Search Results (41)

Variscan two-mica granites are widespread in the Trás-os-Montes region (NE Portugal), yet their emplacement ages, petrogenesis, and relationship with Variscan deformation phases remain poorly constrained. This study integrates U–Pb zircon geochronology, whole-rock geochemistry, and oxygen isotope data to characterise four peraluminous two-mica granites in the Trás-os-Montes area (Fornos, Carviçais, Fonte Santa, and Bruçó) and to refine their tectonomagmatic context within the Central Iberian Zone. All granites are S-type, ilmenite-series, and derived from reduced magmas, as indicated by their strongly peraluminous compositions, mineral assemblages (muscovite ± biotite), absence of magnetite and presence of ilmenite, and high δ¹⁸O values (>11‰), consistent with partial melting of metasedimentary crust. U–Pb ages reveal two distinct magmatic pulses: an older event at ~340 Ma (Fornos and Fonte Santa granites), predating the onset of C3 deformation and likely associated with late C1 crustal thickening to early C2 tectonics, and a younger pulse at ~320–318 Ma (Carviçais and Bruçó granites). These magmatic pulses are linked to contrasting structural controls, with the older granites emplaced within regional-scale antiforms and the younger intrusions localised along structures related to C3 deformation. Together, these results document two discrete crustal melting events separated by ~20 Ma and record a progressive shift from fold-controlled to strike-slip-dominated granite emplacement during Variscan orogenic evolution. Moreover, the study highlights that tungsten mineralisation is preferentially associated with reduced, crust-derived granites emplaced during specific tectonic regimes, providing new constraints for metallogenic models in NW Iberia. Full article

Atlantic salmon populations have declined in many regions and are affected by several natural and anthropogenic factors throughout their lives. We investigated the role of environmental drivers and the effect of dam construction on the trend in catches of spawning adults of a migratory population currently at risk. For this purpose, we examined the salmon catches from 1914 to 2020 in the Minho River (NW Portugal, SW Europe), located at the southern limit of this species’ distribution. There was a decline in catches over time with an inverse and significant relationship between the trend in catches and lagged temperature. Delayed effects of this type may indicate temperature influences on survival during early life history stages. Similarly, the trend in catches decreased with the increasing number of dams. A forecast model built for the period before the construction of the first major dam in this river (before 1955), including lagged temperature, resulted in a decreasing trend in the number of catches. This demonstrates that catches would have declined due to temperature effects even without dam construction. This does not diminish the role of dams in the observed decline; rather, it reveals that temperature-driven declines would have occurred independently. Nonetheless, efficient management and conservation of this imperiled population require further detailed biological information on the number of returning spawning adults and salmons’ survival throughout their life cycle. Full article

The expansion of offshore renewable energy development in Portugal necessitates accurate geological and geotechnical site characterization, especially in regions with limited baseline information. This study focuses on the S. Pedro de Moel area (NW central Portugal), which is characterized by sandy sediments, with the aim of supporting the preliminary design of anchoring and foundation systems for renewable energy structures. An integrated methodology was applied, combining multibeam bathymetry, acoustic backscatter data, high-resolution seismic reflection profiling, sediment sampling, and onshore laboratory testing. Seismic interpretation identified three subsurface units: (1) a deformed carbonated sandstone serving as the acoustic basement; (2) a well-graded sandy gravel layer, up to 8 m thick, interpreted as a marginal marine deposit; and (3) a modern sandy deposit, up to 7 m thick, with variable silt content. Geotechnical analyses yielded effective friction angles for sandy sediments ranging from 39 to 44°, and deformation moduli between 22 MPa and 54 MPa. The sedimentary succession exhibits marked lateral and vertical heterogeneity, which must be considered in engineering design. This cost-effective methodology offers a viable alternative to offshore in situ testing, enabling medium-scale site characterization and providing essential information to support the development of offshore renewable energy infrastructure. Full article

This study assessed the presence, abundance, and characteristics of microplastics (MPs) in farmed Pacific oysters (Crassostrea gigas) and evaluated the efficacy of depuration in reducing MPs under laboratory-controlled and commercial conditions. Oysters cultivated in the Lima estuary (NW Portugal) were sampled in autumn and winter, along with adjacent surface water and sediment, to investigate potential contamination sources. MP concentrations in oysters varied temporally, with higher levels in October 2023 (0.48 ± 0.34 MPs g⁻¹ ww) than in February 2024 (0.09 ± 0.07 MPs g⁻¹ ww), while the environmental levels remained stable across dates. All MPs were fibres, predominantly transparent, followed by blue and black. Fourier-Transform Infrared Spectroscopy (FTIR) confirmed cellulose and polyethylene terephthalate (PET) as dominant polymers in oysters and environmental samples. No clear correlation was found between MPs in oysters and surrounding compartments. Laboratory depuration reduced MPs by 78% within 48 h, highlighting its potential as a mitigation strategy. However, depuration was less effective under commercial conditions, possibly due to lower initial contamination levels. These findings suggest that oysters may act as a vector for human exposure to MPs via seafood consumption. While depuration shows promise in reducing contamination, further research is needed to optimise commercial protocols and enhance the safety of aquaculture products. Full article

