Modelling of estuarine response to sea-level rise during the Holocene: Application to the Guadiana Estuary–SW Iberia

This paper focuses on simulations of the morphological evolution of an estuary during sedimentary infilling that accompanied Holocene sea-level rise. The simulations were conducted using the Estuarine Sedimentation Model, which uses a behaviour-oriented approach, supported by the chronostratigraphy of the estuary's sedimentary sequence. Behaviour curves were computed to represent the relationship between the estuarine channel depth below maximum high tide and the net accretion at a given location relative to the average sedimentation rate of the estuary during the Holocene. The model was validated by comparing the observed present-day bathymetry of the Guadiana River Estuary, southeastern Portugal, with the corresponding simulated bathymetries for nine control sections across the estuary. The best fit between simulated and actual sediment surface elevations was obtained along the cross-sections in the sheltered, low-energy environments of the estuary. The accuracy of the sedimentary stratigraphy of the best-fit model was further established using 16 radiocarbon ages obtained from five boreholes in the estuary. The present approach is particularly suitable for simulating long-term morphological evolution in sheltered estuarine environments where tidally driven vertical aggradation dominates at centennial to millennium timescales. However, the accuracy of simulated sediment surface elevations and consequently the robustness of behaviour-type models based on Geographical Information System platforms can be enhanced by incorporating (i) the impacts of nearshore hydrodynamic processes and episodic flood events in highly energetic channels, and (ii) the impacts of cross-currents in meandering channel sections. (C) 2015 Elsevier B.V. All rights reserved.FCT [SFRH/BD/70747/2010, SFRH/BPD/85335/2012

Integrated coastal management in Latin America : the ever new world

The advancement of Integrated Coastal Zone Management (ICZM) in Latin American countries may vary from established programs to experimental phase implementation and even inexistence. This creates an opportunity for the development of new ideas and experiments, especially in the quite long stretches of littoral where no occupation has yet been planned or consolidated. However there are localized issues that need to be attended with certain degree of urgency, especially in coastal settings that have been urbanized, developed for industry and/or are situated around port facilities. Spain and Portugal implemented the marine and environmental policies of European Union and may be seen as models for public and private ICZM initiatives. These situations created opportunities and needs that are somehow reflected in dedicated scientific production, as well as in social impact and the related capacity building programs. We surveyed some key costal management journals to know how Latin American based academics are doing in their mission of creating, developing and discussing ICZM along our diverse shores stretching along all climatic zones. Capacity building programs and exchange networks were also scrutinized. Results suggest that the thematic participation in the major publication channels is modest and needs to improve in number and diversity of subjects bringing obvious benefits to the policy and decision makers. Capacity building programs are still in its infancy across the region. There are no, or very few, specialized educational programs to form practitioners and scientists at all academic levels. Training programs integrating countries around all aspects of ICZM are even scarcer. Coordinated actions, such as networks across the political borders are one of the many future needs we point out here as being the next frontier for thinkers and managers in the region.A Gestão Integrada da Zona Costeira (GIZC) nos países da América Latina se encontra em diferentes níveis de desenvolvimento, desde programas estabelecidos, passando por níveis experimentais e pela não-existência de iniciativas de GIZC em alguns casos. Isso cria uma predisposição para o desenvolvimento de novas ideias e experiências, especialmente nos longos trechos de litoral, nos quais a ocupação ainda não foi planejada e/ou consolidada. Há, no entanto, questões localizadas que precisam ser atendidas de imediato, especialmente em ambientes costeiros que já foram urbanizados, industrializados ou ainda que se desenvolveram em torno de instalações portuárias. Espanha e Portugal - agora sob a influência da União Europeia - permanecem como nossos modelos de iniciativas de GIZC, tanto públicas quanto privadas. Estas oportunidades e necessidades de alguma forma refletem na produção local científica e seu impacto internacional, bem como em nossos programas de capacitação para a gestão integrada. Nós examinamos publicações de importância para gestão costeira a fim de averiguar como acadêmicos latino-americanos cumprem a sua missão de criar, desenvolver e discutir a GIZC. Analisamos também programas de capacitação e redes estabelecidas. As revistas mais representativas para a comunidade acadêmica de GIZC e que vem sendo publicadas pelo menos nos últimos 30 anos, e que foram brevemente examinadas nesta revisão foram a Ocean and Coastal Management, Coastal Management, Journal of Coastal Research e Journal of Coastal Conservation. Com relação aos programas de capacitação para a GIZC levou-se em consideração estudos recentes que demonstram que a maioria dos temas tratados nos cursos de pós-graduação acadêmicos relacionados com a GIZC não estão diretamente relacionadas com a gestão, mas sim às ciências natural, ou da terra, ou ainda à descrição da dinâmica costeira e ou poluição. Com apoio da Rede Ibero Americana de Gestão Costeira Integrada pode-se chegar a listagem de diversas redes que atuam na América Latina, Espanha e Portugal e que se relacionam com o tema. Os resultados sugerem que a representação nos principais veículos de publicação é tímido e precisa melhorar em número e diversidade de assuntos. Melhorias na publicação científica poderia levar a uma melhor utilização dos temas para o benefício dos tomadores de decisão. A capacitação também ainda está pouco desenvolvida na região. Existem poucos cursos especializados para formar técnicos e cientistas sobre o tema em níveis elevados de educação, ou nível de pós-graduação. Os programas de treinamento em torno de todos os aspectos da GIZC são ainda mais raros. A tendência em se considerar a perspectiva de integração como uma soma de conhecimentos disciplinares, não necessariamente ligados, são apresentadas em iniciativas de capacitação e produção científica. Esta abordagem é considerada falha pois, estas disciplinas, a maior parte do tempo, não se inter-relacionam para fornecer uma perspectiva holística para a gestão. Ações coordenadas, tais como redes, que ultrapassam as fronteiras políticas são uma das muitas necessidades futuras destacadas aqui como sendo a próxima fronteira para os pensadores e gestores da região

