Concentrations of Heavy Metals in Muscle with Relation to the Growth of Two Marine Fish Species

Heavy metal concentrations in muscle and their relation to thegrowth of two marine fish species,including tonguefish( Cynoglossus arel) and mullet( Mugil cephalus),were studied. The samples were collected in Bach Dang estuary andconcentrations of heavy metals( As,Cd,Co,Mn,Cu,Zn,Pb,and V) in muscle of the fisheswere determined. The result showed that the accumulated trend of heavy metal is different between fish species. The concentration of As,Zn,Mn,V,Cu,Pb,Co and Cd in tonguefish were 73. 7 ± 30. 6,22. 82 ± 4.87,3. 44 ± 2. 13,1. 61 ± 0. 15,0. 71 ± 0. 13,0. 45 ± 0. 24,0. 03 ± 0. 02 and 0. 02 ± 0. 02 mg·g-1,respectively. Meanwhile the concentration of Zn,As,V,Mn,Cu,Pb,Co and Cd in mullet were 83. 41 ±19. 68,9. 78 ± 1. 92,1. 36 ± 0. 54,1. 29 ± 0. 51,0. 65 ± 0. 12,0. 42 ± 0. 20,0. 06 ± 0. 03 and0. 03 ± 0. 01mg·g-1,respectively. Comparison of metal levels among thesespecies indicated that the concentrations of As and Mn in tonguefish were significantly higher than those in mullet,whereas Zn levels in mullet were found to be higher than that in tonguefish. There is no significant differences of Cd,Co,Cu,Pb and V levels in muscle between two species. Significant inversed relationshipsbetween concentration levels of metals and lengths of tonguefish were found for Mn,Cu and Zn,butnot for As,Cd,Pb,and V. There were no significant relationships between the heavy metal concentrations and the length of mullet. In general,decreasesof the heavy metal concentrations corresponded to the increases of fish body lengths,particularly for As,Co,Cu,Mn and V and the exception for Cd. Terefore reduced risks were associated with consuming biggermullet fish,and increased risks of As and Cd were associated with consuming bigger tonguefish in Bach Dang river mouth.     

A Case Study of Landholder Attitudes and Behaviour Toward the Conservation of Renosterveld,a Critically Endangered Vegetation Type in Cape Floral Kingdom,South Africa

The attitudes and behaviours of private landholders toward the conservation of a highly transformed and critically endangered habitat, Overberg Coastal Renosterveld (OCR) (a grassy shrubland of the Cape Floral Region, South Africa) are described. Personal, semistructured interviews were conducted with landholders, representing 40 properties in the Overberg region, on topics such as management and utilisation of OCR, the depth of their knowledge of its conservation importance, what they perceive its value to be, and the extent of their willingness to conserve it. General attitudes toward conservation incentives and provincial conservation authorities were also investigated. Farmers more willing to conserve were younger, did not necessarily have a better education, and owned larger farms (>500 ha) with a greater amount of remnant renosterveld (>300 ha) than those less willing to conserve. Attitudes toward the OCR were largely negative, related to associated problem plants and animals and the fact that it is believed not to be economically advantageous to retain it. However, farmers are of the opinion that provision of incentives and increased extension support will provide practical positive inducements for conservation. Landholder education is paramount to prevent further transformation of critically endangered habitats. The success of private-conservation programs depends on the attitudes of landowners toward (1) the particular habitat or species to be conserved (which can vary depending on the type of land use practised and the associated benefits and disadvantages of that habitat type); (2) the conservation agency or extension officers responsible for that area; and (3) willingness of landowners to participate in a conservation program, which is influenced by landowner age, farm size, and the amount of natural habitat left to conserve.     

Conflicting demands on detoxification pathways influence how common brushtail possums choose their diets

Most herbivores eat more and survive better when they have access to a variety of foods. One explanation involves the detoxification of plant secondary metabolites (PSMs). By feeding from a variety of plants that contain different classes of PSMs, animals can use multiple detoxification pathways and presumably consume more food. Although popular, this theory is difficult to test because it requires knowledge of the detoxification pathways of each PSM in the diet. We established that common brushtail possums (Trichosurus vulpecula) use various combinations of oxidation, hydrolysis, and conjugation with glucuronic acid (GA) or glycine to detoxify six PSMs. Compared to their ingestion of a single PSM, possums ate more when offered a choice between two diets containing PSMs that require apparently independent detoxification pathways (benzoate and 1,8-cineole, benzoate and p-cymene, benzoate and orcinol, benzoate and salicin, or orcinol and 1,8-cineole). However, possums still did not eat as much of these diets as they did of a basal diet free of PSMs. This suggests that detoxification pathways are never independent, but are separated instead by degrees. In contrast, possums offered a choice of two PSMs that require competing detoxification pathways (1,8-cineole and p-cymene, 1,8-cineole and salicin, or orcinol and salicin) ate no more than when offered diets containing one of the compounds. There was an exception: even though both rutin and orcinol are detoxified via conjugation with GA, the feeding behavior of possums did not suggest competition for detoxification pathways. This implies that the supply of GA is not limiting. This study provides the first convincing evidence that herbivorous mammals can eat more by selecting mixed diets with a diversity of PSMs that make full use of their detoxification potential. It also emphasizes that other behavioral and physiological factors, such as transient food aversions, influence feeding behavior.     

