Conserving spawning stocks through harvest slot limits and no-take protected areas

The key to the conservation of harvested species is the maintenance of reproductive success. Yet for many marine species large, old, individuals are targeted despite their disproportionate contribution to reproduction. We hypothesized that a combination of no-take marine protected areas (MPAs) and harvest slot limits (maximum and minimum size limits) would result in the conservation of large spawning individuals under heavy harvest. We tested this approach under different harvest intensities with a 2-sex, stage-structured metapopulation model for the Caribbean spiny lobster (Panulirus argus). P. argus is intensively harvested in the Caribbean, and in many localities large, mature individuals no longer exist. No-take MPAs and harvest slot limits combined, rebuilt and maintained large mature individuals even under high harvest pressure. The most conservative model (a 30% MPA and harvest slot limit of 75–105 mm) increased spawner abundance by 5.53E¹² compared with the fishing status quo at the end of 30 years. Spawning stock abundance also increased by 2.76–9.56E¹² individuals at a high harvest intensity over 30 years with MPAs alone. Our results demonstrate the potential of MPAs and harvest slot limits for the conservation of large breeding individuals in some marine and freshwater environments. Decisions on which management strategy best suits a fishery, however, requires balancing what is ecologically desirable with what is economically and socially feasible.     

Photocatalytic formation of hydrogen peroxide over highly porous illuminated ZnO and TiO2thin film

The photocatalytic formation of hydrogen peroxide over ZnO and TiO₂thin films has been investigated in aqueous phase in the presence of molecular oxygen as an electron acceptor. These films are highly porous and showed enhanced catalytic activity in the photochemical formation of hydrogen peroxide. The amount of H₂O₂formed during 2 hour light illumination is 4–6 μM and the rates of formation of hydrogen peroxide of both the films are almost comparable. The yield of hydrogen peroxide increases with the increase in irradiation time and a trend of steady state concentration of H₂O₂is observed in the case of TiO₂thin film. Photodissolution of ZnO particles is observed in some extent during the process of prolonged UV light illumination.     

A 200-year perspective on alternative stable state theory and lake management from a biomanipulated shallow lake

Multiple stressors to a shallow lake ecosystem have the ability to control the relative stability of alternative states (clear, macrophyte-dominated or turbid, algal-dominated). As a consequence, the use of remedial biomanipulations to induce trophic cascades and shift a turbid lake to a clear state is often only a temporary solution. Here we show the instability of short-term manipulations in the shallow Lake Christina (Minnesota, USA) is governed by the long-term state following a regime shift in the lake. During the modern, managed period of the lake, three top-down manipulations (fish kills) were undertaken inducing temporary (5-10 years) unstable clear-water states. Paleoecological remains of diatoms, along with proxies of primary production (total chlorophyll a and total organic carbon accumulation rate) and trophic state (total P) from sediment records clearly show a single regime shift in the lake during the early 1950s; following this shift, the functioning of the lake ecosystem is dominated by a persistent turbid state. We find that multiple stressors contributed to the regime shift. First, the lake began to eutrophy (from agricultural land use and/or increased waterfowl populations), leading to a dramatic increase in primary production. Soon after, the construction of a dam in 1936 effectively doubled the depth of the lake, compounded by increases in regional humidity; this resulted in an increase in planktivorous and benthivorous fish reducing phytoplankton grazers. These factors further conspired to increase the stability of a turbid regime during the modern managed period, such that switches to a clear-water state were inherently unstable and the lake consistently returned to a turbid state. We conclude that while top-down manipulations have had measurable impacts on the lake state, they have not been effective in providing a return to an ecosystem similar to the stable historical period. Our work offers an example of a well-studied ecosystem forced by multiple stressors into a new long-term managed period, where manipulated clear-water states are temporary, managed features.     

Effect of combined application of methyl isothiocyanate and chloropicrin on their transformation

Combining several soil fumigants to increase the broad spectrum of pest control is a common fumigation practice in current production agriculture. In this study, we investigated the effect of combined application of chloropicrin and methyl isothiocyanate (MITC) on their transformations and persistence in the environment. In aqueous solution, no direct reaction between MITC and chloropicrin occurred and relatively slow rates of hydrolysis of these compounds were observed in aquatic environments free of suspended solids. The transformation of chloropicrin, however, was accelerated in aqueous solution with MITC because of a reduction reaction with bisulfide (HS(-)), which is a by-product of MITC hydrolysis. In soil, when fumigants were applied simultaneously, the degradation of MITC was suppressed under the bi-fumigant application due to the inhibition of soil microbial activity and a possible abiotic competition with chloropicrin for a limited number of reaction sites on the surface of soil particles. However, the degradation rate of chloropicrin was significantly enhanced in the bi-fumigant soil system, which was primarily attributed to the reaction of chloropicrin and HS(-). Two sequential application approaches were developed to investigate the feasibility of the combined application of metam sodium (parent compound of MITC) and chloropicrin in soil and assess their potential effects on environmental fate. For both application sequences, the degradation of chloropicrin was accelerated and that of MITC, as a major breakdown product of metam sodium, was inhibited in soil.     

