Portuguese Margin Research Articles

A Southern Portuguese Margin Perspective of Marine Isotope Stage 47—An Interglacial in the 41 kyr World

In order to better understand interglacial climate variability within the 41 kyr world, we produced high-resolution climate records for interglacial Marine Isotope Stage (MIS) 47 (1424–1452 ka) at IODP Site U1387 (36°48′ N, 7°43′ W) on the southern Portuguese margin. Using benthic and planktonic foraminifera stable isotope records, Uk’37 sea-surface temperature (SST), and plankton assemblage data we investigated Mediterranean Outflow Water (MOW) and surface water conditions. The MOW-level records indicate a poorly ventilated and sluggish bottom current during the MIS 48/MIS 47 transition in association with the insolation maximum, whereas a well-ventilated MOW formed a contourite layer during the second insolation maximum. The benthic δ18O record shows a fairly abrupt change during the deglaciation of MIS 48, while the surface waters experienced a terminal stadial event that was associated with initial cooling and freshening followed by stepwise warming until interglacial SST was reached at 1450 ka. Interglacial conditions with SST of 24 °C or higher persisted until 1427 ka, although warm SST prevailed into MIS 46. The persistent and prolonged warmth is attributed to a northward expansion of the subtropical gyre during MIS 47 as reflected by the dominance of subtropical-tropical planktonic foraminifera species and the presence of warm water coccolithophores taxa.

Stratigraphic templates for ice core records of the past 1.5 Myr

Abstract. The international ice core community has a target to obtain continuous ice cores stretching back as far as 1.5 Myr. This would provide vital data (including a CO2 profile) allowing us to assess ideas about the cause of the Mid-Pleistocene Transition (MPT). The European Beyond EPICA project and the Australian Million Year Ice Core project each plan to drill such a core in the region known as Little Dome C. Dating the cores will be challenging, and one approach will be to match some of the records obtained with existing marine sediment datasets, informed by similarities in the existing 800 kyr period. Water isotopes in Antarctica have been shown to closely mirror deepwater temperature, estimated from Mg/Ca ratios of benthic foraminifera, in a marine core on the Chatham Rise near to New Zealand. The dust record in ice cores resembles very closely a South Atlantic marine record of iron accumulation rate. By assuming these relationships continue beyond 800 ka, our ice core record could be synchronised to dated marine sediments. This could be supplemented, and allow synchronisation at higher resolution, by the identification of rapid millennial-scale events that are observed both in Antarctic methane records and in emerging records of planktic oxygen isotopes and alkenone sea surface temperature (SST) from the Portuguese Margin. Although published data remain quite sparse, it should also be possible to match 10Be from ice cores to records of geomagnetic palaeo-intensity and authigenic 10Be/9Be in marine sediments. However, there are a number of issues that have to be resolved before the ice core 10Be record can be used. The approach of matching records to a template will be most successful if the new core is in stratigraphic order but should also provide constraints on disordered records if used in combination with absolute radiogenic ages.

The Deep South Portuguese Margin: An Attempt to Account for Heat Flow Density Variation in this Region

Heat flow data measured in a region characterized by a very high and non-uniform thickness (accretionary prism) of sediments, traversed by strike-slip faults in the E-W direction and thrust faults in the N-S direction, were analyzed. Mud volcanoes have been discovered in the region during the last 20 years. The region includes parts of the borders between the Eurasian and the African plates, at SW of the Iberian Peninsula. Sediment porosity and vertical fluid movements were inferred from thermal conductivity and thermal gradient data. Fault location and boundary of the sediment prism were used to test the results inferred and to explain the scatter in the published heat flow values. Special attention was given to values obtained in regions separating different geologic settings (Gorringe Bank – Horseshoe Plain and Marquês de Pombal fault region). Geoid height values were used to obtain information related with heat flow values from deep parts of the Horseshoe plain and in the Gorringe Bank located in the western part of the region studied outside the accretionary prism of sediments. Information related with the evolution of some transient properties in the region were obtained from geoid height variations using three models made for three different years. Information about the thermal disturbance caused by fluid movements in the region and the heat flow values without them were obtained at the end of the work.

