Browsing by Author "Mendes, Isabel Maria de Paiva Pinto"
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- Benthic foraminifera as palaeo-environmental indicators in the Northern Gulf of CadizPublication . Mendes, Isabel Maria de Paiva Pinto; Dias, João Manuel Alveirinho; Schönfeld, JoachimThis thesis is an investigation of benthic foraminifera as palaeo-environmental indicators on the Northern Gulf of Cadiz continental shelf, northeast Atlantic Ocean. The main objective was to determine the environmental indicator value of living benthic foraminifera and their application to Holocene palaeoenvironmental reconstruction. Relationships between living benthic foraminiferal fauna and both physical and chemical parameters were analysed in surficial samples collected from the continental shelf between the Guadiana and Guadalquivir Rivers. Living benthic foraminiferal faunas were characterised in detail and associations of the most abundant species classified into four groups. These groups allowed the characterisation of the modern environment and associated physical and chemical parameters. Sedimentological and benthic foraminiferal analyses, combined with a chronological framework, were performed on three Holocene sequences from contrasting sedimentary environments. A comparison between the most abundant species in living faunas and those occurring in Holocene shelf sediments was also made. An integrated approach using all the available information sheds light on paleoenvironmental changes, which were distilled into five evolutionary scenarios. Each scenario is a representation of the environmental changes that characterised the three studied environments at different times during the Holocene. They indicate the influence of various factors, including sea-level changes, river discharge and substrate properties, that are mirrored by different benthic foraminiferal assemblages. The thesis demonstrates that the modern ecological preferences of common benthic foraminiferal species have direct applicability to interpreting the palaeoenvironmental record.
- The late holocene evolution of the adra delta subaqueous system (Northern Alboran Sea): seismic-stratigraphic and geomorphic evidence of millennial scale climatic and anthropic effectsPublication . Bárcenas, P.; Lobo, F.J.; Fernández-Salas, L.M.; Mendes, Isabel Maria de Paiva Pinto; López-González, N.; Macías, J.The formation and development of a small Mediterranean deltaic system are investigated through a primary seismic stratigraphic interpretation of a high-resolution seismic profile network, combined with multiple bathymetric data (including multibeam bathymetric imagery) and collated with shallow sediment cores collected with a vibro-corer device. The submarine delta of the Adra River is divided into a basal patchy seismic unit and five wedge-shaped younger seismic units that are related to the Holocene highstand stabilization. Limited age control indicates that the two uppermost seismic units are very recent, most likely related to a dearth of fluvial fluxes led by channel deviations and by sediment retention. The formation of the three older seismic units is correlated to three humid periods during the Middle Holocene, Late Holocene and Little Ice Age, under a general context of progressive aridification of southeastern Iberia. The stacking patterns and spatial distribution of individual seismic units document a history of episodic progradation of successive prodeltaic lobes, with a long-term evolution mediated by climatically-induced changes in the river basin and more recent anthropogenic interventions. Overall, the subaqueous deltaic system registers the complete modification of a deltaic system that evolves from a fluvial-dominated delta to recent wave-dominated wedges. In between, the deltaic system exhibits a progressive asymmetric character, due to the instauration of Atlantic waters on the shelf and their subsequent eastward redistribution. The Adra deltaic system is proposed as an outstanding example of a small deltaic system that reacts almost immediately to the complex interaction between natural changes in the system and anthropogenic interventions in the drainage basin.
