The tower of Babel: Different perceptions and controversies on change and status of North Sea fish stocks in multi-stakeholder settings

Fishermen, scientists, national policy makers, and staff of environmental NGOs (ENGOs) hold different perceptions about temporal patterns in fish stocks. Perception differences are problematic in multi-stakeholder settings, because they elicit controversies and unbalanced disputes. These hinder effective participation, a prerequisite for ‘good governance’ and effective management of sustainable fisheries. This study shows that perceptions of change (‘does the stock increase or decrease?’) and of current status of a fish stock (‘is it doing well or not?’) are influenced by the capturing and processing of information, rather than by interests alone. We focused on the Dutch North Sea fishery on plaice and sole and examined (1) availability and accessibility of information on temporal patterns of these stocks and (2) perception differences between all parties. A first explanation for these differences is the use of different parameters as a measure for stock size. Fishermen focus on catch rates or catch-per-unit-effort (relative stock size), whereas scientists, policy makers, and ENGO-staff mainly use scientific assessments of spawning stock biomass (absolute stock size). Between-group perception differences are further explained by spatial aggregation levels of information, lengths of time series evaluated, and by modes of comparison to qualify the current status of fish stocks. Awareness of information differences and the development of shared information use and processing may release some of the tensions in multi-stakeholder settings debating fisheries management. However, comprehension problems amongst all parties on how spawning stock biomass is reconstructed and how it relates to catch rates in the fishery may pose an enduring barrier.     

Colloidal Control on the Distribution of Rare Earth Elements in Shallow Groundwaters

A 7-year monitoring period of rare earth element (REE) concentrations and REE pattern shapes was carried out in well water samples from a 450 m long transect setup in the Kervidy/Coët-Dan experimental catchment, France. The new dataset confirms systematic, topography-related REE signatures and REE concentrations variability but challenges the validity of a groundwater mixing hypothesis. Most likely, this is due to REE preferential adsorption upon mixing. However, the coupled mixing–adsorption mechanism still fails to explain the strong spatial variation in negative Ce anomaly amplitude. A third mechanism—namely, the input into the aquifer of REE-rich, Ce anomaly free, organic colloids—is required to account for this variation. Ultrafiltration results and speciation calculations made using Model VI agree with this interpretation. Indeed, the data reveal that Ce anomaly amplitude downslope decrease corresponds to REE speciation change, downhill groundwaters REE being mainly bound to organic colloids. Water table depth monitoring shows that the colloid source is located in the uppermost, organic-rich soil horizons, and that the colloid input occurs mainly when water table rises in response to rainfall events. It appears that the colloids amount that reaches groundwater increases downhill as the distance between soil organic-rich horizons and water table decreases. Topography is, therefore, the ultimate key factor that controls Ce anomaly spatial variability in these shallow groundwaters. Finally, the <0.2 μm REE fraction ultimately comes from two solid sources in these groundwaters: one located in the deep basement schist; another located in the upper, organic-rich soil horizon.     

Obfuscating spatial point tracks with simulated crowding

ABSTRACT

Spatial point tracks are of concern for an increasing number of analysts studying spatial behaviour patterns and environmental effects. Take an epidemiologist studying the behaviour of cyclists and how their health is affected by the city’s air quality. The accuracy of such analyses critically depends on the positional accuracy of the tracked points. This poses a serious privacy risk. Tracks easily reveal a person’s identity since the places visited function as fingerprints. Current obfuscation-based privacy protection methods, however, mostly rely on point quality reduction, such as spatial cloaking, grid masking or random noise, and thus render an obfuscated track less useful for exposure assessment. We introduce simulated crowding as a point quality preserving obfuscation principle that is based on adding fake points. We suggest two crowding strategies based on extending and masking a track to defend against inference attacks. We test them across various attack strategies and compare them to state-of-the-art obfuscation techniques both in terms of information loss and attack resilience. Results indicate that simulated crowding provides high resilience against home attacks under constantly low information loss.     

Geochemical and stratigraphic evidence of environmental change at Lynch's Crater, Queensland, Australia

This is one of the first applications of geochemical proxies to define changes in vegetation, hydrology and atmospheric dust influence on a peat deposit in the southern hemisphere. A 6.6 m deep peat record from Lynch's Crater in NE-Queensland, Australia, provides a sensitive  5000 to 30,000 cal years BP archive of environmental change. The deposit consists of 1.5 m of ombrotrophic peat underlain by a minerotrophic peat. Within the minerotrophic section, sponge spicules and diatom fragments offer evidence of prolonged flooding of the peat environment resulting in several layers containing (up to 50%) high inorganic material. The Ca and Mg data display episodes of enhanced dust influx and nutrient recycling and support previous palynological studies that show a Pleistocene to Holocene switch from sclerophyll woodlands to rainforest vegetation.     

