Organic-walled dinoflagellate cyst assemblages in surface sediments of the Ría de Vigo (Atlantic margin of NW Iberia) in relation to environmental gradients

Organic-walled dinoflagellate cyst assemblages were analysed in 31 surface sediment samples from the Ría de Vigo (NW Iberia) to obtain supporting evidence for the interpretation of past environmental signals from sediment cores. Complementarily, the totals of pollen (and pollen from riparian taxa), foraminiferal linings and freshwater algae were also considered to test their value as (palaeo)environmental indicators in fluvio-marine sedimentary environments. Abundances of foraminiferal linings gradually increased towards the ría's mouth, which supports its use as a proxy to infer the degree of marine influence in the sediment record. The ratio of dinoflagellate cysts to pollen and spores (D/P) increased with distance to the main river's mouth (and water depth) in the inner ( 20 m) parts of the ría. Total pollen concentrations decreased with water depth in the outer part but did not show any clear trend in the rest of the ría. No clear pattern in the distributions of pollen from riparian plants and spores from freshwater microalgae was detected. Multivariate analyses (clustering and RDA) performed on dinoflagellate cyst records and environmental data reflected a marked inshore-offshore distribution pattern mainly controlled by a fluvio-marine environmental gradient. Increasing abundances of cysts of Gymnodinium species and heterotrophic cysts as well as higher cyst diversity characterised the deeper environments of the outer ría. These observations suggest a relationship with increased shelf influence and are compatible with the heterotroph upwelling signal described in previous works. A very different cyst association with a predominance of autotrophic cysts characterised the intermediate and inner parts of ría, where exceptionally high cyst abundances of Lingulodinium polyedra (∼ 56–99% and ∼ 200–114,000 cysts.g−1) were reported. Abundances of cysts of L. polyedra positively correlated with shallower and higher river-influenced environments characterised by higher sea-surface temperature. Our results agree with previous studies and reinforce the value of this species as an indicator of warmer and stratified conditions. Moreover, cysts of L. polyedra positively correlated with winter sea-surface nitrate contents, which is compatible with the nutrient enrichment signal (natural or anthropogenic) that has already been described in other deep and stratified estuarine environments and is consistent with historical cyst records obtained in the Ría de Vigo. However, further research is needed to disentangle the nutrient enrichment signal from the influence of other environmental factors.Ministerio de Educación y Ciencia | Ref. CGL2012-33584Xunta de Galicia | Ref. GRC 2015/020Xunta de Galicia | Ref. ED431C 2019/28Xunta de Galicia | Ref. ED481B-2019-074Universidade de Vigo/CISU

The Eurasian Modern Pollen Database (EMPD), version 2

The Eurasian (nee European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60% from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019).Peer reviewe

The Eurasian Modern Pollen Database (EMPD), version 2

The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60 % from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019)Swiss National Science Foundation | Ref. 200021_16959

Climatic and environmental changes during the Pleistocene-Holocene transition : new palynologycal data from the "Rías Baixas" (NW Iberia)

