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Atmospheric dust plays an important role in terrestrial and marine ecosystems, particularly those that are nutrient limited. Despite that most dust originates from arid and semi-arid regions, recent research has shown that past dust events may have been involved in boosting productivity in nutrient-poor peatlands. We investigated dust deposition in a mid-latitude, raised bog, which is surrounded by a complex geology (paragneiss/schist, granite, quartzite and granodiorite). As proxies for dust fluxes, we used accumulation rates of trace (Ti, Zr, Rb, Sr and Y) as well as major (K and Ca) lithogenic elements. The oldest, largest dust deposition event occurred between similar to 8.6 and similar to 7.4 ka BP, peaking at similar to 8.1 ka BP (most probably the 8.2 ka BP event). The event had a large impact on the evolution of the mire, which subsequently transitioned from a fen into a raised bog in similar to 1500 years. From similar to 6.7 to similar to 4.0 ka BP, fluxes were very low, coeval with mid-Holocene forest stability and maximum extent. In the late Holocene, after similar to 4.0 ka BP, dust events became more prevalent with relatively major deposition at similar to 3.2-2.5, similar to 1.4 ka BP and similar to 0.35-0.05 ka BP, and minor peaks at similar to 4.0-3.7, similar to 1.7, similar to 1.10-0.95 ka BP and similar to 0.74-0.58 ka BP. Strontium fluxes display a similar pattern between similar to 11 and similar to 6.7 ka BP but then became decoupled from the other elements from the mid Holocene onwards. This seems to be a specific signal of the granodiorite batholith, which has an Sr anomaly. The reconstructed variations in dust fluxes bear a strong climatic imprint, probably related to storminess controlled by North Atlantic Oscillation conditions. Complex interactions also arise because of increased pressure from human activities.

Atmospheric metal pollution is a major health concern whose roots pre-date industrialization. This study pertains the analyses of ancient human skeletons and compares them with natural archives to trace historical environmental exposure at the edge of the Roman Empire in NW Iberia The novelty of our approach relies on the combination of mercury, lead and lead isotopes. We found over a 700-year period that rural Romans incorporated two times more mercury and lead into their bones than post-Romans inhabiting the same site, independent of sex or age. Atmospheric pollution sources contributed on average 57% (peaking at 85%) of the total lead incorporated into the bones in Roman times, which decreased to 24% after the decline of Rome. These values and accompanying changes in lead isotopic composition mirror changes in atmospheric Pb deposition recorded in local peatlands. Thus, skeletons are a time-transgressive archive reflecting contaminant exposure.

Severe winter windstorms have become an increasingly common occurrence over recent decades in northwestern Europe. Although there exists considerable uncertainty, storminess is projected to increase in the future. On centennial to millennial time scales in particular, the mechanisms forcing storminess remain unsettled. We contribute to available palaeostorm records by reconstructing changes over the last 6670 years using a coastal peat sequence retrieved from the ombrotrophic Laphroaig bog on Islay, southwestern Scotland. We use a combination of ash content, grain size and elemental chemistry to identify periods of greater storminess, which are dated to 6605, 6290-6225, 5315-5085, 4505, 3900-3635, 3310-3130, 2920-2380, 2275-2190, 2005-1860, 1305-1090, 805-435 and 275 cal. a BP. Storm signals in the first half of the record up to similar to 3000 cal. a BP are mainly apparent in the grain-size changes. Samples from this time period also have a different elemental signature than those later in the record. We speculate that this is due to receding sea levels and the consequent establishment of a new sand source in the form of dunes, which are still present today. The most significant events and strongest winds are found during the Iron Ages Cold Epoch (2645 cal. a BP), the transition into, and in the middle of, the Roman Ages Warm Period (2235 and 1965 cal. a BP) and early in the Little Ice Age (545 cal. a BP). The Laphroaig record generally agrees with regionally relevant peat palaeostorm records from Wales and the Outer Hebrides, although the relative importance of the different storm periods is not the same. In general, stormier periods are coeval with cold periods in the region as evidenced by parallels with increased ice-rafted debris in the North Atlantic, highlighting that sea-ice conditions could impact future storminess and storm track position.