Submarine Active Faults and Morpho-Tectonics Around the Iberian Margins: Seismic and Tsunamis Hazards

The aim of this work is to make a synthesis at regional scale focused on the geophysical characterization of submarine faults around the Iberian margin to identify active structures and analyze their development in the framework of the present plate organization. Most of these submarine faults show seabed morphological expressions mapped with high-resolution swath bathymetry data, high-resolution parametric sub-bottom profiles and multichannel seismic profiles. Present active tectonics, deformation, seismicity, and tsunami-affected coastal areas is mainly focused on south Iberia at the Eurasian and Nubia plate boundary. Submarine active faults in these areas are represented by long strike-slip fault systems and arcuate fold-thrust systems. Their development takes place in response to present NW-SE convergence between the Eurasian and Nubia plates. We propose a strain partitioning model of the plate boundary into simple and pure shear zones to explain the distribution and mechanisms of active submarine faults along the Gulf of Cádiz, Gibraltar Arc and Alborán Sea in response to the present-day shear stress orientation. Nevertheless, deformation is also focused in the NW Iberian margin. Thus, along the Galician and Portuguese margin, several submarine faults mapped as thrust fault systems with high-seismic activity along the Iberian ocean-continent transition reflect the re-activation of former structures. We suggest that submarine active faults in the NW and W Iberia are also the response to the eastwards transfer of short-offset transform faults of the Mid Atlantic Ridge into the oceanic Iberian along a weakness as the former plate boundary between the oceanic Iberia and Eurasia domains. The distribution and activity of submarine faults mapped in this work from geophysical and bathymetric data are in good agreement with geodetic data and focal mechanisms.

Benthic foraminiferal response to orbital-scale variability in primary productivity off the Portuguese margin over the last 1.3 Myr

Detailed analyses of benthic foraminiferal fauna and planktonic foraminiferal stable carbon isotopes at IODP Site U1391 were performed to reconstruct orbital-scale variability in primary productivity off the Portuguese margin over the last 1.3 Myr. Q-mode factor analysis of benthic foraminiferal census data from the >250 μm fraction reveals four assemblages, which is mainly controlled by the organic matter flux to the seafloor deriving from surface water productivity. The Sphaeroidina bulloides assemblage accounts for nearly half of the total variance, consisting of S. bulloides, the agglutinated taxa and Lenticulina as major components and Cibicidoides robertsonianus, Planulina ariminensis and Uvigerina peregrina parva as subsidiary species. Cibicidoides wuellerstorfi and Bulimina mexicana are important accessory species of the Cibicidoides pachyderma-dominated assemblage. The miliolids assemblage is dominated by miliolids and B. mexicana with Uvigerina mediterranea as the important associated species. The Praeglobobulimina ovata assemblage is represented by P. ovata along with Globobulimina affinis, Melonis pompiloides, Melonis barleeanum and U. peregrina parva as important accessory species. High productivity often occurs during the interglacial stages and is characterized by the S. bulloides assemblage with subsidiary P. ovata assemblage, while low productivity often occurs during the glacial stages and is marked by the miliolids assemblage and the C. pachyderma assemblage. In addition to the distinct glacial/interglacial variations, there is a long-term decreasing trend in primary productivity recorded by benthic foraminifera, which is supported by a broadly increasing trend in the sediment redness (a*). Continuous wavelet analysis of high productivity-related Factor 1 loading (the S. bulloides assemblage) suggests that variations in primary productivity have a middle Pleistocene transition (MPT)-related shift in cyclicity from the ~41-kyr dominant cycle prior to the MPT to the ~100-kyr dominant cycle after the MPT. Cross-spectral analyses between the Factor 1 loading record and δ18O of Globigerina bulloides reveal the control of global ice volume changes on primary productivity. The high coherency between the Factor 1 loading record and δ13C of G. bulloides on the glacial/interglacial timescale suggests that primary productivity off the Portuguese margin may be largely affected by nutrient availability which was related to the Iberian surface hydrographic changes associated with changes in global ice volume.

The sines contourite depositional system along the SW Portuguese margin: Onset, evolution and conceptual implications

The Sines Contourite Depositional System, located in the Southwest Portuguese Margin, is a central segment of the Iberian Contourite Depositional Complex, built under the influence of the Mediterranean Outflow Water (MOW). This work presents the onset and evolution of this system using multibeam bathymetry, multichannel seismic reflection lines, sediment cores and well data. Six seismic units of Late Miocene through Holocene age have been identified, which defined three evolutionary stages for drift construction: a) an onset and initial stage, from the Latest Miocene to the Late Pliocene (5.33–2.5 Ma), where a sheeted drift was built under a weak flowing MOW; b) a growing stage from the Early to Middle Quaternary (2.5–0.7 Ma), characterized by the deposition of a mounded drift in the south and a sheeted drift in the north, which is correlated with a strengthening of the MOW; and c) a maintenance stage between the Middle Pleistocene and Holocene (0.7 Ma – present), where the modern depositional and erosional contourite features developed associated with three intensification periods of the MOW at 0.7 Ma, 0.4 Ma and 20 ka. The development of the Sines Contourite Depositional System was constrained in the long-term by seafloor paleomorphologies inherited from the Mesozoic rifting phases of the Southwest Portuguese Margin. The NNW-SSE horsts and grabens built during the Mesozoic rifting provided accommodation for drift growth, with limited lateral migration, and locally enhanced the alongslope bottom-current. In short-term, environmental (climate and sea-level) fluctuations modulated changes in bottom-current density and intensity, determining sedimentary cycles in the depositional record, especially during the Quaternary. Our findings emphasize the occurrence of three main plastered morphologies throughout the seismic record, which were compared with other plastered drifts in different continental margins to establish a conceptual model.

