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.     

Biogenic emissions from Pinus halepensis: a typical species of the Mediterranean area

Volatile organic compounds (VOCs) emissions by vegetation present in the Mediterranean area are not well known. They may contribute with anthropogenic VOC emissions to the tropospheric ozone formation that reaches important level in the European Mediterranean region. The present work, carried out as part of the European ESCOMPTE project «fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions», adds a new contribution to the inventory of the main natural hydrocarbons sources likely to participate in the ozone production. The corresponding measurement campaign was conducted in La Barben, a site close to Marseilles (France), with the aim to quantify the terpenic emission pattern and the behaviour of Pinus halepensis, an important Mediterranean species slightly studied.The determination of biogenic emissions from P. halepensis was done by the enclosure of an intact branch in a Teflon cuvette. Main emitted monoterpenes were β trans-ocimene and linalool. The total monoterpenic emission rates thus recorded were found to reach maximum values around 30 μg g_{dry weight}⁻¹ h⁻¹. The normalized emission rates calculated at 30 °C and 1000 μmol m⁻² s⁻¹ with Guenther's algorithm was 14.76, 8.65 and 4.05 μg g_{dry weight}⁻¹ h⁻¹, respectively, for the total monoterpenes, β trans-ocimene and linalool.     

Changes in diatom, pollen, and chironomid assemblages in response to a recent volcanic event in Lake Galletué (Chilean Andes)

Several lakes in Chile are near important volcanic areas where eruption impacts can limit the quality of lacustrine sediments for reconstructing past environmental changes. In this study, we report changes in diatoms, pollen, and chironomids assemblages after a tephra deposition in Lake Galletué (Chilean Andes). A sediment core obtained from Lake Galletué (40 m water depth) was sliced in 1 cm intervals and subsamples were taken to analyze each proxy. ²¹⁰Pb and ¹³⁷Cs activities were measured to obtain the geochronology and mineralogical analyses were performed to determine the mineral composition of the tephra. Diatom species composition and productivity were modified when the lake received the tephra; Aulacoseira granulata decreased and was later replaced by Cyclotella af. glomerata. After the tephra input, Aulacoseira granulata abundance increased to pre-disturbance levels and Cyclotella af. glomerata decreased. These changes seem to suggest a momentary increase in lake nutrient levels after the tephra deposition. Chironomid assemblages also decreased in head capsules just after the tephra deposition, but the most important change was the replacement of Ablabesmyia by Parakiefferiella, probably due to the sedimentological changes produced by the input of coarse tephra grains. Furthermore, unlike other studies, chironomid assemblages in Lake Galletué did not show a decrease drastically in diversity within the tephra layer. The pollen analysis indicated that, prior to the volcanic event, the vegetal community was dominated by Nothofagus sp., Araucaria araucana, and Blechnum sp.-type. After the tephra deposition, the same taxa are dominant, indicating that the volcanic event seems not produce changes in the vegetation. Nevertheless, within the tephra layer it is possible to see an increase in Poaceae, which represent – due to the percolation process – the effect of eruption on the vegetation. According to our results, diatoms were the most sensitive proxy for describing the changes produced by tephra deposition into the aquatic ecosystem and, despite the noticeable changes in its sedimentological properties; the lake seems to have a high resilience capacity, allowing it to return to pre-tephra input conditions.     

Effects on runoff caused by changes in land cover in a Brazilian southeast basin: evaluation by HEC-HMS and HEC-GEOHMS

The Southeast Region of Brazil has undergone major changes in land cover, especially after the eighteenth century. It is currently the most populous region of the country, highly urbanized, with a high degree of industrial and agricultural development. Extensive areas of native vegetation have been replaced by pastures, crops and urban areas, which have increased runoff, causing environmental, economic and social problems related to flooding. The objective of this study was to analyze effects of land cover changes in a basin with rural and urban characteristics on the flow of its main river. Hydrological data, orbital images, soils and topographical maps were used for this purpose. Based on the land cover maps for the years of 1989, 2001 and 2015, and on the hydrological modeling performed using the Hec-HMS 4.1 software, scenarios were simulated and showed that the land cover changes in this basin significantly affect the flow behavior of the main river. The simulated runoff was calibrated using the data observed in the field during 2001, and validation was performed using data from 1989. After the calibration and validation processes, a scenario was simulated where the rainiest month of the whole series measured by the rainfall station (during December 1989) acted on the land cover of 2015. There was an increase in pasture areas and impermeable spaces in the basin, which caused a decrease in infiltration and an increase in surface runoff, and also an increase in the flow peaks and a reduction in the time of concentration. The hydrological modeling was satisfactory, since the uncertainties related to the simulation were low.     

Synoptic conditions and potential causes of the extreme heavy rainfall event of January 2009 over Mindanao Island,Philippines

Natural Hazards - This study investigates the synoptic conditions that led to the heavy rainfall/flood (HRF) event in Mindanao Island, Philippines (122??127°E;...     

Magmatic source and metamorphic grade of metavolcanic rocks from the Granjeno Schist: was northeastern Mexico a part of Pangaea?