Posidonia oceanica (L.) Delile meadows are highly productive coastal marine ecosystems that provide multiple ecosystem services. The seagrass is not always the major contributor to total primary production, however, little is known about long-term changes in the composition of primary producers within seagrass meadows. Understanding compositional shifts within the community of primary producers is crucial to evaluate how climate and anthropogenic change affect the functioning of seagrass ecosystems. Here we analysed marker pigment composition in seagrass cores from two bays of the Cabrera Island (Balearic Islands, Spain) to asses long-term changes in phototrophic community composition and production in seagrass meadows, and identify the environmental factors triggering those changes. The proxy dataset was explored using principal component analyses (PCA): one including the pigment dataset to look for associations between producers' groups, and another one combining the pigment dataset with plausible local and global regulatory factors to assess the environmental drivers of change. Analyses of characteristic pigments and morphological fossils (cysts) showed that the abundance of dinoflagellates increased over the last 150–300 years, coeval with a rise in solar irradiance and air temperature. When compared among embayments, pigments from cyanobacteria predominated in seagrass meadows located at Es Port, a sheltered bay receiving higher terrestrial runoff; whereas pigments from diatoms, seagrasses and rodophytes were more common at Santa Maria, an exposed bay with clearer waters. Water depth also played a role in controlling the phototrophic community composition, with greater abundance of diatoms in the shallowest waters (<5 m). Overall, our results suggested that historical and spatial variation in seagrass meadows' phototrophic community composition was influenced by the interaction between local factors (catchment-bay characteristics) and global climate processes (

Scientists studying seagrasses typically refer to their substratum as sediment, but recently researchers have begun to refer to it as a soil. However, the logistics of sampling underwater substrata and the fragility of these ecosystems challenge their study using pedological methods. Previous studies have reported geochemical processes within the rhizosphere that are compatible with pedogenesis. Seagrass substratum accumulated over the Recent Holocene and can reach several meters in thickness, but studies about deeper layers are scarce. This study is a first attempt to find sound evidence of vertical structuring in Posidonia oceanica deposits to serve as a basis for more detailed pedological studies. A principal component analysis on X-Ray Fluorescence-elemental composition, carbonate content and organic matter content data along a 475 cm core was able to identify four main physico-chemical signals: humification, accumulation of carbonates, texture and organic matter depletion. The results revealed a highly structured deposit undergoing pedogenetical processes characteristic of soils rather than a mere accumulation of sediments. Further research is required to properly describe the substratum underneath seagrass meadows, decide between the sediment or soil nature for seagrass substrata, and for the eventual inclusion of seagrass substrata in soil classifications and the mapping of seagrass soil resources

Blue carbon ecosystems (BCE) play an essential role in the global carbon cycle by removing atmospheric carbon dioxide and storing it as organic carbon (OC) in biomass and sediments. However, organic matter (OM) deposition and degradation/preservation processes are poorly understood, especially on the long-term and at molecular scales. We analysed sediment samples from six cores collected in tidal marshes, mangroves and seagrasses (up to 150 cm long cores spanning up to 10,000 yrs of OC accumulation) from Spencer Gulf (South Australia), by pyrolysis (Py-GC–MS and THM-GC–MS), and we compared the results with elemental and stable isotope data, to decipher OM provenance and to assess degradation/preservation dynamics. The results showed that: (1) the major biopolymers preserved were polysaccharides, polyphenolic moieties (lignin and tannin) and polymethylenic moieties (e.g. cutin, suberin, chlorophyll) with smaller apportions of proteins and resins; (2) the OM originates predominantly from vascular plant materials (in particular lignocellulose) that have been well-preserved, even in some of the oldest sediments; (3) mangroves were found to be the most efficient OC sinks, partially explained by syringyl lignin preservation; (4) seagrasses were shown to store polysaccharide-enriched OM; (5) large proportions of polycyclic aromatic hydrocarbons (PAHs) in surficial tidal marsh and mangrove sediments probably reflect pyrogenic OM from industrial combustion, and; (6) “ecosystem shifts”, i.e. mangrove encroachment in tidal marsh and transition from seagrass to mangrove, were detected. Deposition environment and source vegetation control OC sequestration and there is no specific recalcitrant form of OM that is selectively preserved. For the first time, we demonstrate how analytical pyrolysis in combination with stable isotope analysis can be used to reconstruct (palaeo-)ecological shifts between different BCE. This study improves our knowledge on OC accumulation dynamics and th