Mediterranean Outflow Water dynamics across the middle Pleistocene transition based on a 1.3 million-year benthic foraminiferal record off the Portuguese margin

Reconstruction of the Mediterranean Outflow Water (MOW) dynamics in the geologic past contributes to exploring its influence on the North Atlantic Ocean circulation and global climate. The middle Pleistocene transition (MPT) is one of the most important characteristics of Quaternary climate change, but until now, research on the MOW variability during this time interval has been limited. To decipher the MOW variability over the last 1.3 myr, this work presents the first continuous and high-resolution (∼2 kyr) foraminiferal stable oxygen and carbon isotopes and benthic foraminiferal records from Integrated Ocean Drilling Program (IODP) Site U1391, which was drilled off the Portuguese margin in the Northeast Atlantic Ocean and is currently bathed by the lower MOW core. Based on spectral analysis results of the foraminiferal δ18O record, the MPT peaked from 0.9 to 0.7 Ma. The ‘epibenthos group’ was previously found attached to elevated substrates only within the MOW current and more abundant at higher current velocities, so the relative abundance of the ‘elevated epibenthos group’ was adopted as an indicator of MOW strength in this study. The MOW indicator suggests that the MOW strengthened during MIS 1, MIS 5, MIS 7, MIS 9, MIS 11, MIS 13, MIS 15, MIS 17, early MIS 18 to late MIS 19, MIS 21, MISs 23–25, MISs 28–30, early MIS 34 to MIS 35, early MIS 36 to late MIS 37 and MIS 40 with a ∼100 kyr cycle. Superimposed on the long-term variability of the MOW current, the ∼41-kyr and ∼20-kyr cyclic fluctuations are also evident, whereby the ∼41-kyr cycle is more significant. The results of cross-spectral analyses indicate that the ∼20-kyr cyclic variation in the MOW intensity was drived by the precession forcing; the ∼41-kyr cyclic variation in the pre- MPT MOW dynamics and the ∼100-kyr cyclic variation in the post-MPT MOW dynamics were strongly controlled by the Earth’s obliquity. The variation in the abundance of the elevated epibenthos group was dominated by the ∼41-kyr cycle prior to the MPT and by the ∼100-kyr cycle after the MPT, which suggested there was a MPT-related shift in the MOW dynamics. Benthic δ13C record of the last 0.56 myr shows precessional (23-kyr) and glacial-interglacial (∼100 kyr) cycles, indicating cyclic variations in bottom water ventilation. Enhanced ventilation coincides with precession maxima and reduced ventilation with precession minima. Bottom water was well ventilated by MOW during the interglacial periods and by GNAIW during the glacial periods, and pooly ventilated during the glaical terminations.

Fast and slow components of interstadial warming in the North Atlantic during the last glacial

The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. Here, we present joint marine and terrestrial analyses from the Portuguese Margin, showing a succession of cold stadials and warm interstadials over the interval 35–57 ka. Heinrich stadials 4 and 5 contain considerable structure, with a short transitional phase leading to an interval of maximum cooling and aridity, followed by slowly increasing sea-surface temperatures and moisture availability. A climate model experiment reproduces the changes in western Iberia during the final part of Heinrich stadial 4 as a result of the gradual recovery of the Atlantic meridional overturning circulation. What emerges is that Greenland ice-core records do not provide a unique template for warming events, which involved the operation of both fast and slow components of the coupled atmosphere–ocean–sea-ice system, producing adjustments over a range of timescales.

Millennial-Scale Climate Variability and Dinoflagellate-Cyst-Based Seasonality Changes Over the Last ~150 kyrs at "Shackleton Site" U1385.

