Did reefs exist in the Proterozoic?

Analysis of the growth pattern of stromatolites and relationships of their thick carbonate bodies with host rocks are used to substantiate the lack of reefs sensu stricto, i.e., buildups notably towering above the sea bottom, in the Proterozoic.     

Oyster reefs in 1878 seascape pattern—Winslow revisited

An analysis of Winslow’s 1878 oyster survey data of Tangier Sound relates the Euclidean dimensions of oyster beds to plan-channel morphology, water depths, bottom slopes, and relief. Results show that at a regional scale the Tangier oyster beds followed a benthic seascape density pattern related to the main axial Tangier Sound Channel: its morphology, meanders, and east-west location. The north-south axis of the channel was intersected by estuarine flows into its central-eastern section, where meanders began with a tight meander around a western shoal, followed by wider second and third meanders. The location of the deepest axial depths of the channel’s bottom indicates a lateral, side-to-side switching between opposite beds, and a vertical undulation in a deepening trend to 31 m at the apex of the first meander. The depth then generally shallowed as the channel plan-form meandered southward to the sound’s entrance. Oyster beds flanked the upper sides of the channel, their generally long and narrow linear axes oriented with that of the main channel in width-to-length ratios of <0.4. Bed lengths increased from the north to the second meander, then decreased. The widest (2.3 km), longest (8.3 km), and largest (7 km²) beds laid opposite each other in the channel’s second meander. Eastern beds were generally wider and larger than western beds, and water depths along their channel sides indicate a deepening trend from 3.6 m in the north to 16.5 m in the south, unlike western beds, which reached a maximum depth of 10.4 m north of the meanders. Minimum water depths on the shoal sides of beds varied little, described by mean values of 4.6 m (SD = 1.1) for eastern beds and 3.3 m (SD = 0.56) for western beds. Analysis of profiles indicates that the deeper southeastern beds had variable relief with longer and more gradual slopes into the channel than the shallower northwestern beds with flatter bed-tops and abrupt, steeper transitions into the channel. The profiles indicate variability of a single bed in distributions of oysters and bed morphologies to make analysis at the small scale difficult. However, at the regional scale, a seascape pattern emerges that relates the distributions of oysters to the channel and shoals. This re-examination of the historic database in the context of regional tidal channel patterns provides parameters for considering the interactive role of oysters with hydrodynamics and the structural importance of oyster reefs for land and seascape processes.     

Storm‐dominated sedimentation in a protected basin fringed by coral reefs,Nara Inlet,Whitsunday Islands,Great Barrier Reef,Australia

Hydrodynamic data and samples of bed sediment were collected from Nara Inlet, a small incised embayment in the Whitsunday Islands, central Great Barrier Reef. Measured tidal currents in the inlet do not exceed 0.2 ms^–1 even at spring tides. Swell waves dominate much of the inner shelf of the Great Barrier Reef but are absent from in the inlet due to the presence of a fringing reef at the inlet mouth. On the silty sand floor of the inlet, particle size decreases towards the inlet head. Most of the bed is too coarse to be remobilised by fair‐weather wave and tides, and we predict that bedload sediment transport thresholds are only exceeded in the inlet during cyclones. The observed distribution of bed sediments is consistent with landward dispersal of sediment under storm conditions. Over 20 m of (presumably Holocene) sediments occurs in the inlet and the seismic character of the infill is consistent with the observed textural variation of the modern sediments. We infer that sediment accumulation on the floor of the inlet has been storm dominated throughout much of the Holocene.     

Late Quaternary uplift and subsidence of the west coast of Tanna,south Vanuatu,southwest Pacific: U–Th ages of raised coral reefs in the Median Sedimentary Basin

An X‐ray determinative curve, based on the parameter (Smith &; Gay, 1958) has been derived from twelve analysd plagioclases in the range An₆₂‐₈₇. The line differs from previous calibrations of against anorthite content, and it is suggested that this is due to the differing thermal histories of the materials used.