Atmospheric dust plays an important role in terrestrial and marine ecosystems, particularly those that are nutrient limited. Despite that most dust originates from arid and semi-arid regions, recent research has shown that past dust events may have been involved in boosting productivity in nutrientpoor peatlands. We investigated dust deposition in a mid-latitude, raised bog, which is surrounded by a complex geology (paragneiss/schist, granite, quartzite and granodiorite). As proxies for dust fluxes, we used accumulation rates of trace (Ti, Zr, Rb, Sr and Y) as well as major (K and Ca) lithogenic elements. The oldest, largest dust deposition event occurred between ~8.6 and ~7.4 ka BP, peaking at ~8.1 ka BP (most probably the 8.2 ka BP event). The event had a large impact on the evolution of the mire, which subsequently transitioned from a fen into a raised bog in ~1500 years. From ~6.7 to ~4.0 ka BP, fluxes were very low, coeval with mid-Holocene forest stability and maximum extent. In the late Holocene, after ~4.0 ka BP, dust events became more prevalent with relatively major deposition at ~3.2–2.5, ~1.4 ka BP and ~0.35–0.05 ka BP, and minor peaks at ~4.0–3.7, ~1.7, ~1.10–0.95 ka BP and ~0.74–0.58 ka BP. Strontium fluxes display a similar pattern between ~11 and ~6.7 ka BP but then became decoupled from the other elements from the mid Holocene onwards. This seems to be a specific signal of the granodiorite batholith, which has an Sr anomaly. The reconstructed variations in dust fluxes bear a strong climatic imprint, probably related to storminess controlled by North Atlantic Oscillation conditions. Complex interactions also arise because of increased pressure from human activities.

Seagrass ecosystems are recognised for their role in climate change mitigation, due to their capacity toform organic-rich sediments. The chemical recalcitrance of seagrass organs is one characteristic drivingcarbon storage, but the molecular background of this feature is poorly understood. We assessedmolecular composition changes ofPosidonia australissheaths (SH) and roots plus rhizomes (RR) alonga sediment core, encompassing 3200 cal. yr BP, by means of nuclear magnetic resonance spectroscopy(13C NMR), conventional analytical pyrolysis (Py-GC–MS) and thermally assisted hydrolysis and methy-lation (THM-GC–MS). Significant trends with depth (age) in the composition of both SH and RR remainsofP. australiswere observed from all methods. In general terms, polysaccharides become depleted(degraded) and lignin enriched (selectively preserved) as age increases, and the minor constituents cutin,suberin and condensed tannin are also preferentially depleted during ageing in both fractions. Molecularchanges with ageing were smaller in SH, especially regarding polysaccharides, indicative of a superiorstability compared to RR. The molecular changes observed are most pronounced within the first 75 cmof the record, which reflects the recalcitrance ofP. australisdetritus once it is buried below that depth(corresponding to approximately 700 cal. yr BP). The capacity ofP. australisto act as a long-term carbonsink seems to be mainly related to the resistance of buried lignocellulose materials to decomposition. Theresults on diagenetic effects on the molecular fingerprint of seagrass detritus contribute to our under-standing of carbon sequestration in Blue Carbon ecosystems. Furthermore, data comparison of the meth-ods applied using principal component analysis (PCA) allowed us to identify consistencies, discrepanciesand complementarities

