Review on toxicity testing with marine macroalgae and the need for method standardization--exemplified with copper and phenol

Toxic effects on macroalgae have been compiled. Eighty-two articles have been found in literature during 1959-2000. A total of 120 substances were investigated using 65 different macroalgae species. About one-third of the tested compounds were organic substances (33%), another third metal-organic substances (35%), and the last third were oils (14%), metals (8%), detergents (7.5%) and other inorganic chemicals (2.5%). Half of the substances were only tested once on a single species. Likewise, toxicity data has only been reported for one chemical tested on a single occasion for about half of the 65 species. Thus little is known about the toxic effects on marine macroalgae. The objectives of the previous studies undertaken varied and therefore the toxicity data was presented in numerous ways, e.g. using different exposure times, temperature, light intensity, light regime, salinity, and nutrients, which makes a direct comparison of the data difficult. This review also shows that many stages in the lifecycle of macroalgae are often more sensitive to toxic substances than other aquatic organisms. Consequently, tests using macroalgae may discover toxicity earlier, which would in turn also protect the fauna. If toxic compounds have a negative affect on the distribution and growth of structurally and functionally dominating macroalgae, there may indirectly be a large and harmful influence on the whole marine coastal ecosystem. For this reason tests on macroalgae should be included in control programs along the coasts.     

Early Holocene history of the Baltic Sea, as reflected in coastal sediments in Blekinge, southeastern Sweden

Integrated palaeoecological studies of two fiord sediment sequences in the province of Blekinge, SE Sweden, covering the time span 11,000–5000 cal BP, reveal the timing and the environment for the Ancylus Lake/Littorina Sea transition 9800–8500 cal BP. The first ingression of saline water into the Baltic Sea through the Danish Straits occurred earlier than formerly assumed. New evidence, particularly mineral magnetic and palaeobotanical analyses, demonstrate that on the general trend of the eustatically caused Littorina transgression several minor fluctuations of the water level can be identified between 8500 and 5000 cal years BP. A distinct regression phase around 8100 cal BP is correlated with the Greenland ice-core cold event dated to 8200 ice-core years BP. This is described as a regional climatic catastrophe for the Baltic Sea region. The coastal stratigraphy is compared with the offshore stratigraphy earlier studied. A tentative shore displacement curve for Early and Middle Holocene is presented.     

Estimation of regional meteorological and hydrological drought characteristics: a case study for Denmark

Information on regional drought characteristics provides critical information for adequate water resource management. This study introduces a method to calculate the probability of a specific area to be affected by a drought of a given severity and demonstrates its potential for calculating both meteorological and hydrological drought characteristics. The method is demonstrated using Denmark as a case study. The calculation procedure was applied to monthly precipitation and streamflow series separately, which were linearly transformed by the Empirical Orthogonal Functions (EOF) method. Denmark was divided into 260 grid-cells of 14×17 km, and the monthly mean and the EOF-weight coefficients were interpolated by kriging. The frequency distributions of the first two (streamflow) or three (precipitation) amplitude functions were then derived. By performing Monte Carlo simulations, amplitude functions corresponding to 1000 years of data were generated. Based on these simulated functions as well as interpolated mean and weight coefficients, long time series of precipitation and streamflow were simulated for each grid-cell. The probability distribution functions of the area covered by a drought and the drought deficit volumes were then derived and combined to produce drought severity-area-frequency curves. These curves allowed an estimation of the probability of an area of a certain extent to have a drought of a given severity, and thereby return periods could be assigned to historical drought events. A comparison of drought characteristics showed that streamflow droughts are less homogeneous over the region, less frequent and last for longer time periods than precipitation droughts.     