Bracara Augusta (Braga, Portugal), one of the most important cities of the NW Iberian Peninsula, was founded by the emperor Augustus approximately between the years 16/15 BC. Throughout the Roman period, it has undergone various monumentalisation programmes according to its status, the first one as a convent capital and a later one as a provincial capital. The investigation of the economic cost of construction in the ancient world allows us to understand Roman architecture and the society of builders, both from economic and social perspectives. In recent years, based on the works of Janet DeLaine and Paolo Barresi, despite the large number of variables and the difficulty of quantifying them, a calculation methodology has been developed to approximate the cost of architecture, based on the information contained in two main documents: the Diocletian’s Edict of Prices (301 AD) and the nineteenth-century architecture and engineering manuals summarised by Pegoretti. Our goal is to understand part of the construction process of Roman architecture in the NW Iberian Peninsula, considering the cost of raw materials, namely stone, and the labour required in its preparation and utilisation. In this study, we present a cost proposal associated with the monumentalisation of two of the city’s important buildings: the forum’s large buildings and the theatre. The construction of the city was made fundamentally using local stone, from different quarries, endowing it with notable buildings and requiring a strong contribution from the local elites. Full article

Mountains matter. Rural subsistence communities living in areas with high biodiversity, such as mountains, are hotspots of ecological knowledge. However, modern lifestyles may threaten this unique cultural heritage. Our study aimed to document and analyze information on plants used to fulfill the everyday needs of the people in three rural communities in NW Portugal. Fieldwork was carried out for a period of one year and information was collected through face-to-face semi-structured interviews. A total of 98 species, belonging to 46 families, were identified, and 142 vernacular names were recorded. Ethnobotanical richness was similar among the studied communities. The five most frequently cited species were: Pterospartum tridentatum, Erica arborea, Ruta graveolens, Zea mays and Chamaemelum nobile. Phanerophytes and hemicryptophytes comprise nearly 81% of the list. The top three uses categories (total 14) were: medicine, fuel and ritual. Digestive, skin and respiratory symptoms were the most often conditions treated with plants. Medicinal plants were used fresh and dried, mostly as infusions. The insights gathered here are important for the preservation of the cultural heritage of the local communities. Moreover, the data are of considerable scientific interest because it provides the fundaments for future studies that aim to validate/invalidate specific uses. Full article

Haltern 70 amphorae sherds from Castro do Vieito, a Roman settlement from the NW of Portugal occupied during the early imperial period, were studied by Mössbauer spectroscopy at room temperature and 4.2 K, XRD, and XRF, aiming to understand the firing conditions of their production. Firing in air at 750 and 800 °C were performed in a sherd that was carefully studied. Also, a handle with part of the neck attached and with the potter’s stamp “LH …” was studied. In general, it can be deduced that the amphorae were fired under reducing conditions between 800 and 950 °C, having been subjected to an oxidation process only when already cooling. It was also inferred that the provenance of all the Haltern 70 amphorae found in Castro do Vieito is probably the same and that the stamped amphora also seems to come from the same locality. Full article

The aim of this paper is to describe the surveys performed in order to update the interpretive conceptual circulation model of the Ladeira de Envendos hyposaline hydromineral system (Central Portugal). The geology of the Ladeira de Envendos region is strongly controlled by the Amêndoa-Carvoeiro synform, of Ordovician-Silurian age, presenting continuous and aligned quartzite ridges on the NE flank, that form the basic structure of a set of inselbergs. The physico-chemical analysis of the Ladeira de Envendos natural mineral spring and borehole waters was provided by the Super Bock Group Enterprise (Concessionaire of the Ladeira de Envendos). Furthermore, two sampling campaigns took place to increase knowledge on the isotopic composition of the studied natural mineral waters. The stable (δ²H, δ¹⁸O) isotopic data indicate that local meteoric waters infiltrate around 400 m altitude and evolve to the natural mineral waters (of Cl-Na facies) through a NW–SE underground flow path ascribed to the highly fractured and permeable quartzite rocks. From recharge to discharge, the infiltrated meteoric waters acquire silica (±9 mg/L) due to water–quartzite rock interaction. These natural mineral waters emerge at temperatures around 21 °C, being the up flow of these waters controlled by the rock fractures and local faults. The natural mineral waters mean residence time range between 25 and 40 years, as indicated by the ³H content of these waters, enhancing an active recharge of this hydromineral system. The results obtained indicate existence of three hydrogeological subsystems, ascribed to three inselbergs, with similar groundwater circulation paths. These multi and interdisciplinary studies should be seen as an important contribution to the sustainable management of this type of natural mineral water resources. Full article

