Organic matter sources for tidal marsh sediment over the past two millennia in the Minho River estuary (NW Iberian Peninsula)

Environmental changes during the last 2 millennia in the Minho River tidal marsh (NW Portugal-Spain border) were reconstructed. Changes in the sources of organic matter (OM) delivered to the marsh were evaluated from elemental, isotopic and molecular composition using a 1 m sediment core. Carbon isotopic composition (delta13C) and organic carbon to total nitrogen ratio (Corg/N) provided valuable information concerning the origin of the OM. These parameters indicated a major input from land plants, reaching a maximum at 1100–1200 and 1750–1850 AD. These periods match with major flood events in the NW of the Iberian Peninsula, as reported by several authors. A significant reduction in the terrestrial signature occurred at 6–4 cm (ca. 1960–1985 AD), which is contemporaneous with the construction of several major dams on the Minho River. The distribution of selected lipid biomarkers, including n-alkanes, n-fatty acids and n-alkan-2-ones and specific parameters derived from the molecular distributions, were useful for refining bulk geochemical results. Long chain n- alkanes with an odd number of carbons are indicators of soil-and vascular plant derived terrestrial OM and were dominant throughout the core. In addition, a greater contribution of plankton-derived lipids was observed in the sections corresponding to ca. 1960–1985 AD (6–4 cm) and ca. 100–200 AD (96–94 cm). Although different degradation rates for individual compounds might have partly affected biomarker assemblages, the variations could be attributed to a sharp decrease in the freshwater contribution to the Minho River Estuary (dam construction) and a possible marine highstand, respectively. In addition, several parameters suggested changes in land use (including deforestation and farming) and probably the effects of mining exploitation during the Roman occupation of the area.We acknowledge the funding by the Foundation for Science and Technology (FCT) of Portugal for J.M. M’s PhD. Grant (SFRH/BD/45528/2008) and for the WestLog Project (PTDC/CTE-GIX/105370/2008). E.L. was awarded a Ralph E. Powe Junior Faculty Enhancement Award. This is a contribution to the IGCP Project 588 and to the Geo-Q Research Unit (Aranzadi).Peer reviewe

Shells and humans: molluscs and other coastal resources from the earliest human occupations at the Mesolithic shell midden of El Mazo (Asturias, Northern Spain)

Human populations exploited coastal areas with intensity during the Mesolithic in Atlantic Europe, resulting in the accumulation of large shell middens. Northern Spain is one of the most prolific regions, and especially the so-called Asturian area. Large accumulations of shellfish led some scholars to propose the existence of intensification in the exploitation of coastal resources in the region during the Mesolithic. In this paper, shell remains (molluscs, crustaceans and echinoderms) from stratigraphic units 114 and 115 (dated to the early Mesolithic c. 9 kys cal BP) at El Mazo cave (Asturias, northern Spain) were studied in order to establish resource exploitation patterns and environmental conditions. Species representation showed that limpets, top shells and sea urchins were preferentially exploited. One-millimetre mesh screens were crucial in establishing an accurate minimum number of individuals for sea urchins and to determine their importance in exploitation patterns. Environmental conditions deduced from shell assemblages indicated that temperate conditions prevailed at the time of the occupation and the morphology of the coastline was similar to today (rocky exposed shores). Information recovered relating to species representation, collection areas and shell biometry reflected some evidence of intensification (reduced shell size, collection in lower areas of exposed shores, no size selection in some units and species) in the exploitation of coastal resources through time. However, the results suggested the existence of changes in collection strategies and resource management, and periods of intense shell collection may have alternated with times of shell stock recovery throughout the Mesolithic.This research was performed as part of the project “The human response to the global climatic change in a littoral zone: the case of the transition to the Holocene in the Cantabrian coast (10,000–5000 cal BC) (HAR2010-22115-C02-01)” funded by the Spanish Ministry of Economy and Competitiveness. AGE was funded by the University of Cantabria through a predoctoral grant and IGZ was funded by the Spanish Ministry of Economy and Competitiveness through a Juan de la Cierva grant. We also would like to thank the University of Cantabria and the IIIPC for providing support, David Cuenca-Solana, Alejandro García Moreno and Lucia Agudo Pérez for their help. We also thank Jennifer Jones for correcting the English. Comments from two anonymous reviewers helped to improve the paper

Discerning natural and anthropogenic organic matter inputs to salt marsh sediments of Ria Formosa lagoon (South Portugal)

