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Resilience has become an important theoretical context for interpreting the sustainability of socio-ecological systems because of its applicability to socioeconomic and environmental systems under changing conditions, regardless if changes are slow and less perceptible. Estuarine and coastal ecosystems around the world are constantly changing in response to combined effects of climate drivers and human activities, and many of them may be approaching critical thresholds threatening their healthy functioning and services they provide. However, shifts from one ecological stable state to another can last for long periods, making long-term studies necessary to understand the real nature of these transitions. Estuaries contain sediments that preserve the signature of multiple processes acting upon the coastal system. These records can therefore provide valuable palaeoecological data covering decadal to millennial time-scales and overcome the lack of long-term monitoring data required to investigate these processes. SWe have collected sediment cores from shallow, near-coast sites in the Sado estuary that provides a natural archive of environmental change since the early Holocene. The Sado Estuary is the second largest estuary in Portugal, with an area of approximately 24,000 ha. It is a mesotidal system, well mixed and generally well oxygenated, with a salinity variation depending on the annual precipitation and river flow. Most of the estuary is classified as a natural reserve but it also plays an important role in the local and national economy. Tidal marsh habitats cover about 30% of the total area. The Sado estuary is a good example of a site where human pressures and natural values coexist each other. Using a combined spatial and temporal approach, this work aims to study ecological resilience and regime shifts in this part of the SW Portuguese coast. Thus, we study the sedimentary infill of a number of tidal marshes located in the Sado estuary to assess variability in both sensitivity and exposure to sea level rise (SLR) at a local scale. Site-specific accretion and wetland elevation change are quantified, and temporal trends understood to produce reliable projections of the effect of SLR. Empirical time-series of tidal data and coeval sedimentological records obtained from the study sites regarding wetland response and sea level changes are used to assess past trends that can inform future scenarios of wetland changes and responses. Contemporary data and multiannual to millennial reconstructions provide insights on patterns and drivers of abrupt environmental change in response to SLR and yield important information on the avergae state and natural variability of the coastal system. We expect that our results will provide information on the long-term development and patterns of variability of the Sado estuary in relation to socio-cultural activities, which is vital to understand and mitigate the effects of global change on coastal ecosystems.

Neste trabalho apresentamos os resultados preliminares do estudo de uma sondagem (EDP1) recolhida nas proximidades do Cais do Sodré, na zona baixa de Lisboa, junto à actual margem ribeirinha do Tejo. Estes resultados permitiram a diferenciação de 4 unidades sedimentares principais que mostram um aumento da assinatura antrópica no sedimento ao longo do tempo. A unidade da base (Unidade 1) corresponde a um sedimento depositado em condições estuarinas, num ambiente subtidal de baixa energia. Este padrão de sedimentação é interrompido pela deposição da Unidade 2, que reflecte mais alta energia. Esta unidade é caracterizada por um aumento na densidade e diversidade de espécies de foraminíferos e em bioclastos (Sub-Unidade 2A) e pela incorporação de vários elementos antrópicos (fragmentos de cerâmica atribuídos aos séculos XVII e XVIII) (Sub-unidade 2B). A datação por radiocarbono de fragmento de madeira e a data atribuível aos fragmentos de cerâmica, sugere que a deposição da Unidade 2 pode ter resultado de uma tempestade extrema que ocorreu a 19 de Novembro de 1724 e/ou ao tsunami de 1 de Novembro de 1755. O decréscimo abrupto na densidade de cocólitos na Unidade 2 é compatível com um aumento na taxa de sedimentação. A sedimentação posterior a este evento (Unidades 3 e 4) espelha um retorno às condições estuarinas subtidais mas revela um aumento de energia em relação à Unidade 1, reflectindo uma menor profundidade da coluna de água com passagem para um ambiente subtidal superior. A sedimentação natural na área de estudo é interrompida durante a segunda metade do século XIX com a construção do Aterro da Boavista, um aterro artificial construído com o intuito de reclamar terra ao rio. In this work we present preliminary results of the study of one sediment core (EDP1), collected near Cais do Sodré, Lisbon downtown, close to the present day Tagus riverfront. The results allowed differentiation of 4 major sediment units that present a signature of increasing anthropic influence over time. The lowermost unit (Unit 1) corresponds to a subtidal flat accreting in low energy and brackish conditions. This sedimentation pattern is interrupted by high-energy deposition of Unit 2, characterized by higher density and diversity of the foraminiferal content and high content of other bioclasts remains (Sub-unit 2A) and by the incorporation of several anthropic elements, such as 17th-18th century ceramics (Sub-unit 2B). Given the radiocarbon chronological framework and type and dates of the anthropic materials included in both sub-units of Unit 2, they are tentatively related with either the 1724 extreme storm and/or the 1755 tsunami. The abrupt drop in coccolith densities in this unit is compatible with an increase in sedimentation rate. Later sedimentation (Units 3 and 4) mirrors increasing energy in comparison with Unit 1, reflecting the shallowing of the study area and shift towards upper subtidal conditions, the natural sedimentation having been interrupted in the middle 19th century by the placement of an artificial infill that reclaimed the estuarine margin. The interpretation presented here was developed in the framework of the Lisbon Stories project, which addresses the relationships between the Tagus, the city of Lisbon and its people throughout the last few centuries. publishersversion published

Póster 230 presentado en la Session 2: Soil and peat and terrestrial OM 1.-- Congreso celebrado del 18-23 de septiembre, de 2011, en Interlaken, Suiza., Biogeochemical processes and environmental conditions that lead to the preservation of organic matter (OM) in coastal and marine sediments has been the subject of a wealth of studies in the last decades (Hedges et al., 1999). It is estimated that more than 80% of the total organic carbon preserved in marine sediments is buried in deposits along the continental margins in >terrigenous-deltaic> regions near river mouths. In such semi-enclosed scenarios, significant environmental changes, such as climatic warming, flooding caused by an increase in the riverine water discharge or alteration of the sea level may be reflected in the characteristics of organic carbon supplied to and buried in their sediments.

