Exorbitant mortality of hatchery-reared Atlantic salmon smolts Salmo salar L., in the Meuse river system in the Netherlands

Stocking Atlantic salmon Salmo salar L. in the Meuse river system is unsuccessful, since hardly any adults return upstream. To investigate problems during seaward migration, individual salmon smolts were tracked in the Dutch part of the river Meuse, using the Nedap Trail® system. The study included a comparison for two seasons, one with high (2010) and one with low (2011) discharge conditions. Cultivated smolts (Loire-Allier strain, n = 100 per year) were implanted with telemetry tags and released in the tributary Roer in March, at the beginning of the natural smolt run. The study area was split into four river sections each characterized by different conditions: tributary Roer, main river Meuse extensively dammed, main river Meuse free flowing and the estuary. Mortalities differed considerably between sections. In the free flowing river Meuse the mortalities were relatively low (10 and 25 %). Mortalities were high in the tributary (44 and 45 %), the dammed river (46 and 49 %) and in the estuary (89 and 90 %). Only 2 and 3 % of the smolts escaped into the North Sea. Results are discussed in relation to environmental factors light and discharge and the presence of man-made obstacles: weirs, hydropower plants and a sea lock. A lack of current and delays at man-made obstacles result in disorientation of fish, a higher risk of predation and disturbance of the smolt run timing. Mortality causes must decrease for sustaining a salmon population in the Meuse.     

Two neighborhood-free plot designs for adaptive sampling of forests

Adaptive cluster sampling (ACS) has the potential of being superior for sampling rare and geographically clustered populations. However, setting up an efficient ACS design is challenging. In this study, two adaptive plot designs are proposed as alternatives: one for fixed-area plot sampling and the other for relascope sampling (also known as variable radius plot sampling). Neither includes a neighborhood search which makes them much easier to execute. They do, however, include a conditional plot expansion: at a sample point where a predefined condition is satisfied, sampling is extended to a predefined larger cluster-plot or a larger relascope plot. Design-unbiased estimators of population total and its variance are derived for each proposed design, and they are applied to ten artificial and one real tree position maps to estimate density (number of trees per ha) and basal area (the cross-sectional area of a tree stem at breast height) per hectare. The performances—in terms of relative standard error (SE%)—of the proposed designs and their non-adaptive alternatives are compared. The adaptive plot designs were superior for the clustered populations in all cases of equal sample sizes and in some cases of equal area of sample plots. However, the improvement depends on: (1) the plot size factor; (2) the critical value (the minimum number of trees triggering an expansion); (3) the subplot distance for the adapted cluster-plots, and (4) the spatial arrangement of the sampled population. For some spatial arrangements, the improvement is relatively small. The adaptive designs may be particularly attractive for sampling in rare and compactly clustered populations with critical value of 1, subplot distance equal to the diameter of initial circular plots, or plot size factor of 2.5 for an initial basal area factor of 2.     

The lichen-rich coastal heath vegetation on the isle of Anholt, Denmark — conservation and management

The high conservational value of the lichen-rich vegetation and landscape of the marine foreland Ørkenen on the isle of Anholt is treated from a Danish as well as a European perspective. The sensitivity of the lichen-rich vegetation to physical disturbance is emphasized. The impact of invasive species such asPinus mugo as well as the effect of atmospheric deposition of nutrients on the heaths at Anholt is described. Considerations related to the development of a management plan for Ørkenen are presented.     

The lichen-rich coastal heath vegetation on the isle of Anholt, Denmark — description, history and development

The marine foreland called Ørkenen (=the desert) at Anholt is covered by lichen-richEmpetrum nigrum-Corynephorus canescens heath vegetation on beach ridg e systems formed during the elevation of land after the Weichsel ice age andStereocaulon saxatile-richAmmophila arenaria-Corynephorus canescens vegetation on semi-fixed aeolic dunes. The development of the vegetation at Ørkenen is the result of various kinds of human exploitation, with its maximum in the 16th and 17th century. After the cessation of human use, a slow succession towards closed vegetation with mainlyEmpetrum nigrum andCorynephorus canescens began. The present heath ecosystem, developed on sandy substrate with very little organic matter and a small nutrient supply, is a high priority habitat in Europe.     

Spatial and temporal variation of metal concentrations in adult honeybees (Apis mellifera L.)

