Cascading ecological effects of low-level phosphorus enrichment in the Florida everglades

Few studies have examined long-term ecological effects of sustained low-level nutrient enhancement on wetland biota. To determine sustained effects of phosphorus (P) addition on Everglades marshes we added P at low levels (5, 15, and 30 microg L(-1) above ambient) for 5 yr to triplicate 100-m flow-through channels in pristine marsh. A cascade of ecological responses occurred in similar sequence among treatments. Although the rate of change increased with dosing level, treatments converged to similar enriched endpoints, characterized most notably by a doubling of plant biomass and elimination of native, calcareous periphyton mats. The full sequence of biological changes occurred without an increase in water total P concentration, which remained near ambient levels until Year 5. This study indicates that Everglades marshes have a near-zero assimilative capacity for P without a state change, that ecosystem responses to enrichment accumulate over time, and that downstream P transport mainly occurs through biota rather than the water column.     

Decadal change in vegetation and soil phosphorus pattern across the Everglades landscape

Wetlands respond to nutrient enrichment with characteristic increases in soil nutrients and shifts in plant community composition. These responses to eutrophication tend to be more rapid and longer lasting in oligotrophic systems. In this study, we documented changes associated with water quality from 1989 to 1999 in oligotrophic Everglades wetlands. We accomplished this by resampling soils and macrophytes along four transects in 1999 that were originally sampled in 1989. In addition to documenting soil phosphorus (P) levels and decadal changes in plant species composition at the same sites, we report macrophyte tissue nutrient and biomass data from 1999 for future temporal comparisons. Water quality improved throughout much of the Everglades in the 1990s. In spite of this improvement, though, we found that water quality impacts worsened during this time in areas of the northern Everglades (western Loxahatchee National Wildlife Refuge [NWR] and Water Conservation Area [WCA] 2A). Zones of high soil P (exceeding 700 mg P kg(-1) dry wt. soil) increased to more than 1 km from the western margin canal into the Loxahatchee NWR and more than 4 km from northern boundary canal into WCA-2A. This doubling of the high soil P zones since 1989 was paralleled with an expansion of cattail (Typha spp.)-dominated marsh in both regions. Macrophyte species richness declined in both areas from 1989 to 1999 (27% in the Loxahatchee NWR and 33% in WCA-2A). In contrast, areas well south of the Everglades Agricultural Area, induding WCA-3A and Everglades National Park (ENP), did not decline during this time. We found no significant decadal change in plant community patterns from 1989 and 1999 along transects in southern WCA-3A or Shark River Slough (ENP). Our 1999 sampling also included a new transect in Taylor Slough (ENP), which will allow change analysis here in the future. Regular sampling of these transects, to verify decadal-scale environmental impacts or improvements, will continue to be an important tool for long-term management and restoration of the Everglades.     

MEAD (part II)-Predictions of radioactivity concentrations in the Irish Sea

The predictions from MEAD, a model that simulates the transport of radionuclides in the marine environment, are presented for the Irish Sea. MEAD predictions for (137)Cs and Pu(alpha) are presented following discharges from BNFL Sellafield and the predictions compared to measured data from near the discharge location and further a field in the Irish Sea. The model performs well in most circumstances given the uncertainties involved in both modelling and data collection although some inconsistencies in the predictions are found. MEAD is also compared to other models of radionuclide transport in the Irish Sea.     

A statistical approach to estimating driver responsibility in two-car crashes

A statistical model is developed relating driver age distributions in one-car and two-car crashes to the probability that both of the drivers in a two-car crash are similarly responsible for the crash as are drivers in a single-car crash. The model is applied to (a) passenger car crashes in the years 1975–1980 involving a driver fatality, compiled in the U.S. Fatal Accident Reporting System (FARS), and (b) all police-reported crashes occurring in North Carolina in 1979, supplied by the North Carolina Highway Safety Research Center. Appropriate national and North Carolina driver license data are used to estimate exposure to potential crashes as a function of driver age. The model is found to provide an adequate fit to observed driver age distribution in two-car crashes for both data sets. The results obtained from this fit to the model equations indicate that for two-car crashes involving a driver fatality, both drivers contribute to the responsibility for the crash in about 40% of cases, but for less severe two-car crashes, only one of the two involved drivers is generally responsible.     

Incidence of stress in benthic communities along the U.S. Atlantic and Gulf of Mexico coasts within different ranges of sediment contamination from chemical mixtures

Synoptic data on concentrations of sediment-associated chemical contaminants and benthic macroinfaunal community structure were collected from 1,389 stations in estuaries along the U.S. Atlantic and Gulf of Mexico coasts as part of the nationwide Environmental Monitoring and Assessment Program (EMAP). These data were used to develop an empirical framework for evaluating risks of benthic community-level effects within different ranges of sediment contamination from mixtures of multiple chemicals present at varying concentrations. Sediment contamination was expressed as the mean ratio of individual chemical concentrations relative to corresponding sediment quality guidelines (SQGs), including Effects Range-Median (ERM) and Probable Effects Level (PEL) values. Benthic condition was assessed using diagnostic, multi-metric indices developed for each of three EMAP provinces (Virginian, Carolinian, and Louisianian). Cumulative percentages of stations with a degraded benthic community were plotted against ascending values of the mean ERM and PEL quotients. Based on the observed relationships, mean SQG quotients were divided into four ranges corresponding to either a low, moderate, high, or very high incidence of degraded benthic condition. Results showed that condition of the ambient benthic community provides a reliable and sensitive indicator for evaluating the biological significance of sediment-associated stressors. Mean SQG quotients marking the beginning of the contaminant range associated with the highest incidence of benthic impacts (73–100% of samples, depending on the province and type of SQG) were well below those linked to high risks of sediment toxicity as determined by short-term toxicity tests with single species. Measures of the ambient benthic community reflect the sensitivities of multiple species and life stages to persistent exposures under actual field conditions. Similar results were obtained with preliminary data from the west coast (Puget Sound).     

