Solute transfer across the sediment surface of a eutrophic lake: I. Porewater profiles from dialysis samplers

Porewater profiles often are used to identify and quantify important biogeochemical processes occurring in lake sediments. In this study, multiple porewater profiles were obtained from two eutrophic Swiss lakes using porewater equilibrators (peepers) in order to examine spatial and seasonal trends in biogeochemical processes. Variability in profile shapes and concentrations was small on spatial scales of a few meters, but the uncertainty in calculated diffusive fluxes across the sediment surface was, on average, 35%. Focusing of Fe and Mn oxides toward the lake center resulted in systematic increases in porewater concentrations and diffusive fluxes of Fe²⁺ and Mn²⁺ with increasing water depth; these fluxes are postulated to be regulated by the pH-dependent dissolution of reduced-metal phases. Despite higher concentrations of inorganic carbon, NH ₄ ⁺ , Si and P in pelagic compared to littoral sites, diffusive fluxes of these substances across the sediment surface increased only slightly or not at all with increasing water depth. Porewater profiles did reveal temporal changes in Fe²⁺, Mn²⁺, Ca²⁺ and Mg²⁺ that were an indirect result of the large, seasonal changes in seston deposition, but no clear seasonal variations were found in diffusive fluxes of nutrients across the sediment surface. The intense mineralization occurring at the sediment surface was not reflected in the porewater profiles nor in the calculated diffusive fluxes. Calculated diffusive fluxes across the sediment surface resulted from decomposition occurring primarily in the top 5–7 cm of sediment. Diffusive fluxes from this subsurface mineralization were equal to the solute release from mineralization occurring at the sediment-water interface. Buried organic matter acts as a memory of previous lake conditons; it will require at least a decade before reductions in nutrient inputs to lakes fully reduce the diffusive fluxes into the lake from the buried reservoir of organic matter.     

The use of egg shells to infer the historical presence of copepods in alpine lakes

Copepods (Class Crustacea, Order Copepoda) are rarely included in paleoecological studies of lakes because they lack long-lasting exoskeletal remains. We describe the remains of eggs (egg shells) from Hesperodiaptomus copepods that are well preserved and abundant in alpine lake sediments. We demonstrate that the egg shells are the remains of Hesperodiaptomus eggs based on (i) the similar size and morphology of egg shells collected from sediments and those produced from the hatching of eggs obtained from laboratory-maintained Hesperodiaptomus, and (ii) the finding that diapausing eggs collected from lake sediments and hatched in the laboratory produced copepod nauplii that were morphologically indistinguishable from those hatched from eggs produced by laboratory-maintained Hesperodiaptomus. Egg shells were approximately two orders of magnitude more abundant in sediment cores than were viable diapausing eggs, making egg shells superior to viable diapausing eggs for quantifying the historical presence and abundance of Hesperodiaptomus. These results have important implications for alpine lake restoration as egg shells can be used to identify lakes in which Hesperodiaptomus was eliminated by fish introductions but has failed to return after fish eradication, lakes in which the pre-disturbance conditions are likely to be restored only by reintroductions of this important taxon.     

Reviews

CUL DE SAC: The Question of New Zealand's Future by H. Franklin. 13 x 19 cm, 184 pages. Allen & Unwin: Sydney 1985 (ISBN 0 86861 514 5) $A12.95 (soft).

SHOPPING CENTRE DEVELOPMENT: Policies and Prospects edited by J. A. Dawson and J. D. Lord. 14 x 22 cm, 269 pages. Croom Helm: London 1985 (ISBN 0 7099 0845 8) $A49.95 (hard).

GENTRIFICATION OF THE CITY edited by N. Smith and P. Williams. 13 x 22 cm, xiii and 257 pages. Allen & Unwin: Boston 1986 (ISBN 0 04 301201 9) $A59.00 (hard); (ISBN 0 04 301202 7) $A26.95 (soft).

EUROPE TODAY: Countries and Issues by D. J. Davis and D. C. Flint. 19 x 27 cm, 256 pages. Bell & Hyman: London 1986 (ISBN 0 7135 2518 5) £5.95 (soft).