During the last glacial period, climate conditions in the North Atlantic region were determined by the alternation of relatively warm interstadials and relatively cool stadials, with superimposed rapid warming (Dansgaard‐Oeschger) and cooling (Heinrich) events. So far little is known about the impact of these rapid climate shifts on the seasonal variations in sea surface temperature (SST) within the North Atlantic region. Here, we present a high‐resolution seasonal SST record for the past 152 kyrs derived from Integrated Ocean Drilling Program “Shackleton” Site U1385, offshore Portugal. Assemblage counts of dinoflagellates cysts (dinocysts) in combination with a modern analog technique (MAT), and regression analyses were used for the reconstructions. We compare our records with previously published SST records from the same location obtained from the application of MAT on planktonic foraminifera. Our dinocyst‐based reconstructions confirm the impression of the Greenland stadials and interstadials offshore the Portuguese margin and indicate increased seasonal contrast of temperature during the cold periods of the glacial cycle (average 9.0 °C, maximum 12.2 °C) with respect to present day (5.1 °C), due to strong winter cooling by up to 8.3 °C. Our seasonal temperature reconstructions are in line with previously published data, which showed increased seasonality due to strong winter cooling during the Younger Dryas and the Last Glacial Maximum over the European continent and North Atlantic region. In addition, we show that over longer time scales, increased seasonal contrasts of temperature remained characteristic of the colder phases of the glacial cycle.

Enhanced climate instability in the North Atlantic and southern Europe during the Last Interglacial

Considerable ambiguity remains over the extent and nature of millennial/centennial-scale climate instability during the Last Interglacial (LIG). Here we analyse marine and terrestrial proxies from a deep-sea sediment sequence on the Portuguese Margin and combine results with an intensively dated Italian speleothem record and climate-model experiments. The strongest expression of climate variability occurred during the transitions into and out of the LIG. Our records also document a series of multi-centennial intra-interglacial arid events in southern Europe, coherent with cold water-mass expansions in the North Atlantic. The spatial and temporal fingerprints of these changes indicate a reorganization of ocean surface circulation, consistent with low-intensity disruptions of the Atlantic meridional overturning circulation (AMOC). The amplitude of this LIG variability is greater than that observed in Holocene records. Episodic Greenland ice melt and runoff as a result of excess warmth may have contributed to AMOC weakening and increased climate instability throughout the LIG.

Comparison of living and dead benthic foraminifera on the Portuguese margin: Understanding the taphonomical processes

Abstract Dead benthic foraminifera (> 150 μm) were studied in 23 sediment cores from the Portuguese Margin at water depths between 20 and 2000 m and located on 4 transects off the Douro, Mondego, Tagus and Sado river mouths and 1 transect in the Estremadura. For 10 stations, the dead faunal vertical distribution (0–8 cm) was first investigated in 4 different sediment horizons per core to evaluate the sampling effort necessary to have a representation of the dead fauna deposited under different environmental areas. As a result, it appears that the faunal vertical distribution is constant, except for the deepest environments where fragile taxa were identified in the top layers only. Dead foraminiferal assemblages in the 4–5 cm layer for all stations were then compared to previously published living foraminiferal assemblages (of March 2011) from the same cores to evaluate the taphonomical processes affecting major species. This improves the knowledge of the faunal distribution for a better benthic foraminiferal proxy for paleostudies. There was a considerable loss of some species in the dead fauna. Firstly, this concerns the fragile organic-cemented agglutinated taxa such as Reophax spp., Glomospira charoides, or Bathysiphon spp. Secondly, some calcitic species such as Nonion scaphum, Cancris auriculus, Ammonia beccarii or Bulimina aculeata that were particularly abundant in the living fauna on the inner shelf under the late winter high river discharge conditions, were also far less dominant in the dead fauna. Lastly, other species like Cassidulina carinata, Valvulineria bradyana, and Bulimina marginata systematically showed higher abundance in the dead fauna at the mid shelf. These species, related to eutrophic conditions occurring in summer during the upwelling activity, were therefore not well represented in the living fauna, collected in March. Transport of allochthonous specimens may also account for higher contribution in the dead community of some species like Cibicides lobatulus, Asterigerinata mamilla or Haynesina depressula, especially in coastal environments where hydrodynamic processes (river flood, winter storm, coastal drift) are more vigorous. Several species (U. mediterranea, U. bifurcata, T. agglutinans, H. balthica or B. costata), however, show little or no difference in both abundance and spatial occurrence between the living and dead faunas and provide a stable signal for paleoclimatic investigations.

The hidden biology of the pockmarks located at Estremadura Spur (NE Atlantic)