Honeybees (Apis mellifera L.) have great potential for detecting and monitoring environmental pollution, given their wide-ranging foraging behaviour. Previous studies have demonstrated that concentrations of metals in adult honeybees were significantly higher at polluted than at control locations. These studies focused at a limited range of heavy metals and highly contrasting locations, and sampling was rarely repeated over a prolonged period. In our study, the potential of honeybees to detect and monitor metal pollution was further explored by measuring the concentration in adult honeybees of a wide range of trace metals, nine of which were not studied before, at three locations in the Netherlands over a 3-month period. The specific objective of the study was to assess the spatial and temporal variation in concentration in adult honeybees of Al, As, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, Ti, V and Zn. In the period of July-September 2006, replicated samples were taken at 2-week intervals from commercial-type bee hives. The metal concentration in micrograms per gram honeybee was determined by inductive coupled plasma-atomic emission spectrometry. Significant differences in concentration between sampling dates per location were found for Al, Cd, Co, Cr, Cu, Mn Sr, Ti and V, and significant differences in average concentration between locations were found for Co, Sr and V. The results indicate that honeybees can serve to detect temporal and spatial patterns in environmental metal concentrations, even at relatively low levels of pollution.     

Poultry litter application to loblolly pine forests: growth and nutrient containment

Forestland application of poultry manure offers an alternative to the conventional practice of pastureland application. Before such a practice is considered viable, however, it must be demonstrated that the forest ecosystem is capable of absorbing the nutrients contained in poultry manure, especially nitrogen (N) and phosphorus (P). From the forestry perspective, it must also be demonstrated that tree growth is not diminished. We investigated these questions using loblolly pine (Pinus taeda L.) stands growing in central Mississippi in an area of high poultry production. Stockpiled broiler litter was applied to newly thinned, 8-yr-old stands at 0, 4.6, and 18.6 dry Mg ha-1, supplying 0, 200, and 800 kg N ha-1 and 0, 92, and 370 kg P ha-1, respectively. Levels of nitrate in soil water, monitored at a 50-cm depth with porous cup tension lysimeters, exceeded 10 mg N L-1 during the first two years after application in the 18.6 Mg ha-1 rate but only on two occasions in the first year for the lower rate of application. Phosphate was largely absent from lysimeter water in all treatments. Other macronutrients (K, Ca, Mg, S) were elevated in lysimeter water in proportion to litter application rates. Soil extractable nitrate showed similar trends to lysimeter water, with substantial elevation during the first year following application for the 18.6 Mg ha-1 rate. Mehlich III-extractable phosphate peaked in excess of 100 microg P g-1 soil during the third year of the study for the 18.6 Mg ha-1 rate. The 4.6 Mg ha-1 rate did not affect extractable soil P. Tree growth was increased by the poultry litter. Total stem cross-sectional area, or basal area, was approximately 20% greater after 2 yr for both rates of litter application. Overall, the nutrients supplied by the 4.6 Mg ha-1 rate were contained by the pine forest and resulted in favorable increases in tree growth. The higher rate, by contrast, did pose some risk to water quality through the mobilization of nitrate. These results show that, under the conditions of this study, application of poultry litter at moderate rates of approximately 5 Mg ha-1 to young stands of loblolly pine offers an alternative disposal option with minimal impacts to water quality and potential increases in tree growth.     

Black carbon-dominated PCDD/Fs sorption to soils at a former wood impregnation site

The influence of black carbon (BC) on the sorption of 17 native polychlorinated-p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was studied in five soil samples from a sawmill site where wood used to be impregnated with chlorophenol preservatives. The presence of BC caused measured total organic carbon (TOC)-water distribution ratios (K(TOC)) to be a median factor of 51 (interquartile range 18-68, n=85) higher than modeled amorphous organic carbon (AOC)-water distribution ratios (K(AOC)). K(TOC) was a factor of 73+/-27 above K(AOC) for PCDFs (n=10) and a factor of 20+/-13 (n=7) for PCDDs. The reason for this difference is probably that attaining a planar configuration after sorption to BC is less thermodynamically favorable for PCDDs than for PCDFs. BC-water distribution ratios were calculated from K(TOC), K(AOC) and BC contents, and ranged from 10(9.9) (2,3,7,8-Tetra-CDD) to 10(11.5) l kg(-1) (Octa-CDF). More than 90% of the PCDD/Fs in the soil was calculated to be BC-sorbed. Dissolved organic carbon (DOC)-water distribution ratios were measured to be in the same order of magnitude as K(AOC). This study shows that strong sorption to BC should be included when assessing ecotoxicological risk or modeling transport to groundwater of PCDD/Fs in soil.     