THE WORLD NOW (Australian edition) by A. Reed and R. Pask. 21 x 30 cm, 96 pages. Edward Arnold: Melbourne 1986 (ISBN 0 7131 8225 3) $A12.95 (soft).

THE INDO‐PACIFIC LIBRARY: Set Two — Ten Titles (11 Australia, 12 Burma, 13 French Polynesia, 14 India, 15 Laos and Kampuchea, 16 North and South Korea, 17 Pakistan and Bangladesh, 18 Sri Lanka, 19 Thailand, 20 Vietnam) by G. Houghton and J. Wakefield. 19 x 25 cm, 32 pages each. Macmillan: Melbourne 1987 $A9.95 (hard) each title.

THE INDO‐PACIFIC LIBRARY: Set Two — Macmillan Black Line Masters by G. Houghton and J. Wakefield. Macmillan: Melbourne 1987 (ISBN 0 333 43059 X) $A19.95 (soft).

QUEENSLAND: A Geographical Interpretation (Queensland Geographical Journal, 4th Series, Volume 1) edited by J. H. Holmes. 18 x 24 cm, 343 pages. Boolarong Publications: Brisbane 1986 (ISBN 0817 489X) $A25.00 (soft).

THE ROAD TO BOTANY BAY: An Essay in Spatial History by P. Carter. 14 x 22 cm, xv and 384 pages. Faber and Faber: London 1987 (ISBN 0 571 14551 5) $A29.95 (hard).

AN EVALUATION OF LOCAL AREA ECONOMIC STRATEGY STUDIES (Australian Regional Developments, No. 6) edited by J. D. Conroy. 30 x 21 cm, vii and 102 pages. Australian Government Publishing Service: Canberra 1987 (ISBN 0 644 06161 8).

PRODUCTION, WORK, TERRITORY: The Geographical Anatomy of Industrial Capitalism edited by A. J. Scott and M. Storper. 15 x 23 cm, xix and 344 pages. Allen & Unwin Inc: Boston 1986 (ISBN 0 04 338126 X) $A90.00 (hard); (ISBN 0 04 338127 8) $A38.95 (soft).

ANALYTICAL BEHAVIOURAL GEOGRAPHY by R. G. Golledge and R. J. Stimson. 16 x 24 cm, 345 pages. Croom Helm: London 1987 (ISBN 0 7099 3844 6) $A122.95 (hard).

AMBIGUOUS ALTERNATIVE: Tourism in Small Developing Countries edited by S. Britton and W. C. Clarke. 20 x 21 cm, 194 pages. University of the South Pacific: Suva 1987 (ISBN 982 01 0009); available from Geography Department, University of the South Pacific, Box 1168, Suva, Fiji.

AN ATLAS OF ENVIRONMENTAL AND RUMINANT POPULATION CHARACTERISTICS OF JAVA: A Multivariate Analysis Approach by J. M. Perkins, Armiadi Semali, P. W. Orchard and Rach‐met Rachman. 46 x 31 cm, 71 pages. Forage Research Project, University of New England: Armidale 1986 (ISBN 0 85834 691 5) $A50.00 plus postage (developed countries); $A20.00 plus postage (developing countries).

ANTARCTICA: THE NEXT DECADE. Report of a Study Group (Studies in Polar Research) by A. Parsons et al. 15 x 23 cm, xii and 164 pages. Cambridge University Press: Cambridge 1987 (ISBN 0521 331811) $A65.00 (hard).

THE HUMAN IMPACT ON THE NATURAL ENVIRONMENT by A. Goudie, 25 x 17 cm, x and 338 pages. Basil Blackwell: Oxford 1986 (ISBN 0 631 13758 0) $A29.50 (soft).

ATMOSPHERIC POLLUTION: Causes, Effects and Control Policies by D. Elsom. 15 x 23 cm, x and 319 pages. Basil Blackwell: Oxford 1987 (ISBN 0 631 13813 3) $A122.50 (hard); (ISBN 0 631 15674 7) $A43.95 (soft).