Event Abstract Back to Event The hidden biology of the pockmarks located at Estremadura Spur (NE Atlantic) Clara F. Rodrigues1*, Sofia P. Ramalho1, Vitor Magalhães2 and Marina R. Cunha1 1 University of Aveiro, Departamento de Biologia & CESAM, Portugal 2 Instituto Português do Mar e da Atmosfera (IPMA), Marine Geology and Georesources Division (DivGM), Portugal Pockmarks are crater-like geomorphic features that occur in the seafloor worldwide along both passive and active margins. Their association with subsurface oil and gas makes them interesting features for gas/oil industry. Pockmarks are thought to be formed rapidly, as a consequence of the sudden release of pressurized subsurface gas or pore-water. They can remain active, microseeping gas over long periods of time, or display periods of quiescence between eruptions. Both active and inactive pockmarks show geological and biological characteristics distinct from the surrounding seafloor. The PES project proposes a comprehensive interdisciplinary study of the Estremadura Spur (NE Atlantic) pockmark field. Here we present the first results on the macrofaunal and microbial assemblages in their geologic context. Our investigations indicate that these pockmarks are, at present, inactive. The microbial assemblages comprise several phylotypes associated with the cycling of sulphur and nitrate compounds, as well as numerous known hydrocarbon degraders underlining the variable and reduced activity of the individual pockmarks. The macrofaunal assemblages are composed mainly by detritivores and some of the dominant taxa suggest the occurrence of reduced seafloor conditions. Inactive pockmarks have been studied to a limited extent and our results contribute to ascertain their ecological significance for the biological assemblages in the Portuguese margin. Acknowledgements This work was supported by the PES project (PTDC/GEOFIQ/5162/2014), financed by National funding through the Portuguese Science Foundation (FCT), Financial support to CESAM (UID/AMB/50017 - POCI-01-0145-FEDER-007638), to FCT/MCTES through national funds (PIDDAC), and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. CFR was supported by the FCT grant (SFRH/BPD/107805/2015). Keywords: macrofauna, Microbes, pockmarks, Reduced environments, assemblages Conference: IMMR'18 | International Meeting on Marine Research 2018, Peniche, Portugal, 5 Jul - 6 Jul, 2018. Presentation Type: Oral Presentation Topic: Biodiversity, Conservation and Coastal Management Citation: Rodrigues CF, Ramalho SP, Magalhães V and Cunha MR (2019). The hidden biology of the pockmarks located at Estremadura Spur (NE Atlantic). Front. Mar. Sci. Conference Abstract: IMMR'18 | International Meeting on Marine Research 2018. doi: 10.3389/conf.FMARS.2018.06.00047 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Apr 2018; Published Online: 07 Jan 2019. * Correspondence: Dr. Clara F Rodrigues, University of Aveiro, Departamento de Biologia & CESAM, Aveiro, Portugal, Portugal, clara.rodrigues@ua.pt Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Clara F Rodrigues Sofia P Ramalho Vitor Magalhães Marina R Cunha Google Clara F Rodrigues Sofia P Ramalho Vitor Magalhães Marina R Cunha Google Scholar Clara F Rodrigues Sofia P Ramalho Vitor Magalhães Marina R Cunha PubMed Clara F Rodrigues Sofia P Ramalho Vitor Magalhães Marina R Cunha Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Terrestrial versus marine archives: biostratigraphical correlation of the Middle Pleistocene lacustrine records from central Europe and their equivalents in the deep-sea cores from the Portuguese margin

The palaeolake from Ossowka, eastern Poland, is an unusual example of basin, in which sedimentation lasted from the beginning of the Holsteinian through several climatic oscillations until the Early Saalian, i.e. over a period of ~70,000 years. This provides us with the opportunity of correlating the dynamically changing events on land with their potential equivalents in the marine profiles. Alkenone-based temperature reconstructions using U k′ 37 are an unusual tool in this respect. Nevertheless, as a result, we successfully relate this pollen sequence to the changing SST (sea surface temperature) values in the colder phases of MIS 11. The bipartite Ferdinandovian Interglacial was previously correlated with the upper part of the Cromerian complex (MIS 13 and MIS 15). Having at our disposal limits in the SST alkenone-based record, we clearly identify the stratigraphic position of the second warm phase of MIS 15 and a small fragment of MIS 14. In our opinion, the Rhume Interglacial, identified in Germany, should be located within MIS 13. Using the available orbitally tuned chronology, we also give a substantial input to estimate duration of these terrestrial interglacials, indicating the starting and ending points of their equivalents in the alkenone records

Benthic assemblages from a disturbed region by bottom-trawling fisheries off the SW Portuguese Margin

