Forests and water in South America

South America is experiencing rapid change in forest cover, of both native and planted forest. Forest cover loss is primarily attributable to fire, logging, and conversion of native forest to agriculture, pasture, and forest plantations, and types of change vary within and among the many diverse types of forests in South America. Major changes in forest cover and growing policy concerns underscore an urgent need for research on sustainable forest management and water ecosystem services in South America. Differences in land ownership and management objectives create trade‐offs between wood production and water ecosystem services from forests. Work is needed to quantify how forest change and management affect ecosystem services, such as wood production versus water provision. Current scientific understanding of forest management effects on water ecosystem services in South America has important limitations, including a scarcity of long‐term records and few long‐term integrated watershed studies. Industry, government, universities, and local communities should collaborate on integrated applied studies of forests and water. Data archiving and publically available data are required. The creation of national networks and a multi‐country South America network to identify and implement common water research protocols, share results, and explore their implications would promote common and well‐supported policies. Hydrologists working in South America are well placed to tackle the challenges and opportunities for collaborative research that will maintain the intrinsic values and water ecosystem services provided by South America's forests.     

Beach erosion and recovery during consecutive storms at a steep‐sloping,meso‐tidal beach

This study analyses beach morphological change during six consecutive storms acting on the meso‐tidal Faro Beach (south Portugal) between 15 December 2009 and 7 January 2010. Morphological change of the sub‐aerial beach profile was monitored through frequent topographic surveys across 11 transects. Measurements of the surf/swash zone dimensions, nearshore bar dynamics, and wave run‐up were extracted from time averaged and timestack coastal images, and wave and tidal data were obtained from offshore stations. All the information combined suggests that during consecutive storm events, the antecedent morphological state can initially be the dominant controlling factor of beach response; while the hydrodynamic forcing, and especially the tide and surge levels, become more important during the later stages of a storm period. The dataset also reveals the dynamic nature of steep‐sloping beaches, since sub‐aerial beach volume reductions up to 30 m³/m were followed by intertidal area recovery (–2 < z < 3 m) with rates reaching ~10 m³/m. However, the observed cumulative dune erosion and profile pivoting imply that storms, even of regular intensity, can have a dramatic impact when they occur in groups. Nearshore bars seemed to respond to temporal scales more related to storm sequences than to individual events. The formation of a prominent crescentic offshore bar at ~200 m from the shoreline appeared to reverse the previous offshore migration trend of the inner bar, which was gradually shifted close to the seaward swash zone boundary. The partially understood nearshore bar processes appeared to be critical for storm wave attenuation in the surf zone; and were considered mainly responsible for the poor interpretation of the observed beach behaviour on the grounds of standard, non‐dimensional, morphological parameters. Copyright © 2011 John Wiley & Sons, Ltd.     

Evidences for multiple remagnetization of Proterozoic dykes from Iguerda inlier (Anti-Atlas Belt,Southern Morocco)

No paleomagnetic data exist for Paleo-Mesoproterozoic times of the West African Craton (WAC). Therefore, paleogeographic reconstructions for such old geological times are difficult to constrain. Gaps on the sedimentary record and intense remagnetizations are the major problems that paleomagnetic studies come across. Recent geochronological results for dyke swarms that intrude several Proterozoic inliers of WAC in the Anti-Atlas Belt (southern Morocco) revealed ages between Paleoproterozoic and early Neoproterozoic, opening for the first time a window of opportunity to conduct paleomagnetic studies and tentatively infer about the paleoposition of WAC during Proterozoic. On this scope we conducted a paleomagnetic study on seven Proterozoic dykes of the Iguerda inlier. The meaning of the obtained paleomagnetic directions was evaluated by rock magnetic and mineral analyses, complemented by petrographic observations. Our samples record the presence of a complex history of remagnetization, mostly assigned to several Phanerozoic thermal/chemical events, in particular to the late stages of Pan African orogeny (s.l.), to the Late Carboniferous Variscan orogeny, and even to more recent events. The recognized remagnetization processes are related to widespread metamorphic events under greenschist facies followed by low-temperature oxidation, both responsible for the formation of new magnetic phases, like magnetite and hematite. These events obliterated the primary (magmatic) thermo-remanent magnetization and promoted multiple remagnetizations of the dykes, thermally and chemically. For only one dyke the presence of primary magnetization is possible to infer, though not to confirm, and would place WAC at an equatorial position around 1750 Ma.     

