Reduction of silver solubility by humic acid and thiol ligands during acanthite (beta-Ag2S) dissolution

Precipitation of highly insoluble metal sulfide minerals like acanthite (beta-Ag2S) or red cinnabar (HgS) is in principle an effective means to reduce metal availability and toxicity in contaminated soils. Unfortunately, experiments have shown that red cinnabar may be solubilized in the presence of dissolved organic matter or thiol ligands. To determine whether the same applies to acanthite, a laboratory synthesized beta-Ag2S mineral was incubated for up to 3 weeks in the presence of KNO3, dissolved humic acids, cysteine, methionine and thiosulfate. XPS analysis identified Ag2O (52%), Ag2SO4 (8%) and Ag2S (40%) on the particle surfaces. Ag was released into solution in the presence of KNO3 and methionine, presumably from mixed-oxidation surface layers. Contrary to earlier results with cinnabar, however, humic acids reduced Ag concentrations in solution by about 75%, and cysteine and thiosulfate, each containing a free -SH functional group, almost completely suppressed Ag release into solution.     

An integrated assessment of estrogenic contamination and biological effects in the aquatic environment of The Netherlands

An extensive study was carried out in the Netherlands on the occurrence of a number of estrogenic compounds in surface water, sediment, biota, wastewater, rainwater and on the associated effects in fish. Compounds investigated included natural and synthetic hormones, phthalates, alkylphenol(ethoxylate)s and bisphenol-A. The results showed that almost all selected (xeno-)estrogens were present at low concentrations in the aquatic environment. Locally, they were found at higher levels. Hormones and nonylphenol(ethoxylate)s were present in concentrations that are reportedly high enough to cause estrogenic effects in fish. Field surveys did not disclose significant estrogenic effects in male flounder (Platichthys flesus) in the open sea and in Dutch estuaries. Minor to moderate estrogenic effects were observed in bream (Abramis brama) in major inland surface waters such as lowland rivers and a harbor area. The prevalence of feminizing effects in male fish is largest in small regional surface waters that are strongly influenced by sources of potential hormone-disrupting compounds. High concentrations of plasma vitellogenin and an increased prevalence of ovotestes occurred in wild male bream in a small river receiving a considerable load of effluent from a large sewage treatment plant. After employing in vitro and in vivo bioassays, both in situ and in the laboratory, we conclude that in this case hormones (especially 17 alpha-ethynylestradiol) and possibly also nonylphenol(ethoxylate)s are primarily responsible for these effects.     

Development and environmental application of a genus-specific quantitative PCR approach for Pseudo-nitzschia species

Quantitative polymerase chain reaction (qPCR) for the identification and quantification of microbes has become a common tool for the study of harmful algal blooms (HABs). We developed a qPCR method for the diatom genus Pseudo-nitzschia. Several species of this genus form toxic blooms through the production of the neurotoxin domoic acid (DA). Outbreaks of toxicity attributed to DA along the US west coast have caused sickness and death of marine mammals and seabirds through food web contamination. The method developed here quantifies Pseudo-nitzschia spp. at low abundances in natural samples, thereby, providing a method to improve our understanding of the environmental conditions leading to blooms of these species. This has been accomplished previously by techniques for identification and quantification that are slow and laborious compared to qPCR. The approach was successfully tested and validated using eight species of Pseudo-nitzschia and 33 non-target organisms and employed to follow local bloom dynamics.     

Being well-governed: Including inspectors in a systems approach to fisheries management

Based on 18-months of ethnographic fieldwork in South Africa’s Western Cape province, we suggest ways in which marine resource law enforcement activities can be evaluated at the level of individual fisheries compliance inspectors, to gain a more accurate understanding of the state of marine resource law enforcement. We show that these individual assessments can be scaled up to speak about specific compliance stations, and further, that these local-level assessments can be scaled up to the regional and provincial levels, without losing sight of the needs and value of the individual inspector. This paper contributes to the broader conversation on compliance in marine resource governance, as well as opening a new avenue of discussion: how to incorporate inspector-focussed social indicators. We show that this can be done in ways that take the overlap of the ecological, economic and social dimensions into account, while still being practical in terms of application and evaluation.     

