Toxic effects of a bloom of the diatom Rhizosolenia chunii on shellfish in Port Phillip Bay,Southeastern Australia

A bloom of the diatom Rhizosolenia chunii Karsten sensu Sundström occurred in Port Phillip Bay (38°S; 145°E), southeastern Australia, between late August and mid-October 1987. Coincident with this bloom, mussels (Mytilus edulis planulatus), scallops (Pecten alba) and flat oysters (Ostrea angasi) throughout the Bay developed a bitter taste that was so unpleasant and persistent that mussels became unmarketable for 7 mo. The bitter taste was concentrated in the digestive gland, which also showed extensive inflammation and degeneration. Digestive gland lesions were evident in mussels during September 1987, but became progressively more severe and, in the chronic end-stage were associated with high shellfish mortality 3 to 8 mo after the bloom had ceased. This study provides strong indirect evidence that the bitterness and the toxicity were caused by a bloom of R. chunii. R. chunii is the first species of diatom to be associated with shellfish mortality and, as the mortality occurred many months after the bloom had ceased, we suggest that the toxicity of certain algal blooms may be difficult to detect rather than uncommon.     

Arsenic-speciation in arsenate-resistant and non-resistant populations of the earthworm,Lumbricus rubellus

Arsenic speciation was determined in Lumbricus rubellus Hoffmeister from arsenic-contaminated mine spoil sites and an uncontaminated site using HPLC-MS, HPLC-ICP-MS and XAS. It was previously demonstrated that L. rubellus from mine soils were more arsenate resistant than from the uncontaminated site and we wished to investigate if arsenic speciation had a role in this resistance. Earthworms from contaminated sites had considerably higher arsenic body burdens (maximum 1,358 mg As kg-1) compared to the uncontaminated site (maximum 13 mg As kg-1). The only organo-arsenic species found in methanol/water extracts for all earthworm populations was arsenobetaine, quantified using both HPLC-MS and HPLC-ICP-MS. Arsenobetaine concentrations were high in L. rubellus from the uncontaminated site when concentrations were expressed as a percentage of the total arsenic burden (23% mean), but earthworms from the contaminated sites with relatively low arsenic burdens also had these high levels of arsenobetaine (17% mean). As arsenic body burden increased, the percentage of arsenobetaine present decreased in a dose dependent manner, although its absolute concentration rose with increasing arsenic burden. The origin of this arsenobetaine is discussed. XAS analysis of arsenic mine L. rubellus showed that arsenic was primarily present as As(III) co-ordinated with sulfur (30% approx.), with some As(v) with oxygen (5%). Spectra for As(III) complexed with glutathione gave a very good fit to the spectra obtained for the earthworms, suggesting a role for sulfur co-ordination in arsenic metabolism at higher earthworm arsenic burdens. It is also possible that the disintegration of As(III)-S complexes may have taken place due to (a) processing of the sample, (b) storage of the extract or (c) HPLC anion exchange. HPLC-ICP-MS analysis of methanol extracts showed the presence of arsenite and arsenate, suggesting that these sulfur complexes disintegrate on extraction. The role of arsenic speciation in the resistance of L. rubellus to arsenate is considered.     

Interactions between earthworms and arsenic in the soil environment: a review

Chemical pollution of the environment has become a major source of concern. In particular, many studies have investigated the impact of pollution on biota in the environment. Studies on metalliferous contaminated mine spoil wastes have shown that some soil organisms have the capability to become resistant to metal/metalloid toxicity. Earthworms are known to inhabit arsenic-rich metalliferous soils and, due to their intimate contact with the soil, in both the solid and aqueous phases, are likely to accumulate contaminants present in mine spoil. Earthworms that inhabit metalliferous contaminated soils must have developed mechanisms of resistance to the toxins found in these soils. The mechanisms of resistance are not fully understood; they may involve physiological adaptation (acclimation) or be genetic. This review discusses the relationships between earthworms and arsenic-rich mine spoil wastes, looking critically at resistance and possible mechanisms of resistance, in relation to soil edaphic factors and possible trophic transfer routes.     