Event Abstract Back to Event Benthic assemblages from a disturbed region by bottom-trawling fisheries off the SW Portuguese Margin Sofia P. Ramalho1, 2*, Clara F. Rodrigues1, Mariana Almeida1, Patricia Esquete1, Luciana Génio1, Ascensão Ravara1, Nikolaos Lampadariou3, Ann Vanreusel2 and Marina R. Cunha1 1 University of Aveiro, Departamento de Biologia & CESAM, Portugal 2 Ghent University, Department of Biology, Marine Biology Research Group, Belgium 3 Hellenic Centre for Marine Research, Institute of Oceanography, Greece Bottom trawlers in operation off the SW Portuguese margin target predominantly deep-sea muddy-sediment areas bellow 200m water depth. To better understand the effects caused by this practice on the deep-sea benthic habitats biodiversity, three areas of interest along a continental slope area off the SW Portuguese margin were selected, using Vessel Monitoring Systems (VMS) data and in-situ observations obtained from Remotely Operated Vehicle (ROV) video surveys. These areas included a not trawled area, the main fishing ground and an area adjacent to the main fishing ground. In addition to video surveys, which allowed characterizing mega-epibenthic assemblages, replicate sediment samples across these areas were obtained for the study of macrobenthic assemblages, in terms of total standing stocks (abundance and biomass), total respiration, composition and both taxonomic and trophic diversity. Results showed that, in addition to the habitat heterogeneity associated with the study area, trawling pressure represents an important component of variation of the observed communities. Both fishing grounds that are recurrently impacted by trawling, and the adjacent areas that may be indirectly impacted by the re-suspended sediments and sporadically affected by trawl passages, showed a depletion of both mega-epibenthic and macro-infaunal abundances, lower taxonomic and trophic richness in comparison to undisturbed sites. Moreover, a lower functional redundancy resulting from the loss of species within most feeding guilds was observed in the macrofaunal core assemblage (i.e. characteristic, dominant or frequent taxa) of the areas under trawling disturbance. These results highlight the vulnerability of the deep-sea benthic ecosystems off the SW Portuguese margin to further increases in natural and anthropogenic disturbance or their synergistic effects. Acknowledgements This work was supported by CESAM (UID/AMB/50017) funds, granted by Fundação para a Ciência e a Tecnologia (FCT)/MEC through national funds, and co-funded by FEDER, within the PT2020 Partnership Agreement and Compete 2020. SPR work was funded through a MARES Grant, under Erasmus Mundus programme coordinated by Ghent University (FPA 2011-0016). CFR, PE, AR and LG were supported by the FCT grants SFRH/ BPD/107805/2015, SFRH/BPD/94985/2013, SFRH/BPD/112408/2015 and SFRH/BPD/96142/2013, respectively. Keywords: Mega-epifauna, macrofauna, Upper continental slope, trophic and structural biodiversity; disturbance, bottom-trawling fisheries, West Iberian Margin Conference: IMMR'18 | International Meeting on Marine Research 2018, Peniche, Portugal, 5 Jul - 6 Jul, 2018. Presentation Type: Oral Presentation Topic: Fisheries and Management Citation: Ramalho SP, Rodrigues CF, Almeida M, Esquete P, Génio L, Ravara A, Lampadariou N, Vanreusel A and Cunha MR (2019). Benthic assemblages from a disturbed region by bottom-trawling fisheries off the SW Portuguese Margin. Front. Mar. Sci. Conference Abstract: IMMR'18 | International Meeting on Marine Research 2018. doi: 10.3389/conf.FMARS.2018.06.00143 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Apr 2018; Published Online: 07 Jan 2019. * Correspondence: PhD. Sofia P Ramalho, University of Aveiro, Departamento de Biologia & CESAM, Aveiro, Portugal, Portugal, sofia.pinto.ramalho@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sofia P Ramalho Clara F Rodrigues Mariana Almeida Patricia Esquete Luciana Génio Ascensão Ravara Nikolaos Lampadariou Ann Vanreusel Marina R Cunha Google Sofia P Ramalho Clara F Rodrigues Mariana Almeida Patricia Esquete Luciana Génio Ascensão Ravara Nikolaos Lampadariou Ann Vanreusel Marina R Cunha Google Scholar Sofia P Ramalho Clara F Rodrigues Mariana Almeida Patricia Esquete Luciana Génio Ascensão Ravara Nikolaos Lampadariou Ann Vanreusel Marina R Cunha PubMed Sofia P Ramalho Clara F Rodrigues Mariana Almeida Patricia Esquete Luciana Génio Ascensão Ravara Nikolaos Lampadariou Ann Vanreusel Marina R Cunha Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Vertical distribution of major, minor and trace elements in sediments from mud volcanoes of the Gulf of Cadiz: evidence of Cd, As and Ba fronts in upper layers

Mud volcanoes are feature of the coastal margins where anaerobic oxidation of methane triggers geochemical signals. Elemental composition, percentage of fine particles and loss on ignition were determined in sediment layers of eleven gravity cores retrieved from four mud volcanoes (Sagres, Bonjardim, Soloviev and Porto) and three undefined structures located on the deep Portuguese margin of the Gulf of Cadiz. Calcium was positively correlated to Sr and inversely to Al as well as to most of the trace elements. Vertical profiles of Ba, Cd and As concentrations, and their ratios to Al, in Porto and Soloviev showed pronounced enhancements in the top 50-cm depth. Sub-surface enhancements were less pronounced in other mud volcanoes and were absent in sediments from the structures. These profiles were interpreted as diagenetic enrichments related to the anaerobic oxidation of methane originated from upward methane-rich fluxes. The observed barium fronts were most likely caused by the presence of barite which precipitated at the sulphate-methane transition zone. Cd and As enrichments have probably resulted from successive dissolution/precipitation of sulphides in response to vertical shifts of redox boundaries.