El estudio de los efectos de la variación ambiental en los ecosistemas pasados es clave para desarrollar modelos climáticos y predecir futuros cambios medioambientales, con aplicaciones en campos como los relacionados con la gestión del territorio y la conservación de áreas protegidas. A partir de registros estratigráficos obtenidos de sedimentos marinos (Ría de Vigo y Ría de Arousa) y continentales (laguna de La Roya, Sanabria), se pretende reconstruir los cambios ocurridos en el paisaje durante la transición Tardiglaciar-Holoceno, principalmente mediante el estudio de la composición y distribución de polen y otros palinomorfos no polínicos (como dinocistes, esporas de hongos y esporas de clorófitas). Los objetivos de esta tesis incluyen: 1) la obtención e interpretación de secuencias paleoecológicas de alta resolución en medios marinos someros, 2) la correlación de secuencias marinas y secuencias continentales para obtener una visión más global de los cambios ocurridos en el paisaje del NO ibérico y para evaluar cómo las variaciones en la hidrografía marina afectaron al clima regional, 3) la obtención de una correlación precisa de las secuencias polínicas obtenidas y otros proxy data (reconstrucción extendida de la oscilación del Atlántico Norte, datos isotópicos, variaciones de SST, estratigrafía sísmica secuencial, paleotemperaturas reconstruidas a partir de quironómidos, etc) y 5) la contextualización de las secuencias estratigráficas y correlación con los principales reflectores sísmicos del relleno sedimentario de las rías, para una mejor comprensión de las variaciones del nivel del mar. Un aspecto novedoso de este proyecto consiste en la aplicación de análogos modernos y de nuevas técnicas cuantitativas. Los análogos modernos fueron obtenidos a partir de patrones polínicos de diferentes ambientes modernos y serán comparados numéricamente con patrones polínicos fósiles para incrementar la precisión de las interpretaciones paleoecológicas.O estudo dos efectos da variación ambiental nos ecosistemas pasados é clave indispensable para desenvolver modelos climáticos e predicir futuros cambios medioambientais, con aplicacións en campos como os relacionados coa xestión do territorio e a conservación de áreas protexidas. A partir de rexistros estratigráficos obtidos de sedimentos mariños (Ría de Vigo e Ría de Arousa) e continentais (lagoa de La Roya, Sanabria), preténdense reconstruír os cambios ocorridos na paisaxe durante a transición Tardiglaciar-Holoceno, principalmente mediante o estudo da composición e distribución de pole e outros palinomorfos non polínicos (como dinocistes, esporas de fungos e esporas de clorófitas). Os obxectivos desta tese inclúen: 1) a obtención e interpretación de secuencias paleoecolóxicas de alta resolución en medios mariños pouco profundos, 2) a correlación de secuencias mariñas con secuencias continentais para obter una visión máis global dos cambios acontecidos na paisaxe do NO ibérico e para avaliar cómo as variacións na hidrografía mariña afectaron ó clima rexional, 3) a obtención dunha correlación precisa das secuencias polínicas obtidas con outros proxy data (reconstrución estendida da oscilación do Atlántico Norte, datos isotópicos, variacións de SST, estratigrafía sísmica secuencial, paleotemperaturas reconstruídas a partir de quironómidos, etc) e 5) a contextualización das secuencias estratigráficas e correlación cos principais reflectores sísmicos do recheo sedimentario das rías, para unha mellor comprensión das variacións do nivel do mar. Un aspecto novidoso deste proxecto consiste na aplicación de análogos modernos e de novas técnicas cuantitativas. Estes análogos obtéñense a partir de patróns polínicos de medios modernos e serán comparados numéricamente con rexistros fósiles para mellorar a precisión das interpretacións paleoecolóxicas.To study the effects of the environmental changes on past ecosystems is important to develop climate modelling and predict future environmental changes. The applications of such studies include the management of the land and the conservation of protected areas. We aim to reconstruct the changes occurred in the landscape during the Lateglacial-Holocene transition, by analysing the composition and distribution of pollen and other non-pollen palinomorphs (namely dinocysts, fungal and algal spores) of stratigraphic samples obtained from marine (Ría de Vigo and Ría de Arousa) and continental sediments (laguna de La Roya, Sanabria). The objectives are: 1) to obtain and interpret high-resolution palaeological sequences from shallow marine environments, 2) to correlate marine and continental sequences in order to obtain a general view of the changes occurred in the NO Iberia landscape and evaluate how hydrographical variations affected the regional clime, 3) to perform an accurate correlation of the obtained pollen sequences and other proxy data (extended reconstruction of the North Atlantic Oscillation, isotopic data, sea-surface temperature variations, sequential seismic stratigraphy, palaeotemperatures reconstructions from chironomids, etc.) and 5) to contextualize stratigraphic sequences and correlate them with the main seismic reflectors of the sediments of the rias basins, for a better understanding of the past sea-level fluctuations. A novelty included in the methodology consists on the application of modern pollen analogues and quantitative techniques. These modern analogues have been obtained from pollen patterns of different modern environments and will be compared numerically with fossil assemblages. This could help to improve the palaeoecological interpretation of stratigraphic pollen samples.Xunta de Galicia (PRE/2013/404)Ministerio de Economía y Competitividad de España (CGL2012-33584BTE)Fondos FEDER. Programa operativo de Galicia 2007-2013 (CN 2012-301)GRC2015/020Fundación Barri