To study the long-range transport of atmospheric pollutants from lower latitude industrial areas to the Arctic, we analysed a peat core spanning the last similar to 700 cal. yr (similar to 1300-2000 CE) from southern Greenland, an area sensitive to atmospheric pollution from North American and Eurasian sources. A previous investigation conducted in the same location recorded atmospheric lead (Pb) pollution after similar to 1845, with peak values recorded in the 1970s, and concluded that a North American source was most likely. To confirm the origin of the lead, we present new Pb isotope data from Sandhavn, together with a high-resolution record for mercury (Hg) deposition. Results demonstrate that the mercury accumulation rate has steadily increased since the beginning of the 19th century, with maximum values of 9.3 mu g m(-2) yr(-1) recorded similar to 1940. Lead isotopic ratios show two mixing lines: one which represents inputs from local and regional geogenic sources, and another that comprises regional geogenic and pollution sources. Detrending the Pb isotopic ratio record (thereby extracting the effect of the geogenic mixing) has enabled us to reconstruct a detailed chronology of metal pollution. The first sustained decrease in Pb isotope signals is recorded as beginning similar to 1740-1780 with the lowest values (indicating the highest pollution signature) dated to similar to 1960-1970. The 206Pb/207Pb ratio of excess Pb (measuring 1.222, and reflecting pollution generated Pb), when compared with the Pb isotopic composition of the Sandhavn peat record since the 19th century and the timing of Pb enrichments, clearly points to the dominance of pollution sources fromNorth America, although it did not prove possible to further differentiate the emissions sources geographically.

Posidonia oceanica is a marine phanerogam that buries a significant part of its belowground production forming an organic bioconstruction known as mat. Despite Posidonia seagrass mats have proven to be reliable archives of long-term environmental change, palaeoecological studies using seagrass archives are still scarce. Here we reconstruct four millennia of environmental dynamics in the NE coast of Spain by analysing the carbon and nitrogen stable isotopic composition of P. oceanica sheaths, the proportion of different seagrass organs throughout the seagrass mat and other sedimentological proxies. The palaeoenvironmental reconstruction informs on long-term ecosystem productivity and nutrient loading, which have been linked to global (e.g., solar radiation) and local (e.g., land-use changes) factors. The long-term environmental records obtained are compared with previous palaeoecological records obtained for the area, showing a common environmental history. First, a relative seagrass ecosystem stability at ~4000 and 2000 cal. yr BP. Then, after a productivity peak at ~1400–800 cal. yr BP, productivity shows an abrupt decline to unprecedented low values. The fluctuations in ecosystem productivity are likely explained by increases in nutrient inputs related to human activities – mostly in the bay watershed – concomitantly with changes in total solar radiation. Cumulative anthropogenic stressors after Roman times may have started to affect ecosystem resilience, dynamics and productivity, with more abrupt regime shifts during the last millennium. These results add into recent research showing the potential of seagrass archives in reconstructing environmental change and seagrass post-disturbance dynamics, hence providing unvaluable information for improving the efficiency in managing these key coastal ecosystems.

The study of mercury accumulation in peat cores provides an excellent opportunity to improve the knowledge on mercury cycling and depositional processes at remote locations far from pollution sources. We analyzed mercury concentrations in 150 peat samples from two cores from Rano Aroi (Easter Island, 27° S) and in selected vegetation samples of present-day flora of the island, in order to characterize the mercury cycling for the last ~71 ka BP. The mercury concentrations showed values ranging between 35 and 200 ng g−1, except for a large maxima (~1000 ng g−1) which occurred at the end of the Last Glacial Maximum (LGM, ~20 ka cal BP) in both peat cores. Low temperatures during the LGM would accelerate the atmospheric oxidation of Hg(0) to divalent mercury that, coupled with higher rainfall during this period, most likely resulted in a very efficient surface deposition of atmospheric mercury. Two exceptional short-lived Hg peaks occurred during the Holocene at 8.5 (350 ng g−1) and 4.7 (1000 ng g−1) ka cal BP. These values are higher than those recorded in most peat records belonging to the industrial period, highlighting that natural factors played a significant role in Hg accumulation—sometimes even more so than anthropogenic sources. Our results suggest that wet deposition, linked to atmospheric oxidation, was the main process controlling the short-lived Hg events, both in the mire and in the catchment soils

