Climate change considerations are fundamental to management of deep‐sea resource extraction

Climate change manifestation in the ocean, through warming, oxygen loss, increasing acidification, and changing particulate organic carbon flux (one metric of altered food supply), is projected to affect most deep‐ocean ecosystems concomitantly with increasing direct human disturbance. Climate drivers will alter deep‐sea biodiversity and associated ecosystem services, and may interact with disturbance from resource extraction activities or even climate geoengineering. We suggest that to ensure the effective management of increasing use of the deep ocean (e.g., for bottom fishing, oil and gas extraction, and deep‐seabed mining), environmental management and developing regulations must consider climate change. Strategic planning, impact assessment and monitoring, spatial management, application of the precautionary approach, and full‐cost accounting of extraction activities should embrace climate consciousness. Coupled climate and biological modeling approaches applied in the water and on the seafloor can help accomplish this goal. For example, Earth‐System Model projections of climate‐change parameters at the seafloor reveal heterogeneity in projected climate hazard and time of emergence (beyond natural variability) in regions targeted for deep‐seabed mining. Models that combine climate‐induced changes in ocean circulation with particle tracking predict altered transport of early life stages (larvae) under climate change. Habitat suitability models can help assess the consequences of altered larval dispersal, predict climate refugia, and identify vulnerable regions for multiple species under climate change. Engaging the deep observing community can support the necessary data provisioning to mainstream climate into the development of environmental management plans. To illustrate this approach, we focus on deep‐seabed mining and the International Seabed Authority, whose mandates include regulation of all mineral‐related activities in international waters and protecting the marine environment from the harmful effects of mining. However, achieving deep‐ocean sustainability under the UN Sustainable Development Goals will require integration of climate consideration across all policy sectors.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Global Change Biology published by John Wiley & Sons Lt

Pollen distribution in marine surface sediments from Chilean Patagonia

International audienc

Independent time markers validate Pb-210 chronologies for two shallow Argentine lakes in Southern Pampas

International audienceWe report here the results of detailed Pb-210 analysis from two lake sediment cores collected from Lagunas Encadenadas del Oeste (LEO), located in the southern Argentinean Pampas (37 degrees S, 62 degrees W). Non-exponential and non-monotonic Pb-210, depth-profiles in the sedimentary record of these shallow lacustrine systems indicate the interaction of complex processes behind radionuclide fluxes and lake sedimentation. The chronologies and sediment accumulation rates (SAR) for the lake sediment sequences were modeled using different Pb-210-based mathematical models. Since modeled Pb-210 ages must be validated against independent stratigraphic markers of known age, two chrono-stratigraphic markers were selected to control the upper and lowermost parts of the Pb-210 dated sediments. The younger stratigraphic marker of AD 1980 +/- 2 corresponds to an uppermost organic carbon-rich mud accumulated by 1977-78 matching the most noticeable lake highstand occurred during the 20th century, registered on instrumental and paleolimnological records across the Pampean Plains. The oldest stratigraphic marker corresponds to AD 1878 +/- 10 matching with a high lake productivity and wet phase related to anomalously intense rainfall and flooding events in southeastern South America for AD 1877-1878. When comparing the resulting ages to the stratigraphic markers, our results show that CRS-model (constant rate of supply) performs better than the other models. Thus, these independent chronostratigraphic markers used along the sedimentary records were critical to validate Pb-210-derived ages and therefore to select the most appropriate model to establish the chronological framework of the recent sediments of the LEO system. The CRS-model appears to be an adequate technique for deriving ages and SAR in the LEO sedimentary record and other Pampean lacustrine systems under strong hydrological variability. (C) 2016 Published by Elsevier Ltd

Distribution of natural and man-made radionuclides during the reoccupation of GEOSECS stations 413 and 416 in the Arabian Sea: temporal changes