Assessing PAH and PCB emissions from the relocation of harbour sediments using equilibrium passive samplers

Large-scale dredging of contaminated sediments is taking place in the harbor of Oslo, Norway. The dredged sediment masses are transferred into a confined aquatic disposal facility (CAD) in a natural 70-m deep basin within the Oslofjord. Currently there is no established method to determine how much dissolved contaminants are released during relocation and deposition of these sediments. For this reason we tested the use of equilibrium passive samplers consisting of 55 microm thin polyoxymethylene (POM-55) for studying the release of freely dissolved and thus bioavailable PAHs and PCBs at the disposal site, and found this to be a suitable method. In order to use POM-55 for monitoring PCBs, it was necessary to measure their POM-55/water partition coefficients, which was also presented as part of this study. Elevated turbidity (average 4.1 mg l(-1)) was observed at one side of the basin where no natural sill exists. Analysis of POM-55 at this location before and after deposition revealed that there was an increase in freely dissolved concentrations (C(W,free)) during deposition by a factor 37.5 for PAHs and a factor of 2.9 for PCBs. In addition, during deposition phenanthrene-to-anthracene aqueous concentration ratios at this location (values of 3-4) were more similar to those of the deposited sediments (approximately 2) than to those of the CAD water prior to deposition (approximately 14). This was not observed for the other locations where a natural sill exists at approximately 30 m water depth. The POM-55 equilibrium passive samplers are here shown to be useful tools for measuring and understanding the dynamics involved in the release of dissolved contaminants during sediment relocation.     

The law and economics of reclamation bonds

It is becoming a standard practice for governments to require mining operations to post reclamation bonds. Yet, there have been few theoretical treatments examining the rationale for bonding mechanisms, and even fewer empirical treatments of the effectiveness of bonding. This paper addresses some of these holes in the literature. It begins by examining the rationale underlying reclamation bonds, and discusses the strengths and weaknesses of bonding as a tool for enforcing reclamation requirements. The role of bonding mechanisms is to help enforce standards, not necessarily yield efficient outcomes, and these mechanisms are best viewed as a complement to — not a substitute for — liability rules. The paper also examines the effectiveness of bonding by drawing on evidence from hardrock mining on public lands in the western United States.     

The variability of processes involved in transgene dispersal—case studies from Brassica and related genera

Background, aim, and scope

We strive to predict consequences of genetically modified plants (GMPs) being cultivated openly in the environment, as human and animal health, biodiversity, agricultural practise and farmers’ economy could be affected. Therefore, it is unfortunate that the risk assessment of GMPs is burdened by uncertainty. One of the reasons for the uncertainty is that the GMPs are interacting with the ecosystems at the release site thereby creating variability. This variability, e.g. in gene flow, makes consequence analysis difficult. The review illustrates the great uncertainty of results from gene-flow analysis.

Main features

Many independent experiments were performed on the individual processes in gene flow. The results comprise information both from laboratory, growth chambers and field trials, and they were generated using molecular or phenotypic markers and analysis of fitness parameters. Monitoring of the extent of spontaneous introgression in natural populations was also performed. Modelling was used as an additional tool to identify key parameters in gene flow.

Results

The GM plant may affect the environment directly or indirectly by dispersal of the transgene. Magnitude of the transgene dispersal will depend on the GM crop, the agricultural practise and the environment of the release site. From case-to-case these three factors provide a variability that is reflected in widely different likelihoods of transgene dispersal and fitness of introgressed plants. In the present review, this is illustrated through a bunch of examples mostly from our own research on oilseed rape, Brassica napus. In the Brassica cases, the variability affected all five main steps in the process of gene dispersal. The modelling performed suggests that in Brassica, differences in fitness among plant genome classes could be a dominant factor in the establishment and survival of introgressed populations.

Discussion

Up to now, experimental analyses have mainly focused on studying the many individual processes of gene flow. This can be criticised, as these experiments are normally carried out in widely different environments and with different genotypes, and thus providing bits and pieces difficult to assemble. Only few gene-flow studies have been performed in natural populations and over several plant generations, though this could give a more coherent and holistic view.

Conclusion

The variability inherent in the processes of gene flow in Brassica is apparent and remedies are wished for. One possibility is to expose the study species to additional experiments and monitoring, but this is costly and will likely not cover all possible scenarios. Another remedy is modelling gene flow. Modelling is a valuable tool in identifying key factors in the gene-flow process for which more knowledge is needed, and identifying parameters and processes which are relatively insensitive to change and therefore require less attention in future collections of data. But the interdependence between models and experimental data is extensive, as models depend on experimental data for their development or testing.

Recommendations

More and more transgenic varieties are being grown worldwide harbouring genes that might potentially affect the environment (e.g. drought tolerance, salt tolerance, disease tolerance, pharmaceutical genes). This calls for a thorough risk assessment. However, in Brassica, the limited and uncertain knowledge on gene flow is an obstacle to this. Modelling of gene flow should be optimised, and modelling outputs verified in targeted field studies and at the landscape level. Last but not least, it is important to remember that transgene flow in itself is not necessarily a thread, but it is the consequences of gene flow that may jeopardise the ecosystems and the agricultural production. This emphasises the importance of consequence analysis of genetically modified plants.