A break in slope in the determinative line at about An₇₅ may correspond to the change in lattice type from low intermediate plagioclase, to “body centred” anorthite. Heating of the plagioclases results in an increase in and the disappearance of the discontinuity.     

Bioacoustic application on fisheries management in an artificial reefs’ ecological reserve of Bohai Gulf China

Various techniques have been used in marine fishery resources assessment. Among those, acoustic techniques have high efficiency and wide adaptability, and are environment friendly. Therefore, acoustic techniques played a key/indispensable role in the field of ecosystem-based fishery management. Acoustic surveys were conducted during the wet (May) and dry (November) seasons in 2016 in the artificial reefs ecological reserve of Bohai Gulf and a nearby control region to understand the current situation of fishery resources and explore the effectiveness of underwater artificial constructions by a dual-frequency identification sonar (DIDSON) and a scientific split-beam echosounder (120 KHz, Simrad EY60). Fish densities in various seasons and regions showed significant differences and interaction, with a maximum value of 358020.34 ind/n.mile² in the artificial reefs’ region and a minimum value of 71898.35 ind/n.mile² in the control region during the wet season. Fish densities in defined parallel transects revealed a roughly southward migration trend of small-size individuals from wet season to dry season. Single echo detections in the artificial reefs region demonstrated a wider target strength (TS) range (? 60 ~ ? 30 dB vs ? 60 ~ ? 51 dB) and higher mean TS values (? 55.87 dB vs ? 58.31 dB) than the control region both in the wet and dry seasons, which indicated a more complicated and stable fish community structure in the artificial reefs area. The vertical distribution of single echo detections tracked by the echoview post-processing system showed an apparent downward gathering effect. A positive correlation between TS and water depth was discovered from Pearson correlation analysis in the artificial reefs region during the dry season.     

How precise are U-series coral ages?

U-series dating of fossil reef corals is a well established and widely applied technique in paleoclimate research. Many fossil corals, however, show evidence for post-depositional diagenetic alteration, and it is generally accepted that the accuracy of U-series coral ages is more limited due to coral diagenesis than analytical precision. In recent years, three models have been published that try to correct the effects of diagenesis and allow the calculation of model ages [Thompson W. G., Spiegelmann M. W., Goldstein S. L., and Speed R. C. (2003) An open-system model for U-series age determinations of fossil corals. Earth and Planetary Science Letters210, 365-381; Villemant B., and Feuillet N. (2003) Dating open systems by the ²³⁸U-²³⁴U-²³⁰Th method: application to Quaternary reef terraces. Earth and Planetary Science Letters210, 105-118; Scholz D., Mangini A., and Felis T. (2004) U-series dating of diagenetically altered fossil reef corals. Earth and Planetary Science Letters218, 163-178].Here, we assess the age variability of both conventional ²³⁰Th/U-dating and the three models by application to different sub-samples of individual coral specimens. The age variability, estimated as the 2σ-standard deviation on the individual ages, is compared with the errors quoted by the different methods. Our results show that the errors of conventional ²³⁰Th/U-dating as well as those of the method of Thompson et al. (2003) do not account for the true age variability. The age variability of both methods is in the range of the errors given by the models of Villemant and Feuillet (2003) and Scholz et al. (2004).Furthermore, we show that the widely used reliability criteria are not sufficient to identify all diagenetically altered corals. In contrast, analysis of different sub-samples of one coral specimen allows (i) to estimate the real age variability, (ii) to test if the assumptions of the models are fulfilled, and (iii) to investigate the diagenetic processes in more detail. Thus, this method should generally be applied to obtain more reliable U-series coral ages and errors.     

