Patterns of mussel recruitment in southern Africa: a caution about using artificial substrata to approximate natural recruitment

Quantifying sessile marine invertebrate recruitment often requires destructive sampling or extrapolation from artificial substrata, the latter introducing the danger of artifacts. We measured intertidal mussel recruitment into mussel beds and into brushes at three-month intervals for five years across 3,200 km of southern Africa and determined substrata effects on recruitment rate. Recruitment into mussel beds showed a strong, coast-wide gradient, with high recruitment on the West coast, diminishing on the South coast, and increasing slightly on the East coast. At scales of 10 s of km, brushes reflected natural temporal recruitment variability, with a strong significant linear correlation between recruitment into brushes and into mussel beds. However, the relationship became semi-logarithmic when comparing among locations at a scale of 100 s of km. Artificial substrata thus reflect local natural settlement well but may be a poor indicator of it when spatial scales are large, particularly when mussel bed topography is complex, or localities have very different recruitment densities.     

Interhemispheric comparison of recruitment to intertidal communities: pattern persistence and scales of variation

Recruitment variation can be a major source of fluctuation in populations and communities, making it difficult to generalize results. Determining the scales of variation and whether spatial patterns in the supply of individuals are persistent over time can provide insight into spatial generality and the application of conservation and metacommunity models. We examined these issues using eight-year-long data sets of monthly recruitment of intertidal mussels (Mytilus spp., Perumytilus purpuratus, Semimytilus algosus, Brachidontes granulata) and barnacles (Balanus glandula, Chthamalus dalli, Jehlius cirratus, Notochthamalus scabrosus) at sites spanning > 900 km along the coasts of Oregon-northern California (OR-NCA, 45.47-39.43 degrees N) and central Chile (CC, 29.5-34.65 degrees S). We evaluated four general "null" hypotheses: that despite different phylogenies and great spatial separation of these taxa, their similar life history strategies and environmental settings lead to similar patterns of recruitment (1) between hemispheres, (2) in time, (3) in space, and (4) at larger and smaller spatial scales. Hypothesis 1 was rejected: along the OR-NCA coast, rates of recruitment were between two and three orders of magnitude higher, and patterns of seasonality were generally stronger and more coherent across space and time than along CC. Surprisingly, however, further analysis revealed regularities in both time and space for all species, supporting hypotheses 2 and 3. Temporal decorrelation scales were 1-3 months, and characteristic spatial scales of recruitment were approximately 250 km. Contrary to hypothesis 4, for the ecologically dominant species in both hemispheres, recruitment was remarkably persistent at larger mesoscales (kilometers) but was highly stochastic at smaller microscales (meters). Across species, increased recruitment variation at large scales was positively associated with increased persistence. Our results have several implications. Although the two regions span distinct latitudinal ranges, potential forcing processes behind these patterns include similar large-scale climates and topographically locked hydrographic features, such as upwelling. Further, spatial persistence of the recruitment patterns of most species at the mesoscale supports the view that marine protected areas can be powerful conservation and management tools. Finally, persistent and yet contrasting spatial patterns of recruitment among competing species suggest that recent metacommunity models might provide useful representations of the mechanisms involved in species coexistence.     

Determining the optimum number of increments in composite sampling

Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum number of increments to use in composite sampling. Composite sampling terminology and theory are outlined and a method is developed which accounts for different sources of variation in compositing and data analysis. This method is used to define and understand the process of determining the optimum number of increments that should be used in forming a composite. The blending variance is shown to have a smaller range of possible values than previously reported when estimating the number of increments in a composite sample. Accounting for differing levels of the blending variance significantly affects the estimated number of increments.

Development of dioxin toxicity evaluation method in human milk by enzyme-linked immunosorbent assay--assay validation for human milk

In this study, the development of a toxicity evaluation method for dioxins in human milk by enzyme-linked immunosorbent assay (ELISA) was reported. A total of 17 human milk samples were tested by ELISA and by gas chromatography/mass spectrometry (GC/MS) to assess whether the ELISA performed on samples obtained from primiparas could be considered as reliable enough for identifying a dioxins contamination in human milk. The concept of toxicity equivalent quantity (TEQ) screening was validated by comparing TEQ values for a set of human milk samples to the ELISA responses predicted for those samples. A fairly good correlation (r=0.920) between immunoassay and GC/MS was achieved for human milk. This ELISA should be useful for biological samples monitoring.     

Bioenhancement of NAPL pool dissolution: experimental evaluation

Experiments were conducted to quantify nonaqueous phase liquid (NAPL) pool dissolution and its enhancement by in situ biodegradation. The experiments were performed using square cross-section, glass-bead packed column reactors with a small pool of a toluene-in-dodecane mixture (toluene mole fraction, X(tol) approximately 0.02 or 0.09). Experimental quasi-steady-state toluene dissolution fluxes were determined using a 14C-carbon mass-balance approach during water flushing with and without biodegradation. The experiments demonstrated a statistically significant bioenhancement of the toluene dissolution flux of up to roughly twofold at average pore water velocities of approximately 0.1 and 1 m/day when the toluene mole fraction was low ( approximately 0.02); however, little or no bioenhancement was observed with the higher mole fraction ( approximately 0.09). Although it cannot be determined conclusively, the weight of evidence based on biomass measurements and model analyses suggests that the reduced bioenhancement for the high mole fraction was due to higher dissolved toluene concentrations, which may have caused toxicity effects. Importantly, even though NAPL dissolution was not bioenhanced in every case, the biodegradation reduced toluene concentrations to low levels in the reactor effluents.     

