Se ha analizado el registro sedimentario reciente del estuario del Nalón a partir de dos sondeos intermareales que han sido datados mediante 210Pb y 137Cs. Los resultados muestran por primera vez sus ...asociaciones características de foraminíferos bentónicos, constituidas por un total de 46 especies, así como los importantes cambios experimentados por estas asociaciones, en consonancia con las variaciones en el magnetismo ambiental, como consecuencia, posiblemente, de las actividades mineras desde 1850 CE que sugieren unas condiciones ambientales deterioradas. Estas malas condiciones persistieron durante décadas, incluso más allá del cese de la minería de mercurio y carbón, hasta el siglo XXI cuando se ha comenzado a observar una leve recuperación ambiental.
Distinguishing between natural and anthropogenic processes in sedimentary records from estuaries with legacy pollutants is an essential task, as it provides baselines to predict future environmental ...trajectories of coastal areas. Here, we have addressed the recent transformation history of the mining-impacted Nalón Estuary (Asturias, N Spain). Surface and core sediment records from marshes and tidal flats were examined through a broad multidisciplinary approach, involving micropaleontological (benthic foraminifera), sedimentological (grain-size), geochemical (trace metals, major element Al and total organic carbon), physical (magnetic susceptibility, frequency-dependent magnetic susceptibility and large microplastics) and radioisotopic (210Pb, 137Cs and 239+240Pu) proxies. Results suggest that the interplay between natural (high fluvial influence and extreme hydrological events) and anthropogenic (coal and mercury mining disposals) factors induced strong sedimentation-erosion processes, further shaping the recent evolution of the estuary. Short-time scale and intense sedimentation processes were revealed by overall high sediment accumulation rates, the dilution of some geological signatures and the rapid formation of a marsh in the lower estuary bay. The increasing mining fingerprints during the 20th century were shortly interrupted by the catastrophic riverine flooding of 1938. Conversely, current erosional processes by fluvial influence led to the remobilization of contaminated sedimentary materials and exposure of mining-legacy Hg levels in tidal flats from the middle sector. Fluvial activity, floodings and taphonomic biases exerted a major control on benthic foraminifera since the 19th century, although Hg ecotoxicological effects on modern assemblages at certain areas within the estuary cannot be discarded. These findings, along with the documented enhanced erosion of marshes with ‘trapped’ pollutants (Hg, coal microparticles and microplastics), highlight the importance of monitoring the environmental and geomorphic processes taking place in historically-contaminated estuaries.
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•Natural and human driving forces interacted influencing sedimentation-erosion processes.•High sedimentation was induced by natural turbidity and mining disposals.•Extreme flooding affected sedimentary deposits impacted by mining.•Fluvial erosion caused the remobilization of mercury-contaminated tidal sediments.•Erosion of marshes containing high levels of Hg, coal microparticles and abundant microplastics should be monitored.
Galician rías provide several ecosystem services of great ecological and economic significance in the northwestern Iberian margin, requiring a good environmental quality for sustainable harnessing. ...More paleoenvironmental reconstructions extending to their preindustrial state are needed to predict their evolution under natural and human-induced perturbations, such as ongoing anthropogenic global warming. This study's aim is twofold: first, characterize the current environmental conditions governing the inner Ría of Ferrol (Galicia, NW Spain) and address its recent natural and anthropogenic evolution. Therefore, a multiproxy approach (benthic foraminifera, grain size, pollen content, trace metals, Al, total organic and inorganic carbon contents, total nitrogen content, δ13C, magnetic susceptibility, 210Pb and 137Cs radiotracers, and microplastics) has been applied to intertidal surface and sediment core samples. The benthic foraminiferal results exhibit typical inner ría assemblages, primarily driven by natural ría-estuarine dynamics, with a higher dominance of brackish species (H. germanica, A. morphogroup tepida), fewer living individuals and marine allochthonous taxa toward the continental end-member. The foraminiferal standing crops and surface trace metal concentrations do not reflect strong anthropogenic impacts, although areas with elevated magnetic susceptibility have been detected, probably associated with nearby industrial activities. The recent sedimentary deposits reveal anthropogenic impacts at local and regional scales, with different environmental shifts. Local impacts were triggered by physical interventions in the inner ría, with the construction of the As Pías Bridge in 1968 and the great urban-industrial development of Ferrol city and surrounding localities experienced since the late 19th century. Land-use changes have driven regional scale changes, corresponding to reforestation plans with the introduction of anthropogenic plant species for industrial purposes initiated in the 1940s. The stratigraphic analysis of sediment cores has unveiled high levels of contaminants (Zn and microplastics) in the innermost sector as the primary environmental concerns. In this sediment-infilling and restricted area, potential dredging activities could release them leading to their possible bioavailability. Although past adverse environmental conditions cannot be discarded, sedimentary intervals with negligible presence of microfauna in the innermost area have mostly been attributed to taphonomic processes involving calcareous dissolution and disaggregation of agglutinated tests, likely caused by carbonate-undersaturated conditions and organic matter metabolization by microbial activity respectively.