North Atlantic climate variability since AD 1350 recorded in δ 18O and skeletal density of Bermuda corals

The reconstruction of the climatic history during the past several hundred years requires a sufficient geographical coverage of combined climate proxy series. Especially in order to identify causal connections between the atmosphere and the ocean, inclusion of marine records into composite climate time series is of fundamental importance. We present two skeletal δ ¹⁸O chronologies of coral skeletons of Diploria labyrinthiformis from Bermuda fore-reef sites covering periods in the nineteenth and twentieth centuries and compare them with instrumental temperature data. Both time series are demonstrated to display sea-surface temperature (SST) variability on inter-annual to decadal time scales. On the basis of a specific modern δ ¹⁸O vs instrumental SST calibration we reconstruct a time series of SST anomalies between AD 1350 and 1630 covering periods during the Little Ice Age. The application of the coral δ ¹⁸O vs temperature relationship leads to estimates of past SST variability which are comparable to the magnitude of modern variations. Parallel to δ ¹⁸O chronologies we present time series of skeletal bulk density. Coral δ ¹⁸O and skeletal density reveal a strong similarity during Little Ice Age, confirming the reliability of both proxy climate indicators. The past coral records, presented in this study, share features with a previously published climate proxy record from Bermuda and a composite time series of reconstructed Northern Hemisphere summer temperatures. The coral proxy data presented here represent a valuable contribution to elucidate northern Atlantic subtropical climate variation during the past several centuries. Received: 9 November 1998 / Accepted: 13 September 1999     

Stable nitrogen and carbon isotope (δN and δC) variability in shallow tropical Pacific soft coral and black coral taxa and implications for paleoceanographic reconstructions

Soft corals and black corals are useful proxy tools for paleoceanographic reconstructions. However, most work has focused on deep-water taxa and few studies have used these corals as proxy organisms in shallow water (<200 m). To facilitate the use of stable nitrogen and carbon isotope (δ¹⁵N and δ¹³C) records from shallow-water soft coral and black coral taxa for paleoceanographic reconstructions, quantification of the inherent variability in skeletal isotope values between sites, across depth, and among taxa is needed. Here, skeletal δ¹⁵N and δ¹³C values were measured in multiple colonies from eleven genera of soft corals and two genera of black corals from across a depth transect (5-105 m) at two sites in Palau located in the tropical western Pacific Ocean. Overall, no difference in skeletal δ¹⁵N and δ¹³C values between sites was present. Skeletal δ¹⁵N values significantly increased and δ¹³C values decreased with depth. This is consistent with changes in isotope values of suspended particulate organic matter (POM) across the photic zone, suggesting that the primary food source to these corals is suspended POM and that the stable isotopic composition of POM controls the skeletal isotopic composition of these corals. Thus, to compare the isotope records of corals collected across a depth range in the photic zone, first order depth corrections of −0.013‰ m⁻¹ and +0.023‰ m⁻¹ are recommended for δ¹⁵N and δ¹³C, respectively. Average depth-corrected δ¹⁵N values were similar between black corals and soft corals, indicating that corals in these orders feed at a similar trophic level. In contrast, average depth-corrected δ¹³C values of black corals were significantly lower than that of soft corals, potentially resulting from metabolic processes associated with differing skeletal compositions among the orders (i.e., gorgonin vs. chitin based). Thus, a correction of +1.0‰ is recommended for black corals when comparing their δ¹³C-based proxy records to soft corals. After correcting for both the depth and order effects, variability in δ¹⁵N values among corals within each genera was low (standard deviation (SD) of the mean <±0.5‰), with the exception of Acanthorgorgia. The calculated SD of <±0.5‰ provides a first order guideline for the amount of variability that could be expected in a δ¹⁵N record, and suggests that these corals may be useful for δ¹⁵N-based paleoceanographic reconstructions. Variability in δ¹³C values among corals within genera was also low (standard deviation of the mean <±0.5‰) with the exception of Rhipidipathes and Villogorgia. Similar to δ¹⁵N, records from the genera studied here with the exception of Rhipidipathes and Villogorgia may be useful for δ¹³C-based paleoceanographic reconstructions. Overall, using the recommendations developed here, stable isotope records from multiple sites, depths and taxa of these corals can be more rigorously compared.     

