Denitrification enzyme activity of fringe salt marshes in New England (USA)

Coastal salt marshes are a buffer between the uplands and adjacent coastal waters in New England (USA). With increasing N loads from developed watersheds, salt marshes could play an important role in the water quality maintenance of coastal waters. In this study we examined seasonal relationships between denitrification enzyme activity (DEA) in salt marshes of Narragansett Bay, Rhode Island, and watershed N loadings, land use, and terrestrial hydric soils. In a manipulative experiment, the effect of nutrient enrichment on DEA was examined in a saltmeadow cordgrass [Spartina patens (Aiton) Muhl.] marsh. In the high marsh, DEA significantly (p < 0.05) increased with watershed N loadings and decreased with the percent of hydric soils in a 200-m terrestrial buffer. In the low marsh, we found no significant relationships between DEA and watershed N loadings, residential land development, or terrestrial hydric soils. In the manipulation experiment, we measured increased DEA in N-amended treatments, but no effect in the P-amended treatments. The positive relationships between N loading and high marsh DEA support the hypothesis that salt marshes may be important buffers between the terrestrial landscape and estuaries, preventing the movement of land-derived N into coastal waters. The negative relationships between marsh DEA and the percent of hydric soils in the adjacent watershed illustrate the importance of natural buffers within the terrestrial landscape. Denitrification enzyme activity appears to be a useful index for comparing relative N exposure and the potential denitrification activity of coastal salt marshes.     

5,000 year-old spermatozoa in Quaternary Ostracoda (Crustacea)

Fossil spermatozoa are recorded for the first time in freshwater ostracods (small bivalved crustaceans) from Holocene sediments at sites in the United Kingdom and Germany. Exceptional conditions at these sites have resulted in the preservation of chitinous "soft parts", including limbs, the remains of Zenker's Organs (sperm pumps that are part of the male reproductive apparatus in cypridoidean ostracods) and spermatozoa from eight different species. Comparisons are made with spermatozoa from living ostracods and the implications of these discoveries for evolutionary studies of reproductive modes are discussed.     

Longitudinal changes in bone lead concentration: implications for modelling of human bone lead metabolism

In this study, 539 occupationally exposed subjects received in vivo bone lead measurements using 109Cd excited K X-ray fluorescence (109Cd K XRF). Of these subjects, 327 had previously been measured five years earlier. Measurements were made from both tibia and calcaneus samples, taken to reflect cortical and trabecular bone, respectively. Changes in tibia lead concentration related negatively to initial tibia lead concentration and positively to both lead exposure between the measurement dates and initial calcaneus lead concentration. This finding confirmed and strengthened the interpretation of an earlier study involving fewer subjects. With the larger data set it was possible to examine subgroups of subjects. This showed that people aged less than 40 years had a shorter half-life for the release of lead from the tibia (4.9, 95% CI 3.6-7.8 years) than did those older than 40 (13.8, 95% CI 9.7-23.8 years). Similarly, less intensely exposed subjects (lifetime average blood lead < or = 25 micrograms dL-1) had a shorter tibia lead half-life (6.2, 95% CI 4.7-9.0 years) than those with a lifetime average blood lead > 25 micrograms dL-1 (14.7, 95% CI 9.7-29.9 years). Age and measures of lead exposure were strongly correlated; nevertheless, age matched subgroups with high and low intensity exposures showed clearance rates that were significantly different at the 10% level, with the lower exposure intensity again being associated with the faster clearance. These findings imply that current models of human lead metabolism should be examined with a view to adjusting them to account for kinetic rates varying with age and probably also with exposure level.     