Measurement of natural and man-made 14C and 3H and man-made 90Sr, 239,240Pu and 241Am at two GEOSECS stations, GX 413 and 416 reoccupied two decades later are reported. Deeper penetration of nutrient and oxygen-poor intermediate waters along with man-made radionuclides, especially at GX 413 (near Bab el Mandab), are noticeable. The one-dimensional advection-diffusion model using pre-nuclear 14C data supports this observation as the vertical advection velocity at GX 413 is 11.8 m/y compared to the 3.6 m/y in the central north Arabian Sea (GX 416)

Recent clastic sedimentation processes in Lake Puyehue (Chilean Lake District, 40.5°S)

International audienceClastic sedimentation processes in Lake Puyehue (40.5°S; 72.5°W, Chile), are described based on correlation of high-resolution seismic profiles and multidisciplinary analysis of short sediment cores from two contrasting coring sites (PU-I and PU-II). Two main sedimentary environments are recognized in this oligotrophic lake: (i) a proximal one, which includes the delta of the main tributary (the Golgol River) and is a deep flat basin with a ponded geometry and limited acoustic penetration, and (ii) a distal one that is composed of several sub-basins highlighting a drape geometry and better acoustic penetration. Based on the correlation of seismic data and sediment cores dated by radionuclides and the identification of tephra layers (Rininahue1907, Cordon Caulle 1921–22 and 1960), we argue that clastic sedimentation results essentially from the development of homopycnal flows at the end of the winter season in this monomictic lake. Whereas distal clastic environments (PU-II coring site) are dominated by biogenic production and appear to have been little affected by the 1960 Chilean earthquake (Mw 9.5) and nearby volcanic eruptions, this may not be the case for more proximal clastic environments (PU-I coring site) which also experience sporadic hyperpycnal flows during major flood events. In May–June 1960, for example, as several earthquake-triggered landslides dammed the course of the Golgol River and ca. 7 × 106 m3 of volcaniclastic sediments fell over the drainage basin of the lake during the earthquake-induced Puyehue–Cordon–Caulle eruption, successive outbursts in the Golgol valley induced a mega-flood in Lake Puyehue. This hyperpycnal flow reworked a mixture of volcaniclastic and regolith-derived sediments from the catchment, as well as lacustrine sediments surrounding the Golgol delta (during the rising limb of the flood). These recently reworked sediments are strikingly enriched in excess 210Pb activity suggesting that positive anomalies in the activity of this isotope can be used to determine the source area of clastic sediments

Regional vegetation and climate changes during the last 13 kyr from a marine pollen record in Seno Reloncaví, southern Chile

International audienceA marine pollen record from Seno Reloncaví (southern Chile, 41°S) illustrates temperate rainforest changes during the last 13 cal kyr BP. Our study shows the end of the last Termination at ~ 11.5-12 cal kyr BP coincident with the expansion of Weinmannia, illustrating disturbance and warming conditions, at the expense of cold-resistant conifers (Fitzroya-Pilgerodendron and Podocarpus). Warming conditions are strengthened at 10.7 cal kyr BP by the increase of heliophytic taxa (Eucryphia-Caldcluvia) characteristic of the Valdivian rainforest. These heliophytic taxa reach their maximum expansion between 9.6 and 7.4 cal kyr BP and point to warm and dry conditions during the Holocene Climatic Optimum. After 7.4 cal kyr BP, vegetation changes indicate variable climate conditions superimposed on a cooling trend associated with an increase in precipitation after ~ 6-5 cal kyr BP, shown by the expansion of the cold-resistant conifers. During the late Holocene, after 2.8 cal kyr BP, the continuous expansion of cold-resistant conifers marks an increase of cool and wet conditions. The comparison between marine and terrestrial pollen records highlights the similar trends and timing of vegetation changes that allows to complete the regional pattern of vegetation changes around Seno Reloncaví. In comparison with the terrestrial pollen records, this marine pollen record provides a more regional signal of vegetation/climate changes and clearly demonstrates the sensitivity of marine pollen records to past vegetation and climate change

Análisis espacial y temporal de campos de dunas submarinas en la costa de Yucatán, México