Peatlands in northern latitudes sequester one third of the world’s soil organic carbon. Mineral dusts can affect the primary productivity of terrestrial systems through nutrient transport but this process has not yet been documented in these peat-rich regions. Here we analysed organic and inorganic fractions of an 8900-year-old sequence from Store Mosse (the “Great Bog”) in southern Sweden. Between 5420 and 4550 cal yr BP, we observe a seven-fold increase in net peat-accumulation rates corresponding to a maximum carbon-burial rate of 150 g C m−2 yr−1 – more than six times the global average. This high peat accumulation event occurs in parallel with a distinct change in the character of the dust deposited on the bog, which moves from being dominated by clay minerals to less weathered, phosphate and feldspar minerals. We hypothesize that this shift boosted nutrient input to the bog and stimulated ecosystem productivity. This study shows that diffuse sources and dust dynamics in northern temperate latitudes, often overlooked by the dust community in favour of arid and semi-arid regions, can be important drivers of peatland carbon accumulation and by extension, global climate, warranting further consideration in predictions of future climate variability.

Wood is a lignocellulosic and biodegradable material widely used for diverse applications. The complex nature of wood is due to its structure and chemical composition, which are closely related to tree taxonomy and to environmental factors of growing locations. Studies on wood chemical composition are of interest and permit to gain deeper understanding. In this light, the aim of this thesis was to develop tools for identification of species and provenance based on organic chemical parameters of wood used for shipbuilding in the Iberian Peninsula (16th to 18th century). The methodology developed in this thesis, concerned the combination of multivariate data analysis methods, together with wood chemical characterisation techniques (FTIR and Py-GC-MS).

Data in this article are related to the chemical characterization ofvarious oak wood samples. Data have been obtained by theapplication of Fourier Transform Infrared (FTIR) spectroscopy andpyrolysis-gas chromatography-mass spectrometry (Py–GC–MS) toliving tree species and shipwreck wood fragments. Measurementswere performed on individual rings in order to facilitate theunderstanding of the variability in wood chemical compositionalong the radial cores, i.e. the same kind of material traditionallyused for dendrochronological analysis. The data in this article islabelled according to the anatomical sections of the wood (sap-wood, transition wood and heartwood) where the samples weretaken. The experimental background and the results can be foundin the related research article,“Chemometric tools for identifica-tion of wood from different oak species and their potential forprovenancing of Iberian shipwrecks (16th–18th centuries CE)”(Traoré et al., 2018)

Among the ecosystem services provided by the seagrass Posidonia oceanica, its role as a carbon sink has received growing attention during the last decade. The sequestration and stabilization of carbon in soils are tightly linked to the activity of its microbial community. EcoPlates (Biolog) comprise a semi-quantitative tool for the assessment of microbial functional activity that generates profiles of microbial carbon source utilization. In this study, the aerobic and anaerobic carbon consumption in a healthy P. oceanica meadow was compared throughout depths down to 130 cm. After 11 d, the average well color development, Shannon-Wiener diversity index (H’), and kinetics of carbon consumption were assessed. Both the aerobic and anaerobic metabolisms showed carbon consumption at all depths. Color observations indicated that carbohydrates, amino acids and polymers were mainly consumed, while carboxylic acids, amines and miscellaneous compounds presented low or no consumption at all. Carbon consumption kinetics were similar for both metabolisms. The results suggest a pronounced stratification of the microbial community controlled by oxygen availability. Despite the higher aerobic metabolism in the top 40 cm, the anaerobic metabolism was dominant, supporting high sequestration of carbon in P. oceanica meadows.