Studies of water quality in the Ouro Preto region,Minas Gerais,Brazil: the release of arsenic to the hydrological system

Ouro Preto county is south-east of Quadrilatero Ferrifero in the state of Minas Gerais, one of the most known Brazilian mining regions, producing gold, topaz gems and several kinds of iron and manganese ores. However, these activities are the main forms of environmental degradation, affecting the surface and groundwater which is used for public supply and are the source of heavy metal contamination, including mercury and arsenic. The mining and predatory prospecting activity (garimpos) has been carried out in Minas Gerais since the seventeenth century. At that time, hundreds of placer gold deposits were discovered on the streams in the region of Ouro Preto and Mariana, causing the first big gold rush in Brazilian history. This work presents public supply water quality data from a seasonal cycle, from September 1999 (winter) to February 2000 (summer). Chemical and physical-chemical parameters were assessed with the content of heavy metals. Leaching tests with rock samples to assess contribution to the metal content of water were carried out. Elements in the rocks have been determined and water analysis allowed the hydrogeochemical classification of water. Leaching tests demonstrate the oxidizing conditions under which the As (and the other elements) is being mobilised to the hydrological system. As and Fe are elements dispersed in the drainage of the regions. This is due to the high amounts of sulfide and to the iron formations of the region.     

Late Quaternary glacier and sea-ice history of northern Wijdefjorden,Svalbard

The deglaciation history and Holocene environmental evolution of northern Wijdefjorden, Svalbard, are reconstructed using sediment cores and acoustic data (multibeam swath bathymetry and sub-bottom profiler data). Results reveal that the fjord mouth was deglaciated prior to 14.5±0.3 cal. ka BP and deglaciation occurred stepwise. Biomarker analyses show rapid variations in water temperature and sea ice cover during the deglaciation, and cold conditions during the Younger Dryas, followed by minimum sea ice cover throughout the Early Holocene, until c. 7 cal. ka BP. Most of the glaciers in Wijdefjorden had retreated onto land by c. 7.6±0.2 cal. ka BP. Subsequently, the sea-ice extent increased and remained high throughout the last part of the Holocene. We interpret a high Late Holocene sediment accumulation rate in the northernmost core to reflect increased sediment flux to the site from the outlet of the adjacent lake Femmilsjøen, related to glacier growth in the Femmilsjøen catchment area. Furthermore, increased sea ice cover, lower water temperatures and the re-occurrence of ice-rafted debris indicate increased local glacier activity and overall cooler conditions in Wijdefjorden after c. 0.5 cal. ka BP. We summarize our findings in a conceptual model for the depositional environment in northern Wijdefjorden from the Late Weichselian until present.     

Nonsulfide and sulfide-rich zinc mineralizations in the Vazante, Ambrósia and Fagundes deposits, Minas Gerais, Brazil: Mass balance and stable isotope characteristics of the hydrothermal alterations

The Vazante Group hosts the Vazante nonsulfide zinc deposit, which comprises high-grade zinc silicate ore (ZnSiO₄), and late-diagenetic to epigenetic carbonate-hosted sulfide-rich zinc deposits (e.g. Morro Agudo, Fagundes, and Ambrósia). In the sulfide-rich deposits, hydrothermal alteration involving silicification and dolomitization was related with ground preparation of favorable zones for fluid migration (e.g. Fagundes) or with direct interaction with the metalliferous fluid (e.g. Ambrósia). At Vazante, hydrothermal alteration resulted in silicification and dolomite, siderite, jasper, hematite, and chlorite formation. These processes were accompanied by strong relative gains of SiO₂, Fe₂O_3(T), Rb, Sb, V, U, and La, which are typically associated with the nonsulfide zinc mineralization. All sulfide-rich zinc ores in the district display a similar geochemical signature suggesting a common metal source from the underlying sedimentary sequences.Oxygen and carbon isotope compositions of hydrothermally altered rocks reveal a remarkable alteration halo at the Vazante deposit, which is not a notable feature in the sulfide-rich deposits. This pattern could be attributed to fluid mixing processes involving the metalliferous fluid and channelized meteoric water, which may control the precipitation of the Vazante nonsulfide ore. Sulfide deposition resulted from fluid–rock interaction processes and mixing between the ascending metalliferous fluids and sulfur-rich tectonic brines derived from reduced shale units.     