Deep-Sea Mega-Epibenthic Assemblages from the SW Portuguese Margin (NE Atlantic) Subjected to Bottom-Trawling Fisheries

Bottom trawling fisheries are a common threat to the health of continental margins worldwide. Together with numerous environmental and biological processes, physical disturbance induced by trawlers can largely shape the benthic habitats and their associated assemblages. At the SW Portuguese Margin, crustacean bottom trawlers have exploited deep-sea habitats for a few decades, but its effects on the benthic biodiversity are practically unknown. During the spring-summer of 2013 and 2014, several Remotely Operated Vehicle (ROV) video transects were used to investigate mega-epibenthic abundance, composition and diversity in soft-sediment areas subjected to varying trawling pressures off Sines and Setubal (200-800 m). Differences in mega-epibenthic assemblages were linked with environmental changes (depth, grain size, primary productivity) and trawling disturbance. The effect of trawling was assessed between segments with similar habitat characteristics, i.e. muddy-sand bottoms between 300–500 m. Areas subjected to intensive trawling pressure showed a generally flattened seabed, with abundant recent trawl marks (up to 3 scars/100 m), indicating that the seabed physical integrity was compromised. Significant negative correlations were detected between various mega-epibenthic diversity indices (S, H’ and ET(20)) and trawling pressure (h.cell-1.y-1). Furthermore, the distinct mega-epibenthic assemblages and absence of several sessile erect morphospecies at both low and highly disturbed locations by trawling off Sines, namely all seapen morphospecies found in non-trawled areas, demonstrates the negative influence of trawling fisheries on the benthic component of the study area. Also, low dissimilarity between assemblages from the main fishing grounds and the adjacent low-disturbance locations, suggests that the potentially negative influence of trawling can extend beyond the targeted areas (e.g. by the plumes of re-suspended sediments). The observed deleterious effects of trawling on mega-epibenthic fauna together with the intensification of trawling pressure in the study area, stress the need for adequate monitoring programs and regulatory measures to halt the long-term loss of biodiversity and allow the sustainability of fisheries at the SW Portuguese Margin.

Indoor air quality in preschools (3- to 5-year-old children) in the Northeast of Portugal during spring–summer season: pollutants and comfort parameters

ABSTRACTIndoor air quality at schools (elementary, primary) has been the subject of many studies; however, there are still relative few data regarding preschool (3- to 5-year-old children) environments. This investigation determined the concentrations of particulate matter (PM)2.5, total volatile organic compounds (TVOC), formaldehyde, carbon monoxide (CO), and ozone (O3) as well as the levels of carbon dioxide (CO2), temperature, and relative humidity (RH) in the indoor and outdoor air of two preschools situated in different geographical regions of Portugal. The indoor concentrations of TVOC, CO, O3, and CO2 were predominantly higher at the end of school day compared to early morning periods. The TVOC and CO2 concentrations were higher indoors than outdoors suggesting predominantly an indoor origin. Outdoor air infiltrations were the major contributing source of CO and O3 to indoor air in both preschools. The concentrations of all pollutants were within the limits defined by national regulations and international organizations, except for TVOC that exceeded 8–12-fold higher than the recommendation of 0.2 mg/m3 proposed by European Commission. The levels of CO2 were below the protective guideline of 2250 mg/m3 (Portuguese legislation); however, the observed ranges exceeded the Portuguese margin of tolerance (2925 mg/m3) at the end of school days, indicating the impact of occupancy rates particularly at one of the preschools. Regarding comfort parameters, temperature exerted a significant influence on O3 concentrations, while RH values were significantly correlated with TVOC levels in indoor air of preschools, particularly during the late afternoon periods.