Sedimentary organic matter (OM) origin and molecular composition provide useful information to understand carbon cycling in coastal wetlands. Core sediments from threors' Contributionse transects along Ria Formosa lagoon intertidal zone were analysed using analytical pyrolysis (Py-GC/MS) to determine composition, distribution and origin of sedimentary OM. The distribution of alkyl compounds (alkanes, alkanoic acids and alkan-2-ones), polycyclic aromatic hydrocarbons (PAHs), lignin-derived methoxyphenols, linear alkylbenzenes (LABs), steranes and hopanes indicated OM inputs to the intertidal environment from natural-autochthonous and allochthonous-as well as anthropogenic. Several n-alkane geochemical indices used to assess the distribution of main OM sources (terrestrial and marine) in the sediments indicate that algal and aquatic macrophyte derived OM inputs dominated over terrigenous plant sources. The lignin-derived methoxyphenol assemblage, dominated by vinylguaiacol and vinylsyringol derivatives in all sediments, points to large OM contribution from higher plants. The spatial distributions of PAHs (polyaromatic hydrocarbons) showed that most pollution sources were mixed sources including both pyrogenic and petrogenic. Low carbon preference indexes (CPI > 1) for n-alkanes, the presence of UCM (unresolved complex mixture) and the distribution of hopanes (C-29-C-36) and steranes (C-27-C-29) suggested localized petroleum-derived hydrocarbon inputs to the core sediments. Series of LABs were found in most sediment samples also pointing to domestic sewage anthropogenic contributions to the sediment OM.EU Erasmus Mundus Joint Doctorate fellowship (FUECA, University of Cadiz, Spain)EUEuropean Commission [FP7-ENV-2011, 282845, FP7-534 ENV-2012, 308392]MINECO project INTERCARBON [CGL2016-78937-R]info:eu-repo/semantics/publishedVersio

Bromine soil/sediment enrichment in tidal salt marshes as a potential indicator of climate changes driven by solar activity: New insights from W coast Portuguese estuaries

This paper aims at providing insight about bromine (Br) cycle in four Portuguese estuaries: Minho, Lima (in the NW coast) and Sado, Mira (in the SW coast). The focus is on their tidal marsh environments, quite distinct with regard to key biophysicochemical attributes. Regardless of the primary bromide (Br-) common natural source, i.e., seawater, the NW marshes present relatively higher surface soil/sediment Br concentrations than the ones from SW coast. This happens in close connection with organic matter (OM) content, and is controlled by their main climatic contexts. Yet, the anthropogenic impact on Br concentrations cannot be discarded. Regarding [Br] spatial patterns across the marshes, the results show a general increase from tidal flat toward high marsh. Maxima [Br] occur in the upper driftline zone, at transition from highest low marsh to high marsh, recognized as a privileged setting for OM accumulation. Based on the discovery of OM ubiquitous bromination in marine and transitional environments, it is assumed that this Br occurs mainly as organobromine. Analysis of two dated sediment cores indicates that, despite having the same age (AD ~1300), the Caminha salt marsh (Minho estuary) evidences higher Br enrichment than the Casa Branca salt marsh (Mira estuary). This is related to a greater Br storage ability, which is linked to OM build-up and rate dynamics under different climate scenarios. Both cores evidence a fairly similar temporal Br enrichment pattern, and may be interpreted in light of the sun-climate coupling. Thereby, most of the well-known Grand Solar Minima during the Little Ice Age appear to have left an imprint on these marshes, supported by higher [Br] in soils/sediments. Besides climate changes driven by solar activity and impacting marsh Br biogeodynamics, those Br enrichment peaks might also reflect inputs of enhanced volcanic activity covarying with Grand Solar Minima.This work was partly supported by IDL through the UID/GEO/50019/2013 program, by C2 TN through the UID/Multi/04349/2013 program, and is a contribution of the project WestLog (PTDC/CTE/105370/2008), funded by the Fundação para a Ciência e a Tecnologia (FCT). João Moreno benefits from a FCT PhD grant (SFRH/BD/87995/2012). J.J. Gómez-Navarro acknowledges the funding provided through the contract for the return of experienced researches, resolution R-735/2015 of the University of Murcia.info:eu-repo/semantics/publishedVersio

Interpretation of benthic foraminiferal stable isotopes in subtidal estuarine environments