Spatial Analysis of Airborne Geophysical Data Applied to Geological Mapping and Mineral Prospecting in the Serra Leste Region, Carajás Mineral Province, Brazil

The Serra Leste region, located in the northeast portion of Carajás Mineral Province (PA), hosts important chrome-PGE, Au–Pd–Pt, Cu–Mo–Au, iron, and manganese deposits and occurrences related to different geological settings. We present a regional prospective model with focus on PGE mineralizations based on airborne geophysics (magnetometry, gamma-ray spectrometry and time domain electromagnetometry) and geological data. Geological and geophysics data analysis indicate a plausible correspondence between areas with meta-mafic–ultramafic rocks and low values in gamma spectrometry, mainly for the thorium channel. The meta-ultramafic units of the complexes, the main host rock of the PGE mineralization, are well defined by analytic signal from the anomalous magnetic field and by the apparent conductance anomalies derived from the GEOTEM system. The combination of the derivative products with updated geological data of the Serra Leste region and PGE-Luanga deposit enable to establish a regional prospective model for PGE and the identification of new targets within the studied area.     

Magnetotactic bacteria from the human gut microbiome associated with orientation and navigation regions of the brain

Journal of Oceanology and Limnology - Magnetotactic bacteria (MTB), ubiquitous in soil and fresh and saltwater sources have been identified in the microbiome of humans and many animals. MTB...     

Be data from meltwater channels suggest that Jameson Land, east Greenland, was ice-covered during the last glacial maximum

Along the northeast Greenland continental margin, bedrock on interfjord plateaus is highly weathered, whereas rock surfaces in fjord troughs are characterized by glacial scour. Based on the intense bedrock weathering and lack of glacial deposits from the last glaciation, interfjord plateaus have long been thought to be ice-free throughout the last glacial maximum (LGM). In recent years there is growing evidence from shelf and fjord settings that the northeast Greenland continental margin was more extensively glaciated during the LGM than previously thought. However, little is still known from interfjord settings. We present cosmogenic ¹⁰Be data from meltwater channels and weathered sandstone outcrops on Jameson Land, an interfjord highland north of Scoresby Sund. The mean exposure age of samples from channel beds (n = 3) constrains on the onset of deglaciation on interior Jameson Land to 18.5 ± 1.3–21.4 ± 1.9 ka (for erosion conditions of 0–10 mm/ka, respectively). This finding adds to growing evidence that the northeast Greenland continental margin was more heavily glaciated during the LGM than previously thought.     

Mesoarchean (3.0 and 2.86 Ga) host rocks of the iron oxide–Cu–Au Bacaba deposit,Carajás Mineral Province: U–Pb geochronology and metallogenetic implications

The Bacaba iron oxide–copper–gold deposit, situated within a WNW–ESE-striking shear zone in the Carajás Domain, Carajás Mineral Province, is hosted by the Serra Dourada Granite, the Bacaba Tonalite, and crosscutting gabbro intrusions, which were intensely affected by sodic (albite–scapolite), potassic, chloritic, and hydrolytic hydrothermal alteration. This deposit is located 7 km northeast of the world-class Sossego iron oxide–copper–gold deposit and might represent a distal and deeper portion of the same or related hydrothermal system. The U–Pb laser ablation inductively coupled plasma–mass spectrometry data for zircon from a sodically altered sample of the Serra Dourada Granite yielded a 2,860±22 Ma (MSWD=11.5) age. Three samples from the Bacaba Tonalite, including one with potassic alteration and two with Cu–Au mineralization, rendered the 3,001.2±3.6 Ma (MSWD=1.8), 2,990.9±5.8 Ma (MSWD=1.9), and 3,004.6±9 Ma (MSWD=2.2) ages, respectively. The ca. 2.86 and ca. 3.0 Ga ages are interpreted as the timing of the igneous crystallization of the Serra Dourada Granite and the Bacaba Tonalite, respectively, and represent the oldest magmatic events recognized in the Carajás Domain. The Serra Dourada Granite and the Bacaba Tonalite are interpreted to greatly predate the genesis of the Bacaba deposit. A genetic link is improbable in the light of the similarities with the Sossego deposit, which is also hosted by younger ca. 2.76 Ga metavolcano-sedimentary units of the Itacaiúnas Supergroup. In this context, the iron oxide–copper–gold deposits in the southern sector of the Carajás Domain could be mainly controlled by important crustal discontinuities, such as a regional shear zone, rather than be associated with a particular rock type. These results expand the potential for occurrences of iron oxide–copper–gold deposits within the Mesoarchean basement rocks underlying the Carajás Basin, particularly those crosscut by Neoarchean shear zones.