Consistency of implications of three role stressors across four countries

Relationships between role stressors (ambiguity, overload, and conflict), anxiety, commitment (affective and continuance), and turnover intention were examined. These variables were measured via a survey of 1396 nurses in a total of 15 hospitals in Hungary, Italy, the United Kingdom, and the United States. Three role stressors were expected to predict anxiety and indirectly predict intention to leave. Anxiety was expected to predict affective and continuance commitment, and anxiety, affective commitment, and continuance commitment were expected to predict intention to leave the hospital. Although mean score differences were expected across countries, direction of the relationships between variables were expected to be the same, which would indicate consistency regarding the implications of three role stressors across countries. AMOS's structural equations modeling program was used to test a multi‐group manifest variable path analysis. Results yielded support for the proposed relationships (NFI = 0.93; TLI = 0.89). It was tentatively concluded that stress is a culture‐general process. Copyright © 2005 John Wiley & Sons, Ltd.     

Phosphorus leaching in manure-amended Atlantic Coastal Plain soils

Targeting the sources of phosphorus (P) and transport pathways of drainage from agricultural land will assist in the reduction of P loading to surface waters. Our research investigated the vertical movement of P from dairy manure and broiler litter through four Atlantic Coastal Plain soils. A randomized split-plot design with two main-plot tillage treatments (no tillage [NT] and chisel tillage [CH]) and five manure P rate split-plot treatments was used at each location. The split-plot P rates were 0, 100, 200, 300, and 400 kg P ha(-1) yr(-1). Four consecutive years of manure application began at all sites 5 yr before sampling. Soils were sampled to a depth of 150 cm from each split plot in seven depth increments and analyzed for soil test phosphorus (STP), water-extractable soil phosphorus (WSP), and degree of phosphorus saturation (DPS). The DPS of the 0- to 15-cm depths confirmed that at the 100 kg P ha(-1) yr(-1) application rate, all sites exceeded the threshold for P saturation (30%). At depths greater than 30 cm, DPS was typically below the 30% saturation threshold. The DPS change points ranged from 25 to 34% for the 0- to 90-cm depths. Our research concluded that the risk of P leaching through the matrix of the Atlantic Coastal Plain soils studied was not high; however, P leaching via macropore bypass may contribute to P loss from these soils.     

The effect of habit as a behavioural response in risk reduction programmes

A company's decision to implement a risk reduction programme must take account of employees' behavioural responses to the target risk. Hazard reporting by train drivers is examined in semi-structured interviews and a questionnaire study. It is suggested that the behavioural response of drivers, in terms of writing a report, depends on how the hazard is perceived. The response to “trivial” and “routine” hazards is habitual non-reporting, being characterized by a lack of risk evaluation. However, hazards that are evaluated as posing a significant risk are reported. Possible ways of breaking habitual responses to hazards, using behavioural change programmes, are discussed, and it is argued that management commitment is essential for their success.     

THE RESTON (VIRGINIA) LAKE-USE SURVEY: PUBLIC PERCEPTIONS AND MANAGEMENT IMPLICATIONS1

ABSTRACT: A public attitude survey was developed by a citizen committee and mailed to all residences (14,747) in the planned, suburban community of Reston, Virginia, which is responsible for maintaining four small, recreational impoundments. Over 18 percent of survey forms were returned, and characteristics of the survey sample suggest that the suite of respondents was representative of the Reston community as a whole. Of those respondents indicating a preferred lake use, 48 percent chose walking or looking as most important; boating as second at 27 percent; and fishing was third, favored by only 8 percent. Citizens feel strongly (94 percent) that the lakes are valuable community assets. Appearance was the characteristic most valued by 62 percent of respondents, and 58 percent considered degradation of water quality either the first or second most important ecological issue affecting local lakes. These findings provide a decisive public mandate for lake management activities related to visual quality. In response to this survey, the Reston Association, a homeowners' organization responsible for the lakes, increased public access of visual enjoyment, intensified litter control, expanded activities in public education on lake management and ecology, and continued a long-term program of water quality monitoring.     

Work-home conflict among nurses and engineers: Mediating the impact of role stress on burnout and satisfaction at work

Using structural equation modeling, this paper compares a more traditional, unmediated model of work-based role stress and its consequences on job satisfaction and burnout to two models in which the role stress-affective work outcome relationship is mediated (partially and completely) by work-home conflict across two samples of public sector professionals: engineers and nurses. The findings indicate that a model in which role conflict and overload have both direct and indirect effects—via work-home conflict—on job burnout and satisfaction (‘Partial Mediation’ model) achieves a better overall ‘fit’ than two alternative models. Furthermore, the findings suggest that while the two groups perceive many aspects of the work-home relationship differently, for both groups, work-based role conflict is an important antecedent of work-home conflict, and increased burnout an important direct consequence of work-home conflict. Finally, on the basis of the findings, the authors conclude that perspectives which view the work and non-work realms as independent must be reconsidered, and that the nature of the work-home relationship may, to a great extent, be contingent upon the way different occupational groups perceive their work situations.