Diagnostic indicators of elevated nitrogen deposition

Tissue N content of mosses, which has been shown to be an indicator of enhanced N, was studied at a range of locations dominated either by wet or dry deposited and oxidised and reduced forms of N. Tissue N responded differently to wet and dry deposited N. For a 1 kg ha(-1) y(-1) increase in N deposition, tissue N increased by 0.01% at wet deposition sites but by 0.03% at sites dominated by dry deposited NH3. Tissue N at wet deposition sites responded more to concentrations of NO3- and NH4+ in precipitation (r(2) 0.63) than to total N deposition (r(2) 0.27), concentration explaining 66% of the variation in tissue N, wet deposition 33%. The study clearly concludes that tissue N concentration in mosses provides a good indication of N deposition at sites where deposition is dominated by NH3, and is also valuable in identifying vegetation exposed to large concentrations of NH4+ or NO3-, in wet deposition dominated areas, such as hilltops and wind exposed woodland edges.     

Distribution,life history,and production of three species of <Emphasis Type="Italic">Neomysis</Emphasis> in Akkeshi-ko estuary,northern Japan

Spatial and seasonal distribution pattern, life history and production of three species of Neomysis (Mysidacea) which commonly occur in northwestern subarctic Pacific coastal waters, were investigated throughout the year in the Akkeshi-ko estuary, northern Japan. The most abundant species Neomysis awatschensis (annual mean density: 179.8 inds. m⁻², biomass: 108.8 mg DW m⁻²) occurred at the inner part of the estuary including low salinity areas with no clear preference for the seagrass bed. The second most abundant Neomysis mirabilis (mean density: 95.8 inds. m⁻², biomass: 90.1 mg DW m⁻²) occurred at relatively saline seagrass site throughout the year. Occurrence of Neomysis czerniawskii in the estuary was limited to the seagrass bed during summer when their population mainly consisted of juveniles, suggesting that this species is a seasonal migrant between the estuary and the marine environment. Both N. awatschensis and N. mirabilis populations were composed of two generation types, a larger sized overwintering and smaller sized spring/summer generations; however, each species had a different reproductive strategy. N. awatschensis was characterized by fast growth to maturity at a smaller size than N. mirabilis with a relatively high fecundity during warm season, suggesting that this species is an r-strategist which can utilize opportunistically a wide variety of habitats. In contrast, the seagrass bed resident N. mirabilis was a K-strategist which matures at a larger size producing fewer but larger offspring. The annual production of N. awatschensis (0.57–0.70 g DW m⁻², mean of the whole estuary) and N. mirabilis (0.58–0.68 g DW m⁻², mean of the seagrass bed) at their respective habitats was comparable. Consequently, species-specific life history and distribution pattern are concluded to allow Neomysis spp. to coexist in the estuary and the high carrying capacity of seagrass bed is suggested to contribute to maintain their high biomass level.     

Status report on flood warning systems in the United States

One of the major changes in flash-flood mitigation in the past decade is the number of communities that have implemented warning systems. The authors conducted a survey of 18 early-warning systems in the United States developed by communities or regions to provide protection against flash floods or dam failures. Problems revealed by the study included the following: equipment malfunctions, inadequate maintenance funding, inconsistent levels of protection and expenditure, inconsistent levels of expectations and formalization, varying levels of local commitment to the systems, underemphasis on response capability, and a tendency to over-rely on warning systems. The study also revealed some unanticipated benefits experienced by the survey communities: the warning systems serve as valuable data collection tools, a great deal of interagency cooperation has been demonstrated, and warning systems offer increased alternatives to structural modification projects. The interjurisdictional nature of drainage basins, the evolving roles of the various federal agencies involved in flood mitigation, and the lack of governmental standards of operations for flood warning systems are issues that must be considered as communities make decisions regarding the adoption of warning systems. The record on these systems is too short for a precise assessment of how successful they are; however, results of the study indicate that if the goal of reducing loss of life and property from flooding is to be achieved, warning systems must be only one part of a comprehensive flood loss reduction program.     

Linking molecular interactions to consequent effects of persistent organic pollutants (POPs) upon populations

There is great concern about the potential adverse effects of persistent organic pollutants (POPs) on wildlife. Threats come from toxic chemicals with long half lives in the environment that were released worldwide on a large scale in the past, at a time when little was known of their potential effects on the environment. Although the Stockholm Convention (2001) initially targeted 12 POP chemicals--organochlorinated compounds--for the reduction/elimination of releases, the problem can be extended to persistent toxic substances more generally. Therefore, identifying early biomarkers for possible toxic effects to populations in the long term is a challenge for ecotoxicologists. Regional decline in fish, bird and/or invertebrate populations resulting from exposure to POPs, such as DDT (dichlorodiphenyltrichloroethane), PCBs (polychlorinated biphenyls), PCDD (polychlorinated dibenzo-p-dioxins), and TBT (tributyltin) could be related to some biochemical, endocrine and physiological effects in individuals. Examples of known mechanisms of POP ecotoxicity will be illustrated in the first part. The next parts will be devoted to (i) data gaps and limitations to extrapolation from lower to higher levels of biological organization, (ii) confusing factors in field studies and the combined effects of persistent toxic pollutants and (iii) recommendations for the design and interpretation of experimental studies.     

Biomarkers and community indices as complementary tools for environmental safety

Research on biomarkers as early bioindicators of perturbation in populations and individuals has been gaining ground over the last decade. This ecotoxicological approach relies on the fact that changes occur at low levels of organization before the community is affected and thus they can be monitored to assess environmental safety. Changes may concern behavior, physiology, biochemistry, or genomic structure and functioning, and may impair population dynamics in the long-term.Ecotoxicity studies based on biomarkers allow us to measure the impact of environmental stressors and to easily follow the evolution of the systems towards degradation or restoration. Over and above their use as simple indices of exposure to specific pollutants, biomarkers can give an insight into ecosystem health.The results of our experience in field studies involving ecotoxicologists and ecologists will be presented in order to illustrate the relevance of such an integrating strategy for environmental quality assessment.