Food web structure of three Mediterranean stream reaches along a gradient of anthropogenic impact

Anthropogenic impact can alter food web structure through changes in species interactions. In this study, we explored the food web of three Mediterranean stream reaches (two seasonal and one permanent) along an anthropogenic impact gradient to test the hypothesis that increasing impact simplifies food webs. To test this, we applied the isotopic (δ13C and δ15N) niche concept to compare reaches using isotopic metrics (isotopic richness, divergence, dispersion, evenness, and redundancy). The isotopic indices were useful to identify differences in food web architecture among the three reaches. The least impacted site had the highest isotopic richness, dispersion, and isotopic redundancy, suggesting higher ecological resilience at this site. The effect of disturbance in the remaining two sites was masked by the presence of invasive crayfish, which increased isotopic divergence and was responsible for higher food-chain length in the most impacted reach, but not in the moderately impacted reach. Consumers displayed generalistic feeding habits, with Bayesian mixing models indicating that they relied primarily on a mixture of periphyton, other macroinvertebrates, and to a lesser extent, detritus. Some taxa displayed changes in their dietary habitats depending on the site, indicating that the same type of taxa fed on distinct foods at each stream reach

Determination of the regional background in Holocene sediments of the Guadiana River estuary (SW of Spain)

This main aim of this work is the determination of the regional background in Holocene sediments of the Guadiana River estuary. These background values are essential in order to establish the environmental quality of the most recent sediments, and to evaluate the possible incidence that some processes associated to human activities (acid mine drainage, urban effluents) could produce in these sediments. For this purpose, a sedimentological and geochemical characterization have been done in two sediment cores from the lower Guadiana basin, in which Al normalized concentration has been calculated for the most important metals and metalloids present in these sediments (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn).The results obtained have allowed us the determination of the regional background in these sediment

Drought, fire and grazing precursors to large-scale pine forest decline

Aim Temperate forests are currently facing multiple stresses due to climate change, biological invasions, habitat fragmentation and fire regime change. How these stressors interact with each other influences how, when and whether ecosystems recover, or whether they adapt or transition to a different ecological state. Because forest recovery or collapse may take longer than a human lifetime, predicting the outcomes of different stressor combinations remains difficult. A clearer vision of future forest trajectories in a changing world may be gained by examining collapses of forests in the past. Here, we use long-term ecological data to conduct a post-mortem examination of the decline of maritime pine forests (Pinus pinaster Ait.) on the SW Iberian Peninsula 7000-6500 years ago. Location Portugal and Spain. Methods We compared four palaeoecological records-two with pine declines and two without-using a multiproxy approach. Bioclimatic differences between the four sites were explored. Proxies for past vegetation and disturbance (fire and grazing) were compared with independent palaeoclimatic records. We performed functional traits analysis and used phase plots to examine the causes of pine decline. Results The pine decline represents a critical transition in SW Iberia, which lies close to maritime pine's bioclimatic limits. Prolonged drought likely killed trees and suppressed the fires that normally stimulate pine germination and pinewood recovery. Increased grazing pressure facilitated the rapid spread of resprouter shrubs. These competed with pine trees and ultimately replaced them. Our data highlight complex interactions between climate, fire, grazing and forest resilience. Main Conclusions The pine decline occurred at least a century after post-fire resprouters overtook obligate seeders in the vegetation, constituting an early-warning signal of forest loss. Fire suppression, resprouter encroachment and grazing may threaten the persistence of Mediterranean forests as droughts become more frequent and extreme.PTDC/AAC--CLI/108518/2008info:eu-repo/semantics/publishedVersio

