Response of Benthic Foraminifera to organic matter quantity and quality and bioavailable concentrations of metals in Aveiro Lagoon (Portugal)

This work analyses the distribution of living benthic foraminiferal assemblages of surface sediments in different intertidal areas of Ria de Aveiro (Portugal), a polihaline and anthropized coastal lagoon. The relationships among foraminiferal assemblages in association with environmental parameters (temperature, salinity, Eh and pH), grain size, the quantity and quality of organic matter (enrichment in carbohydrates, proteins and lipids), pollution caused by metals, and mineralogical data are studied in an attempt to identify indicators of adaptability to environmental stress. In particular, concentrations of selected metals in the surficial sediment are investigated to assess environmental pollution levels that are further synthetically parameterised by the Pollution Load Index (PLI). The PLI variations allowed the identification of five main polluted areas. Concentrations of metals were also analysed in three extracted phases to evaluate their possible mobility, bioavailability and toxicity in the surficial sediment. Polluted sediment in the form of both organic matter and metals can be found in the most confined zones. Whereas enrichment in organic matter and related biopolymers causes an increase in foraminifera density, pollution by metals leads to a decline in foraminiferal abundance and diversity in those zones. The first situation may be justified by the existence of opportunistic species (with high reproduction rate) that can live in low oxic conditions. The second is explained by the sensitivity of some species to pressure caused by metals. The quality of the organic matter found in these places and the option of a different food source should also explain the tolerance of several species to pollution caused by metals, despite their low reproductive rate in the most polluted areas. In this study, species that are sensitive and tolerant to organic matter and metal enrichment are identified, as is the differential sensitivity/tolerance of some species to metals enrichment.CNPq [401803/2010-4]; [PEst-OE/CTE/UI4035/2014]info:eu-repo/semantics/publishedVersio

Coastal Upwelling and Radiocarbon—Evidence for Temporal Fluctuations in Ocean Reservoir Effect off Portugal During the Holocene

This paper focuses on the use of the radiocarbon content of marine shells collected along the Portuguese coast as a proxy for the intensity of coastal upwelling off of Portugal. Differences in the 14C ages of closely associated marine mollusk shells and terrestrial material (charcoal or bones) from several Portuguese archaeological contexts seem to be significant throughout the Holocene. Delta-R values range from 940 +/50 to 160 +/40 14C yr. Five of these values are significantly higher than the modern value (250 +/25 14C yr), while the remaining values are lower. The modern value was calculated by measuring the 14C content of live-collected, pre-bomb marine mollusk shells. This value is in accordance with an active upwelling of strong intensity that currently occurs off of Portugal. Some primary observations based on data presented here can be made: i) during the Holocene important changes have occurred in the ocean reservoir effect off the Portuguese coast; ii) these fluctuations may be correlated with regional oceanographic changes, namely with changes in the strength of coastal upwelling; and iii) these changes suggest some sort of variability of the climatic factors forcing coastal upwelling off of Portugal.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Atlantic sea surface temperatures estimated from planktonic foraminifera off the Iberian Margin over the last 40Ka BP

Sea surface temperatures (SSTs) were reconstructed from planktonic foraminiferal assemblages in two sediment cores off the NW Iberian Continental Margin for the last 40 kyr. Results of this work were compared with published SSTs estimated in six cores from the Iberian Margin and the delta O-18 data from NGRIP ice core of Greenland. Longitudinal and latitudinal SST changes were identified in several intervals related to alterations in the hydrographic conditions off the Iberian Peninsula, namely the influence of the upwelling system, the intensity of Paleo-Portugal and Paleo-Azores Currents, and the positions of the Polar and Arctic Fronts. During the Holocene, the SSTs were quite stable along the west Iberian Margin when compared with the last glaciation. However, during the Last Glacial Maximum (LGM) SSTs were not much lower than during the Holocene. The Portugal Current, as an eastward descending branch of the North Atlantic Drift, should have been quite vigorous in transporting warm water to the west Iberian Margin, which could have moderated the SSTs during the LGM. However, our results suggest a much higher instability during the LGM than previously reported and much lower SSTs at 42 degrees N. The lowest SSTs during the last 40 ka were recorded during the Heinrich Stadials (HS) and the Younger Dryas (YD). During the HS, SSTs at the northwest Iberian Margin were lower than today by about 10 to 16 degrees C as a result of the invasion of cool and low-salinity water masses and the increased transport of icebergs from the northern seas. The Polar Front was persistently situated at 42 degrees N for similar to 3 ka during the HS1, and a comparable present-day Arctic Front should have been present up to the latitude of 40 degrees N during the HS2, HS3, and HS4 off the west Iberian Peninsula. The HS were recorded all along the west Iberian Margin. However, an overall trend of increasing of mean SSTs from north to south of similar to 8 degrees C during the HS1, of similar to 10 degrees C during the HS2b and HS3, of similar to 11 degrees C during the HS2a, and of similar to 4 degrees C during the HS4 was recorded. These gradients also were present during the YD of similar to 9 degrees C and the LGM of similar to 4 degrees C and may be related to the strong influence of the Paleo-Azores Current in southern areas

Atlantic sea surface temperatures estimated from planktonic foraminifera off the Iberian Margin over the last 40 Ka BP

Sea surface temperatures (SSTs)were reconstructed fromplanktonic foraminiferal assemblages in two sediment cores off the NWIberian Continental Margin for the last 40 kyr. Results of this work were compared with published SSTs estimated in six cores from the Iberian Margin and the δ18O data from NGRIP ice core of Greenland. Longitudinal and latitudinal SST changes were identified in several intervals related to alterations in the hydrographic conditions off the Iberian Peninsula, namely the influence of the upwelling system, the intensity of Paleo-Portugal and Paleo-Azores Currents, and the positions of the Polar and Arctic Fronts. During the Holocene, the SSTswere quite stable along thewest IberianMarginwhen comparedwith the last glaciation. However, during the Last Glacial Maximum(LGM) SSTswere notmuch lower than during the Holocene. The Portugal Current, as an eastward descending branch of the North Atlantic Drift, should have been quite vigorous in transporting warm water to the west Iberian Margin, which could have moderated the SSTs during the LGM. However, our results suggest a much higher instability during the LGMthan previously reported and much lower SSTs at 42°N. The lowest SSTs during the last 40 ka were recorded during the Heinrich Stadials (HS) and the Younger Dryas (YD). During the HS, SSTs at the northwest Iberian Margin were lower than today by about 10 to 16 °C as a result of the invasion of cool and low-salinity water masses and the increased transport of icebergs from the northern seas. The Polar Front was persistently situated at 42°N for ~3 ka during the HS1, and a comparable present-day Arctic Front should have been present up to the latitude of 40°Nduring the HS2, HS3, andHS4 off thewest Iberian Peninsula. The HS were recorded all along the west Iberian Margin. However, an overall trend of increasing of mean SSTs from north to south of ~8 °C during the HS1, of ~10 °C during the HS2b and HS3, of ~11 °C during the HS2a, and of ~4 °C during the HS4 was recorded. These gradients also were present during the YD of ~9 °C and the LGM of ~4 °C and may be related to the strong influence of the Paleo-Azores Current in southern areas

Available concentrations (μg kg^-1) in the studied sites of: a) Zn, b) Pb, c) As, d) Cu and e) Hg, in the three mobile phases (S1, S2 and S3).

<p>Legend: OvCh—Ovar Channel, MuCh—Murtosa Channel, EsCh—Espinheiro Channel, AvC—Aveiro city canals, AvH—Aveiro Harbor</p