Here we present a novel approach for the interpretation of stable isotope signatures recorded in benthic foraminifera from subtidal estuarine environments. The stable isotopic composition (δ<sup>18</sup>O and δ<sup>13</sup>C) of living <i>Ammonia tepida</i> and <i>Haynesina germanica</i> is examined at four stations in the Auray River estuary (Gulf of Morbihan, France) sampled in two contrasting seasons, spring 2006 and winter 2007. Comparing benthic foraminiferal δ<sup>18</sup>O measurements with theoretical oxygen isotopic equilibrium values, calculated on the basis of water temperature and salinity measurements in the upper and lower estuary, i.e., T-S-δ<sup>18</sup>O<sub><i>eq.</i></sub> diagrams, strongly suggests that foraminiferal faunas sampled at the four stations calcified during different periods of the year. This interpretation can be refined by using the benthic foraminiferal δ<sup>13</sup>C, which is mainly determined by the mixing of sea and river water. In the upper estuary foraminifera mainly calcified in early spring and winter, whereas in the lower estuary calcification mainly took place in spring, summer and autumn. This new method provides insight into the complexity of estuarine benthic foraminiferal stable isotope records. In addition, it can also be used to obtain new information on preferred calcification periods of benthic foraminiferal taxa in different parts of the estuary

Puglia 2003 -Final Conference Project IGCP 437 Coastal Environmental Change During Sea-Level Highstands: A Global Synthesis with implications for management of future coastal change Project 437 Foraminiferal response to the Holocene environmental developm

Abstract The Bay of Biscay coastal area is a typical inundation coastline, formed as a consequence of the eustatic sea-level rise that followed the last deglaciation. Erosive processes are dominant along the southern area (named Cantabrian coast of Spain), as constant wave attack causes active cliff destruction. Short and narrow estuaries are separated from the open sea by sandbars, beaches and dune deposits. The eastern area of the Bay of Biscay (known as Aquitaine coast of France) is mainly a straight and continuous sandy beach backed by a coastal dune system fixed during the 19th century. These extensive dune fields formed when sand deposits on the continental shelf were reworked during the Holocene sea-level rise. The morphology and extent of the different estuarine sedimentary environments are constantly altered by erosion and deposition of sediments, and they are sensitive to even small changes in sea level

Recent anthropogenic impacts on the Bilbao estuary, northern Spain: geochemical and microfaunal evidence

The distributions of a range of elements (including137Cs and210Pb) have been studied in surface sediments and 0·5 m cores from the Bilbao Estuary (Cantabrian coast, northern Spain) to determine recent and historical sediment contamination. Benthic foraminifera have also been examined to infer recent ecosystem changes. High concentrations of a range of metals are observed in three cores and in surface-scrapes. Observed concentrations depend on the proximity to sources of pollutants. Living foraminifera are absent from surface sediments in the upper estuary, and are scarce in the middle and lower estuary, due to persistent anoxia in the estuarine channel, and possibly, high pollutant concentrations. High metal concentrations in sediment core profiles, combined with the sporadic presence of foraminifera, indicate that environmental degradation has persisted in this estuary for at least the last 40 years. This degradation has been caused by the discharge of untreated industrial and domestic effluents. Surface sediments show a few transported living foraminifera of species that have been identified as dominant in nearby, less-polluted estuarine environments. Successful recolonization by these species may occur if the sediment conditions improve sufficiently. Foraminiferal assemblages could therefore be used as environmental quality indicators to assess the effectiveness of current regeneration schemes implemented under strategic local authority plans

Application of pyrolysis-GC/MS for the characterisation of environmental changes in the salt marshes of the Tagus estuary(Portugal)

2 pages, 1 figure, 3 references.-- Póster presentado al citado congreso en la Sesión I: Environment and Pollution (E) Nº 121.-- Book of Abstracts of the Communications presented to the 26th International Meeting on Organic Geochemistry (IMOG), held in Costa Adeje, Tenerife – Spain, September 15 – 20, 2013.Salt marshes and estuaries are key environments for organic matter (OM) burial, which plays an essential role in the global carbon cycle (López-Capel et al., 2006). Common to these environments is the diversity of OM sources, which is usually composed by a complex mixture of terrestrial and marine residues originated from the decomposition of vegetal, animal and microbial organisms (Hedges and Keil, 1999). Concomitantly, anthropogenic contaminants are transported and deposited.Peer reviewe