Palynological evidence for environmental and climatic change in the lower Guadiana valley, Portugal, during the last 13 000 years

Pollen analysis of a 48 m AMS radiocarbon-dated sediment sequence from the Guadiana estuary provides the first record of Lateglacial and Holocene vegetation history in the Algarve province of Portugal. This paper focuses on the record of terrestrial pollen taxa, which document a series of forest expansions and declines during the period 13 000 cal. BP to 1600 cal. BP and provide insights into climate evolution in southwestern Iberia. The main vegetation phases identified in the Guadiana valley are (1) Lateglacial interstadial (Allerød) forest with Quercus and Pinus under a temperate, moist, continental climate; (2) a Younger Dryas forest decline (Quercus) and expansion of pinewoods, xeric scrub and open ground habitats (with Juniperus, Artemisia, Ephedra distachya type, Centaurea scabiosa type) under arid and cold conditions; (3) an early Holocene forest/scrub/open-ground vegetation mosaic developing under a warm, dry and continental climate; (4) a maximum of Quercus forest and thermomediterranean evergreen taxa (Olea, Phillyrea, Pistacia) reflecting a warm, moist oceanic climate between c. 9000 cal. BP and c. 5000 cal. BP; and (5) the expansion of shrublands with Cistaceae and Ericaceae under a drier climatic regime and increasing anthropogenic activity since c. 5000 cal. BP. Holocene episodes of maximum climatic aridity are identified in the record of xerophytic taxa (Juniperus, Artemisia, Ephedra distachya type) centred around 10 200 cal. BP, 7800 cal. BP, 4800 cal. BP, 3100 cal. BP and 1700 cal. BP. Regional comparisons suggest a correlation of arid phases across southern Iberia and northwest Africa, which can be related to abrupt North Atlantic coolings (Bond events).Research Council studentship for WJF (NERC/S/A/2001/06109), with the support of Trinity College and the Department of Geography, University of Cambridg

Holocene evolution of a barrier island system, Ria Formosa, South Portugal

Holocene evolution of the Ria Formosa barrier island system was studied through the examination of a large subsurface dataset acquired from 191 boreholes and five seismic refraction profiles. Two boreholes with total depths of 26 and 16.5 m were selected for a multi-proxy detailed laboratory analysis, including mean grain size distribution, organic matter (OM) content, color variation, shell identification, and benthic foraminifera assemblages. Selected cores are thought to be representative of the identified depositional sub-basins. Subsurface age data from 16 AMS C-14 dated samples were plotted against depth and resulted in a coherent age model of sedimentary infill. The system evolution was largely controlled by sediment availability, accommodation space, and Holocene sea level rise, first at a rapid rate of 7 mm/yr from 10 kcal yr BP to 7.25 kcal yr BP, followed by a slowdown to 1.1 mm/yr until present. A conceptual model for the origin and Holocene evolution of the Ria Formosa barrier island system implies three main steps, leading to the present system geomorphology: (1) marine flooding of incised palaeovalleys by the rapid transgression of palaeovalleys in the early Holocene(2) development of a proto-barrier island chain perched on Pleistocene detritic headlands and steeper interfluve areas during the early to middle Holoceneand (3) full development of the barrier islands chain and enclosing of the coastal lagoon, followed by the maturation of the system with subsequent siltation and salt marsh expansion from the middle Holocene until present. The onset of barrier system formation dates back to ca. 8 kcal yr BP, predating previously proposed age.SIHER project [PTDC/CTE-GIX112236/2009]EU Erasmus Mundus Joint Doctorate in Marine and Coastal Management (MACOMA) fellowship grant, under University of AlgarveEU Erasmus Mundus Joint Doctorate in Marine and Coastal Management (MACOMA) fellowship grant, under University of Cadi