On the diurnal ranges of Sea Surface Temperature (SST) in the north Indian Ocean

This paper describes the variability in the diurnal range of SST in the north Indian Ocean using in situ measurements and tests the suitability of simple regression models in estimating the diurnal range. SST measurements obtained from 1556 drifting and 25 moored buoys were used to determine the diurnal range of SSTs. The magnitude of diurnal range of SST was highest in spring and lowest in summer monsoon. Except in spring, nearly 75–80% of the observations reported diurnal range below 0.5°C. The distributions of the magnitudes of diurnal warming across the three basins of north Indian Ocean (Arabian Sea, Bay of Bengal and Equatorial Indian Ocean) were similar except for the differences between the Arabian Sea and the other two basins during November–February (winter monsoon) and May. The magnitude of diurnal warming that depended on the location of temperature sensor below the water level varied with seasons. In spring, the magnitude of diurnal warming diminished drastically with the increase in the depth of temperature sensor. The diurnal range estimated using the drifting buoy data was higher than the diurnal range estimated using moored buoys fitted with temperature sensors at greater depths. A simple regression model based on the peak solar radiation and average wind speed was good enough to estimate the diurnal range of SST at ∼1.0 m in the north Indian Ocean during most of the seasons except under low wind-high solar radiation conditions that occur mostly during spring. The additional information on the rate of precipitation is found to be redundant for the estimation of the magnitude of diurnal warming at those depths.     

Land disposal of river and lagoon dredged sediments

The Jacarepaguá lagoon system, in the Western part of the city of Rio de Janeiro, Brazil, with an area of 8 km² receives the contributions of a number of rivers crossing largely populated and industrial areas without adequate sanitation and drainage. Since 1996 studies have been carried out to assist future dredging works and disposal of rivers and lagoons sediments. These studies included full characterization of these sediments and evaluation of the contamination of the dredged material with emphasis on the assessment of heavy metals. The present paper report these studies to assess a large dredging programme of about 3.8 million m³ of the river basins and 4 million m³ of lagoons sediments to be disposed inland.     

A geophysical survey on the archaeological site of Mugardos (NW Iberian peninsula)

Archaeological indications near Mugardos (Ferrol, NW Spain) suggest the existence of a Roman settlement. In fact, in the area were found pavements, walls with north-south and east-west orientations and some structures that endured heating. These remains are covered by soil, more than 1 m thick, and lie over schists. In order to determine the archaeological potential of the area and to delimit future excavations a geophysical survey, consisting of a joint resistivity and magnetic survey, was planned and carried out. The square array of electrodes was used and the data are discussed as apparent square array resistivity maps and azimuthal inhomogeneity ratio (AIR) maps. The magnetic survey included total field measurements using sensor heights of 0.30 and 2.30 m above the ground, so that a magnetic gradient could be computed.A combined interpretation of both resistivity and magnetic data is discussed. Later excavations have confirmed the geophysical interpretation.     

Signification structurale des anomalies gravimetriques de la partie sud du craton de Sao Francisco (Bresil)

The relationships between the cratonic area and orogenic belts of the southern part of the state of Minas Gerais (Brazil) are analyzed using data from a recent Bouguer anomaly map. The interpretation was carried out using inverse-anomaly approach and statistical analysis. The stable area is characterized by elongate anomalies trending NNE-SSW which correspond to a higher level of the basement under the upper Precambrian sedimentary cover (Bambui and Macaübas groups). They can be related to rejuvenated NNE-SSW-trending fractures.The gravity trends are either deformed or interrupted over the Brasilian fold belt where an important negative linear anomaly is present. This anomaly is produced by a thick sequence of folded sedimentary or metasedimentary terrains which can be interrupted as miogeoclinal units.The Alfenas mobile belt is characterized by a strong positive anomaly, probably associated with heavy infracrustal rock complexes (granulites, charnockites).A crustal thickening, probably associated with a pre-Brazilian continental collision, can be inferred from a long-wavelength linear negative anomaly.