Nutrient cycling by fish supports relatively more primary production as lake productivity increases

Animals can be important in nutrient cycling in particular ecosystems, but few studies have examined how this importance varies along environmental gradients. In this study we quantified the nutrient cycling role of an abundant detritivorous fish species, the gizzard shad (Dorosoma cepedianum), in reservoir ecosystems along a gradient of ecosystem productivity. Gizzard shad feed mostly on sediment detritus and excrete sediment-derived nutrients into the water column, thereby mediating a cross-habitat translocation of nutrients to phytoplankton. We quantified nitrogen and phosphorus cycling (excretion) rates of gizzard shad, as well as nutrient demand by phytoplankton, in seven lakes over a four-year period (16 lake-years). The lakes span a gradient of watershed land use (the relative amounts of land used for agriculture vs. forest) and productivity. As the watersheds of these lakes became increasingly dominated by agricultural land, primary production rates, lake trophic state indicators (total phosphorus and chlorophyll concentrations), and nutrient flux through gizzard shad populations all increased. Nutrient cycling by gizzard shad supported a substantial proportion of primary production in these ecosystems, and this proportion increased as watershed agriculture (and ecosystem productivity) increased. In the four productive lakes with agricultural watersheds (>78% agricultural land), gizzard shad supported on average 51% of phytoplankton primary production (range 27-67%). In contrast, in the three relatively unproductive lakes in forested or mixed-land-use watersheds (>47% forest, <52% agricultural land), gizzard shad supported 18% of primary production (range 14-23%). Thus, along a gradient of forested to agricultural landscapes, both watershed nutrient inputs and nutrient translocation by gizzard shad increase, but our data indicate that the importance of nutrient translocation by gizzard shad increases more rapidly. Our results therefore support the hypothesis that watersheds and gizzard shad jointly regulate primary production in reservoir ecosystems.     

Hydrodechlorination of dichlorobiphenyls over Ni-Mo/Al2O3 catalysts prepared by spray-drying method

The hydrodechlorination (HDCl) process of 2,3-, 2,4- and 2,5-dichlorobiphenyls was studied over a sulphided Ni-Mo/Al(2)O(3) catalyst in a stirred autoclave at a hydrogen pressure of 3 MPa. The catalysts were prepared by spray-drying. They were characterized by N(2) adsorption, thermogravimetry and scanning electron microscopy with X-ray microanalysis. The reaction temperature of the catalytic HDCl process was varied in the range of 230-290 degrees C. Polychlorinated biphenyls (PCBs) free transformer oil was used as reaction medium. The HDCl degree of dichlorobiphenyl isomers was in the range of 82-93%. The efficiency in the chlorine removal was found to be related to the position of the substituted chlorine atom and decreased as follows 2,4-dichlorobiphenyl approximately 2,5-dichlorobiphenyl>2,3-dichlorobiphenyl. For comparison, the HDCl process of 2,3-dichlorobiphenyl (2,3-PCB) without catalyst was also studied. The chlorine removal was 85% for the catalytic HDCl of 2,3-PCB whereas non-catalytic process led only to 16% of dechlorination in the same operating conditions, i.e. at 290 degrees C after 120 min. Monodichlorobiphenyls were not detected in the reaction products. The data for both catalytic and non-catalytic conversion of 2,3-PCB fit to a first-order model. Kinetic constants and the activation energy of the overall HDCl reaction of 2,3-PCB to biphenyl were evaluated. Compared to non-catalytic process, a nearly threefold decrease in the activation energy was observed in the presence of Ni-Mo/Al(2)O(3) catalyst prepared by spray-drying (48 kJ mol(-1) vs. 124 kJ mol(-1)).     

Impact of sewage sludge spreading on heavy metal speciation in tropical soils (Réunion, Indian Ocean)

This study was designed to evaluate the impact of sewage sludge spreading on tropical soilborne heavy metal speciation. Sludgeborne heavy metal speciation was also assessed, and the potential mobility of the elements was classified as follows: Zn>Ni>Cu approximately Cr. Two sequential extraction procedures were applied to study Cr, Cu, Ni and Zn speciation in control soils and sludge-amended soils. We demonstrated that sewage sludge spreading over a 2-year period did not have an impact on soilborne heavy metal concentrations but affected speciation of the most mobile fractions of Ni and Zn. Both protocols were consistent for the organic matter fractions, with an increase in Cu, Zn and Cr concentrations in the amended soil as compared to the control soil. In addition, we highlighted that the two protocols characterized different pools of organic matter and that organic compounds remained in the solid matrix after extraction. With respect to the reducible fraction, completely opposite results were obtained with the two protocols and the solid residue study revealed that the two schemes were ineffective in characterizing iron and manganese fractions.     

Baseline mercury and zinc concentrations in terrestrial and coastal organisms of Admiralty Bay, Antarctica

This paper provides the first quantitative information on mercury in soil, coastal sediment, and in characteristic organisms of terrestrial and shallow coastal marine ecosystems from Admiralty Bay (King George Island, Antarctica). As expected for a remote area, mercury content is low in abiotic components of the ecosystem, and probably similar to natural levels. Mercury also occurs in very low concentrations in the vegetation, invertebrates and fish. These low mercury levels may be due to sulphide formation in reducing sediments of this environment. Higher concentrations of mercury occurred in bird feathers and mammal hair, indicating biomagnification. This was not found for Zinc. These results may be useful as a reference background to detect future inputs of trace elements in this remote area of the earth. Terrestrial vegetation and bird feathers are suggested as target regional biomonitors.