Phytoremediation assessment of native plants growing on Pb–Zn mine site in Northern Tunisia

Pollution by heavy metals presents an environmental concern, and their toxicity threats soil, water, animals and human health. Phytoremediation can be used as a solution to remediate contaminated soils. The aim of this study was to identify native plants collected from tailings: material of Pb–Zn mine sites of Fedj Lahdoum and Jebel Ressas (two abandoned mines located, respectively, in the northwest of Tunisia and in the south of Tunis City). The tolerance of plant to heavy metals (lead, zinc and cadmium) is evaluated. Soil samples were collected and analyzed for Pb, Zn and Cd concentration. The total soil Pb, Zn and Cd are, respectively, reached 6132 mg kg^?1, 11,052 mg kg^?1 and it doesn’t exceed 479 mg kg^?1 for Cd. The highest content of Zn in plants was detected in shoots of Rumex bucephalophorus (1048 mg kg^?1), and the highest Pb concentration was detected in roots of Chrysopogon zizanioides (381 mg kg^?1), while for Cd Silene colorata it accumulated the highest content in roots (51 mg kg^?1). From all plants, only 12 have a translocation factor for Pb which is higher than one. Among all plants, only 17 have a translocation factor that is higher than one for Zn, while for Cd only 13 plants indicate TF > 1. As for the biological absorption coefficient, all samples indicate a rate which is lower than one. These plants can be primarily hyper accumulators and useful in remediation of lead- and zinc-contaminated soils after further biochemistry researches in mechanism of accumulation and translocation of heavy metals in plants.     

Trajectories of unstably growing cracks in mixed mode I–II loading of marble beams

Summary The knowledge of the stress field under which a crack in an engineering material or a rock is propagated and the trajectory it follows during its growth, is very important. In this paper the prediction of the crack growth trajectory and its initial angle _c under mixed mode I–II loading is studied experimentally in marble beams. The three point bending test is used, together with the strain energy density theory (SED) of Linear Elastic Fracture Mechanics (LEFM). Experimental results are compared with theoretical predictions. The experimental results showed that: marble behaved as a brittle material; crack propagation was unstable and its trajectory followed, mainly, the grain boundaries; the prediction of the critical angle _c and the first part of the trajectory, from the crack tip up to the point G, where a global minimum of the strain energy density is reached, can satisfactorily be made with the SED theory. Beyond point G, the initial stress field is different, and for application of the SED theory, the boundary conditions need redefinition.     

Mercury in river sediments, floodplains and plants growing thereon in the drainage area of the Idrija mine, Slovenia

Half a millennium mercury production at Idrija is reflected in increased mercury contents in all environmental segments. The bulk of roasting residues from the middle of the 19th century to 1977 was discharged directly into the Idrijca River, and the material was carried at high waters to the Soca River and farther into the Adriatic Sea. It has been estimated that 45500 tons of mercury were emitted into the environment during the operating period of the mine, which ceased production in 1994. In the lower reaches of the Idrijca the riverine deposits with high mercury contents have been, and will be in the future a source of mercury polluted sediment. Stream sediments were monitored at the same locations along the Idrijca and Soca rivers （70 kin） every 5 years since 1991 （1991-2005）. Grain size distribution was determined by dry sieving and fractions for geochemical analysis were prepared （〈0.04 and 〈0.125 mm）. Soils on river terraces were sampled at 5 localities in the lower course of Idrijca. At two locations of the terrace profiles the samples of averaged meadow forage and plantain （Plantago lanceolata） were collected within a 50-meters radius. We found that there was no decrease in mercury concentration in active river sediments during the last 20 years. Upstream from the Idrija Town the mercury concentrations in active river sediments vary from 1 to 10 mg/kg （average 3.3 mg/kg）. From Idrija to Spodnja Idrija the mercury concentrations increase extremely and vary greatly （32-4,121 mg/kg, the average is 734 mg/kg）. From Spodnja ldrija to the Idrijca-Soca confluence is the average 218 mg/kg, and 57 mg/kg downstream in the Soca River sediments.     

