Search

International audience; The original article was published with missing information in Table 1. The complete Table 1 is now provided: this correction stands to correct the original article.

The Antarctic Circumpolar Current (ACC) is the world’s strongest zonal current system that connects all three major ocean basins of the global ocean and therefore integrates and responds to global climate variability. Its flow is largely driven by strong westerly winds and constricted to its narrowest extent in the Drake Passage. Transport of fresh and cold surface and intermediate water masses through the Drake Passage (cold-water route) strongly affects the Atlantic Meridional Overturning Circulation together with the inflow of Indian Ocean water masses (warm-water route). Both oceanographic corridors are critical for the South Atlantic contribution to Meridional Overturning Circulation changes. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, the Pacific sector of the ACC lacks information on its Cenozoic paleoceanography from deep-sea drilling records. To advance our knowledge and understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO2, International Ocean Discovery Program (IODP) Expedition 383 recovered sedimentary sequences at (1) three sites located in the central South Pacific (U1539, U1540, and U1541), (2) two sites at the Chile margin (U1542 and U1544), and (3) one site from the pelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Because of persistently stormy conditions and the resulting bad weather avoidance, we were not successful in recovering the originally planned Proposed Site CSP-3A in the central South Pacific in the Polar Frontal Zone. The drilled sediments at Sites U1541 and U1543 reach back to the late Miocene, and those at Site U1540 reach back to the early Pliocene. High sedimentary rate Pleistocene sedimentary sequences were drilled both in the central South Pacific (Site U1539) and along the Chile margin. Taken together, the sites represent a depth transect from ~1100 m at the Chile margin site (U1542) to ~4070 m in the central South Pacific (Site U1539) and allow investigation of changes in the vertical structure of the ACC, a key issue for understanding the role of the Southern Ocean in the global carbon cycle. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic-, carbonate-, and opal-based proxies to address our objectives of reconstructing with unprecedented stratigraphic detail surface to deep-ocean variations and their relation to atmosphere and cryosphere changes through stadial to interstadial, glacial to interglacial, and warmer than present time intervals.

The future of agriculture and its economic, sanitary and ecological sustainability depend on a significant and expected evolution of crop protection practices, which today are too dependent on the use of synthetic pesticides. It is within this framework that biocontrol tools based on the use of plants or plant extracts are developed. Reunion's chemiodiversity presents a great wealth and promising prospects in this context. The challenge of the BIOPIPER project was the sustainable production of the natural extracts of two Piperaceae, with the prospect of their use within the framework of the agroecological protection of crops against pests. Within this framework, the aims of the study presented here were to i/assess the biocidal properties of the essential oils obtained from deferent ecotypes of Piper borbonense against pests of economic importance worldwide, ii/ compare the sensitivity of some of these pests and their natural enemies towards these essential oils and iii/ identify the potential toxic compounds involved and assess whether or not their proportions and presence are modified in wild vs cultivated plants. Contact tests on filter papers impregnated with essential oils showed that they were highly toxic to a large range of pest insects (LD50 ranged between 36 and 183 mg/cm2). Comparison of toxicity of essential oils on some pests and their natural enemies indicated that the later were less sensitive but still affected by these oils. Five phenylpropanoids dominated the composition of active essential oils: asaricin, safrole, elemicin, dillapiole and myristicin. Although some variations were observed depending on ecotypes, the presence and proportion of these compounds were comparable whether the plants were harvested in nature or cultivated. Suitable and selective modes of application of the biocidal essential oils identified remain to be studied.

The Antarctic Intermediate Water (AAIW) is a key player in global-scale oceanic overturning processes and an important conduit for heat, fresh water, and carbon transport. The AAIW past variability is poorly understood mainly due to the lack of sedimentary archives at intermediate water depths. We present records of benthic stable isotopes from sediments retrieved with the seafloor drill rig MARUM-MeBo at 956m water depth off northern Chile (GeoB15016, 27 degrees 29.48S, 71 degrees 07.58W) that extend back to 970ka. The sediments at this site are presently deposited at the boundary between AAIW and Pacific Deep Water (PDW). For previous peak interglacials, our results reveal similar benthic C-13 values at site GeoB15016 and of a newly generated stack of benthic C-13 from various deep Pacific cores representing the average PDW. This suggests, unlike today, the absence of AAIW at the site and the presence of nearly pure PDW. In contrast, more positive C-13 values at site GeoB15016 compared to the stack imply a considerable AAIW contribution during cold phases of interglacials and especially during glacials. Besides, we used three short sediment cores to reconstruct benthic C-13 values from the AAIW core during the last glacial and found a C-13 signature similar to today's. Assuming that this was the case also for the past 970 kyr, we demonstrate that sea level changes and latitudinal migrations of the AAIW formation site can only account for about 50% of the full range of past C-13 increases at site GeoB15016 during cold periods. Other processes that could explain the remaining of the positive C-13 anomalies are increases in glacial AAIW production and/or deeper convection of the AAIW with respect to preceding interglacials.

Terrace systems indicate that the Seno Otway and Skyring, and the Última Esperanza fjord formed the largest interconnected proglacial lake system of southern Patagonia (5700 km²) during the early deglaciation (

Glacial millennial-scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well-dated and high resolution sediment records. Here we present new surface water records from sediment core MD07-3128 recovered at 53 degrees S off the Pacific entrance of the Strait of Magellan. The alkenone-derived sea surface temperature (SST) record reveals a very strong warming of ca. 8 C over the last Termination and substantial millennial-scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (delta(18)O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial-scale SST fluctuations are very similar to those observed in the well-dated SST record from ODP Site 1233 (41 degrees S) and the temperature record from Drowning Maud Land Antarctic ice core supporting the hemispheric-wide Antarctic timing of SST changes. However, differences in our new SST record are also found including a long-term warming trend over Marine Isotope Stage (MIS) 3 followed by a cooling toward the Last Glacial Maximum (LGM). We suggest that these differences reflect regional cooling related to the proximal location of the southern Patagonian Ice Sheet and related meltwater supply at least during the LGM consistent with the fact that no longer SST cooling trend is observed in ODP Site 1233 or any SST Chilean record. This proximal ice sheet location is documented by generally higher contents of ice rafted debris (IRD) and tetra-unsaturated alkenones, and a slight trend toward lighter planktonic delta(18)O during late MIS 3 and MIS 2.