The marine sedimentary deposits are a widely attended theme in the world because of its oceanographical, ecological, social and economical transcendence. Those deposits are part of very important sediment reservoirs on the coast that feed and protect sandy beaches, and are key habitat for several benthic species. On the coast of Yucatan (Mexico) there are conspicuous sedimentary deposits forming well structured and outstanding submarine dune swarms, close to the shoreline at the localities of Dzilam de Bravo, San Felipe and El Cuyo. The objective of this research was to assess the spatial disposition and inter-decadal movements of these dune fields. We used standardized satellite images analyses, validated with seismic profiles and a basic sedimentological description of the identified structures in the field. The dunes showed different magnitude position changes, with estimated net annual movement rates between 2.94 m year-1 and 10.83 m year-1, heading mainly northwest. The spatial disposition of these dunes was confirmed by the field data, the smallest dunes detected with the satellite images were 0.31 m high, conformed by medium, conformed by medium and fine sand sediments. It is suggested that the orientation of the shore line and wave incidence, jointly with the dominant currents in the zone, determine the formation of these sediment accumulations in the region. This evaluation presents an innovative and confident approach for the study of submarine dunes in shallow waters, using remote sensing incomes and standardized spatial analyses. These findings set basis for a systematic monitoring of these marine systems, and contributes with original information on the study and understanding of the coastal marine processes in Mexico.Los depósitos marinos sedimentarios son un tema de estudio ampliamente abordado debido a su trascendencia oceanográfica, ecológica, social y económica, ya que forman parte de los reservorios más importantes de sedimentos, alimentan y protegen las playas, y son el hábitat de numerosas especies bentónicas. En la costa del estado de Yucatán (México) existen campos conspicuos de depósitos sedimentarios que forman dunas submarinas bien estructuradas y sobresalientes en el litoral, aledaños a los puertos de Dzilam de Bravo, San Felipe y El Cuyo. El objetivo de este trabajo fue evaluar la conformación espacial de estos campos de dunas y sus movimientos registrados en décadas. Para esto se utilizaron técnicas estandarizadas de análisis de imágenes satelitales, validadas con perfiles sísmicos del sub-fondo y un análisis sedimentológico básico para verificación de las estructuras identificadas en campo. Las dunas mostraron cambios en su posición de distintas magnitudes, estimándose tasas de movimiento anual neto de entre 2,94 m año-1 y 10,83 m año-1, en sentido dominante hacia el noroeste. La disposición espacial de las dunas fue confirmada por los datos de campo, reportándose el registro de dunas con alturas mínimas de 0,31 m con las imágenes satelitales, conformadas principalmente por sedimentos del tipo arena fina y media. Se sugiere que la orientación de la línea de costa, en conjunto con la orientación del oleaje y corrientes dominantes actúa de forma determinante sobre la formación de estas acumulaciones sedimentarias en la región. Este trabajo presenta una aproximación innovadora y confiable para el estudio de dunas submarinas en aguas someras con base en herramientas de percepción remota y análisis espaciales estandarizados. Los hallazgos aquí reportados sientan bases para el monitoreo sistemático de estos sistemas marinos, y contribuye con información inédita en el estudio y entendimiento de los procesos marinos y costeros en México

Morphological and sedimentological assessment of submarine dune fields on the coast of Yucatan, Mexico

Conspicuous sedimentary deposits forming well-structured and prominent submarine dunes are found on the coast of Yucatan (Mexico), close to the ports of Dzilam de Bravo, San Felipe, and El Cuyo. The objective of this study was to evaluate the morphological and sedimentological features of these submarine dunes. Sub-bottom seismologic profiles were obtained and standardized sedimentological analyses were performed on sediment samples collected at the three study sites. Both the height and wavelength of dunes were different between the three sites, mean heights ranging from 0.84 to 2.28 m and mean wavelengths from 98 to 330 m. Most of the dunes showed a wellmarked asymmetry, which is related to the direction of their movements. Their granulometric composition was dominated by medium, moderately well-sorted sand. This study provides bases for future systematic monitoring of these peculiar ecosystems, including information to be considered for the evaluation of their ecological role in the marine system.