SEA SURFACE STUDIES: A Global View edited by R. J. N. Devoy. 16 x 24 cm, 649 pages. Croom Helm: London 1987 (ISBN 0 7099 0871 7) £55.00 (hard).     

Econometric analysis on the effect of port state control inspections on the probability of casualty: Can targeting of substandard ships for inspections be improved?

This article is based on 183,819 port state control inspections from various port state control regimes and casualties from three different data sources for a time period of 6 years. It is the first time an analysis on a combined dataset of this magnitude has been performed. Binary logistic regression is used to measure the effect of inspections on the probability of casualty, which can be measured for very serious casualties but not for serious or less serious casualties. In addition, the magnitude of improvement areas for targeting substandard vessels is determined and the models further show how targeting of substandard ships on a combined dataset can be improved. In addition, the analysis also compares the fishing fleet with the commercial fleet.     

Comparative Rates of Western Juniper Afforestation in South‐Central Oregon and the Role of Anthropogenic Disturbance*

We examine changes in canopy cover for adult western juniper from the 1960s to 1994 in central Oregon using repeat aerial photography. We compare changes at four sites with a land‐use history of minimal anthropogenic disturbance to changes on adjacent sites that have a disturbance history more typical of central Oregon rangelands. Canopy cover increased at all sites, but afforestation on sites with domestic livestock grazing was greater. The potential driving forces common to all sites include a long fire‐free interval, early twentieth‐century favorable climatic conditions, biological inertia, and atmospheric CO₂ enrichment.     

The Variance-Based Cross-Variogram: You Can Add Apples and Oranges

The variance-based cross-variogram between two spatial processes, Z₁ (·) and Z₂ (·), is var (Z₁ ( u ) – Z₂ ( v )), expressed generally as a bivariate function of spatial locations uandv. It characterizes the cross-spatial dependence between Z₁ (·) and Z₂ (·) and can be used to obtain optimal multivariable predictors (cokriging). It has also been called the pseudo cross-variogram; here we compare its properties to that of the traditional (covariance-based) cross-variogram, cov (Z₁ ( u ) – Z₁ ( v ), Z₂ ( u ) – Z₂ ( v )). One concern with the variance-based cross-variogram has been that Z₁ (·) and Z₂ (·) might be measured in different units (apples and oranges). In this note, we show that the cokriging predictor based on variance-based cross-variograms can handle any units used for Z₁ (·) and Z₂ (·); recommendations are given for an appropriate choice of units. We review the differences between the variance-based cross-variogram and the covariance-based cross-variogram and conclude that the former is more appropriate for cokriging. In practice, one often assumes that variograms and cross-variograms are functions of uandv only through the difference u – v. This restricts the types of models that might be fitted to measures of cross-spatial dependence.     

Environmental considerations in the fertilizer use decision

 The increase in the use of fertilizer in agricultural production has been associated with a substantial increase in agricultural productivity in the United States. This increase in fertilizer use has been driven by a variety of economic forces including variations in the price of output and changing relative factor prices. Associated with the increase in the use of fertilizer have been adverse environmental consequences that are not reflected in the costs and returns of agricultural production. That is, externalities exist whose cost need to be internalized. Because the use of fertilizer has been shown to respond to market forces, it is efficient to use the market to control the use of fertilizer. This can be done through, for example, the use of a fertilizer tax. Received: 31 December 1996 · Accepted: 13 May 1997     

The optimum distance at which to determine the size of a giant air shower

To determine the size of an extensive air shower it is not necessary to have knowledge of the function that describes the fall-off of signal size from the shower core (the lateral distribution function). In this paper an analysis with a simple Monte Carlo model is used to show that an optimum ground parameter can be identified for each individual shower. At this optimal core distance, r_opt, the fluctuations in the expected signal, S(r_opt), due to a lack of knowledge of the lateral distribution function are minimised. Furthermore it is shown that the optimum ground parameter is determined primarily by the array geometry, with little dependence on the energy or zenith angle of the shower or choice of lateral distribution function. For an array such as the Pierre Auger Southern Observatory, with detectors separated by 1500 m in a triangular configuration, the optimum distance at which to measure this characteristic signal is close to 1000 m.