The potential origins and palaeoenvironmental implications of high temporal resolution δO heterogeneity in coral skeletons

δ¹⁸O was determined at high spatial resolution (beam diameter ∼30 μm) by secondary ion mass spectrometry (SIMS) across 1-2 year sections of 2 modern Porites lobata coral skeletons from Hawaii. We observe large (>2‰) cyclical δ¹⁸O variations that typically cover skeletal distances equivalent to periods of ∼20-30 days. These variations do not reflect seawater temperature or composition and we conclude that skeletal δ¹⁸O is principally controlled by other processes. Calcification site pH in one coral record was estimated from previous SIMS measurements of skeletal δ¹¹B. We model predicted skeletal δ¹⁸O as a function of calcification site pH, DIC residence time at the site and DIC source (reflecting the inputs of seawater and molecular CO₂ to the site). We assume that oxygen isotopic equilibration proceeds at the rates observed in seawater and that only the aqueous carbonate ion is incorporated into the precipitating aragonite. We reproduce successfully the observed skeletal δ¹⁸O range by assuming that DIC is rapidly utilised at the calcification site (within 1 h) and that ∼80% of the skeletal carbonate is derived from seawater. If carbonic anhydrase catalyses the reversible hydration of CO₂ at the calcification site, then oxygen isotopic equilibration times may be substantially reduced and a larger proportion of the skeletal carbonate could be derived from molecular CO₂. Seasonal skeletal δ¹⁸O variations are most pronounced in the skeleton deposited from late autumn to winter (and coincide with the high density skeletal bands) and are dampened in skeleton deposited from spring to summer. We observed no annual pattern in sea surface temperature or photosynthetically active radiation variability which could potentially correlate with the coral δ¹⁸O. At present we are unable to resolve an environmental cue to drive seasonal patterns of short term skeletal δ¹⁸O heterogeneity.     

New Viséan rugose corals from west slopes of Urals

Two new species of Early Carboniferous colonial Rugosa discovered in collections from the western slopes of the Central Urals provide additional data on geographic ranges of Aulina and Paralithostrotion. Aulina kosvensis is the first fasciculate species of the genus to be described from the U. S. S. R. It was found in the Upper Viséan Ladeininskii horizon. Paralithostrotion talkaense is described on material from the Ladeininskii and Ust'sarbaiskii horizons and considered to be of upper Viséan(?) and Namurian age. In connection with this investigation, the type material of Paralithostrotion jermolaevi Gorskiy and Tschernowiphyllum podboriense Dobrolyubova, which are the type species of the two genera, was restudied and found to be congeneric. Tschernowiphyllum Dobrolyubova, 1958, is therefore a junior synonym of Paralithostrotion Gorskiy, 1938. As revised, Paralithostrotion is considered to be a doubtful lithostrotionid lacking a genuine columella and having tabulae that are concave to horizontal. The corallum is fasciculate with connecting processes, which open into a corallite at one end but at the other terminate blindly against a neighboring corallite. Two opposing septa are longer than the other majors and generally overlap in the axial region. The dissepimentarium is narrow and may not be developed. - H. Duncan.     

Barite and barium in sediments and coral skeletons around the hydrocarbon exploration drilling site in the Træna Deep,Norwegian Sea

Barite and barium concentrations in bottom sediments and coral skeletons from the vicinity of the hydrocarbon exploration well drilled in 1992–1993 in the Træna Deep, Norwegian Sea have been studied to assess the spreading of the drilling mud and related ecological effects on Lophelia petrusa coral reefs. Sand size barite crystals derived from the drilling mud and elevated Ba concentrations in surface (0–2 cm) sediments were found up to 4 km from the exploration drilling site. ²¹⁰Pb-dating results on sediment cores indicate that Ba-rich surface intervals (0–2 cm) record ca. 20 years of sedimentation history, and connect Ba enrichment with exploration drilling. The geographic distribution of Ba contents in sediments allowed the reconstruction of the drilling mud dispersal pattern showing transport eastward from the drilling site, consistent with the prevailing current directions. The presence of relatively coarse-grained sediments and barite crystals trapped in coral polyps, ca. 500 m down current from the drilling site, reflects the elevated turbulence and sediment supply during the drilling activity. This elevated sediment dispersion likely placed a stress upon the coral reefs, but due to strong currents that effectively dilute episodic drilling waste and sediment discharges, the damage does not appear significant.     