Stewardship of Natural Resources: Definition, Ethical and Practical Aspects

Stewardship is potentially a usefulconcept in modernizing management philosophies. Use ofthe term has increased markedly in recent years, yetthe term is used loosely and rarely defined in landmanagement literature. The connections between thispractical usage and the ethical basis of stewardshipare currently poorly developed. The followingdefinition is proposed: ``Stewardship is theresponsible use (including conservation) of naturalresources in a way that takes full and balancedaccount of the interests of society, futuregenerations, and other species, as well as of privateneeds, and accepts significant answerability tosociety.' A religious interpretation would require thephrase ``and ultimately to God' to be added.Stewardship has both secular and religiousinterpretations and it will be desirable to developboth of these aspects in parallel. A task forphilosophers is to establish whether the ethical basisof stewardship is sufficient to address environmentalconcerns or whether it is necessary to embrace widerethical approaches. Stewardship occupies similarground to several other concepts of use and managementof resources, particularly sustainability. It canbuild on sustainability by encouraging a broader viewof who and what should benefit from managementactivity. In particular, it focuses attention on therole of managers in providing public benefit and onenvisaging other species as a form of ``stakeholder' inmanagement decisions. Stewardship is applicable acrossthe widest range of fields of resource use and alsohas relevance to aspects of land tenure and propertyrights. Application of stewardship will require someadjustments in the roles of private managers/ownersvis-à-vis government. It might providemanagers with an expanded role and, importantly, amore positive image, both of themselves and in theeyes of the public. Stewardship could alsobe developed in a way that has relevance to citizensin general (as opposed to managers and owners ofresources), through their interactions with naturalresources as consumers.     

Design conditions for learning in community service contexts

In this study, we investigated team‐based community service projects as action learning initiatives designed to facilitate two learning outcomes: community learning (knowledge of social, cultural, or economic issues) and personal learning (self‐awareness of managerial attitudes and abilities). We developed hypotheses to predict critical input conditions for action learning that promote community and personal learning. We tested these hypotheses with data collected from 381 MBA students and their team leaders who participated in a variety of community service projects. Results demonstrated that design conditions (task characteristics, social interactions, and affective responses) influenced community and personal learning differently. We supplemented survey results with interview and observational data from a subset of participants and conclude with a discussion of the theoretical implications for action learning and practical recommendations for designing community service programs. Copyright © 2001 John Wiley & Sons, Ltd.     

Kyoto or Not: Opportunities in Carbon Trading Are Here

Companies that proactively seek opportunities in greenhouse gas emissions trading an early market advantage. © 2000 Environmental Financial Products LLC. All rights reserved. Used with permission.     

Testing the evolution of increased competitive ability (EICA) hypothesis in a novel framework

The "evolution of increased competitive ability" (EICA) hypothesis proposes that escape from natural enemies, e.g., after transcontinental introductions, alters the selection regime because costly defenses no longer enhance fitness. Such an evolutionary loss of defenses enables resources to be directed toward growth or other traits improving performance. We tested the EICA hypothesis in a novel framework in which the natural enemy is the traveler that follows its widespread host by accidental or deliberate (biocontrol) introductions. In a greenhouse experiment we used populations of Senecio vulgaris from North America, Europe, and Australia that differ in the history of exposure to the rust fungus Puccinia lagenophorae. Contrary to what is predicted by EICA, we found no evidence for increased levels of resistance to the rust fungus in plant populations with a longer history of rust exposure (Australia). Similarly, there was no evidence for reduced fecundity in these populations, although vegetative vigor, measured as secondary branching and growth rate, was lower. The maintenance of high rust resistance in populations with no (North America) or only a short history (Europe) of rust exposure is surprising given that resistance seems to incur considerable fitness costs, as indicated by the negative association between family mean resistance and fitness in the absence of disease observed for all three continents. The comparison of population differentiation in quantitative traits with estimates of differentiation in amplified fragment length polymorphic (AFLP) markers suggests that a number of fitness-related traits are under divergent selection among the studied populations. The proposed framework to test changes in the evolutionary trajectory underlying EICA can be employed in an expanded range of systems. These may include investigations on a cosmopolitan weed or crop when an antagonist is expanding its geographic range (such as our study), studies along a chronosequence of introduction time with expected increasing accumulation of natural enemies over time, or comparisons between introduced plant populations that differ in exposure time to biocontrol organisms.     

A chemical trait creates a genetic trade-off between intra- and interspecific competitive ability

The importance of non-resource-based mechanisms of competition between plant species has been increasingly recognized, but little is known about how genetic variation and evolutionary changes in the underlying competitive traits might affect species coexistence. I found that genetic variation in sinigrin concentration, a putative allelopathic agent in Brassica nigra, affected the fitness of three heterospecific neighbor species but did not affect neighboring B. nigra individuals. Investment in sinigrin led to a negative genetic correlation between intra- and interspecific competitive ability, which over many generations could provide a strong stabilizing force maintaining both species and genetic diversity in this system.