Transformation of a tundra river from heterotrophy to autotrophy by addition of phosphorus.

Continuous enrichment of an arctic river with only 10 parts per billion phosphate-phosphorus caused an immediate growth of attached algae for more than 10 kilometers downstream, showing that phosphorus alone limited photosynthesis. As a result of the increased photosynthesis, there was an increase in bacterial activity in films on rocks on the bottom of the stream. The major source of energy became the photosynthetic carbon fixed in the stream rather than the organic material entering from the surrounding tundra, and the overall metabolism of the stream shifted from heterotrophy to autotrophy. An increase in the size and developmental stage of some of the dominant aquatic insects illustrates the food limitation in this nutrient-poor habitat.

Microbiological safety of drinking water: United States and global perspectives.

Waterborne disease statistics only begin to estimate the global burden of infectious diseases from contaminated drinking water. Diarrheal disease is dramatically underreported and etiologies seldom diagnosed. This review examines available data on waterborne disease incidence both in the United States and globally together with its limitations. The waterborne route of transmission is examined for bacterial, protozoal, and viral pathogens that either are frequently associated with drinking water (e.g., Shigella spp.), or for which there is strong evidence implicating the waterborne route of transmission (e.g., Leptospira spp.). In addition, crucial areas of research are discussed, including risks from selection of treatment-resistant pathogens, importance of environmental reservoirs, and new methodologies for pathogen-specific monitoring. To accurately assess risks from waterborne disease, it is necessary to understand pathogen distribution and survival strategies within water distribution systems and to apply methodologies that can detect not only the presence, but also the viability and infectivity of the pathogen.

The role of diagnosticity in stereotype formation: perceiving group means and variances.

Three experiments tested the hypotheses that while forming stereotypes of social groups, people abstract the central tendency and variability of different attribute dimensions to determine which ones best differentiate the groups and that more differentiating dimensions are more likely to become stereotypical in the sense of becoming strongly associated with the groups in memory. Supporting these hypotheses. Experiment 1 found that, after viewing behaviors performed by members of 2 groups, Ss characterized the groups more in terms of attribute dimensions indicating larger differences between the central tendencies of the groups, and Experiment 2 showed that this effect did not occur when Ss formed impressions of only 1 group. Experiment 3 found that Ss also characterized groups more in terms of attribute dimensions indicating lower within-group variability.

Characteristics of sorption losses of polychlorinated biphenyl congeners onto glass surfaces.

Sorption losses to glass surfaces of five polychlorinated biphenyl (PCB) congeners in aqueous solutions were investigated. Adsorption/desorption experiments were conducted under conditions that simulated actual sample handling procedures for environmental samples. It was found that the adsorption loss is related to the degree of chlorination. PCB congener 180 lost the most onto glass surfaces, followed by congeners 138, 101/28, and 52, in decreasing order. More PCB adsorption occurred onto glass under conditions of agitation and higher temperature (22 degrees C) during the five-day experimental period. The salinity effect ("salting out effect") was also observed in this work. The efficiency of desorption (rinsing three times with solvent) was found to be ineffective in extracting adsorbed PCBs. It was necessary to use mechanical shaking for extraction. Storage of samples up to five days resulted in sorption losses as much as 30%, 17%, 30%, 40%, and 55% of PCB 28, 52, 101, 138, and 180, respectively. Sorption losses need to be considered when conducting water sampling or toxicological studies to avoid underestimation of the actual PCB concentrations and their toxic effects.

Coating effects on the glass adsorption of polychlorinated biphenyl (PCB) congeners.