Measuring the impact of rehabilitation services on the quality of life of disabled people in Cambodia

The present study aimed to measure the quality of life (QOL) of disabled people in Cambodia and the impact of rehabilitation services. The categories of services were: physical rehabilitation (prosthetics/orthotics with physiotherapy); community-based rehabilitation; and (3) labour market assistance. The 164 respondents were from a range of urban and rural settings. The results suggest that QOL was substantially lower among disabled Cambodians who had received no rehabilitation services compared to those who had received one of the three categories of rehabilitation services. QOL scores tended to be highest, however, among those who had received a combination of all three services. The results also highlighted the vulnerability of certain sub-groups who may need specific provision in planning, policy-making and service delivery. The present study suggests that an integrated approach may be the best way to maximise the impact of individual rehabilitation services in Cambodia.     

SAGE: A NEW PARTICIPANT-VALUE METHOD FOR ENVIRONMENTAL ASSESSMENT1

SAGE, a proposed method for environmental assessment, focuses on eliciting and incorporating value weights in multiple-objective decision making. In this method, the value weights are inferred from the tradeoffs that people make in choices about alternatives. These weights are applied to scaled scores for accounts based on measurable attributes of each objective. In order to indicate the political ramifications of decisions and to facilitate sensitivity analysis, the values held by various groups are presented in matrix from arrayed by group affiliation or by judgment types that share common values. Results of a trial application of SAGE to a land use/watershed management problem in a growing urban area are presented.     

Book reviews

Traffic Mix Model

(TRRU Research Report No. 30).

A Methodology for Estimating Recreation Traffic Flows.

August 1977, University of Edinburgh. 144 pps.

“Recreation in the Highlands and Islands”

Tourism and Recreation Research Unit, University of Edinburgh, December 1976.

Research Report No. 22, 411pp with tables and diagrame; Research Report No. 31, 145 with tables and diagrams.

Tourism and Recreation in the Chichester Area: a basis for planning

Tourism and Recreation Research Unit, Research Report No. 35, University of Edinburgh.

The Real Wealth of Nations

S. R. Eyre

Arnold, London, 1978. £7.95.

Landscape Construction

M. F. Downing

E. & F. N. Spon, London, 1977

Planning and Organizing for Social Change. Action Principles from Social Science Research.

Jack Rothman

Columbia University Press. 628 p.p.

Models and Cities and Regions

A. G. Wilson, P. H. Rees, C. M. Leigh (editors) 1977

Wiley, £12.75.

Ecology and Ekistics

C. A. Doxiadis Edited by Gerald Dix

Paul Elek, London 1977. Environmental Studies Series. 91 p.p. Paperback. £3.75.

Tackling Urban Deprivation : The Contribution of Area‐Based Management

T. Mason, K. Spencer, C. Vielba and B. Webster

Institute of Local Government Studies, University of Birmingham, Dec. 1977. 93p.p. No price stated.

Marketing Geography : with special reference to retailing

R. L. Davies

Methuen, 1976. £3.45.

“Public Participation in Planning”

Edited by W. R. D. Sewell and J. T. Coppock

J. Wiley & Sons Ltd., Chichester, 1977. 208 p.p. £9.00.

“The Individual Citizen and Public Participation”

William Hampton and Raymond Walker

Linked Research Project into Structure Planning, Interim Research Paper. 13, 1978. 24 p.p. £1.00.

A Future for Planning Science Fiction Cities

Town Planning discussion paper No. 27. Stephen Wood

U.C.L. 1977.

“The Bicycle Planning Book “

Mike Hudson (editor)

Open Books Publishing Ltd. and Friends of the Earth, 1978. Paperback, £1.95.

Residential Location and Urban Housing Markets

G. K. Ingram (1977) (ed.)

Cambridge, Mass : Ballinger Publishing Co., for the National Bureau of Economic Research.     

Assessing potential risks to wildlife and sportsmen from exposure to dioxin in pulp and paper mill sludge spread on managed woodlands

Potential human and wildlife exposures to TCDD in landspread pulp and paper mill sludge in the State of Maine were evaluated by means of a human health and an ecological risk assessment methodology. The highest historical concentrations of TCDD reported for these sludges do not present a risk to American woodcock, selected as an indicator species for this analysis. Concentrations of TCDD as high as 50 ppt in soil are not likely to produce adverse effects in the embryonic/hatchling stage of the woodcock. This soil concentration of TCDD does not present a significant risk to sportsmen and their families that may consume birds which inhabit these sites.