Adult brook trout (Salvelinus fontinalis) were exposed to concentrations of acid, Al, and Ca representative of acidic and acid-sensitive surface waters. At low pH (4.42–5.03), survival and growth were reduced by elevated Al concentrations (486 μg/L) and low Ca concentrations (0.5 mg/L). Fecundity (number of eggs per female) was reduced by exposure to some treatment combinations, but this effect was mediated through reduced growth; number of eggs per unit body weight was not related to treatment. Viability of eggs from ail parental exposures was high when incubated in neutral water. In spite of this high viability, eggs from parents exposed to low Ca concentrations showed greater mortality when incubated in the parental exposure conditions than did eggs from unexposed parents. Although the potential for such "carryover effects" cannot be discounted, we conclude that impairment of egg production is not a likely mechanism for loss of brook trout populations from acidic surface waters.

The hypothesis of this study was that tannins from Chinese tallow leaves have a negative effect upon terrestrial and aquatic reducer organisms and thereby may affect the overall rate of tallow litter decomposition. Species diversity and population size of aquatic reducers was lower in forest than adjacent grassland ponds; litter bags showed no difference in weight loss between bags which excluded reducers and those which did not. Differences in physical factors between habitats did not explain the paucity of reducers although rainfall permitted emigration of grassland organisms to forest ponds, yielding a temporary decrease in diversity.Tannin concentration in ephemeral ponds was altered by rainfall but leaching from leaves and soil continuously maintained tannin in ponds. Laboratory experiments showed that tannin was not directly toxic but inhibition of feeding caused high mortality in Asellus militaris and Crangonyx shoemackerii.Population density and reproduction of the terrestrial reducer (Armadillidium vulgare) was asynchronous with autumn leaf fall. Ground, leached leaves were consumed at much greater rate in laboratory experiments than unground, unleached leaves; in addition, mortality from starvation on the latter was high. These results suggest tallow leaves are not utilized by reducers until tannins are leached and the physical structure altered by rainfall and/or microbial action. Aquatic reducers are relatively unimportant in processing autumn leaf fall due to continual tannin leaching into ephemeral ponds from surrounding soil. Physical and microbial condition of leaves and leaching of tannin preceed spring and summer utilization by terrestrial isopods.

Leopard frog (Rana spp.) tadpoles exposed to esfenvalerate in the laboratory experienced a decrease in activity at concentrations as low as 1.3 pg/L and exhibited a convulsive, twitching response at concentrations of 3.6 pg/L. The 96-h median lethal concentration was 7.29 pg/L. Temperature influenced amphibian mortality; the mortality concentration-response slope at 22°C was significantly greater than at 18°C. Tadpoles exposed in a pond showed the same responses (inactivity, convulsive actions, and death) at similar concentrations as laboratory test organisms. Surviving tadpoles from laboratory tests resumed normal behavior 1 week after being placed into clean water, but most of those tadpoles that exhibited convulsive behavior during initial exposure eventually died. Tadpoles surviving pond exposures showed no later mortality, but rather exhibited a negative density-growth relation. Measured pyrethroid concentrations in ponds and streams adjacent to sprayed fields do not exceed levels associated with convulsive twitching or mortality in larval amphibians; however, they do exceed concentrations associated with inactivity and fish and invertebrate mortality, which may indirectly affect larval amphibians.

Leopard frog (Rana spp.) tadpoles exposed to esfenvalerate in the laboratory experienced a decrease in activity at concentrations as low as 1.3 μg/L and exhibited a convulsive, twitching response at concentrations of 3.6 μg/L. The 96‐h median lethal concentration was 7.29 μg/L. Temperature influenced amphibian mortality; the mortality concentration‐response slope at 22°C was significantly greater than at 18°C. Tadpoles exposed in a pond showed the same responses (inactivity, convulsive actions, and death) at similar concentrations as laboratory test organisms. Surviving tadpoles from laboratory tests resumed normal behavior 1 week after being placed into clean water, but most of those tadpoles that exhibited convulsive behavior during initial exposure eventually died. Tadpoles surviving pond exposures showed no later mortality, but rather exhibited a negative density‐growth relation. Measured pyrethroid concentrations in ponds and streams adjacent to sprayed fields do not exceed levels associated with convulsive twitching or mortality in larval amphibians; however, they do exceed concentrations associated with inactivity and fish and invertebrate mortality, which may indirectly affect larval amphibians.

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