Persistent organic pollutants in European background air: derivation of temporal and latitudinal trends

Data are presented for polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyls ethers (PBDEs) and selected organochlorine compounds (OCs) in passive air samplers (PAS) along a rural/remote latitudinal transect from southern UK to northern Norway during 2002-2004. This study is part of an ongoing campaign, using semi-permeable membrane devices (SPMDs) as PAS over two year intervals since 1994. Data for PCBs, selected OCs and PBDEs are compared with that from previous campaigns. Absolute sequestered amounts of selected PCB congeners have decreased in a first order fashion between 1994-2004, with an average atmospheric clearance rate of 4.1 +/- 0.6 years and continue to fractionate with latitude. HCB has also declined between 1998-2004, with a clearance rate of 6 +/- 2.4 years. Data on DDT and its breakdown products indicate little fresh release in Europe. Comparison of PBDEs in 2000-02 and 2002-04 indicates site differences, generally with increases at UK sites and decreases in Norway. BDE-28, 47 and 49 decreased with increasing latitude (p < 0.04), while the other congeners did not show any significant latitudinal dependence. Transect data are presented for PAHs the first time. Three- and 4-ringed compounds dominated the mixture present in the SPMD. The PAH composition of the SPMDs at site 3 was compared to the average composition taken by active sampling at the same site. SPMD performance for sampling PAHs leaves many uncertainties, but they can be successfully used to semiquantitatively detect PAHs in the atmosphere. Fluorene and phenanthrene increased with latitude (p > 0.05), while 1-methylphenanthere, fluoranthene, benzo[b]fluoranthene and indeno[123-cd]pyrene decreased. Results are discussed in terms of sources, long-range atmospheric transport, global fractionation and clearance processes.     

Preliminary Studies on the Population Genetics of the Central Stoneroller (Campostoma anomalum) from the Great Miami River Basin, Ohio

Molecular approaches are particularly useful for measuring genetic diversity and were applied to samples of central stonerollers obtained from sites along tributaries to the Great Miami River in Ohio. We used Random Amplified Polymorphic DNA (RAPD) analysis to assess the level of genetic diversity within and among these populations. RAPD analysis generates genetic profiles that were used to develop indices of genetic similarity. The RAPD method provides a cost effective means of generating an arbitrary sample of anonymous loci across the genome and generate a virtually unlimited set of loci for use in genetic analysis in the absence of specific sequence information. These attributes make RAPDs well suited for use in evaluating the diversity and assessing the potential vulnerability to exposure of populations across multiple spatial scales. The results demonstrate that a significant amount of structuring exists among populations analyzed to date and that a trend exists towards genetic diversity being an inverse function of site distance from the main stem as well as a being directly related to stream order. This indicates that populations farthest from main conduits or in lower order streams, and thereby most isolated, may be the most vulnerable populations to stressor exposure. It is hoped that information pertaining to genetic diversity, when integrated with other metrics of resource condition, will aid in making scientifically grounded decisions on resource management that enhance the probability of population survival and preserve natural evolutionary processes.     

Feeling interrupted—Being responsive: How online messages relate to affect at work

Being constantly connected to others via e‐mail and other online messages is increasingly typical for many employees. In this paper, we develop and test a model that specifies how interruptions by online messages relate to negative and positive affect. We hypothesize that perceived interruptions by online messages predict state negative affect via time pressure and that perceived interruptions predict state positive affect via responsiveness to these online messages and perceived task accomplishment. A daily survey study with 174 employees (a total of 811 day‐level observations) provided support for our hypotheses at the between‐person and within‐person level. In addition, perceived interruptions showed a negative direct association with perceived task accomplishment. Our study highlights the importance of being responsive to online messages and shows that addressing only the negative effects of perceived interruptions does not suffice to understand the full impact of interruptions by online messages in modern jobs.     

Community vulnerability to changes in the winter road viability and longevity in the western James Bay region of Ontario’s Far North

Regional Environmental Change - A network of winter roads that consists of snow-ice roads over land, muskeg, and frozen lakes and rivers has been and continues to be a critical seasonal lifeline in...     

Investigating the role of smartness for sustainability: insights from the Smart Grid domain

Over the past decades, information and communication technologies (ICT) established themselves as the key force towards more effective and efficient usage of resources in our society, namely via better use of available information, automation, stakeholder involvement, and decision support. By analyzing recent advancements in knowledge offered by ICT, it is possible to identify their strong correlation with the principles, aims, and interests of sustainability science, which can be highly inspired by ICT-intensive domains. In this paper, we study the theoretical background on system thinking as an interpretative lens able to support better understanding of dimensions and dynamics involved in the domain of sustainability, and examine the role of ICT in advancing sustainability goals. Then, we analyze the domain of the Smart Grid as a prominent example of complex technological contribution in face of the challenges of sustainability, and present the insights from this domain, which are turned into sustainability guidelines for other domains, linking smartness, and sustainability in the light of systems thinking and Smart Grid experience. In summary, the core recommendation of this work is the employment of information technology to widen the scope of the sustainability “game” by sliding activities in time and space, and in engaging more “players” in the game, which is now made possible thanks to the advancement in ICT.