Annotated record of the detailed examination of Mn deposits from R/V "Jean Charcot" GEOMANCHE 76/2 stations

This report presents the preliminary results of the study of rocks and sediments obtained by dredging during four cruises of the R/V Jean Charcot and R/V Le Suroit during a cooperative program between CNEXO and CEPM (CH 58: April 1975; SU 01: December 1975; CH 66: February 1976; and CH 67: March 1976). Several dredges on the continental slope of the Goban Spur recovered "granitic" rocks on two morphological structures, Granite Cliff and "Menez Bihan" (Pautot et al., 1976), in water depths ranging from 3200 to 4200 meters. According to the radiometric age and petrology, the granodiorite appears to have a close affinity with similar igneous facies which have been described in Iberia (Capdevilla et al., 1973) and attributed to the Variscan intrusive episode which is also found in the nearby continental area (southwest Great Britain and Brittany, France). They often are coated by a centimeter-thick layer of ferromanganiferous deposits (Shaaf et al., 1977).

Annotated record of the detailed examination of Mn deposits from R/V "Le Suroit" GEOMANCHE75/1 stations

We report here preliminary results from the detailed sampling of granitic basement at a depth of 4.000 m at the lower edge of the Armorican continental margin near 48°N and 12°W. We consider that we have sampled here the extreme lateral limit of the continental crust where local exposures emerge from under a cover of Cainozoic,Mesozoic and probable Palaeozoic sediments.

Geochemistry and age models of sediments from the Celtic margin

The sedimentary sections of three cores from the Celtic margin provide high-resolution records of the terrigenous fluxes during the last glacial cycle. A total of 21 14C AMS dates allow us to define age models with a resolution better than 100 yr during critical periods such as Heinrich events 1 and 2. Maximum sedimentary fluxes occurred at the Meriadzek Terrace site during the Last Glacial Maximum (LGM). Detailed X-ray imagery of core MD95-2002 from the Meriadzek Terrace shows no sedimentary structures suggestive of either deposition from high-density turbidity currents or significant erosion. Two paroxysmal terrigenous flux episodes have been identified. The first occurred after the deposition of Heinrich event 2 Canadian ice-rafted debris (IRD) and includes IRD from European sources. We suggest that the second represents an episode of deposition from turbid plumes, which precedes IRD deposition associated with Heinrich event 1. At the end of marine isotopic stage 2 (MIS 2) and the beginning of MIS 1 the highest fluxes are recorded on the Whittard Ridge where they correspond to deposition from turbidity current overflows. Canadian icebergs have rafted debris at the Celtic margin during Heinrich events 1, 2, 4 and 5. The high-resolution records of Heinrich events 1 and 2 show that in both cases the arrival of the Canadian icebergs was preceded by a European ice rafting precursor event, which took place about 1-1.5 kyr before. Two rafting episodes of European IRD also occurred immediately after Heinrich event 2 and just before Heinrich event 1. The terrigenous fluxes recorded in core MD95-2002 during the LGM are the highest reported at hemipelagic sites from the northwestern European margin. The magnitude of the Canadian IRD fluxes at Meriadzek Terrace is similar to those from oceanic sites.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

(Table 2) Age determination of Irminger Basin sediment cores

High-resolution records of coarse lithic content and oxygen isotope have been obtained in a piston core from the Irminger Basin. The last glacial period is characterized by numerous periods of increased iceberg discharges originating partly from Iceland and corresponding to millennial-scale instabilities of the coastal ice sheets and ice shelves in the Nordic area. A comparison with midlatitude sediment cores shows that ice-rafted material corresponding to the Heinrich events was deposited synchronously from 40° to 60°N. There are thus two oscillating systems: every 5-10 kyr massive iceberg armadas are released from large continental ice caps, whereas more frequent instabilities of the coastal ice sheets in the high latitude regions occur every 1.2-3.8 kyr. At the time of the Heinrich events the synchroneity of the response from all the northern hemisphere ice sheets attests the existence of strong interactions between the two systems.

Seawater carbonate chemistry and calcification during experiments with maerl beds, 2007

Maerl community respiration, photosynthesis and calcification were measured seasonally in the Bay of Brest (France). The dynamics of oxygen, carbon and carbonate fluxes at the water-sediment interface were assessed using benthic chambers. Community respiration (CR) fluctuated in accordance with the seasonal changes in water temperature, from 1.5 mmol C m**-2 h**-1 in winter to 8.7 mmol C m**-2 h**-1 in summer. Mean gross community production (GCP) varied significantly among seasons, according to incident irradiance and temperature, from 3.4 mmol C m**-2 h**-1 in winter to 12.7 mmol C m-2 h-1 in summer. Mean annual Pmax for the P-E curve was estimated to 13.3 mmol C m-2 h-1. Carbonate precipitation only occurred during light incubations and varied seasonally from 0.7 mmol CaCO3 m-2 h-1 in winter to 4.2 mmol CaCO3 m-2 h-1 in summer. Mean annual Pmax was 3.2 mmol CaCO3 m-2 h-1. Annual CR was estimated to 407.4 g C m**-2 yr**-1, and GCP, to 240.9 g C m**-2 yr**-1. Maerl communities are, therefore, heterotrophic systems (GCP:CR = 0.6), and are a source of CO2 for surrounding environments. In addition, CO2 released by calcification averaged 39.2 g C m**-2 yr**-1. Maerl community annual carbonate production was estimated to 486.7 g CaCO3 m**-2 yr**-1; they are therefore one of the most important carbonate producers in shallow coastal waters.