•Inner ría sediments allow a precise (paleo)environmental reconstruction.•The overall current environmental state of the inner ría is good.•Historical environmental shifts at local and regional scales have been detected.•Zn and microplastics, main contaminants, could be made bioavailable after dredging.•Azoic intervals resulted from taphonomic biases, not only from anthropogenic impacts.
Antropozenoa: "Urre koloreko iltze"-aren bila Irabien, María Jesús; Cearreta, Alejandro; García-Artola, Ane ...
EKAIA Euskal Herriko Unibertsitateko Zientzia eta Teknologia Aldizkaria,
01/2022
42
Journal Article
Odprti dostop
Antropozeno hitzak, gizakia, Holozeno Epokaren aurreko dinamika naturalak aldatzeko gai eta indar geologiko erabakigarri bihurtu den denbora tarte geologikoari egiten dio erreferentzia. 2009az ...geroztik, Antropozenoko lantaldea Antropozenoa ikuspegi geologikotik definitzen zentratu da, Estratigrafiari buruzko Nazioarteko Batzordeak ezarritako arauak jarraituz eta, hortaz, zer unitate kronoestratigrafikoa, beheko mugaren adina eta haren markatzaile estratigrafiko nagusiak adierazten dituzten proposamenak eginez. Erradionuklido artifizialek (137Cs, 241Am, 239Pu, 240Pu) potentzial handia eskaintzen dutela dirudi, ingurunean sinkronikoki agertzen direlako 1950 inguruko “Great Acceleration” prozesuaren ondorioz. Hala eta guztiz ere, oraindik azterketa sakonagoak behar dira denbora geologiko hau formalizatzeko behar diren irizpide estratigrafiko guztiak betetzen dituen GSSP egokia aurkitzeko. Lan honen helburua Antropozenoko lantaldearen jarduera, Antropozeno kontzeptua egituratzen duten eztabaida-elementu nagusiak eta orain arte lortutako ondorio nagusiak laburbiltzea da.
The historical anthropogenic impact on sediments from the Basque Mud Patch (southern Bay of Biscay) is explored using a multidisciplinary approach including the analysis of natural (210Pb) and ...artificial (137Cs, 239/240Pu) radiotracers, major elements (Al, Mn), metals (Zn, Pb, Cu, Cr), Pb isotopic ratios, and foraminiferal and pollen contents. The study of three short cores (19–46 cm), despite being hindered by the effects of biomixing, allow the calculation of a sedimentation rate of 1 ± 0.1 mm yr−1. Distribution with depth of Al-normalised concentrations of metals reflects an increasing trend since 1880 CE, related to the industrialization of the Basque coastal area. According to the Sediment Quality Guidelines applied, contents of Zn and Pb appear as a potential cause of concern, given that they exceed the values from which adverse biological effects can be occasionally expected. However, foraminiferal assemblages do not show recognizable changes along the cores following increasing trace metal concentrations. Finally, pollen results reveal an increasing trend of coniferous taxa and a parallel reduction of authochthonous Deciduous Quercus, probably as a consequence of reforestation works. Data obtained confirm that effects of coastal anthropogenic activities extend to the adjacent shelf, where muddy deposits are likely to act as a trap for contaminants.
The multi-proxy study of sediment cores from Lake Isoba (43° 02′ N, 5° 18′ W; 1400 m a.s.l.) allows a detailed assessment of the past hydrological and environmental dynamics in north-western Iberia ...resulting from the interplay between climate variability and anthropogenic impact. The combination of diatom stratigraphy, sedimentology and high-resolution elemental geochemistry along with a robust chronological framework (established by
210
Pb,
137
Cs and
14
C dating) provides a detailed environmental reconstruction for the past ~ 500 years. Abrupt changes in the fossil diatom assemblages indicate a high sensitivity of this small lake to past environmental change and allow identifying four major stages related to the main climate fluctuations of the Little Ice Age (LIA) and recent warming. High lake levels, enhanced runoff and higher productivity characterised the middle phase of the LIA (~ 1550 to 1630 CE), indicating an overall wet climate. Conversely, shallow lake levels, decreased runoff and relatively low productivity prevailed during the last phase of the LIA and the onset of the Industrial Era (~ 1630 to 1925 CE), likely due to colder and drier conditions. High lake levels and higher carbonate input occurred after ~ 1925 CE until the 1980s CE, when our data show an abrupt drop in lake levels probably caused by a regional negative rainfall anomaly related to climate warming during the past decades. Finally, since ~ 1997 CE a remarkable and abrupt increase in the lake nutrient load and turbidity is detected, probably associated with the replacement of transhumant sheep flocks with staying cattle. The main environmental changes reconstructed at Lake Isoba mostly agree with other palaeoclimatic records from northern Spain. However, the hydrological patterns reconstructed are opposed to those observed on the northern slopes of the Cantabrian Mountains. The recent and strong impact of land-use changes on the lake, causing more ecological disruptions than previous climate changes, is noteworthy and demonstrates the high sensitivity of mountain lakes to human activities in a global change context.
