatory failure without glutathione peroxidase involvement in the black bullhead (Ictalurus melas).

The relationship between coelomic injections of mercuric chloride doses and osmoregulatory responses was measured. Response parameters were weight increases and blood osmolarity decreases 72 hr after dose administration. Massive edema and large decreases in blood osmolarity could be completely prevented by subcutaneous injections of equimolar sodium selenite. Mercury induced damage did not involve alterations of either selenium-dependent or non-selenium-dependent glutathione peroxidase activities.

Protective action of selenium against mercury in northern creek chubs.

We found selenium dixoide an effective antagonist to the toxic effects of mercuric chloride in the northern creek chub (Semotilus atromaculatus). Selenium pretreatment increased the whole body accumulation of mercury at lower environmental Hg concentrations. It decreased mercury accumulation in survivors at higher, acutely toxic concentrations.

Mercuric chloride uptake by eggs of the ricefish and resulting teratogenic effects.

Eggs collected from adult Japanese Medaka were incubated for 16 days in solutions containing 10, 15, 20, and 30 ppb mercury as mercuric chloride. The mean hatchability of control eggs was 46.7 percent. Experimental eggs incubated in 10 ppb and 15 ppb mercury had hatching percentages of 58.3 and 20.8 respectively (Chi Square = 12.8, Pless than.0005). None of the 20 ppb or 30 ppb experimental eggs hatched. Nemorrhaging, blood vessel deterioration and loss of blood cells were observed in 79 percent of the 15 ppb experimental eggs and all the 20 and 30 ppb experimental eggs. Neither the control nor the 10 ppb experimental eggs demonstrated any of these abnormalities. The LC100 for 384 hours was between 20 ppb and 30 ppb. The 10, 15, 20 and 30 ppb experimental eggs concentrated mercury directly from the incubating solution 1,600, 1,900, 2,700, and 1,900 times, respectively. The total concentration of mercury in these eggs after 16 consecutive days was 16,000, 29,000, 54,000, and 56,000 respectively.