Monitoring climate variability over the past 116 years in coral oxygen isotopes from Ningaloo Reef, Western Australia

 116-year record of coral skeletal δ¹⁸O is presented from a colony of Porites lutea from Ningaloo Reef, western Australia. Interannual variability of sea-surface temperatures (SST) inferred from skeletal δ¹⁸O is dominated by a 9.5-year period, and may constitute a characteristic signal of the Leeuwin Current. On long-terms coral skeletal δ¹⁸O indicates a near-continuous increase of SST at Ningaloo Reef over one century. The skeletal δ¹⁸O time series was checked for the presence of seasonal cooling events resulting from major volcanic eruptions. An ∼1  °C cooling is evident following the eruption of Pinatubo in 1991, which reproduces the results of previous investigations. However, only weak or no signals can be related to the eruptions of Krakatau (1883) and Agung (1963). Received: 9 November 1998 / Accepted: 12 April 1999     

Lead accumulation and phytostabilization potential of dominant plant species growing in a lead–zinc mine tailing

Screening out plants that are hyper-tolerant to certain heavy metals plays a fundamental role in remediation of mine tailing. In this study, nine dominant plant species growing on lead–zinc mine tailing and their corresponding non-mining ecotypes were investigated for their potential phytostabilization of lead. Lead concentration in roots of these plants was higher than in shoots, and the highest concentrations of lead were found in Athyrium wardii: 15542 and 10720 mg kg⁻¹ in the early growth stage (May) and vigorous growth stage (August) respectively, which were 426 and 455 times higher than those of the non-mining ecotypes. Because of poor lead translocation ability, lead accumulation in roots reached as high as 42 mg per plant. Available lead in the rhizosphere soils of A. wardii was 310 mg kg⁻¹, which was 17 times higher than that of the non-rhizosphere soil. Lead concentrations of roots for the nine mining ecotypes were positively correlated with available lead in the rhizosphere soils, whereas a negative correlation was observed in the non-mining ecotypes. These results suggest that A. wardii was the most promising candidate among the tested species for lead accumulation in roots, and it could be used for phytostabilization in lead polluted soils.     

Coral- and oyster-microbialite patch reefs in the aftermath of the Triassic–Jurassic biotic crisis (Sinemurian,Southeast France)

The end of the Triassic and the Early Jurassic are intervals characterised by profound biotic and environmental changes, accompanied by dramatic decreases in marine fauna diversity. Corals were strongly affected and assemblages underwent a severe reduction; compared with those of the Upper Triassic, the Early Jurassic is traditionally defined as holding a “reef gap”. A Sinemurian coral-microbialites patch reef, located in southern France in the Hérault department (Le Perthus locality), is here described. This bioconstruction developed in a shallow mixed siliciclastic-carbonate inner ramp setting. The reef volume is composed of up to 70% of an intercoral facies mostly microbialites, with subordinated sediments (approximately 20–30% of the intercoral facies). Therefore, the patch reef can be defined as a coral-microbialite bioconstruction, in which microbialites were the main framebuilders. The coral assemblage has low diversity and is dominated by massive to branching colonies of Chondrocoenia clavellata. This highlights the reef diversity after the T/J boundary crisis. The Le Perthus patch reef could have acted as an edge for the dominant currents and probably induced reductions in hydrodynamic energy and sedimentation on one of its sides. Consequently, it could have triggered the growth of small lateral bioconstructions, composed of oysters and microbialites, uniquely on one of its sides. The evolution of the facies shows that the Le Perthus patch reef grew in a shallowing-upward setting accompanied by an increase in siliciclastic inputs. The rate of bioerosion and the faunal assemblage suggest that the bioconstructions could have been developed in a mesotrophic environment.     