The present work aims to evaluate the MP contamination of zooplankton and its impact on MP trophic transfers at the lower levels of the food web in a field study. During 1 year, seasonal surveys were conducted to collect zooplankton and water samples from different sites in two estuaries, the Douro and Lima estuaries (NW, Portugal). The zooplankton was quantified and identified into major zooplanktonic groups. Dedicated protocols that had been previously optimized were used to assess the MP presence in the water samples and in two of the most abundant zooplankton groups (copepods and chaetognaths). The results showed the presence of MPs in all water samples, with similar MP concentrations in both estuaries (Lima: 2.4 ± 2.0 MPs m⁻³; Douro: 2.3 ± 1.9 MPs m⁻³). In general, no temporal or spatial variations were observed. Fibres, blue and of a small size (<1 mm), were the most common characteristics of the MPs found in the water and zooplankton, indicating that water can be a source of MPs for zooplankton. Chaetognatha exhibited higher MP contamination in the Lima (2.9 ± 3.1 MPs ind⁻¹) and Douro (2.0 ± 2.8 MPs ind⁻¹) estuaries than Copepoda, which tended to have lower levels of MP contamination (Lima: 0.95 ± 1.12 MPs ind⁻¹; Douro: 1.1 ± 1.2 MPs ind⁻¹). Such differences in the MP concentrations between these two categories of zooplanktonic organisms indicate a possible MP trophic transfer at the lower levels of the food web. The results highlight the novel possibility of an MP trophic transfer in zooplankton and the need to fully assess the impacts of MPs in real scenarios. Full article

Zooplankton are key components of estuarine trophic networks. However, routine monitoring is hindered by the difficulty of morphology-based identification. DNA-based methods allow us to circumvent some of these hurdles, providing precise species identifications regardless of the taxonomic expertise of the investigator or the developmental stage of the specimens. However, the process is dependent on the completeness of the reference libraries. In this study, we sought to evaluate the potential of DNA metabarcoding to assess the seasonal (summer, autumn, and early spring) and spatial dynamics of zooplankton (four locations spanning ca. 6 km) in the Lima estuary (NW Portugal). Two genetic markers were used: the cytochrome c oxidase subunit I and the V4 hypervariable region of the ribosomal 18S rRNA genes. Overall, 327 species were recovered, and both markers displayed minute overlap (7% were detected with both markers). Species richness, composition, and taxonomic distinctness were majorly influenced by the season, with a declining tendency from summer (highest number of exclusive species, n = 74) to spring. Second to season, the taxa composition was influenced by spatial variation where the most downstream site displayed the highest number of exclusive species, n = 53. A total of 16 non-indigenous species were detected using metabarcoding, but only one (Austrominus modestus) has been documented out in the estuary. In conclusion, both the seasonal and spatial gradients influenced the recovered richness, composition, and taxonomic distinctness, confirming the great aptitude of DNA metabarcoding for providing higher density monitoring and shedding new light on the composition and dynamics of complex zooplankton communities. Full article

Sandspits are important natural defences against the effects of storm events in estuarine regions, and their temporal and spatial dynamics are related to river flow, wave energy, and wind action. Understanding the impact of extreme wave events on the morphodynamics of these structures for current conditions and future projections is of paramount importance to promote coastal and navigation safety. In this work, a numerical analysis of the impact of a storm on the sandspit of the Douro estuary (NW Portugal) was carried out considering several mean sea level conditions induced by climate change. The selected numerical models were SWAN, for hydrodynamics, and XBeach, for hydrodynamic and morphodynamic assessments. The extreme event selected for this study was based on the meteo-oceanic conditions recorded during Hurricane Christina (January 2014), which caused significant damage on the western Portuguese coast. The analysis focused on the short-term (two days) impact of the storm on the morphodynamics of the sandspit in terms of its erosion and accretion patterns. The obtained results demonstrate that the mean sea level rise will induce some increase in the erosion/accretion volumes on the seaward side of the sandspit. Overtopping of the detached breakwater and the possibility of wave overtopping of the sandspit crest were observed for the highest simulated mean sea levels. Full article

The interaction between tide, river runoff, and wind in coastal lagoons induces complex salinity gradients, which are remarkable when the meteorological forcing is exacerbated. This work aims to characterize the salinity structure under extreme freshwater and wind events in the Ria de Aveiro coastal lagoon (Portugal). The Delft3D model was implemented and validated in 3D mode and used to perform simulations forced with extreme freshwater and wind scenarios. Results show that forcing conditions determine salinity stratification intensity and location. Generally, stratification increases as the freshwater increases, while the salinity intrusion moves downstream. Extreme wind tends to destroy stratification but fails to promote full-depth mixing, which is also dependent on the wind direction, as shown for the Espinheiro channel. The salinity intrusion is also impacted by wind events, being NW storms responsible for an upstream salt transport along the Mira channel and a downstream transport along the Espinheiro channel, and SW storms for an upstream displacement of the salinity intrusion along the São Jacinto channel. Finally, it is observed that the advection of a freshwater plume from the Vouga River into the middle of the São Jacinto channel under high freshwater scenarios causes an unusual local salinity pattern. This plume can either be pushed upstream or prevented from entering the channel, depending on the wind direction. Full article