The effects of coating materials on polychlorinated biphenyl (PCB) adsorption in aqueous solution were assessed in an attempt to minimize PCB sorption loss during sampling processes. A coating material, which enhances PCB adsorption and allows adsorbed PCBs to be readily extracted by solvents, can act as a sampling concentrator to reduce PCB losses from both adsorption and evaporation. Several coating materials were evaluated, including paraffin oil, silicone oil, dimethyldichlorosilane (Sylon-CT), Prosil 28 and polydimethylsiloxane (PDS) with viscosity 0.65, 50 (PDS 50), and 500 (PDS 500) cSt. PDS and silicone oil enhanced adsorption for all five congeners examined (IUPAC No. 28, 52, 101, 138, and 180). Sylon-CT, paraffin oil and Prosil 28 had inconsistent effects on adsorption of different congeners. Desorption of adsorbed PCBs onto all coating types was assessed. The recovery efficiency of extracting PCBs with solvents was enhanced greatly with all coatings as opposed to non-coated surfaces, with the exception of paraffin oil. Coating with silicon oil, PDS 50, and 500 resulted in virtually 100% recovery of adsorbed PCBs. It was also found that Teflon containers were poor substitutes for glass containers and failed to minimize PCB losses. Among the materials studied, the best coating that could be used as a sampling concentrator was PDS 500.

Detection of Cryptosporidium sp. in two new seal species, Phoca vitulina and Cystophora cristata, and a novel Cryptosporidium genotype in a third seal species, Pagophilus groenlandicus, from the Gulf of Maine.

Data on the geographic distribution and host specificity of Cryptosporidium spp. are critical for developing an understanding of likely transmission patterns in nature. During a molecular-based survey of fecal samples from 293 terrestrial and aquatic animals in Maine, USA, we detected Cryptosporidium sp. in 11 harbor seals (Phoca vitulina), 1 hooded seal (Cystophora cristata), and 1 harp seal (Pagophilus groenlandicus). None of the terrestrial or freshwater mammal fecal samples or bird samples tested positive for Cryptosporidium sp. However, the sequencing results of the small subunit (ssu) rRNA gene indicate that the seals were infected with an undescribed species of Cryptosporidium , previously isolated only from ringed seals (Phoca hispida) in northern Quebec, Canada. In addition, the Cryptosporidium sp. detected in the harp seal is significantly different from the previously observed Cryptosporidium sp. in other seals. We confirmed the genetic distinctiveness of this Cryptosporidium genotype and the identity of the other Cryptosporidium sp. seal ssu rRNA sequences by using data from the 70-kDa heat shock protein gene. Based on phylogenetic reconstructions of both genes, it seems that either Cryptosporidium canis or C. felis are sister species to the seal associated Cryptosporidium spp. Our findings extend the range of " Cryptosporidium sp. seal" well south of the 55th parallel, add other species to the list of seals affected by Cryptosporidium sp., and highlight the presence of unrecognized population and potentially species level variation in Cryptosporidium.

Microcalorimetric Approach to Determine Relationships between Energy Supply and Metabolism in River Epilithon.

In a study to determine the relative importance of various apparent molecular weight fractions to the metabolism (heat output) of attached microorganisms in rivers, a marked lack of response to gross changes in the external organic matter supply was noted over the course of several hours. Such a response by a mixed autotrophic-heterotrophic community could be attributed to the autotrophs being the sole organic energy source for the heterotrophs. However, substantial metabolic activities were noted in attached microbial communities grown in darkness (algae free), thus indicating that riverborne organic matter was a major energy source. This paradox was attributed to a proposed lag in the availability of dissolved and colloidal organic matter to the heterotrophic microorganisms.

Legionellosis: ecological factors of an environmentally 'new' disease.

This review paper discusses environmental factors influencing multiplication, persistence and virulence of Legionella. The differing modes of transmission of legionellosis are discussed in relation to the epidemiology and clinical manifestations of the disease. Characteristics of pathogenicity of Legionella are compared to other pathogens. Implications for prevention are presented, and areas where further research is needed are discussed.

Inexpensive flow microcalorimeter for measuring heat production of attached and sedimentary aquatic microorganisms.

A relatively inexpensive flow microcalorimeter is described which is capable of detecting heat outputs as low as 3 muW (precision, +/-2%). Its use is illustrated on river epilithon (0.8 to 6.8 muW cm), river sand (9.8 muW cm), and marine sand (15.3 muW cm); however, it could be used to detect the heat output from any biotic material over which a flow of water can be passed, provided that such an action would not be disruptive to chemical and biological equilibria.

