Ploidy-, gender-, and dose-dependent alteration of selected biomarkers in Clarias gariepinus treated with benzo[a]pyrene

Naturally-occurring and artificially-induced polyploids have been documented in various fish species but to date no comparison has been reported of the impacts of ploidy on fish biomarker responses to organic pollutants. This study describes effects of ploidy, gender, and dose on biliary fluorescent aromatic compound (FAC) concentrations, hepatic ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST) activities in one of the most commonly cultured warm-water species, the African catfish Clarias gariepinus. Recently matured male and female diploid and triploid fish were intraperitoneally (i.p.) injected with 0, 5 or 25 mg/kg benzo[a]pyrene (BaP) and liver and gallbladder were sampled 48 hr later. No significant differences were found between ploidies in bile concentrations of 7,8 dihydrodiolbenzo[a]pyrene (7,8D BaP), 1-hydroxybenzo[a]pyrene (1-OH BaP) or 3-hydroxybenzo[a]pyrene (3-OH BaP). However, concentrations of the biliary FACs did differ between males and females at different dose of injection with generally higher concentrations in females at the low dose of BaP and higher concentrations in males at the higher BaP concentration. Hepatic EROD activity did not exhibit gender-dependent difference, whereas it was significantly higher in triploids than diploids. GST activities were not significantly influenced by any of the tested factors. This work advanced our understanding of the role of ploidy, gender, and dose in biotransformation of pollutants in fish.     

Effects of the Heavy Metals Copper and Zinc on Zooxanthellae Cells in Culture

The growth of symbiotic algal cells (zooxanthellae) isolated from the coral, Montipora verrucosa under the influence of the heavy metals copper (Cu) and Zinc (Zn) was investigated. Zooxanthellae cells cultured in f/2 enriched seawater medium were subjected to a maximum Cu level of 42µg.l-1, Zn concentration of 509µg.l-1, and various combinations of the two metals, in ecotoxicological bioassays lasting up to 28 days. A Cu level of 40µg.l-1 caused significantly depressed specific growth rates of cell cultures obtained using a standard growth model. Low concentrations of the metals Cu and Zn in combination elicited synergistic effects of sublethal toxicity. The use of cultured zooxanthellae cells in bioassays investigating sublethal effects of heavy metal stress has relevant applications in the field of pollution monitoring.     

Atmospheric transport of atrazine: a simple device for its detection

Thin-layer chromatography plates were exposed at three different locations in Bavaria for 3-week periods during the growing season of maize. The adsorption of traces of atrazine was detected by thin-layer chromatography, GC-MS, and by an enzyme immunoassay. It was restricted to the sowing season, which coincides with the application of atrazine. The herbicide could not be detected after this time. The simplicity of the adsorption device, combined with a serological assay, render this procedure suitable for detecting airborne organic pollutants.     

Process evaluation for optimization of EDTA use and recovery for heavy metal removal from a contaminated soil

This study aimed to establish an optimized, closed loop application of ethylenediaminetetraacetic acid (EDTA) in heavy metal removals from a contaminated soil through integrating EDTA recovery/regeneration and metal precipitation processes in the treatment train. Three divalent heavy metals were investigated, namely, Pb, Cd, and Ni. The extractability of the metals by EDTA followed the decreasing order of CdPb>Ni. The first part of this study was to search for the optimal use of the fresh EDTA in removing these heavy metals from the contaminated soil. The second part of this study was devoted to the recovery/regeneration of the spent EDTA which followed the sequential processes involving (1) complex destabilization by adding ferric ion (Fe(III)) to liberate Pb, Cd, and Ni, (2) precipitation of the liberated Pb, Cd, and Ni in phosphate (PO4(3-)) forms, and (3) precipitation of the excess Fe(III) which eventually produced free EDTA for reuse. The process variables were dosages of Fe(III) and PO4(3-), pH and reaction times. Laborious trial experiments would be needed in searching for the optimum conditions for the above processes. To expedite this exercise, a geochemical equilibrium model, MINTEQA2, was used to find the thermodynamically favorable conditions for recoveries of both EDTA and heavy metals. This was then followed by experimental examination of the process kinetics to observe for the optimal reaction time for each thermodynamically favorable process. This study revealed that 2 h of reaction time each for the complex destabilization reaction and the metal phosphate precipitation reaction was sufficient to achieve equilibrium. With the optimized process condition identified in this study, a total of 95%, 89% and 90% of the extracted Pb, Cd and Ni, respectively, could be precipitated from the spent EDTA solution, with 84% EDTA recovery. The reused EDTA maintained more than 90% of its preceding extraction power in each cycle of reuse.     

MODELING OF NONPOINT SOURCE POLLUTION OF NITROGEN AT THE WATERSHED SCALE1

ABSTRACT: The Watershed Nutrient Transport and Transformation (NTT-Watershed) model is a physically based, energy-driven, multiple land use, distributed model that is capable of simulating water and nutrient transport in a watershed. The topographic features and subsurface properties of the watershed are refined into uniform, homogeneous square grids. The vertical discretization includes vegetation, overland flow, soil water redistribution and groundwater zones. The chemical submodel simulates the nitrogen dynamics in terrestrial and aquatic systems. Three chemical state variables are considered (NO₃^-_-, NH₄⁺, and Org-N). The NTT-Watershed model was used to simulate the fate and transport of nitrogen in the Muddy Brook watershed in Connecticut. The model was shown to be capable of capturing the hydrologic and portions of the nitrogen dynamics in the watershed. Watershed planners could use this model in developing strategies of best management practices that could result in maximizing the reductions of nitrogen export from a watershed.     

Optimum size limit for a fishery with a limited fishing season

In the management of a fishery with many year-classes, a standard objective is to maximize the biomass yield. If the fishing effort is fixed, this objective can be attained by prescribing an optimum size limit. This implies that only fish which are larger than the optimum size limit should be caught. The theory for computing the optimum size limit when fishing is carried out continuously is well established. In contrast the theory for computing the optimum size limit when the fishing season is limited to the same period in each year has not been developed in spite of the fact that many fisheries are exploited in this manner. A fishing season may be limited because the weather or the migration patterns of the fish population permits fishing only during a certain period in the year. A fishing season may also be limited because it is necessary to reduce the fishing mortality in order to conserve the fish population.A theory for computing the optimum size limit when the fishing season is limited is developed in this paper. It is applied to a hypothetical fishery. The data for this example comes from the North Sea plaice fishery. It is found that for a given fishing effort the optimum size limit is 44.5 cm if fishing is carried out continuously, 41.3 cm if fishing is limited to 6 months in a year and 28.7 cm if fishing is limited to a period of one tenth of a year in each year.