Résumé

Nous présentons une carte des anomalies de Bouguer du Sud de l'Etat de Minas Gerais réalisée à partir des données déjà existantes et d'un levé récent (2000 stations) effectués dans le cadre des accords CNRS-CNP_q avec la collaboration de l'ORSTOM et du DNPM^*.Lánalyse des anomalies gravimétriques et de leur direction amène à distinguer un domaine cratonique et des zones orogéniques. L'interprétation à l'aide de l'analyse statistique et par problème inverse des anomalies allongées NNE—SSW qui caractérisent la zone stable montre la présence sous la couverture sédimentaire du Précambrian supérieur (groupes Bambui et Macaübas) de zones hautes du socle liées à de grandes fractures anciennes NNE—SSW ayant rejouées à plusieurs époques. On note également des discontinuités NW—SE importantes.Ces directions sont soit déformées, soit brutalement interrompues au niveau des plissement brésiliens auxquels est associée une anomalie négative linéaire importante. Cette anomalie peut être décomposée en une anomalie liée à un sillon de terrains sédimentaires ou métasédimentaires plissés correspondant à des dépôts miogéosynclinaux (Miogéoclinaux) et en une autre de grande longueur d'onde correspondant probablement à un épaississement crustal.Cette structure profonde peut être la conséquence d'une tectonique de collision antébrésilienne contemporaine de la mise en place tectonique des granulites et charnockites de la ceinture mobile Alfenas dont la gravimétrie permet d'apprécier l'importance.     

Oxidative stress in the mussel Mytella guyanensis from polluted mangroves on Santa Catarina Island,Brazil

Digestive glands of the mangrove mussel Mytella guyanensis, collected at one non-polluted site (site 1) and two polluted sites (sites 2 and 3), were analysed for different antioxidant defenses, lipid peroxidation and DNA damage. Thiobarbituric acid-reactive substance (TBARS) and 8-oxo-7,8-dihydro-2'-deoxyguanosine levels were enhanced at the polluted sites. With the exception of superoxide dismutase, the activities of catalase and glutathione peroxidase were also higher at the polluted sites. Greater increases were observed in glutathione reductase, glutathione S-transferase and etoxyresorufine-O-deethylase activities at the polluted sites. Conversely, reduced glutathione content was higher at the control site. Trace metal contents in mussels collected at polluted sites were increased compared to the control site, and there were strong positive correlations between TBARS and Cu and Pb contents. M. guyanensis is routinely exposed to an oxidative stress condition at both polluted sites, and considering xenobiotic bioaccumulation in bivalve molluscs, the mangrove mussel represents an excellent bioindicator for environmental monitoring studies.     

Hydrography and water masses in the southeastern Arabian Sea during March–June 2003

This paper describes the hydrographic observations in the southeastern Arabian Sea (SEAS) during two cruises carried out in March–June 2003 as part of the Arabian Sea Monsoon Experiment. The surface hydrography during March–April was dominated by the intrusion of low-salinity waters from the south; during May–June, the low-salinity waters were beginning to be replaced by the highsalinity waters from the north. There was considerable mixing at the bottom of the surface mixed layer, leading to interleaving of low-salinity and high-salinity layers. The flow paths constructed following the spatial patterns of salinity along the sections mimic those inferred from numerical models. Time-series measurements showed the presence of Persian Gulf and Red Sea Waters in the SEAS to be intermittent during both cruises: they appeared and disappeared during both the fortnight-long time series.     

BRAMS model performance for significant event involving Brazilian platform ship

Natural Hazards - After a storm displaced the P-70 platform ship located in Guanabara Bay to the coast on January 30, 2020, a numerical investigation was carried out with the BRAMS (Brazilian...