Evaluating environmental drivers of spatial variability in free-living nematode assemblages along the Portuguese margin

Abstract. Understanding processes responsible for shaping biodiversity patterns on continental margins is an important requirement for comprehending anthropogenic impacts in these environments and further management of biodiversity. Continental margins perform crucial functions linked to key ecological processes which are mainly structured by surface primary productivity and particulate organic matter flux to the seafloor, but also by heterogeneity in seafloor characteristics. However, to what extent these processes control local and regional biodiversity remains unclear. In this study, two isobathic parallel transects located at the shelf break (300–400 m) and upper slope (1000 m) of the western Iberian margin were used to test how food input and sediment heterogeneity affect nematode diversity independently from the spatial factors geographical distance and water depth. We also examined the potential role of connectedness between both depth transects through molecular phylogenetic analyses. Regional generic diversity and turnover were investigated at three levels: within a station, between stations from the same depth transect, and between transects. High variability in food availability and high sediment heterogeneity at the shelf-break transect were directly linked to high diversity within stations and higher variation in community structure across stations compared to the upper slope transect. Contrastingly, environmental factors (food availability and sediment) did not vary significantly between stations located at the upper slope, and this lack of differences were also reflected in a low community turnover between these deeper stations. Finally, differences in nematode communities between both transects were more pronounced than differences within each of the isobathic transects, but these changes were paralleled by the previously mentioned environmental changes. These results suggest that changes in community structure are mainly dictated by environmental factors rather than spatial differences at the western Iberian margin. Furthermore, phylogenetic relationships revealed no evidence for depth-endemic lineages, indicating regular species interchanges across different depths.

Deep-sea crustacean trawling fisheries in Portugal: quantification of effort and assessment of landings per unit effort using a Vessel Monitoring System (VMS)

Mapping and quantifying bottom trawling fishing pressure on the seafloor is pivotal to understand its effects on deep-sea benthic habitats. Using data from the Vessel Monitoring System of crustacean trawlers along the Portuguese margin, we have identified the most exploited areas and characterized the most targeted habitats and water depths. We estimated a total trawling effort of 69596, 66766, and 63427 h y−1 for the years 2012, 2013, and 2014 respectively which, considering the total landings estimated for this gear, yield values of 20.76, 21.06, and 19.11 kg of landed fish per trawled hour. The main trawling pressure is exerted in the South and Southwest Portuguese margins, on muddy and muddy-sand bottoms between 200 and 700 m water depths, while in the North and Central-West coasts a minor effort, at shallower waters and across a wider range of habitats, is also applied. The most landed species are crustaceans such as rose shrimp and Norway lobster, although this varies importantly between the different regions of Portugal, being fish and cephalopods the main captures in the Northern ports. We discuss the consequences of trawling for the impacted communities as well as the characteristics of the commercialization of these captures in Portugal.

Benthic foraminiferal assemblages and bottom water evolution off the Portuguese margin since the Middle Pleistocene

The upper 250 meter-long sediment core of Site U1391 (1085m water depth) retrieved from the Portuguese margin in the Northeast Atlantic Ocean was adopted for the benthic foraminiferal analyses to disclose the variations in Mediterranean Outflow Water (MOW) intensity over the last ~0.9Ma. Benthic foraminifera are abundant at this site and mainly composed of the hyaline forms (80%, such as Cibicidoides/Cibicides spp., Globobulimina spp., Bulimina spp., Uvigerina spp., Melonis spp., Sphaeroidina bulloides, Hoeglundina elegans, Gyroidinoides spp., Lenticulina spp. and Planulina ariminensis), while the agglutinated and porcelaneous forms have only 5% and 14.1% on average, respectively.Down-core variations of the benthic foraminifera show glacial-interglacial contrasts, especially those of Lenticulina spp. and Planulina ariminensis, which is also supported by the benthic foraminiferal cluster analysis. During the interglacial periods, the fauna are dominated by Sphaeroidina bulloides, Lenticulina spp., Planulina ariminensis, Dentalina spp., Cibicidoides robertsonianus and the agglutinated forms, while by Cibicidoides pachyderma, Praeglobobulimina ovata, Praeglobobulimina pupoides, Bulimina mexicana, Uvigerina mediterranea, Bolivinita quadrilatera and mililoids during the glacial periods.Benthic foraminiferal faunal data at Site U1391 was detailed analyzed to disclose the bottom water property over the last ~0.9Ma. Variations of the character species or assemblages, such as Planulina ariminensis, and the “elevated epibenthos” group suggest that the MOW intensity has typical glacial-interglacial cycles, strengthening during the interglacial periods and weakening during the glacial periods, and reaches its peak at MIS 11. The strongest MOW intensity during MIS 11 confirms the climatic influence of waving sea level on the MOW current by its +20m high-stand above the present sea level.The agglutinated benthic foraminifera have a significantly positive correlation with the MOW index of “elevated epibenthos”, which suggests that their abundance can be used to monitor the hydrodynamic conditions of bottom water off the Portuguese margin. Consistent with the MOW intensity, the lower miliolids content implies a lower salinity which supported the stronger vertical density gradient during the interglacial periods in this region; while the glacial ocean has a higher salinity with a weak vertical density gradient/MOW intensity.