Little is known about the impact of human activities during Roman times on NW Iberian mining landscapes beyond the geomorphological transformations brought about by the use of hydraulic power for gold extraction. We present the high-resolution pollen record of La Molina mire, located in an area intensely used for gold mining (Asturias, NW Spain), combined with other proxy data from the same peat core to identify different human activities, evaluate the strategies followed for the management of the resources and describe the landscape response to human disturbances. We reconstructed the timing and synchronicity of landscape changes of varying intensity and form occurred before, during and after Roman times. An open landscape was prevalent during the local Late Iron Age, a period of relatively environmental stability. During the Early Roman Empire more significant vegetation shifts took place, reflected by changes in both forest (Corylus and Quercus) and heathland cover, as mining/metallurgy peaked and grazing and cultivation increased. In the Late Roman Empire, the influence of mining/metallurgy on landscape change started to disappear. This decoupling was further consolidated in the Germanic period (i.e., Visigothic and Sueve domination of the region), with a sharp decrease in mining/metallurgy but continued grazing. Although human impact was intense in some periods, mostly during the Early Roman Empire, forest regeneration occurred afterwards: clearances were local and short-lived. However, the Roman mining landscape turned into an agrarian one at the onset of the Middle Ages, characterized by a profound deforestation at a regional level due to a myriad of human activities that resulted in an irreversible openness of the landscape.

In the Early Modern Age (XVI-XVII centuries), the construction of oceanic ships was essential for the development of cultural encounters in what became the Era of Discovery and European expansion. This is the case of the Iberian empires. They impose unprecedented demands on Iberian forests for the supply of lumber. Forestry and maritime power were inextricably linked. This project will address this issue. The prerequisite for such an approach is to combine the knowledge derived from Humanities and Life Sciences.

We combine high-resolution soil sampling with lead (Pb) analyses (concentrations and stable isotopes) in two temperate podzols, together with previous data obtained with selective Al and Fe dissolution techniques. We aim to assess how atmospheric Pb is incorporated into the soils during pedogenesis. Partial least squares modelling for Pb concentrations shows that the podzolization process has the largest effect on Pb concentration (803% of the variance). The proportion of inorganic secondary compounds, the input of fresh organic matter from the soil surface and the relative abundance of Fe versus Al are responsible for a small part of the Pb concentration variance. Lead isotopic composition (Pb-206/Pb-207 ratios) depends on soil organic matter content either fresh/poorly humified (573% of the variance) or humified (247% of the variance). The Pb linked to inorganic compounds and the overall podzolization process play a minor role in isotopic signature (53 and 37% of the variance respectively). Soil pH appears to be the controlling variable of the different transport and retention mechanisms. The relatively low isotopic ratios observed in spodic horizons result from geogenic Pb released through the preferential dissolution of the isotopically distinct most weatherable minerals of the parent material in the eluvial horizons, which undergoes downward mobilization. An accurate knowledge of soil reactive components and formation mechanisms is essential to a correct diagnose of the scope of Pb pollution and a more effective design of remediation strategies.

Even though pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC–MS) is widely used for molecular characterization of wood, its abilities to determine the taxonomy (species), provenance and the nature and intensity of degradation of archaeological woods are hardly explored. We performed principal component analysis (PCA) on Py-GC–MS data of sound woods and shipwreck woods of Pinus sp. and Quercus sp., to identify the impact of diagenesis on pyrolysis fingerprints. It was found that the proportion of most polysaccharide products decreased significantly upon diagenesis with the exception of 3-hydroxy-2-methyl-2-cyclopenten-1-one, which remains relatively well preserved. Furthermore, the guaiacyl lignin products were generally well preserved with the exception of 4-propylguaiacol, the relative contribution of which decreased considerably. New indices are proposed to establish the preservation state of shipwreck wood (shipwreck wood preservation index; SWPI) on the basis of polysaccharides (SWPIPS) and guaiacyl lignin (SWPILG) and syringyl lignin (SWPILS) fingerprints. Stepwise multiple linear regressions analyses applied on FTIR data of the same samples are indicative of the consistency of both techniques and the potential to identify changes in wood chemistry as a result of degradation. Other factors that influence wood composition, such as the differences between soft- and hardwood lignin and sap- and heartwood were also recognized