Evaluation of environmental effects on metal transport from capped contaminated sediment under conditions of submarine groundwater discharge.

Previous studies conducted in our laboratories have shown that submarine groundwater discharge (SGD) can significantly increase metal fluxes from capped contaminated sediment to the overlying water. Five columns were set up in the laboratory to evaluate the effects of environmental factors such as groundwater pH, sediment depth, and groundwater flow rate on metal transport from capped contaminated sediment under conditions of SGD. Acidified groundwater discharge was shown to enhance the mobility of all tested metals except Mo. Although much of the released metal was adsorbed by the capping material, significant increases of initial or steady-state fluxes to the overlying water were observed for Ni, Cu, Zn, Cd, Pb, and Mn. Additional sediment depth enhanced steady-state fluxes for all tested metals except Mo, Cd, and Pb. Increased SGD rates did not significantly change the average metal concentration in the outflow to the overlying water for most metals; however, all metal releases were higher due to the greater flow at increased SGD rates. The residence time and the redox conditions may be important in evaluating environmental effects on capping efficiency.

Capping efficiency for metal-contaminated marine sediment under conditions of submarine groundwater discharge.

Theoretical estimations and laboratory studies suggest that capping can effectively retard contaminant transport from sediments under undisturbed conditions. However, contaminated near-shore areas, commonly selected as capping sites, are frequently subjected to submarine groundwater discharge (SGD). Column experiments were set up in the laboratory to simulate metal transport through sediment and capping material in the presence and absence of SGD. In the absence of SGD, capping enhanced Mo flux and initial Mn flux while having no effect in retarding Fe flux, presumably due to altered redox conditions. This effect was more pronounced in the presence of SGD (4.7 x 10(-4) m/h specific discharge). Capping enhanced Cd flux and initial fluxes of Ni, Cu, and Zn under conditions of simulated SGD, which may be caused by co-transport with Mn and Fe and oxidation of sulfide. Capping retarded Cr and Pb fluxes and steady-state Ni, Cu, Zn, and Fe fluxes in the presence of simulated SGD. However, capping efficiency decreased relative to that with no SGD. Elevated Mn concentration was detected at the capping surface with simulated SGD. Results indicate that advective flow may lead to significantly higher metal fluxes than those under undisturbed conditions.

Developmental effects of pcbs on the hard clam (Mercenaria mercenaria).

Development of hard clam (Mercenaria mercenaria) larvae was examined as a potential biomarker of exposure to polychlorinated biphenyls (PCBs). Clams from clean sites in Massachusetts Bay were thermally induced to spawn in the laboratory using seawater, and the gametes were collected and pooled by sex prior to fertilization. The larvae were cultured in seawater amended with Aroclor 1254, at concentration ranges bracketing environmentally relevant levels. A dose-response relationship was observed for larval development in the presence of Aroclor 1254; at higher doses, fewer larvae developed to the normal straight-hinge, or D-shaped stage, relative to the controls, while the number of abnormally shaped larvae increased.

Microbial degradation of polymeric coatings measured by electrochemical impedance spectroscopy.

This paper reports results of biodegradation studies of polyimide coatings exposed to a mixed fungal culture using electrochemical impedance spectroscopy (EIS). The fungal consortium was originally isolated from degraded polyimides and identified species include Aspergillus versicolor, Cladosporium cladosporioides, and a Chaetomium species. Actively growing fungi on polyimides yield distinctive EIS spectra through time, indicative of failure of the polymer integrity compared to the uninoculated controls. An initial decline in coating resistance was related to the partial ingress of water molecules and ionic species into the polymeric matrices. This was followed by further degradation of the polymers by activity of the fungi. The relationship between the changes in impedance spectra and microbial degradation of the coatings was further supported by scanning electron microscopy, showing extensive colonization of the polyimide surfaces by the fungi. Our data indicate that EIS can be a sensitive and informative technique for evaluating the biosusceptibility of polymers and coatings.