Sulfide tolerance and detoxification in shallow-water marine fishes

Hydrogen sulfide is a potent inhibitor of aerobic respiration. Sulfide is produced in sediments, and many species of fish live in association with the bottom. Tolerance tests, enzyme assays, and chromatography of sulfur compounds in thirteen species of shallow-water marine fishes (collected in San Diego, California, USA in 1987–1988) indicate adaptations to sulfide that vary with habitat and lifestyle. Tidal-marsh inhabitants, like Gillichthys mirabilis and Fundulus parvipinnis, have higher tolerance to sulfide (96 h LC₅₀ at 525 to 700 M) relative to outer-bay and open-coast inhabitants (surviving <12 h at much lower concentrations). The cytochrome c oxidase of all species shows high activity and susceptibility to sulfide poisoning, with 50% inhibition at 30 to 500 nM in various tissues. The two marsh species are able to survive at sulfide concentrations already inhibitory to their cytochrome c oxidase and fatal to other species. All species detoxify sulfide by oxidizing it to thiosulfate. All have sulfide-oxidizing activity in the blood, spleen, kidney, liver and gills, which correlates significantly with heme content. Thiosulfate appears in the tissues of sulfide-exposed fish and builds up to high concentrations (up to 2 mM) with stronger and longer exposure. Unexposed fish contain little or no thiosulfate. Sulfide is barely detectable in the tissues, even in high-sulfide exposure tests. We suggest that fish blood, in having high sulfide-oxidizing activity and no cytochrome c oxidase, can act as a short-term first line of defense against sulfide, and thus minimize the amount that reaches the vital organs. The results of this study indicate that sulfide is a significant environmental factor influencing the ecological distribution of marine fishes.     

Relation of particle-size spectrum and food abundance to particle selectivity in the mud snail Hydrobia totteni (Prosobranchia: Hydrobiidae)

We studied the relationship between particle-size selectivity and variable particle-size distribution in the American mud snail Hydrobia totteni Morrison (Prosobranchia: Hydrobiidae) collected in the summer of 1979 and 1982, from saltmarsh mudflats at Flax Pond, Old Field, New York, USA. Using individual size fractions of native sediment, snails fed fastest on intermediate-sized particles (41 to 63 m); this pattern was related to diatom abundance, which was similarly greatest on the intermediate particle-size classes. These results conform to another study, which found a quite different relationship between feeding rate and particle size, but a similarly strong correlation between particle size and diatom abundance. Snails were fed a range of particle-size distributions of glass beads. As median particle size increased, preference shifted towards smaller particles. This shift cannot be explained by feeding rates determined from individual particle-size classes. The most reasonable alternative model is a shift towards feeding on fine particles that occur among the coarser particles that are not ingested. Our data suggest that diatom growth on certain particle sizes is as important to particle selectivity as the particle sizes themselves. Particle size preference cannot be extrapolated from studies of feeding rates on individual size classes since selectivity is qualitatively different in mixtures of various size classes.     

Metal distribution in incineration residues of municipal solid waste (MSW) in Japan

This study aimed to identify distribution of metals and the influential factors on metal concentrations in incineration residues. Bottom ash and fly ash were sampled from 19 stoker and seven fluidized bed incinerators, which were selected to have a variety of furnace capacity, furnace temperature, and input waste. In the results, shredded bulky waste in input waste increased the concentration of some metals, such as Cd and Pb, and the effect was confirmed by analysis of shredded bulky waste. During MSW incineration, lithophilic metals such as Fe, Cu, Cr, and Al remained mainly in the bottom ash while Cd volatilized from the furnace and condensed to the fly ash. About two thirds of Pb and Zn was found in the bottom ash despite their high volatility. Finally, based on the results obtained in this study, the amount of metal in incineration residues of MSW was calculated and the loss of metal was estimated in terms of mass and money. A considerable amount of metal was found to be lost as waste material by landfilling of incineration residues.     

Denitrification in a coastal plain riparian zone contiguous to a heavily loaded swine wastewater spray field

Riparian zones are recognized as landscape features that buffer streams from pollutants, particularly nitrogen. The objectives of this experiment were to (i) assess denitrification activity within a riparian zone and (ii) determine the influence of physical, chemical, and landscape features on denitrification. This experiment was conducted from 1994 to 1997 in North Carolina on a riparian zone contiguous to a spray field that was heavily loaded with swine lagoon wastewater. Denitrification enzyme activity (DEA) was measured on soils collected from (i) the soil surface, (ii) midway between the soil surface and water table, and (iii) above the water table. The DEA ranged from 3 to 1660 microg N(2)O-N kg(-1) soil h(-1). The DEA was highest next to the stream and lowest next to the spray field. Nitrate was found to be the limiting factor for denitrification. The DEA generally decreased with soil depth; means for the surface, middle, and bottom depths were 147, 83, and 67 microg N(2)O-N kg(-1) soil h(-1), respectively. These DEA values are higher than those reported for riparian zones adjoining cropland of the southeastern United States, but are lower than those reported for a constructed wetland used for treatment of swine wastewater. Regression analysis indicated that soil total nitrogen was the highest single factor correlated to DEA (r(2) = 0.65). The inclusion of water table depth, soil depth, and distance from the spray field improved the R(2) to 0.86. This riparian zone possessed sufficient soil area with high denitrifying conditions to be a significant factor in the removal of excess nitrogen in the ground water.     