Assessing Linkages in Stream Habitat,Geomorphic Condition,and Biological Integrity Using a Generalized Regression Neural Network

Watershed managers often use physical geomorphic and habitat assessments in making decisions about the biological integrity of a stream, and to reduce the cost and time for identifying stream stressors and developing mitigation strategies. Such analysis is difficult since the complex linkages between reach‐scale geomorphic and habitat conditions, and biological integrity are not fully understood. We evaluate the effectiveness of a generalized regression neural network (GRNN) to predict biological integrity using physical (i.e., geomorphic and habitat) stream‐reach assessment data. The method is first tested using geomorphic assessments to predict habitat condition for 1,292 stream reaches from the Vermont Agency of Natural Resources. The GRNN methodology outperforms linear regression (69% vs. 40% classified correctly) and improves slightly (70% correct) with additional data on channel evolution. Analysis of a subset of the reaches where physical assessments are used to predict biological integrity shows no significant linear correlation, however the GRNN predicted 48% of the fish health data and 23% of macroinvertebrate health. Although the GRNN is superior to linear regression, these results show linking physical and biological health remains challenging. Reasons for lack of agreement, including spatial and temporal scale differences, are discussed. We show the GRNN to be a data‐driven tool that can assist watershed managers with large quantities of complex, nonlinear data.     

A Cu tolerant population of the earthworm Dendrodrilus rubidus (Savigny, 1862) at Coniston Copper Mines, Cumbria, UK

Dendrodrilus rubidus were sampled from a mine spoil soil at Coniston Copper Mine, an abandoned Cu mine in Cumbria, UK and a Cu-free control site. Earthworms were maintained for 14d in both Kettering loam and a Moorland soil amended with Cu nitrate. Mortality, condition index, weight change and tissue concentration were determined. In both soils D. rubidus native to the mine site were able to tolerate significantly higher soil Cu concentrations (MWRT, p相似文献   

Enhancing Justice and Sustainability at the Local Level: Affordable Policies for Urban Governments

There are creative, affordable ways to address community development and also achieve goals of environmental sustainability. Approximately thirty case studies, based on interviews and usually also site visits, were completed during 2005. The case studies examined community gardening and urban agriculture, the greening of publicly controlled urban electricity and bus agencies, reuse centers and local business associations in the United States. Policy recommendations for city governments that emerged from the case studies are summarized here. There are many opportunities for financially pressed cities to assist the development of 'just sustainability' projects with minimal financial commitments. They can do so by rechannelling the purchasing decisions of public agencies, building partnerships with community organizations and developing the small business sector.     

Digestion and assimilation of protein by Mytilus trossulus (Bivalvia: Mollusca) fed mixed carbohydrate/protein microcapsules

Cross-linked walled protein microcapsules have previously been developed and shown to be ingested, digested and assimilated by suspension-feeding bivalves. In this study, we examined the effect of adding carbohydrate to protein capsules on the utilization of encapsulated protein by mussels (Mytilus trossulus) in a series of in vitro enzyme incubations and an in vivo feeding experiment. Two types of carbohydrate (amylose and maltodextrin) were separately encapsulated at a carbohydrate to protein ratio of 1:1 by weight. In vitro carbohydrate and protein leakage rates from mixed carbohydrate/protein capsules were low [e.g. <4% (24h)^-1] compared to previously reported leakage rates for protein capsules [e.g. 5 to 20% (24h)^-1]. Proteolytic breakdown of mixed carbohydrate/protein capsules by mussel-style extracts was similar to that for protein capsules, when the encapsulated carbohydrate was amylose, a straight-chain (-1,4-linkage) polysaccharide; however, capsules containing maltodextrin, which is partially comprised of -1,6-linkages, were not as readily digestible in vitro. In contrast to results from in vitro enzyme assays, maltodextrin/protein capsules were utilized in vivo by mussels with similar efficiencies to those for protein and amylose/protein capsules. These findings demonstrate that utilization of microencapsulated protein by mussels cannot be accurately predicted from results of in vitro enzyme assays. Importantly, up to 50% of the dry weight of cross-linked walled protein microcapsules can be replaced with carbohydrate without significantly affecting encapsulated protein digestion and assimilation efficiencies for M. trossulus.     

Enhancing Justice and Sustainability at the Local Level: Affordable Policies for Urban Governments*

Abstract

There are creative, affordable ways to address community development and also achieve goals of environmental sustainability. Approximately thirty case studies, based on interviews and usually also site visits, were completed during 2005. The case studies examined community gardening and urban agriculture, the greening of publicly controlled urban electricity and bus agencies, reuse centers and local business associations in the United States. Policy recommendations for city governments that emerged from the case studies are summarized here. There are many opportunities for financially pressed cities to assist the development of ‘just sustainability’ projects with minimal financial commitments. They can do so by rechannelling the purchasing decisions of public agencies, building partnerships with community organizations and developing the small business sector.