Habitat utilization and alteration by the invasive burrowing isopod, Sphaeroma quoyanum, in California salt marshes

In recent years the pace of exotic species introduction and invasion has accelerated, particularly in estuaries and wetlands. Species invasions may affect coastal ecosystems in many ways. Alteration of sedimentary environments, through structure formation and burrowing, has particularly dramatic effects on coastal habitats. This study examines modification of channel bank and marsh edge habitat by the burrowing Australasian isopod Sphaeroma quoyanum Milne Edwards, in created and natural salt marshes of San Diego Bay and San Francisco Bay. Abundance and distribution patterns of this isopod species, its relationships with habitat characteristics, and its effects on sediment properties and bank erosion were examined seasonally, and in several marsh microhabitats. Mean isopod densities were 1541 and 2936 individuals per 0.25 m² in San Francisco Bay, and 361 and 1153 individuals per 0.25 m² in San Diego Bay study sites during December and July 1998, respectively. This isopod forms dense, anastomosing burrow networks. S. quoyanum densities did not differ as a function of location within creeks or location in natural versus created marshes. Burrows, which are on average 6 mm wide and 2 cm long, were associated with firm sediments containing high detrital biomass. Although erosion is a natural process along salt marsh banks, enclosure experiments demonstrated that isopod activities can enhance sediment loss from banks. In areas infested with S. quoyanum, losses may exceed 100 cm of marsh edge per year. The effects of habitat alteration by this invading species are likely to increase in severity in the coastal zone as these ecosystems become degraded. Received: 30 March 2000 / Accepted: 21 September 2000     

Developmental and behavioral effects of embryonic exposure to the polybrominated diphenylether mixture DE-71 in the killifish (Fundulus heteroclitus)

Exposures to penta polybrominated diphenylether (PeBDE) cause neurobehavioral toxicity in developing mice and rats. As levels of these ubiquitous contaminants are increasing in the environment, this raises concern that wildlife may also suffer such effects, with consequences for their ability to catch prey and avoid predators. PeBDE levels in wild-caught fish have been steadily escalating over the past fifteen years. To our knowledge, behavioral consequences of piscine embryonic exposure to PeBDE has not yet been studied. The objectives of this investigation were to characterize effects on development in an environmentally relevant fish model, and test for latent behavioral effects following cessation of exposure. Embryos from the estuarine minnow, Fundulus heteroclitus, were exposed from day 0-7 post fertilization to the industrial PeBDE mixture, DE-71 (0.001 to 100 microg l(-1)). Embryos were assayed for hatching success, development, and microsomal enzyme cytochrome P4501A (CYP1A) activity, which was determined by analysis of in ovo ethoxy-resorufin-O-deethylase (EROD) activation in embryos. Larval fish were assayed for predation ability, activity level, and fright response to a simulated predator. Juvenile fish were assayed for learning ability in a three-chambered fish maze. No induction of embryonic EROD activity was observed, nor was a high dose of DE-71 able to inhibit EROD activity induced by beta-naphthoflavone. No deformities were detected, but a subtle developmental asymmetry with respect to tail curvature direction was observed, and a hatching delay of up to 4.5 days was noted. Behavioral test results suggest that embryonic exposure to DE-71 may alter activity level, fright response, predation rates, and learning ability in subsequent life stages.     

Air sampling of fungal spores on filters. An investigation on passive sampling and viability

In this study, glycerol was tested as a collection substrate for passive bioaerosol sampling. Filters (mixed cellulose acetate and nitrate) were soaked in glycerol and exposed for an aerosol from three different fungal species: Penicillum commune, Aspergillus versicolor and Paecilomyces variotii. The passive sampling method was compared with a closed-face polycarbonate filter sampling method. Exposure was performed in an exposure chamber. The total number of spores was determined by microscopic techniques, and the cultivable number was determined by cultivation on Malt Extract Agar dishes. The glycerol soaked filter demonstrated a good correlation with the closed-face sampler with regard to the total count. Spores stored in a pumped filter cassette were not affected by storage for up to 7 days. On the other hand, the culturability of the spores was markedly decreased after 1 day when stored on glycerol soaked filters.     