Sorption of sulfonamide pharmaceutical antibiotics on whole soils and particle-size fractions

Residues of pharmaceutical antibiotics are found in the environment, whose fate and effects are governed by sorption. Thus, the extent and mechanisms of the soil sorption of p-aminobenzoic acid and five sulfonamide antibiotics (sulfanilamide, sulfadimidine, sulfadiazine, sulfadimethoxine, and sulfapyridine) were investigated using topsoils of fertilized and unfertilized Chernozem and their organic-mineral particle-size fractions. Freundlich adsorption coefficients (K(f)) ranged from 0.5 to 6.5. Adsorption increased with aromaticity and electronegativity of functional groups attached to the sulfonyl-phenylamine core. Adsorption to soil and particle-size fractions increased in the sequence: coarse silt < whole soil < medium silt < sand < clay < fine silt and was influenced by pH. Sorption nonlinearity (1/n 相似文献   

Field dissipation of acetochlor in two New Zealand soils at two application rates

The persistence of pesticides in soils has both economic and environmental significance and is often used as a key parameter in pesticide risk assessment. Persistence of acetochlor [2'-ethyl-6'-methyl-N-(ethoxymethyl)-2-chloroacetylanilide] in two New Zealand field soils was measured over two years and the data were used to identify models that adequately describe acetochlor persistence in the field. Acetochlor was sprayed onto six fallow plots (3 x 9 m each) at each site at the recommended rate (2.5 kg a.i. ha(-1)) and at twice that rate. Acetochlor concentrations were measured in soil cores. Simple first-order kinetics (Model 1) adequately described acetochlor persistence in Hamilton clay loam soil (Humic Hapludull, Illuvial Spadic) at the high application rate, but overestimated it at the low application rate. A quadratic model (Model 2), a first-order double-exponential model (Model 3), a first-order biphasic model (Model 4), or a two-compartment model (Model 5) better described acetochlor persistence at the low application rate. The time for 50% (DT50) and 90% (DT90) of initial acetochlor loss was approximately 9 and 56 d, and 18 and 63 d at low and high application rates, respectively. The more complex Models 2 through 5 also better described the biphasic dissipation of acetochlor in Horotiu sandy loam soil (Typic Orthic Allophanic) than Model 1, with Model 1 significantly underestimating acetochlor concentrations on the day of application at both application rates. The DT50 and DT90 values were 5 and 29 d and 7 and 31 d at low and high application rates, respectively. Overall, application rate significantly affected the DT50 and DT90 values in the Hamilton soil, but not in the Horotiu soil. Faster acetochlor loss in the Horotiu soil possibly resulted from the higher soil organic carbon content that retained more acetochlor near the soil surface where higher temperature and photolysis accelerated the loss.     

Physiological and Biochemical Effects of Simulated Acid Rain on Phaseolus Vulgaris Var. HUR-15

Pot experiments were performed to determine the effects of simulated acid rain on Phaseolus vulgaris var. HUR-15. Seeds of Phaseolus vulgaris var. HUR-15 were exposed to simulated acid rain at pH values of 5.1, 4.1, 3.1, 2.1 and 1.1 and a control level of pH 6.8. Plants were harvested at three stages, i.e. pre, peak and post-flowering stages. Seedlings succumbed at pH 1.1. Necrosis developed on the leaves of plants treated with water of pH 2.1, resulting in adverse effect on chlorophyll content. They died after peak-flowering. Root and shoot length and dry weight were reduced with the lowering in pH. Carbohydrate, nitrogen and protein contents decreased with the decrease in pH level, adversely affecting their nutrient value.     

A basidiomycete isolated from the skeleton of<Emphasis Type="Italic"> Pocillopora damicornis</Emphasis> (Scleractinia) selectively stimulates short-term survival of coral skeletogenic cells

Endolithic fungi bore through the extracellular calcium carbonate skeleton of reef-building scleractinian corals, both healthy and dead, and effect net erosion of coral reefs. Potential fungal interactions with coral tissue were investigated using an in vitro approach suggested by earlier observations of skeletal repair cones at the site of fungal perforation in Porites sp. A fungal strain was isolated from the skeleton of a long-term culture of healthy, tissue-covered, Pocillopora damicornis Linnaeus colonies maintained in a recirculating system in Monaco. As coral soft tissue spontaneously dissociated in vitro, the skeleton became exposed and hyaline hyphae emerged radially from 15% of the total clipped branches. In this study, which was performed between January 2001 and March 2003, 35 skeleton–hypha explants were embedded in agar-based solid medium, yielding 60% hyphal growth. A fungal strain (F19-3-1) of the dominant (80%) morphology was isolated and propagated in agar-based solid medium. The strain was identified by 18S and 26S rDNA gene sequence analysis as a basidiomycete in the genus Cryptococcus. Co-cultures were used to provide experimental exposure of coral soft tissue to the fungus. The fungus extended the survival of coral cells by 2 days, selectively maintaining skeletogenic cell types. This effect may be interpreted as stimulation by the fungus of a short-term coral defense response.Communicated by J.P. Grassle, New Brunswick