Soajo Mountain is located in the northwestern Iberian Peninsula near the border between Portugal and Spain. Its highest elevation is 1416 m at the Pedrada summit. During the Pleistocene, the cascade cirques on the east flank and the icefield that covered the flattened surface of the high plateau generated several glacier valleys. This study presents a paleoglacial reconstruction of the relict glacial landscape in Soajo Mountain for the Glacial Maximum Extent (GME) through the following methods: (1) a detailed geomorphological map supported by high-resolution orthophotography, digital elevation models with a spatial resolution of 70 cm, and field surveys; (2) the delineation of the glacial surface, and the calculation of the glacial flowlines to obtain the numerical model of the ice thickness; and (3) an estimation of the paleoELA altitudes. The paleoglacial reconstruction, using GlaRe methodology, reveals a glacial surface of 16 km², including an icefield on the Lamas de Vez plateau (mean elevation of 1150 m) and a radial glacial flow to the east and north. The arrangement of the glaciated area attests to the topographic, lithological, and structural conditioning on the development of small glacial tongues, with an emphasis on the ice tongue flowing northwards, with a thickness of 173 m and a length of 2.92 km. The Soajo GME paleoglacier comprises three main glacial sectors: Lamas de Vez Icefield, Vez and Aveleira Valleys, and the Eastern Glacial Sector. These paleoglaciers have achieved maximum ice volumes of 214.4 hm³, 269.2 hm³, and 115.8 hm³, respectively, with maximum ice thicknesses of 127 m, 173 m, and 118 m, respectively. On the west flank, a smaller paleoglacier named Branda da Gémea recorded an ice volume of 24.3 hm³ and a maximum ice thickness of 110 m. According to the ELA-AABR method, Soajo Mountain has one of the lowest ELA values in the Iberian NW, ranging from 1085 to 1057 m. This is due to its oceanic location, an orographic barrier effect, and the influence of the polar front. Full article

Scavenging fauna plays an integral role in ecosystem functioning, nutrient cycling and circulating organic matter. Thus, baseline data of scavenger assemblages on the NW coast of the Iberian Peninsula that provides information on the abundance of species in different habitats is crucial to understanding the distribution of this understudied group. Two different types of baited traps, to capture scavenging megafaunal and scavenging benthopelagic macrofaunal assemblages, were deployed to compare them among rocky, pebbled and sandy bottoms at shallow subtidal on the northern coast of Portugal. Results showed significant differences in the structure of scavenger assemblages. Scavenging megafaunal assemblages differed between sandy and the other two studied habitats, whereas benthopelagic macrofaunal assemblages differed between pebbles and rocky habitats. This suggests that different drivers seem to shape the structure of benthopelagic macrofauna and megafauna. Regarding megafauna, the dominance of Tritia gastropods in sand habitats in comparison with its absence in rock and its very low abundance in pebbles was mainly responsible for the differences. However, in benthopelagic macrofauna, differences in assemblages between pebbles and rock were more related to changes in the relative abundance of crustacean species (Cirolana cranchii and Socarnes erythrophthalmus) that were less abundant in pebbles. Full article

The influence of the colour of photo-selective nets on Actinidia deliciosa yield, fruit quality and progression of the bacterial kiwifruit canker (Pseudomonas syringae pv. actinidiae, Psa) need to be characterised due to increasing use of these nets, mainly to protect from hail and storms. From May 2019 onwards, pearl (Pn), yellow (Yn) and grey (Gn) nets were installed permanently in a ‘Hayward’ kiwifruit orchard in NW Portugal and uncovered plants were used as the control. Compared to outside conditions for both seasons, the blue:red ratio and the mean air temperature were higher (mean increase of 12.7% and 0.6 °C, respectively) and the photosynthetic active radiation (PAR) was lower (10.8% less between budbreak and bloom) under the Pn. Crop yield, compared to the control, decreased by 40.3% under the three nets in 2020, and by 23.9% under the Yn and Gn in 2021. Yield and fruit grade under the Pn were similar to that of uncovered crops in 2021, and fruit grade was overall higher under the Pn compared to the Yn and Gn. Photo-selective nets did not affect the fruit quality parameters. Psa progression decreased under the Pn compared to the control during two months in both seasons, although this beneficial impact needs further evaluation. Full article