Post‐excavation deterioration of the Copney Bronze Age Stone Circle Complex: A geomorphological perspective

Post‐excavation deterioration of stones from under blanket peat at the Copney Bronze Age Stone Circle Complex in County Tyrone, Northern Ireland, proceeded through widespread scaling, flaking, and splitting of stones. Investigation showed that prior to burial the porphyritic stones already possessed a complex legacy of geological weaknesses derived from hydrothermal alteration and tectonic deformation. Analysis indicated that significant alteration occurred during approximately 2000 years of burial under acidic peat cover, with development of a secondary porosity, alteration of primary minerals, and the opening of preexisting lines of weakness within the stones. Burial under peat also resulted in “bleaching” the stones so that they appeared white in color following excavation. These alterations during burial left the stones in a significantly weakened state and particularly susceptible to the effects of subaerial weathering processes. Data underline the potential fragility of excavated stonework and highlight the need to plan for its aftercare before complete excavation is undertaken. © 2010 Wiley Periodicals, Inc.     

Simulating soil‐water movement under a hedgerow surrounding a bottomland reveals the importance of transpiration in water balance

The objective of this study was to quantify components of the water balance related to root‐water uptake in the soil below a hedgerow. At this local scale, a two‐dimensional (2D) flow domain in the x–z plane 6 m long and 1·55 m deep was considered. An attempt was made to estimate transpiration using a simulation model. The SWMS‐2D model was modified and used to simulate temporally and spatially heterogeneous boundary conditions. A function with a variable spatial distribution of root‐water uptake was considered, and model calibration was performed by adjusting this root‐water uptake distribution. Observed data from a previous field study were compared against model predictions. During the validation step, satisfactory agreement was obtained, as the difference between observed and modelled pressure head values was less than 50 cm for 80% of the study data. Hedge transpiration capacity is a significant component of soil‐water balance in the summer, when predicted transpiration reaches about 5·6 mm day^?1. One of the most important findings is that hedge transpiration is nearly twice that of a forest canopy. In addition, soil‐water content is significantly different whether downslope or upslope depending on the root‐water uptake. The high transpiration rate was mainly due to the presence of a shallow water table below the hedgerow trees. Soil‐water content was not a limiting factor for transpiration in this context, as it could be in one with a much deeper water table. Hedgerow tree transpiration exerts a strong impact not only on water content within the vadose zone but also on the water‐table profile along the transect. Results obtained at the local scale reveal that the global impact of hedges at the catchment scale has been underestimated in the past. Transpiration rate exerts a major influence on water balance at both the seasonal and annual scales for watersheds with a dense network of hedgerows. Copyright © 2007 John Wiley & Sons, Ltd.     

Environmental setting of deep-water oysters in the Bay of Biscay

We report the northernmost and deepest known occurrence of deep-water pycnodontine oysters, based on two surveys along the French Atlantic continental margin to the La Chapelle continental slope (2006) and the Guilvinec Canyon (2008). The combined use of multibeam bathymetry, seismic profiling, CTD casts and a remotely operated vehicle (ROV) made it possible to describe the physical habitat and to assess the oceanographic control for the recently described species Neopycnodonte zibrowii. These oysters have been observed in vivo in depths from 540 to 846 m, colonizing overhanging banks or escarpments protruding from steep canyon flanks. Especially in the Bay of Biscay, such physical habitats may only be observed within canyons, where they are created by both long-term turbiditic and contouritic processes. Frequent observations of sand ripples on the seabed indicate the presence of a steady, but enhanced bottom current of about 40 cm/s. The occurrence of oysters also coincides with the interface between the Eastern North Atlantic Water and the Mediterranean Outflow Water. A combination of this water mass mixing, internal tide generation and a strong primary surface productivity may generate an enhanced nutrient flux, which is funnelled through the canyon. When the ideal environmental conditions are met, up to 100 individuals per m² may be observed. These deep-water oysters require a vertical habitat, which is often incompatible with the requirements of other sessile organisms, and are only sparsely distributed along the continental margins. The discovery of these giant oyster banks illustrates the rich biodiversity of deep-sea canyons and their underestimation as true ecosystem hotspots.