Diuron mobility through vineyard soils contaminated with copper

The herbicide diuron is frequently applied to vineyard soils in Burgundy, along with repeated treatments with Bordeaux mixture (a blend of copper sulfate and calcium hydroxide) that result in elevated copper concentrations. Cu could in principle affect the fate and transport of diuron or its metabolites in the soil either directly by complexation or indirectly by altering the populations or activity of microbes involved in their degradation. To assess the effect of high Cu concentrations on diuron transport, an experiment was designed with ten undisturbed columns of calcareous and acidic soils contaminated with 17--509 mg kg(-1) total Cu (field-applied). Grass was planted on three columns. Diuron was applied to the soils in early May and in-ground lysimeters were exposed to outdoor conditions until November. Less than 1.2% of the diuron applied was found in the leachates as diuron or its metabolites. Higher concentrations were found in the effluents from the grass-covered columns (0.1--0.45%) than from the bare-soil columns (0.02--0.14%), and they were correlated with increases in dissolved organic carbon. The highest amounts of herbicide were measured in acidic-soil column leachates (0.98--1.14%) due to the low clay and organic matter contents of these soils. Cu also leached more readily through the acidic soils (32.8--1042 microg) than in the calcareous soils (9.5--63.4 microg). Unlike in the leachates, the amount of diuron remaining in the soils at the end of the experiment was weakly related to the Cu concentrations in the soils.     

Biotoxizitätstests mit PAK

There is great need for toxicity tests with higher plants for the investigation and monitoring of chemicals in the environment — especially for tests which are quick, easy, and inexpensive. Such tests should add to and improve current guidelines, e.g., OECD- and BBA-Guidelines. This article describes the nodulation of leguminous plants withRhizobium bacteria used in a bioassay with polycyclic aromatic hydrocarbons (PAH). Plants growing on a solid medium were exposed simultaneously to bacteria and PAH. This axenic culture system allows to observe the impact of PAH on plant growth and the interaction between plant and bacteria (nodulation). Dose-response-experiments indicated that nodulation measured as number of nodules per plant, was more sensitive to the inhibition by PAH than other plant growth parameters.     

Dietary carotenoids and male mating success in the guppy: an environmental component to female choice

Summary This study examined the relationship between dietary carotenoids, female choice, and male mating success in the guppy, Poecilia reticulata. Using a split-brood design, male siblings were either raised on a diet enhanced with astaxanthin and canthaxin or fed a basal diet without carotenoids. Males were photographed, and the location, size, and brightness of their red and orange pigment spots on the body were measured. Courtship behaviors were recorded during visual and mating trials. Males fed the carotenoid-enhanced diet had red and orange spots that averaged 2.5 times brighter, spent significantly more time near the female in visual response trials, were preferred by females in visual choice tests, and had a higher mating success than their siblings raised on the carotenoid-free diet. Diet did not affect male size, location or size of the red and orange pigment spots, or the intensity of courtship behavior. The results of this study show that females respond to environmentally-induced variation in the expression of a secondary sexual trait and that this has important consequences for male mating success.     

Female choice of multiple male criteria in guppies: interacting effects of dominance,coloration and courtship

Summary I experimentally examined the relative importance of social dominance, color patterns, and courtship behavior in male mating and reproductive success in the guppy Poecilia reticulata. Female choice of males is based on a complex set of behavioral and morphological traits. The results of 59 paired-male one-female visual choice and mating trials showed that male mating success was positively correlated with dominance, courtship intensity, and male coloration. Only dominant males engaged in full copoulations, and they sired two-thirds of the broods. An analysis of the paternity of broods and results of mating trials showed that a female's visual response when the sexes are separated by a glass partition is a good predictor of a male's reproductive success when the partition is removed and they are allowed to mate. A canonical correlation analysis of male behavioral and morphological traits indicated that female visual response and male mating success were positively correlated with male courtship and with agonistic behavior. However, the relative importance of color varied. Carotenoid and iridescent spots were important both in attracting the female's attention and in enhancing male mating success. Melanins were not correlated with either mating success or female response. There was a relatively low correlation (48%) between male behavioral and morphological variables and female response variables (full copulation and female visual response). These results suggest that female choice is subtle, and is based on a complex suite of male behavioral and morphological traits as well as on competitive interactions among males.