Aim
Pinewood decline and scrubland expansion are major features of Late Holocene vegetation history in the Cantabrian Range. However, the drivers of this remarkable vegetation shift remain to be ...investigated. Here, we aim at disentangling the role of past land use and climate in shaping the high‐elevation Cantabrian landscape during the past two millennia.
Location
Cantabrian Range (northern Iberia).
Taxa
Pinus sylvestris, Betula, Ericaceae, Juniperus, Poaceae.
Methods
We conducted high‐resolution multiproxy palaeoecological analyses (pollen, plant macrofossils, microscopic charcoal and dung fungi) on lake sediments from Lago del Ausente to reconstruct vegetation, fire occurrence and grazing through time. The chronology is based on 14C (terrestrial plant macrofossils) and 210Pb dating, and Bayesian age‐depth modelling (‘rbacon’). We carried out cross‐correlation analysis to quantify vegetation responses to fire.
Results
Between 250 and 900 CE, the vegetation above 1700 m a.s.l. consisted of subalpine scrubland and scattered P. sylvestris trees/stands. Pinewoods with Betula were widespread at slightly lower elevation. This vegetation was resilient to moderate fire disturbance associated with limited pastoral activities. In contrast, enhanced fire occurrence alongside heavier pastoralism led to the demise of pinewoods and their replacement with Betula stands, subalpine scrublands, and meadows between 900 and 1100 CE. Later, the subalpine scrubland‐birch tree line did not respond to Little Ice Age cooling. However, further intensification of transhumant herding between 1300 and 1860 CE (‘La Mesta’) triggered birch decline and the establishment of the modern treeless landscape.
Main conclusions
The extant high‐elevation vegetation of the Cantabrian Range is largely the legacy of intensive land use starting more than one millennium ago. Recurrent and severe fires to promote pasturelands led to the regional extirpation of the previously widespread Pinus sylvestris. Future management should aim at preserving the valuable cultural open landscape of mountain scrubland and meadows and also at restoring patches of ancient pine‐birch woodlands.
The lipid content of a high mountain lake (Lake Isoba) allowed the reconstruction of the paleoenvironmental changes and anthropic influence in Northern Spain during the last 550 years. Fatty acids ...(FAs) and n-alkan-2-ones indicate little degradation of OM. Three units were delimited. During Unit A (ca. 1460–1780 CE) high carbon preference index values, predominance of high-molecular-weight saturated FAs, and good correspondence between the predominant n-alkane and saturated FA chains indicate higher OM input and evidence of minimal degradation, linked to the cold and dry Little Ice Age, that favoured the OM input derived mainly from land plants, and the reduced bacterial activity. In Unit B (ca. 1780–2006 CE) the n-alkane and saturated FA profiles showed a remarkable mismatch suggestive of preferential microbial synthesis of long chain saturated FAs from primary OM and/or bacterial activity (predominance of low-molecular-weight saturated FAs but with a bimodal distribution), in coincidence with a decrease in OM input, which could be linked to the global warming that started in the second half of the 19th century. Although OM continued deriving mainly from terrigenous plants, aquatic macrophytes increased their contribution to the OM indicating the amelioration of environmental conditions. Evidence of considerable phytoplankton productivity and microbial activity was significant in Unit C (ca. 2006–2018 CE) coinciding with the highest concentrations of n-alkanes and saturated FAs, linked to warmer and drier conditions, and to greater anthropogenic influence. In addition, organic sulfur and gammacerane indicates loss of oligotrophy, and the record of faecal stanols, particularly that of 24-ethylcoprostanol, strongly evidences notable and rising water pollution associated with increasing cattle ranching in the lake catchment during the past 10–15 years.
•Higher land plants input and little degradation took place during the Little Ice Age.•Higher aquatic macrophytes input and greater degradation occurred from 1780 to 2006.•Phytoplankton productivity and microbial activity has been significant since 2006.•Faecal stanols revealed pollution from herbivores since the 15th century.•Faecal stanols pollution markedly increased since 2006.
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