Seasonal patterns of pollen sedimentation in Lake Montcortès (Central Pyrenees) and potential applications to high-resolution paleoecology: a 2-year pilot study

14 páginas, 2 tablas, 10 figuras.Lakes with varved sediments are especially well suited for paleoecological study, from annual to even seasonal resolution. The interpretative power of such high-resolution paleoenvironmental reconstructions relies on the availability of modern analogs with the same temporal resolution. We studied seasonal pollen sedimentation in varved Lake Montcorte`s, Central Pyrenees (Spain), as a modern analog for highresolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a 2-year period (fall 2013 to fall 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus (pine) and Quercus (oak), followed a clear seasonal pattern that peaked during the spring/summer, coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed formost pollen types, as substantial amounts of pollen were found in the traps outside of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition, corresponding to spring/summer and fall/winter. This pattern is consistent with existing interpretation of the sediment varves, specifically, that varves are formed by two-layer couplets that represent the same seasonality as pollen. We concluded that pollen sedimentation in Lake Montcorte`s exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen assembalges, and relationships between the pollen and meteorological variables. Thus, varved sediments provide a potentially powerful tool for paleoecological reconstruction at seasonal resolution. This method could be used not only to identify paleoenvironmental trends, but also to identify annual layers and therefore date sediments, even in the absence of evident sediment laminations. A satisfactory explanation of PSL will require further studies that examine internal lake dynamics and pollen production/dispersal patterns.This work was funded by the Ministry of Economy and Competitivity (project MONT-500; reference CGL2012-33665; PI: Teresa Vegas-Vilarru´bia).Peer reviewe

Seasonal patterns of pollen sedimentation in Lake Montcortès (Central Pyrenees) and potential applications to high-resolution paleoecology: a two-year pilot study.

Lakes with varved sediments are especially well suited for paleoecological study, from annual to even seasonal resolution. The interpretative power of such high-resolution paleoenvironmental reconstructions relies on the availability of modern analogs with the same temporal resolution. We studied seasonal pollen sedimentation in varved Lake Montcorte`s, Central Pyrenees (Spain), as a modern analog for highresolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a 2-year period (fall 2013 to fall 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus (pine) and Quercus (oak), followed a clear seasonal pattern that peaked during the spring/summer, coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed for most pollen types, as substantial amounts of pollen were found in the traps outside of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition, corresponding to spring/summer and fall/winter. This pattern is consistent with existing interpretation of the sediment varves, specifically, that varves are formed by two-layer couplets that represent the same seasonality as pollen. We concluded that pollen sedimentation in Lake Montcorte`s exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen assembalges, and relationships between the pollen and meteorological variables. Thus, varved sediments provide a potentially powerful tool for paleoecological reconstruction at seasonal resolution. This method could be used not only to identify paleoenvironmental trends, but also to identify annual layers and therefore date sediments, even in the absence of evident sediment laminations. A satisfactory explanation of PSL will require further studies that examine internal lake dynamics and pollen production/dispersal patterns

Accidentes de trabajo en un hospital de agudos

FUNDAMENTO: El mejor conocimiento de los determinantes y circunstancias de producción de los accidentes laborales, favorecerá la implantación de medidas correctoras. El objetivo de este trabajo es describir la evolución temporal de los accidentes de trabajo (AT) y determinar los factores de riesgo de baja médica en el Hospital Dr. Peset de Valencia. MÉTODOS: Descripción y análisis retrospectivo de los accidentes de trabajo producidos en el Hospital Dr. Peset de Valencia durante los años 1992 a 1995. Se estimó por métodos deterministas la tendencia y estacionalidad de las series (índices estacionales, IE). Se aplicó un modelo de regresión logística para identificar los factores pronósticos de baja médica y determinar su probabilidad de ocurrencia . RESULTADOS: Las tasas más elevadas de AT se produjeron entre los trabajadores de cocina y lavandería (10,00 AT por 100 trabajadores-año. Los AT con baja médica mantienen una tendencia cercana a cero siendo febrero el mes con I.E más elevado (IE=139,8). Los que cursan sin baja médica tienen una tendencia positiva (r²=0,23, p<0,0001), siendo mayo el mes de mayor siniestralidad (IE=134,2). La probabilidad de que el accidente curse con baja médica aumenta significativamente con la edad, cuando se produce por la tarde, si ha tenido lugar en cocina/lavandería, y si se trata de un esguince o tendinitis. CONCLUSIONES: la actuación sobre la siniestralidad en los AT que cursen con IT, debería centrarse sobre los trabajos menos cualificados y en las áreas de cocina y lavandería

Seasonal patterns of pollen sedimentation in Lake Montcortès (Central Pyrenees) and potential applications to high-resolution paleoecology: a two-year pilot study.