A perusal on the correlation of pesticide application on tobacco growing in the districts of NWFP-Pakistan and cancers incidence

Tobacco is an important cash crop in Pakistan. It is a sensitive plant prone to many bacterial, fungal, and viral diseases. It is also attacked by several species of worms, beetles and moths. Therefore high levels of pesticides are used to grow tobacco. The obvious benefits from the use of the pesticides are so spectacular that some of the problems associated with their use are not recognized. However, many of these pesticides are highly toxic and have impacts on tobacco workers, especially occupational exposures, which are the direct victims of pesticides poisoning. The victims include many children, pregnant women and elders who all participate in tobacco production. Pesticides either cause or exacerbate a number of illnesses in farmers and farm workers when they are exposed to them. So, occupational exposure is probably one of the most important impacts on tobacco farmers, since they and their families are exposed constantly to a large amount of pesticides. This exposure can lead to many serious problems. No study has been done to identify the effects of tobacco pesticides on human health especially on farmers health in Pakistan. The objective of this paper is to establish a correlation of pesticides application on tobacco crop with cancer incidence in the tobacco growing districts of NWFP- Pakistan.     

Metal dispersion in groundwater in an area with natural and processed black shale – Nationwide perspective and comparison with acid sulfate soils

Black shale is often rich in sulfides and trace elements, and is thus a potential environmental threat in a manner similar to acid sulfate soils and active or abandoned sulfide mines. This study aims at characterising how exposed and processed (mined and burnt) black shale (alum shale) in Degerhamn, SE Sweden, affects the chemistry (Al, As, Ba, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Mo, Ni, K, Si, Na, Sr, S, U, V and Zn) of the groundwater. There were large variations in groundwater chemistry between nearby sampling points, while the temporal variations generally were small. Acidic groundwater (around pH 4), found in deposits of burnt and carbonate-poor shale where the conditions for sulfide oxidation were favourable, was strongly elevated in Al, U and several chalcophilic metals (Cd, Co, Cu, Ni and Zn). Cadmium and U were also, together with Mo, abundant in many of the near-neutral waters, both in the non-mined black shale bedrock and in the deposits of burnt shale. An extrapolation to a national level suggests that the dispersion of Ni from naturally occurring black shale is similar to that from anthropogenic point sources, while for Cd and As it is assessed to be approximately one tenth of that from point sources. The processed shale was, however, a much larger source of metals than the black shale bedrock itself, showing this material’s potential as a massive supplier of metals to the aquatic environment. A comparison of waters in contact with the processed Cambrian–Ordovician black shale in Degerhamn and acid sulfate soils of the region shows that these two sulfide-bearing materials, in many respects very different, delivers basically the same suite of trace elements to the aquatic environment. This has implications for environmental planning and protection in areas where these types of materials exist.     

Knowledge,influence, and firm-level change: A geographic analysis of board membership associated with Canada’s growing and declining businesses

Clarification of the factors that drive business expansion and contraction is among the most important topics that can be addressed by research in economic geography and related disciplines. This study analyzes the development of Canadian business by examining the connection between firm-level growth and decline and elite knowledge and influence connections that Canadian businesses use to link themselves to other corporations and cities nationally and globally. The research focuses on the inter-firm and inter-city linkages embodied in the boards of directors of Canada’s leading corporations. Corporate directorships have an important geographic dimension, as firms invite people from a variety of places and backgrounds to serve on their boards. This study finds that board member selection practices among Canadian firms can be linked directly to business growth and decline. Benchmarking board composition against firm expansion and decline in terms of inflation-adjusted annual revenue change over the 1991–2006 period, this study shows that growing Canadian firms are associated with directors from a much broader range of national and international cities than firms that experienced decline over the same period. Firm growth in Canada thus appears to be related to boards encompassing diverse members from national and international locations, while firm decline appears to be associated with boards including more local and regional members. The conclusion interprets the implications of board member diversity and suggests that broadly-based boards can play a role in encouraging firm growth through access to elite knowledge and influence networks.