Soil organic carbon represents the largest terrestrial carbon pool, being one of the most relevant components in the carbon cycle budget and climate change feedbacks. The scientific community and policymakers expressed the need for spatially information about its distribution. This work aims to develop statistical methods to quantify topsoil organic carbon by using spectroscopic data as a tool for digital soil mapping. Firstly, it was explored the capacity of spectroscopy for map soil organic carbon content at regional scale using topsoil samples from Galicia (NW-Spain). Next, it was developed a spatially non-stationary approach that allows mapping soil organic carbon content and also identifying the factors more relevant for its accumulation in Europe. Finally, it was evaluated the capacity of digital soil mapping methods for monitoring the soil organic carbon stocks expected under different climate change scenarios using for such purpose legacy data from Santa Cruz Island (Galapagos).

The Mediterranean seagrass Posidonia oceanica maintains a biodiverse ecosystem and it is a world-wide important carbon sink. It grows for millennia, accumulating organic-rich soils (mats) beneath the meadows. This marine habitat is protected by the European Union; however, it is declining rapidly due to coastal development. Understanding its response to disturbances could inform habitat restoration, but many environmental impacts predate monitoring programs (<50 years). This research explores the palaeoecological potential of Posidonia mats to reconstruct six thousand years of environmental change that could have affected Posidonia meadows and, in turn, left an imprint on the mats. Palynological, microcharcoal, magnetic susceptibility and glomalin-related soil protein (GRSP) analyses on Posidonia mats enabled us to detect climate- and human-induced environmental processes impacting on the seagrass during the Late Holocene. The pollen and microcharcoal records reconstructed anthropogenic disturbances attributed to agriculture. The record of GRSP shows that agrarian activities affected continental soil quality. Changes in magnetic susceptibility reveal that enhanced soil erosion was caused by both climate (major flooding events in the NW Mediterranean) and humans (cultivation) which impacted on the Posidonia mat. Finally, increased human impact is linked to eutrophication of coastal waters since Roman-Medieval times. Synthesis. This study shows that climate and land-use changes in the western Mediterranean resulted in enhanced loadings of terrigenous material to the coastal zone since the Late Holocene, likely disturbing the Posidonia meadows and their mat carbon accumulation dynamics. Under the current global change scenario in which CO2 emissions are projected to increase, restoring carbon sinks is a priority. Seagrass habitat restoration should consider not only the coastal perturbations, but also the continental ones at a catchment scale to preserve the socio-econ

Mercury (Hg) is a naturally occurring element that is found throughout the world. Due to the toxicity of its methylated forms (MeHg) to wildlife and human health, Hg is considered a metal of major environmental concern. According to numerous health and governmental organizations, billions of people are currently at risk of high exposure to poisoning by Hg due to a diet rich in fish (high content of MeHg) or by exposure to Hg emitted from artisanal and small-scale gold mining, mainly in low- and middle-income countries. Several industrial processes such as fuel combustion, cement production, metal smelting, large-scale gold mining with non-Hg methods as well as commercial Hg mining, has been emitted thousands of tons of Hg directly to the atmosphere since 1850. In addition to human related processes, several natural processes emit Hg to the environment, such as volcanic activity (geothermal vents, volcanoes) and emissions from natural enriched soils. Other types of Hg cycling mechanisms such as forest fires or oceanic emissions are considered mixed natural-anthropogenic sources. Primary sources transfer Hg from slow-cycling lithospheric reservoirs to the fast cycling atmospheric, oceanic and the terrestrial environments, thereby increasing the global pool of Hg in surface reservoirs. After deposition, Hg can be reemitted from the surface reservoirs to the atmosphere, therefore constituting a secondary source. Recycling from surface reservoirs results in an effective lifetime of 1.6 years before transfer to soil and deep ocean pools. Due to its volatility as Hg0 and the redox transformations of Hg in the environment, deposition and release are influenced by multiple environmental factors including seasonality, vegetation cover, temperature, light, moisture, atmospheric turbulence and the presence of reactants.