Lakes with varved sediments are especially well suited for paleoecological study, from annual to even seasonal resolution. The interpretative power of such high-resolution paleoenvironmental reconstructions relies on the availability of modern analogs with the same temporal resolution. We studied seasonal pollen sedimentation in varved Lake Montcorte`s, Central Pyrenees (Spain), as a modern analog for highresolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a 2-year period (fall 2013 to fall 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus (pine) and Quercus (oak), followed a clear seasonal pattern that peaked during the spring/summer, coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed for most pollen types, as substantial amounts of pollen were found in the traps outside of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition, corresponding to spring/summer and fall/winter. This pattern is consistent with existing interpretation of the sediment varves, specifically, that varves are formed by two-layer couplets that represent the same seasonality as pollen. We concluded that pollen sedimentation in Lake Montcorte`s exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen assembalges, and relationships between the pollen and meteorological variables. Thus, varved sediments provide a potentially powerful tool for paleoecological reconstruction at seasonal resolution. This method could be used not only to identify paleoenvironmental trends, but also to identify annual layers and therefore date sediments, even in the absence of evident sediment laminations. A satisfactory explanation of PSL will require further studies that examine internal lake dynamics and pollen production/dispersal patterns

Historical shifts in oxygenation regime as recorded in the laminated sediments of lake Montcortès (Central Pyrenees) support hypoxia as a continental-scale phenomenon

Este artículo contiene 16 páginas, 9 figuras.Recent expansion of anoxia has becomea global issue and there is potential forworsening under global warming. At the same time, obtaining proper long-term instrumental oxygen records is difficult, thus reducing the possibility of recording long-term changes in oxygen shifts that can be related with climate or human influence. Varved lake sediments provide the better time frame to study this phenomenon at high resolution. We tracked the oxic/anoxic shifts of the varved LakeMontcortès since 1500 CE, and tried to recognise anthropogenic and climatic influences combining biological and geochemical proxies. Four main scenarios emerged: 1) years with abrupt sediment inputs (A); 2) years with outstanding mixing and oxygenation of the water column (B); 3) years with strong stratification, anoxia, intense sulfur bacterial activity and increased biomass production (C); 4) yearswith stratification and anoxia, but relatively less biomass production (D). In line with current limnologic trends, high supra-annual variability in the occurrence of oxygenation events was observed. Interestingly, at least 45.3% of the years were mixing years and, like the meromictic ones, were mostly clustered into groups of consecutive years, thus alternating years of monomixis with years of meromixis. Most years of D belong to the period 1500–1820 CE, when human activities were the most intense. Most years of A belonged to the climatic unstable period of 1850–1899 CE. Years of B were irregularly distributed but were best represented in the period 1820–1849 CE.Most years of C belonged to the 20th century. More than 90% of the years with climatic instrumental records belonged to B and C. Current climate warming seems to be taking control over the oxygenation capacity of the lake, especially since the second half of the 20th century. Our results support recent findings related to hypoxia spreading at the global scale.Funding was granted by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (projects MONT-500, ref. CGL2012-33665; GLOBALKARST, ref. CGL2009-08145), the Institute of Catalan Studies (PIRIMOD and POLMONT), and the CatalanUniversity and Research Management Agency (AGAUR) (project 2014 SGR 1207). Training research grantswere awarded toM. Carmen Trapote and Núria Pérez-Zanón and funded by MINECO (BES-2013-065846) and the University Rovira i Virgili (Martí Franquès program, 2104PMF-PIPF-22), respectively.Peer reviewe

Modern Analogue Approach Applied to High-Resolution Varved Sediments—A Synthesis for Lake Montcortès (Central Pyrenees)

Este artículo contiene 23 páginas, 10 figuras.In Quaternary paleosciences, the rationale behind analogical inference presupposes that former processes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesised the results of di erent modern analogue studies performed in a varved lake. We discuss their potential value to obtain best results from high resolution past records. Di erent biogeochemical contemporary processes revealed seasonality and year-to-year variability, e.g., calcite precipitation, lake oxygenation, production and deposition of pollen and phytoplankton growth. Fingerprints of the first two of these processes were clearly evidenced in the varve-sublayers and allow understanding related to past events. Pollen studies suggested the possibility of identifying and characterizing seasonal layers even in the absence of varves. Marker pigments in the water column were tightly associated with phytoplankton groups living today; most of them were identified in the sediment record as well. We observed that 50% of these marker pigments were destroyed between deposition and permanent burying. In another study, seasonality in the production/distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and derived temperature estimates were investigated in catchment soils and particles settling in the lake. The signatures of brGDGTs in depositional environments mainly were representative of stable conditions of soils in the catchment that last over decades; no brGDGTs seemed to be produced within the lake. The main contribution of this review is to show the advantages and limitations of a multiproxy modern-analogue approach in Lake Montcortès as a case study and proposing new working hypotheses for future research.Research funding was granted by the Spanish Ministry of Economy and Competitivity (MINECO/FEDER) with the projects MONT-500, ref. CGL2012-33665; GLOBALKARST, ref. CGL2009-08145), the Institute of Catalan Studies with the projects PIRIMOD and POLMONT, and the Catalan University and Research Management Agency (AGAUR) with the projects 2014 SGR 1207, 2017 SGR 1116).Peer reviewe