[EN]: The lipid biomarker distribution in a sediment core fromMinho river tidal-marshes (NW Iberian Peninsula) was studiedusing gas chromatography-mass spectrometry (GC/MS) in order to evaluate changes in the sources and distribution of organic matter (OM) in the estuary during the last centuries. The distribution of terrestrial and phytoplankton biomarker inventory reflected an heterogeneous mixture of OM from marine and terrestrial sources. Lignin derived phenols, triterpenoids and long chain n-alkanes with an odd number of carbons are indicators of soil-and vascular plant-derived continental OM, being more abundant on the topmost sections of the core. In addition, a conspicuous contribution from plankton-derived OM (e.g. short chain fatty acids and alcohols, phytosterols) is observed in the deepest sections of the core. However, in general the lipid biomarker assemblage found indicate the existence of a complex input of organic matter (OM) to this estuarine area, from both river run-off and marine depositions. Temporal variations observed could also be attributed to terrigenous contributions after flooding events from Miño river, although a differential degradation of individual biomarkers should not be neglected when interpreting biomarker assemblages in this geodynamically active environment. [ES]: Con el objetivo de evaluar las variaciones en las fuentes y distribución de la matería orgânica (MO) durante los últimos siglos, se estudia la distribución de biomarcadores lipídicos en una secuencia sedimentaria de las marismas del río Miño (NW Península Ibérica) mediante Cromatografía de Gases¿Espectrometria de Masas (CG/MS) . La distribución de biomarcadores terrestres y marinos muestra una mezcla heterogénea de MO con diferente orígen. Los fenoles derivados de la lignina, triterpenoides y n-alcanos de cadena larga con número impar de carbonos proceden de plantas superiores, indicadores de MO de origen continental , se encuentran com mayor abundancia en las secciones superiores del sondeo. Los lípidos derivados del plancton marino (ej., acidos grasos y alcoholes de cadena corta, fitosteroles) se encontraron con mayor abundancia relativa en las secciones mas profundas del sondeo. Sin embargo, la distribución global de los biomarcadores lipídicos estudiados muestra la complejidad de las fuentes de MO en este estuario, y que incluye las descargas del río y deposiciones de sedimentos marinos. Algunas variaciones observadas pueden deberse a contribuciones de MO terrígena debidas a descargas elevadas procedentes del río Miño. No obstante, a la hora de interpretar los cámbios observados en la distribución de determinados biomarcadores en este ambiente geodinámicamente activo, se debe tener en cuenta la posible ocurrencia de fenómenos de degradación preferencial o selectiva en el sedimento.

Identification of past tsunamis is important for risk assessment and management of coastal areas. Obtaining accurate and precise ages of sediments originating from such extreme marine coastal floods is crucial for a reliable estimation of the recurrence interval of these often devastating events. We present here the results of quartz optical dating and 14C dating of two sites (Boca do Rio and Martinhal) on the Algarve coast (southern Portugal). These sites contain deposits of the great tsunami of November 1, 1755. The sections were described using sedimentological techniques; at both sites tsunami-laid sands and gravels were identified, intercalated between estuarine muds. Quartz luminescence ages from these sedimentary successions were derived using standard SAR-OSL dating using multi-grain sub-samples. A multiple sampling strategy was employed with several samples taken from the AD 1755 tsunami deposit and from the sediments bracketing the tsunami layer. Our SAR-OSL protocol was shown to be appropriate using dose recovery measurements (measured/given dose ratio of 1.004 0.007, n ¼ 165). The several OSL ages from the 1755 tsunamigenic deposits are internally reproducible but yield age overestimates of between 20 and 125% (60–310 years respectively); this is in agreement with values reported in the literature for similar deposits. The age overestimation of the tsunami-laid sands is presumably due to the rapid erosion and deposition of older sediments, with insufficient light exposure for complete bleaching during the tsunami event itself. The absence of significant bleaching during the tsunami is also suggested by the shape of the dose distributions based on sub-samples made up of only about 100 grains. Analysis of the distributions with the minimum-age model seems to yield the expected age for two of the three distributions. It is important to note that age offsets of a few tens of years to a few hundred years rapidly become insignificant when dating older (>1 to few ka) tsunami layers.

Proceedings of the 8th International Coastal Symposium, ICS 2004, Itajaí/Itapema, Santa Catarina, Brazil, 14 to 19 March 2004 Submitted by Paula Serrano (paula.serrano@ineti.pt) on 2015-06-28T15:19:46Z No. of bitstreams: 1 34836.pdf: 505234 bytes, checksum: fa8f65db35b277151039b39fdbf534fd (MD5) Approved for entry into archive by Paula Serrano (paula.serrano@ineti.pt) on 2015-06-28T15:19:57Z (GMT) No. of bitstreams: 1 34836.pdf: 505234 bytes, checksum: fa8f65db35b277151039b39fdbf534fd (MD5) Made available in DSpace on 2015-06-28T15:19:57Z (GMT). No. of bitstreams: 1 34836.pdf: 505234 bytes, checksum: fa8f65db35b277151039b39fdbf534fd (MD5) Previous issue date: 2006