Passive sampling in combination with thermal desorption and gas chromatography as a tool for self-assessment of chemical exposure

Diffusive samplers for monitoring of air quality are user-friendly devices that can normally be operated by the user himself. Hence these samplers are suitable for self-assessment. Practical and work organisational aspects of self-assessment of chemical exposure were studied in different occupational settings. It was found that the diffusive sampler used in these studies, the Perkin-Elmer tube in combination with thermal desorption, worked well for the purpose and could be correctly handled by the individuals using it. The results from self-assessments agreed well with expert measurements carried out by an occupational hygienist. However, in order to obtain a sustainable system of self-assessment strong organizational support is needed.     

Note On a Slurry Method of Particle Induction

A slurry method of induction of test particles into a high-temperature, high-pressure gaseous flow stream is presented. The method can provide accurate control and sensitive adjustment of the particle feed and can have an ameliorative effect on particle statistics.     

Implementing Pollution Prevention: Incentives and Irrationalities

Widespread pollution prevention will turn on creative use of incentives, since prevention means decentralized changes in raw materials, products, production processes and disposal practices—in short, new ways of doing business—that are difficult to achieve through information transfer or regulatory mandates alone. But past experience with incentives and the context in which these approaches are used will shape both regulators’ attitudes and industry willingness to respond. Thus the choice of incentive mechanism (s) may well determine the extent to which “prevention” is implemented—as well as the extent to which implementation yields environmentally-sound rather than perverse results. Approaches now being debated could produce such perverse effects by treating recyclables as pollution and assuming all reductions towards zero are equally desirable, regardless of net risks reduced or costs incurred by waste generators. Another alternative— tradeable permits progressively reducing the amount of waste received by disposal facilities—could help agencies think through such consequences, force needed decisions on how much “prevention” of which “pollution” is appropriate, and encourage investment to reduce commercial as well as municipal waste. This alternative implies that the criteria for “appropriate prevention” are reduction in waste needing disposal and in overall environmental impact; that recycling should be equated with source reduction in waste management hierarchies, not placed on a lower rung; and that Air Toxics provisions of the pending Clean Air Act may require some adjustments if prevention is not to be aborted by the threat that voluntary reduction steps will become national requirements, for existing sources as well as new ones.     

The Use of Health Risk Assessment to Estimate Desirable Sampling Detection Limits

Abstract

The inclusion of non-detected chemicals in a health risk assessment may lead, in some cases, to estimated risks that exceed regulatory thresholds, because one must use the detection limit or half of the detection limit. This study presents a methodology which will allow one to estimate appropriate detection limits by conducting a health risk assessment prior to the source sampling program. The advantages and shortcomings of various levels of detail in the risk assessment to determine those detection limits are discussed. The application of the methodology is demonstrated with a case study of the potential health effects of power plant stack emissions.     

Regulation of benthic algal and animal communities by salt marsh plants: impact of shading

Plant cover is a fundamental feature of many coastal marine and terrestrial systems and controls the structure of associated animal communities. Both natural and human-mediated changes in plant cover influence abiotic sediment properties and thus have cascading impacts on the biotic community. Using clipping (structural) and light (shading) manipulations in two salt marsh vegetation zones (one dominated by Spartina foliosa and one by Salicornia virginica), we tested whether these plant species exert influence on abiotic environmental factors and examined the mechanisms by which these changes regulate the biotic community. In an unshaded (plant and shade removal) treatment, marsh soils exhibited harsher physical properties, a microalgal community composition shift toward increased diatom dominance, and altered macrofaunal community composition with lower species richness, a larger proportion of insect larvae, and a smaller proportion of annelids, crustaceans, and oligochaetes compared to shaded (plant removal, shade mimic) and control treatment plots. Overall, the shaded treatment plots were similar to the controls. Plant cover removal also resulted in parallel shifts in microalgal and macrofaunal isotopic signatures of the most dynamic species. This suggests that animal responses are seen mainly among microalgae grazers and may be mediated by plant modification of microalgae. Results of these experiments demonstrate how light reduction by the vascular plant canopy can control salt marsh sediment communities in an arid climate. This research facilitates understanding of sequential consequences of changing salt marsh plant cover associated with climate or sea level change, habitat degradation, marsh restoration, or plant invasion.