Ostracodes do Estuário do Rio Arade, Algarve - Portugal

The detrended correspondence analysis (DCA) applied to the relative abundance of ostracoda species and physical-chemical, sedimentological and geochemical parameters allowed to identified four sectors in the estuary of the Arade River: Sector I - located between the mouth of estuary and Portimão City and is characterized by the largest number of species of ostracoda, higher salinity and pH, sandy sediment and higher protein concentration. This sector has the largest marine influence with high phytoplankton productivity; Sector II - located in the vicinity of Parchal City, it is characterized by the highest value of diversity H' and the occurrence of the species Leptocythere lacertosa, Herpetocypris helenae and Leptocythere porcellanea. In this sector was identified the highest concentration of sulfur and fine sediments; Sector III - located between Silves and Parchal cities, has the highest concentration of organic carbon, fine sediment and biopolymers (carbohydrates, lipids and proteins). In this sector were identified only the dominant species in the estuary (Loxoconcha elliptica, Cytherois fischeri e Leptocythere lacertosa); Section IV - located in the Silves City, this sector had the highest lipid content and the silt fraction of the whole estuary. The sectors identified in Arade River Estuary, this is characterized as the most confined where the effluents from Silves City are deposited. The DCA analysis showed that the Loxoconcha ellipitica is the most characteristic species of this sector, and it can be considered with a confined environments bioindicator.A análise de correspondência destendenciada (DCA) aplicada à abundância relativa das espécies de ostracodes e aos parâmetros físico-químicos, sedimentológicos e geoquímicos permitiu dividir o estuário do rio Arade em quatro setores: Setor I -- localiza-se entre a foz e a cidade de Portimão, que foi caracterizado pelo maior número de espécies de ostracodes, valores mais altos de salinidade e pH, sedimento arenoso e maior concentração de proteínas no sedimento. Este setor foi considerado com maior infuência marinha, alta produtividade fitoplanctônica; Setor II -- localizado nos arredores da cidade de Parchal, foi caracterizado pelo maior valor de diversidade H' e pela ocorrência das espécies Leptocythere lacertosa, Herpetocypris helenae e Leptocythere porcellanea. Neste setor foi identificada a maior concentração de enxofre e de sedimentos finos; Setor III -- localizado entre as cidades de Parchal e Silves, este setor apresentou grande concentração de carbono orgânico, sedimento fino e de biopolímeros (carboidratos, lipídios e proteinas). Neste setor foram identificadas somente as espécies dominantes do estuário (Loxoconcha elliptica, Cytherois fischeri e Leptocythere lacertosa); Setor IV -- localizado na cidade Silves, este setor apresentou a maior concentração de lipídios e da fração silte de todo o estuário. Dentre os setores identificados, este é o mais confinado, onde há deposição dos efluentes da cidade Silves. A análise em DCA demonstrou que a espécie Loxoconcha elliptica é a espécie mais característica deste setor e por isso, pode ser considerada como um bioindicador de ambientes confinados

Sea level changes : causes, time scales and the history of their recognition

Sea level changes provoked by multiple forcings that act in a wide range of time scales attracted human interest for several millennia. However, the bases of modern understanding of this phenomenon and its quantitative expression were achieved during the last two centuries. At present, owing to a series of altimetric observations made by 4 satellite missions in the last 30years, the mean sea level (MSL) rise calculated for the whole Earth is estimated to be 3-3.5 mm per year, with at least half of this value being attributable to human-induced climate warming. About 125,000 years ago, during the last interglacial (Eemian) that was warmer than the current period, the MSL was about 5 m higher than today. Approximately 116,000 years ago, the sea level began to decline as a result of gradual cooling of the climate that led to glaciation, which in the Northern Hemisphere had a climax at 20-30 ka BP. The transition from the last glacial maximum to the current warm period, covering the last 20,000years, includes the transfer of about 35 106 km3 of water from melting ice caps of the Northern Hemisphere to the oceanic reservoir, causing an increase in sea level of about 130 m. The average rate of MSL rise was about 10 mm per year, although over the last seven millennia, the MSL rising rate dropped to about 1-1.5 mm per year. These changes are considered representative of the natural variability of the Earth's climate system over the past 2 million years