- Novel field experiment on alkalinity enhancement in intertidal environments—a trailblazer for natural climate solutionsPublication . Mendes, Isabel Maria de Paiva Pinto; Lübbers, J.; Schönfeld, J.; Baldermann, A.; Carrasco, Rita; Cravo, Alexandra; Gomes, Ana; Grasse, P.; Stamm, F. M.One recently proposed approach to reduce atmospheric CO2 concentrations is marine alkalinity enhancement. This technique increases the CO2 uptake capacity of seawater through weathering of fine-grained (mafic) rocks and minerals in marine environments. The weathering process has been extensively tested in laboratory studies and verified by numerical models. Field experiments scaling the CO2 uptake under natural conditions are still lacking. In a methodological approach, a novel in situ experiment was designed and installed in a salt marsh at Ria Formosa coastal lagoon, southern Portugal. The experiment comprised deployments of different sizes of olivine and basalt substrates, and a control site, which were tidally submerged twice a day. A monthly monitoring scheme of supernatant and porewater properties from each deployment and control site was established, and procedures for temperature, salinity, oxygen, pH, total alkalinity, nutrient, and trace metal analyses were defined. This paper is devoted to the methods and describes the design, a protocol for the analyses, and an evaluation of experimental performance and reliability. Data from the first 6 months are presented for validation of the experiment. They demonstrated elevated total alkalinity in water samples, mostly in porewater after the deployments, while salinity, oxygen, and pH reflect the control conditions. Significant alkalinity differences were observed between the treatments and the natural background conditions monitored at the control site, during the 6 months of the experiment. The methodological approach is presented with strengths, limitations, and recommendations for an upscaling as CO2 removal measure, servicing, and subsequent investigations.
- Western Mediterranean shelf-incised submarine canyons: multi-proxy evidence of Late Holocene natural and human-induced environmental changesPublication . López-Quirós, Adrián; Puga-Bernabéu, Ángel; José Lobo, Francisco; Ruíz-Caballero, Elvira; Cerrillo-Escoriza, Javier; Pérez-Asensio, José N.; Mendes, Isabel Maria de Paiva Pinto; Mena, Anxo; Puche-Polo, Natalia; Alberjón-Peñas, Tomás; Wacker, LukasSubmarine canyons play a critical role in continental margin sediment transport, functioning both as sediment traps and conduits. This study examines the depositional dynamics of the Motril, Carchuna, and Calahonda canyons in the northern Alboran Sea (western Mediterranean) to assess their role in Holocene sediment storage and transfer. Comprehensive sedimentological and elemental geochemical analyses reveal distinct sedimentation patterns driven by geomorphology, diverse transport mechanisms, and hydroclimatic variability. The Motril Canyon primarily functioned as a river-fed sediment trap, accumulating fine-grained terrigenous material from the Guadalfeo River. At the same time, the Carchuna Canyon was dominated by longshore drift and turbidity currents mobilizing coarse-grained sediments. In contrast, the Calahonda Canyon displays an intermediate behavior, influenced by alongshore drift and fluvial inputs. The Late Holocene sedimentary record from the Motril Canyon provides a high-resolution sedimentary archive of paleoenvironmental changes over the last similar to 2000 years Current Era, reflecting both climatic variability and human-induced landscape alterations. Four phases are identified based on the relationships between sediment physical and mineral-chemical characteristics: the Iberian Roman Humid Period (2600-1600 cal. yr Before Present), characterized by diminished terrigenous input despite increased late-phase humidity; the Dark Ages (1500-1000 cal. yr BP), marked by elevated sedimentation linked to soil erosion and intensified land use; the Medieval Climate Anomaly (1050-650 cal. yr BP), where persistent fine-grained deposition was driven largely by anthropogenic land degradation; and the Little Ice Age (650-150 cal. yr BP), which witnessed heightened sedimentation due to increased rainfall and river discharge. A decline in fluvial-derived material during the Industrial Period indicates a shift towards overall drier conditions, associated with changes in precipitation patterns and land use. These findings underscore the interplay between natural climatic fluctuations and human activities influencing western Mediterranean margin sedimentation. While the Motril Canyon does not serve as a direct conduit to deep waters, it nonetheless records the progressive aridification and anthropogenic impacts experienced in southern Iberia. Furthermore, the contrasting sediment dynamics observed in the Carchuna and Calahonda canyons highlight the inherent complexity of shelf-to-slope sediment transfer. This complexity underlines the necessity to consider human influences when interpreting Late Holocene paleoenvironmental records.