The geochemistry of the metavolcanic rocks from the Granjeno Schist in northeastern Mexico indicates an origin in different tectonic environments: mid‐ocean ridge and ocean island. High ratios of Hf/Th and Th/Nb (4.4–14 and 0.08–0.15), low ratios of LaN/YbN and LaN/SmN (0.74–1.7 and 0.60–1.4) and depleted LREE patterns in metabasalt display mid‐ocean ridge characteristics. In contrast, the pattern of trace‐element ratios and REEs in metabasalt and metapillow lava 60 km to the west indicates a magma source with ocean‐island basalt characteristics. Both areas were metamorphosed during the Late Carboniferous (300 ± 4 Ma). Estimated metamorphic conditions deduced from white mica and chlorite compositions, distinguish greenschist facies (350 °C and 4 kbar) for the mid‐ocean ridge basalt, and prehnite–pumpellyite facies (250 °C and 2.5 kbar) for the ocean‐island‐type basalt. This metamorphism took place at an active continental margin during Pennsylvanian time. Our new tectonic model, which differs from earlier models, suggests that the origin of the Granjeno Schist is related to a subduction zone located at the western margin of Pangaea, active after Laurentia–Gondwana collision. Copyright © 2015 John Wiley & Sons, Ltd.     

Improvement in PWV estimation from GPS due to the absolute calibration of antenna phase center variations

Climatology of column-integrated atmospheric water vapor over Spain has been carried out by means of three techniques: soundings, sun photometers and GPS receivers. Comparing data from stations equipped with more than one of these instruments, we found that a large discontinuity occurred on November 6, 2006, in the differences between the data series from GPS receivers and those from the other two techniques. Prior to that date, the GPS data indicate a wet bias of 2–3 mm for all stations when compared with sounding or photometer data, whereas after that date this bias practically reduces to zero. The root mean square error also decreases about half of its value. On November 6, 2006, the International GNSS Service adopted an absolute calibration model for the antennas of the GPS satellites and receivers instead of the relative one. This change is expected to be an improvement, increasing the accuracy of station position determination and consequently benefiting post-processing products such as zenith total delay from which the atmospheric water vapor content is calculated.     

Studies of multiple stellar systems – III. Modulation of orbital elements in the triple-lined system HD 109648

The triple-lined spectroscopic triple system HD 109648 has one of the shortest periods known for the outer orbit in a late-type triple, 120.5 d, and the ratio between the periods of the outer and the inner orbits is small, 22:1. With such extreme values, this system should show orbital element variations over a time-scale of about a decade. We have monitored the radial velocities of HD 109648 with the CfA Digital Speedometers for 8 yr, and have found evidence for modulation of some orbital elements. While we see no definite evidence for modulation of the inner binary eccentricity, we clearly observe variations in the inner and the outer longitudes of periastron, and in the radial velocity amplitudes of the three components. The observational results, combined with numerical simulations, allow us to put constraints on the orientation of the orbits.     

Water masses in the Caribbean Sea and sub-annual variability in the Guajira upwelling region

The study of water masses is important as they transport water properties affecting the biosphere and ocean dynamics. In this study, we revisit water masses in the Caribbean Sea using climatology and 11 months of observations at different depths from 3 moorings placed in the Guajira upwelling region, providing some new findings. The Caribbean Surface Water (CSW) seasonal variability is studied at the mixed layer depth. Salinity differences between CSW and the saltier North Atlantic Subtropical Underwater (SUW) determine static stability spatial and temporal variations, with implications for regional ocean dynamics. Besides, we assess the climatologic distribution of water masses below the salinity maximum using the optimum multiparameter analysis and the Thermodynamic Equation of Seawater 2010, defining their source water indices when entering the Caribbean Sea. The SUW, with its core at ~ 150 m depth, occupies 16% of the Caribbean Sea volume, complemented by 38% of Antarctic Intermediate Water, with its core at ~ 700 m depth and North Atlantic Deep Water, which as bottom water occupies 46% of the volume. Hydrographic observations do not differ from climatology, regardless of their large sub-annual variations decreasing with depth. Daily time series of dominant water fractions at different depths correlate at each mooring, indicating a common forcing. Besides, rotated wind stress, which is an indicator of the Guajira upwelling, correlates regularly with water mass fractions down to 700 m depth. However, during strong wind shifts, upwelling seems to affect them down to 1450 m depth.

     

Everyday Encounters with Activist Scholarship

In light of the grave challenges ahead under the Trump administration and the rise of right-wing populism in the West, it is critical that geographers across subdisciplines embrace activist and engaged scholarship. Opportunities for such engagement often emerge organically in our everyday lives at the intersection between personal interests, ethics and commitments, and nascent research agendas. In this article, I share two experiences with community-engaged and activist research: (1) establishing the Los Puentes Spanish–English dual-language immersion program in partnership with a low-income rural North Carolina public school system and (2) collaborating on the Building Austin, Building Injustice participatory action research project with a community-based workers center to document and lobby for improvements to construction workers’ conditions in Austin, Texas. Through a situated and positioned personal account, I seek to not only provide two examples of activist research but also illustrate the diversity of encounters and how they can emerge in unlikely places and outside conventional “activist” arenas. In conclusion, I draw on lessons learned through these experiences to reflect on the various challenges and opportunities for activist scholarship within geography in the future.