Response of a coral-associated crustacean community to eutrophication

Seventy-five samples of the crustacean fauna associated with the coral Madracis mirabilis (Duchassaing and Michelotti) were obtained at five sites along the west coast of Barbados in 1985. Samples were analyzed to determine whether any community response to eutrophication was evident. Ordination (multidimensional scaling) and classification (group average clustering) based on Bray-Curtis dissimilarity measures separated the fauna of highly eutrophied sites from those that were less eutrophied. Dominance plots based on relative abundance and log-normal plotting methods were ineffective in distinguishing the fauna of eutrophied sites. The crustacean fauna responded to eutrophication mainly by reduction of density of animals. No differences in species richness, number of site endemic species or rare species were observed between highly eutrophied and less eutrophied sites. Nine indicator species of eutrophy were identified on the basis of strong density differences between sites.     

Biosolids-derived nitrogen mineralization and transformation in forest soils

Utilization of biosolids through land application is becoming increasingly popular among wastewater managers. To minimize the potential contamination of receiving waters from biosolids-derived nitrogen (N), it is important to understand the availability of N after land application of biosolids. In this study, four secondary biosolids (two municipal and two pulp and paper industrial biosolids) were used in a laboratory incubation experiment to simulate N mineralization and transformation after land application. Municipal biosolids were from either aerobically or anaerobically digested sources, while pulp and paper industrial biosolids were from aerated wastewater stabilization lagoons. These biosolids were mixed with two New Zealand forest soils (top 100 mm of a volcanic soil and a brown soil) and incubated at two temperatures (10 and 20 degrees C) for 26 wk. During incubation, mineralized N was periodically leached from the soil-biosolids mixture with 0.01 M CaCl2 solution and concentrations of NH4 and NO3 in leachate were determined. Mineralization of N from aerobically digested municipal biosolids (32.1%) was significantly more than that from anaerobically digested biosolids (15.2%). Among the two pulp and paper industrial biosolids, little N leached from one, while as much as 18.0% of total organic N was leached from the other. As expected, mineralization of N was significantly greater at 20 degrees C (average 22.8%) than at 10 degrees C (average 9.7%). It was observed that more N in municipal biosolids was mineralized in the brown soil, whereas more N in pulp and paper industrial biosolids mineralized in the volcanic soil. Transformation of NH4 to NO3 was affected by soil type and temperature.     

Chromate reduction by chromium-resistant bacteria isolated from soils contaminated with dichromate

Extensive use of hexavalent chromium [Cr(VI)] in various industrial applications has caused substantial environmental contamination. Chromium-resistant bacteria isolated from soils can be used to remove toxic Cr(VI) from contaminated environments. This study was conducted to isolate chromium-resistant bacteria from soils contaminated with dichromate and describes the effects of some environmental factors such as pH, temperature, and time on Cr(VI) reduction and resistance. We found that chromium-resistant bacteria can tolerate 2500 mg L(-1) Cr(VI), but most of the isolates tolerated and reduced Cr(VI) at concentrations lower than 1500 mg L(-1). Chromate reduction activity of whole cells was detected in five isolates. Most of these isolates belong to the genus Bacillus as identified by the 16S rRNA gene sequencing. Maximal Cr(VI) reduction was observed at the optimum pH (7.0-9.0) and temperature (30 degrees C) of growth. One bacterial isolate (Bacillus sp. ES 29) was able to aerobically reduce 90% of Cr(VI) in six hours. The Cr(VI) reduction activity of the whole cells of five isolates had a K(M) of 0.271 (2.61 mM) to 1.51 mg L(-1) (14.50 mM) and a V(max) of 88.4 (14.17 nmol min(-1)) to 489 mg L9-1) h(-1) (78.36 nmol min(-1)). Our consortia and monocultures of these isolates can be useful for Cr(VI) detoxification at low and high concentrations in Cr(VI)-contaminated environments and under a wide range of environmental conditions.     

Surface runoff losses of copper and zinc in sandy soils

Increased anthropogenic inputs of Cu and Zn in soils have caused considerable concern relative to their effect on water contamination. Copper and Zn contents in surface soil directly influence the movement of Cu and Zn. However, minimal information is available on runoff losses of Cu and Zn in agricultural soils, and soil-extractable Cu and Zn in relation to runoff water quality. Field experiments were conducted in 2001 to study dissolved Cu and Zn losses in runoff in Florida sandy soils under commercial citrus and vegetable production and the relationship between soil-extractable Cu and Zn forms and dissolved Cu and Zn concentrations in runoff water. Five extraction methods were compared for extracting soil available Cu and Zn. Concentrations of dissolved Cu and Zn in runoff were measured and runoff discharge was monitored. Mean dissolved Cu in field runoff water was significantly correlated with the extractable Cu obtained only by 0.01 mol L(-1) CaCl2, Mehlich 1, or DTPA-TEA methods. Dissolved Zn in runoff water was only significantly correlated with extractable Zn by 0.01 mol L(-1) CaCl2. The highest correlations to dissolved Cu in runoff were obtained when soil-available Cu was extracted by 0.01 mol L(-1) CaCl2. The results indicate that 0.01 mol L(-1) CaCl2-extractable Cu and Zn are the best soil indexes for predicting readily released Cu and Zn in the sandy soils. Both runoff discharge and 0.01 mol L(-1) CaCl2-extractable Cu and Zn levels had significant influences on Cu and Zn loads in surface runoff.     

Importance of Sediment–Water Interactions in Coeur d’Alene Lake,Idaho, USA: Management Implications

A field study at Coeur dAlene Lake, Idaho, USA, was conducted between October 1998 and August 2001 to examine the potential importance of sediment–water interactions on contaminant transport and to provide the first direct measurements of the benthic flux of dissolved solutes of environmental concern in this lake. Because of potential ecological effects, dissolved zinc and orthophosphate were the solutes of primary interest. Results from deployments of an in situ flux chamber indicated that benthic fluxes of dissolved Zn and orthophosphate were comparable in magnitude to riverine inputs. Tracer analyses and benthic-community metrics provided evidence that solute benthic flux were diffusion-controlled at the flux-chamber deployment sites. That is, effects of biomixing (or bioturbation) and ground-water interactions did not strongly influence benthic flux. Remediation efforts in the river might not produce desired water-quality effects in the lake because imposed shifts in concentration gradients near the sediment–water interface would generate a benthic feedback response. Therefore, development of water-quality models to justify remediation strategies requires consideration of contaminant flux between the water column and underlying sediment in basins that have been affected by long-term (decadal) anthropogenic activities.     

Development and Adoption of a Simple Nonpoint Source Pollution Model for Port Phillip Bay,Australia

New computing tools and approaches allow tailored development of software to meet the needs of environmental managers. The processes required for such tailoring fit well with adaptive management concepts where, as knowledge and system understanding develop among managers, the software can be developed or replaced to match. This paper reports on development and adoption of a simple nonpoint source pollution modeling tool, including technical aspects of data support for modeling and social aspects of software design. The software, named FILTER, used a unit load model to generate expected pollutant loads from subcatchments of Port Phillip Bay, Australia. Monitoring data were used for calibration to modify the delivery of generated pollutants to receiving waters. Spatial, tabular, and charting software components were used to provide alternative forms of output visualization. FILTER was developed using a process that resulted in manager-stakeholders taking responsibility for setting of model parameter values and operation of the user interface, thereby encouraging uptake. The inclusive development process, tailoring of the software to manager needs and styles of usage, and matching of model complexity to data and knowledge, resulted in a successful application that has become the current agreed system representation among disparate stakeholder organizations.