Osmotic, ionic and haematological response of the Port Jackson shark Heterodontus portusjacksoni and the common stingaree Trygonoptera testacea upon exposure to diluted seawater

The osmo-ionoregulatory responses of sub-adult Port Jackson sharks, Heterodontus portusjacksoni (Meyer, 1793), and the stingaree Trygonoptera testacea (Müller and Henle, 1841), were investigated following the transfer from full-strength seawater (100% SW) to either 75 or 50% SW for up to 168 h. The plasma osmotic pressure was similarly reduced in both species and remained slightly hyper-osmotic to the diluted seawater after 168 h. The increase in the body weight of H.␣portusjacksoni transferred to diluted seawater was double that of T.testacea, with the greater haemodilution reflected by a short-term reduction in haematocrit and in haemoglobin concentration. The haemodilution exhibited by H. portusjacksoni also resulted in a greater reduction in plasma [Na], [Cl], [urea] and [trimethylamine oxide] compared with T. testacea. The ability of T. testacea to minimize body-weight gain in diluted seawater was most probably due to increased net water efflux. The persistent elevation in the body weight of both species, despite the apparent recovery of plasma-water volume, was indicative of elevated tissue water. Chronic exposure of H. portusjacksoni to 50% SW altered erythrocyte ion concentrations and plasma/erythrocyte ion ratios, which could have serious implications for cellular homeostasis, respiratory gas transport and acid-base status. The greater control of water and ionic status exhibited by T.testacea, compared with that of H.portusjacksoni, allows the stingarees to penetrate into the more dilute, upper estuarine waters. Received: 22 August 1997 / Accepted: 1 April 1998     

Secchi Disc Relationships1

ABSTRACT: The problem of estimating bulk light extinction coefficients in surface water impoundments is examined. It is shown that the bulk extinction coefficient can be accurately estimated from the Secchi disc depth. In addition, the equation derived is significantly different from that derived by Poole and Atkins in 1929. This empirical expression for the extinction coefficient is then used to develop a semiempirical expression for the euphotic depth as a function of the Secchi disc depth.     

Sampling Broad Habitat change to assess biodiversity conservation action in Northern Ireland

A habitat monitoring programme, the Northern Ireland Countryside Survey, carried out by the University of Ulster for the Department of the Environment for Northern Ireland, is described. It was based on a random sample of quarter kilometer grid squares, stratified by multivariate land classification. Estimates of change in habitat area between 1987-1992 and 1998 are presented and used to assess policy-related priorities for biodiversity conservation action in widespread habitats in Northern Ireland (NI). The basis of the assessment is Broad Habitats, a classification developed as part of the United Kingdom (UK) Biodiversity Action Plan. Improved Grassland, Neutral Grassland and Bog Broad Habitats occupy the largest area of NI, which holds a large proportion of the UK Neutral Grassland and Fen Marsh and Swamp Broad Habitat resource. The greatest net area increases with time were in Improved Grassland (33%), Coniferous Woodland (12%) and Broadleaved, Mixed and Yew Woodland (9%). The greatest net area decreases were in Neutral Grassland (-32%), Arable and Horticulture (-25%), Fen, Marsh and Swamp (-19%), Bog (-8%) and Calcareous Grassland (-7%). These changes are a function of agriculture, public and private forestry, building construction and peat cutting for fuel. The Key biodiversity issue is seminatural Broad Habitat loss, in particular, Neutral Grassland and Fen, Marsh and Swamp, highlighting the lack of effective action for protecting biodiversity in the countryside as a whole. The extent to which current land use is shown to be driving change, indicates that biodiversity conservation action through implementing landscape-scale agri-environment measures could deliver major biodiversity gains. The reliable information on recent changes, provided by the Northern Ireland Countryside Survey, has been used to guide conservation planning. Future re-survey will allow the effectiveness of the conservation strategy as it applies to the countryside as a whole, to be determined. As decisions on land use increasingly have a strong European dimension, concerted action for protecting biodiversity in the countryside as a whole is needed. This would be promoted by a structured sampling approach, based on standard habitat mapping procedures.     

CONTROL OF STREAMBANK EROSION DUE TO BED DEGRADATION WITH VEGETATION AND STRUCTURE1

ABSTRACT: Combinations of vegetation and structure were applied to control streambank erosion along incised stream channels in northwest Mississippi. Eleven sites along seven channels with contributing drainage areas ranging from 12–300 km² were used for testing. Tested configurations included eroding banks protected by vegetation alone, vegetation with structural toe protection, vegetation planted on re-graded banks, and vegetation planted on regraded banks with toe protection. Monitoring continued for up to 10 years, and casual observation for up to 18 years. Sixteen woody and 13 nonwoody species were tested. Native woody species, particularly willow, appear to be best adapted to stream-bank environments. Sericea lespedeza and Alamo switchgrass were the best nonwoody species tested. Vegetation succeeded in reaches where the bed was not degrading, competition from kudzu was absent, and bank slopes were stabilized by grading or toe protection. Natural vegetation invaded planted and unplanted stable banks composed of fertile soils. Designs involving riprap toe protection in the form of a longitudinal dike and woody vegetation appeared to be most cost-effective. The exotic vine kudzu presents perhaps the greatest long-term obstacle to restoring stable, functional riparian zones along incised channels in our region. (KEY TERMS: vegetation; streambank protection; bioengineering; stream restoration; channel incision; riparian zone.)     

A chance-constrained goal programming model to evaluate response resources for marine pollution disasters

This paper develops a model to aid Coast Guard managers in formulating appropriate policies with respect to planning for various types of equipment required to contain major pollution incidents. The model is elaborated in terms of three primary stages of response: offloading, containment, and removal. The zero order rule of chance constrained programming is used to obtain a deterministic equivalent of the original chance constrained model. This is then replaced by a goal programming formulation to allow for plans that come “as close as possible” to desired quality and risk levels for each pertinent region and type of incident. Numerical examples illustrate potential uses of the model with special emphasis on its value for budgetary (equipment) planning by central management that extends to evaluation of risk and performance quality levels, as well as the usual dual evaluator approaches for evaluating initially prescribed levels for equipment and their efficiency coefficients.     

Another look at the locus of control–organizational commitment relationship: it depends on the form of commitment

Previous studies imply that individuals with an external locus of control (LOC) are less likely to be committed to their organizations. More recent work on organizational commitment has suggested that commitment is not a unidimensional construct and can take several forms (e.g., affective and continuance). Using a sample of 232 employees of a Canadian governmental agency, we examined the relations between LOC and two different forms of organizational commitment that have been found to have different antecedents and consequences. We found that internal LOC was associated with affective commitment and external LOC was associated with continuance commitment. Implications for research and practice are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Method to recover and reuse chromated copper arsenate wood preservative from spent treated wood

The volume of chromated copper arsenate (CCA) treated wood products coming out of service is expected to increase dramatically during the next decade. There is a need for an alternative waste management approach to landfilling. This paper investigates the variables affecting extraction of CCA components from wood particles and the potential to oxidize and reuse the recovered chemicals. Most of the CCA components could be extracted by 10% H2O2 at 50 degrees C in 6 h with an average extraction efficiency of 95% for Cr, 94% for Cu and 98% for As. The extract containing Cr(III), Cu(II) and As(V) could be oxidized in several stages by aqueous 2.5% w/w H2O2 in less than 2 h to a condition where it was compatible with CCA treating solutions and could be reused for treating new wood. When the recovered extract was mixed with fresh CCA solution in different ratios, the mixed CCA-C solutions had similar solution stability as freshly prepared CCA-C solution and treated wood had similar leaching properties as wood treated with fresh solution.