Eric Douville

Northeastern Atlantic cold-water coral reefs and climate

U-series age patterns obtained on reef framework-forming cold-water corals collected over a nearly 6000-km-long continental margin sector, extending from off Mauritania (17 degrees N; northwest Africa) to the southwestern Barents Sea (70 degrees N; northeastern Europe), reveal strong climate influences on the geographical distribution and sustained development of these ecosystems. Over the past three glacial-interglacial cycles, framework-forming cold-water corals (Lophelia pertusa and Madrepora oculata) seem to have predominantly populated reefs, canyons, and patches in the temperate East Atlantic and the Mediterranean Sea. Above 50 degrees N corals colonize reefs in the northern East Atlantic primarily during warm climate periods with the biogeographic limit advancing from similar to 50 degrees N to similar to 70 degrees N. We propose that north-south oscillations of the biogeographic limit of reef developments are paced by ice ages and may occur synchronously with north-south displacement of cold nutrient-rich intermediate waters and surface productivity related to changes of the polar front.

PAIRED 14C AND 230Th/U DATING OF SURFACE CORALS FROM THE MARQUESAS AND VANUATU (SUB-EQUATORIAL PACIFIC) IN THE 3000 TO 15,000 CAL YR INTERVAL

Paired radiocarbon and 230Th/U dating was performed on 13 surface corals from submerged reefs in the Marquesas and from raised terraces in Vanuatu. The absolute ages of the corals analyzed ranged from 3000 to 15,000 cal yr. Estimates of the difference between the absolute and 14C ages of these corals are in agreement with previous determinations up until 11,500 cal yr. The resulting mean sea surface reservoir age R is determined at 390 60 yr for the Marquesas region (9S), which is slightly higher than the R value at 280 50 yr for the Tahiti Islands (18S). Multiple 14C analyses of 2 corals from the Marquesas present scattered 14C ages at ~12,000 and ~15,100 cal yr. This could be attributed to rapid changes of the 14C content of surface waters around the Marquesas Islands or to a subtle submarine diagenesis.

14C sources and distribution in the vicinity of La Hague nuclear reprocessing plant. Part I: Terrestrial environment

COGEMA-La Hague nuclear reprocessing plant in the Cotentin Peninsula (northwest France) releases in the atmosphere about 19 TBq.yr (super -1) of radiocarbon. Three experiments in a terrestrial environment with sampling of a bio-indicator like furze were performed in 1997, 1998, and 1999, and additional air samples in the chimney plume were measured. Results presented here establish the (super 14) C distribution in the La Hague environment and suggest that a part of the (super 14) C content in the vegetation near the coast results from a (super 14) CO (sub 2) degassing of seawater supplied with the liquid waste from the nuclear plant.

Neodymium isotopic composition in foraminifera and authigenic phases of the South China Sea sediments: Implications for the hydrology of the North Pacific Ocean over the past 25 kyr

epsilon Nd and normalized Rare Earth Elements (REE) patterns of benthic and planktonic foraminifera and Fe-Mn coatings precipitated on sediments have been investigated for the South China Sea (SCS) to (1) assess the reliability of the extraction of past seawater epsilon Nd in the SCS and to (2) reconstruct past hydrological changes during the last 25 kyr. Reductively cleaned mono-specific planktonic foraminifera (Globigerinoides ruber) and mixed benthic foraminifera in core-top sediments from 1500 to 2400 m display similar epsilon Nd values to those of the modern Pacific Deep Water (PDW) (epsilon Nd of -3.9 to -4.4). Furthermore, the epsilon Nd of the reductive cleaning solutions shows similar epsilon Nd values to ones obtained on cleaned foraminifera. Combined with PAAS-normalized REE patterns, these results confirm that the oxidative and reductive cleaning procedure applied to foraminifera does not totally remove all of the Fe-Mn coatings and that epsilon Nd values yielded by cleaned planktonic foraminifera retain the epsilon Nd imprint of the bottom and/or pore water. epsilon Nd values obtained from a leaching procedure carried out on the bulk non-decarbonated sediments are comparable to the epsilon Nd values of the modern PDW, whereas a similar leaching procedure applied to decarbonated sediments reveals a bias due to contamination with Nd deriving from lithogenic particles. In core MD052904, seawater epsilon Nd, reconstructed from planktonic foraminifera, indicates that the last glacial period is characterized by lower epsilon Nd (-5.2 +/- 0.2 to -6.4 +/- 0.3) than the late Holocene (-4.1 +/- 0.2). Assuming that Nd input from river does not change strongly the epsilon Nd of the PDW of the northern SCS, these epsilon Nd variations suggest a higher relative proportions of southern-sourced water in the deep water of the western subtropical Pacific Ocean during the last glacial period.

A core‐top study of dissolution effect on B/Ca in Globigerinoides sacculifer from the tropical Atlantic: Potential bias for paleo‐reconstruction of seawater carbonate chemistry

It has been recently shown that B/Ca in planktonic foraminiferal calcite can be used as a proxy for seawater pH. Based on the study of surface sediments (multi-cores) retrieved along a depth transect on the Sierra Leone Rise (Eastern Equatorial Atlantic), we document the decrease of B/Ca and Mg/Ca of Globigerinoides sacculifer shells with increasing water depth and dissolution. This effect of dissolution on B/Ca may potentially represent a severe bias for paleo-pH reconstructions using this species. Samples of G. sacculifer were analyzed independently at two laboratories for B/Ca and Mg/Ca. Both sets of results show a systematic decrease of B/Ca and Mg/Ca along the depth transect, with an overall loss of ~14 mmol/mol (~15%) for B/Ca and of ~0.7 mmol/mol (~21%) for Mg/Ca between the shallowest (2640 m) and the deepest (4950 m) sites. Because of this dissolution effect, surface water pH reconstructed from B/Ca of G. sacculifer decreases by ~0.11 units between the shallowest site and the deepest site, a magnitude similar to the expected glacial/interglacial surface water pH changes.

Three centuries of heavy metal pollution in Paris (France) recorded by urban speleothems

The first record of urban speleothems used to reconstruct the history of heavy metal pollution of shallow groundwaters is presented. Two speleothems grew during the last 300 years in an underground aqueduct in the north-eastern part of Paris. They display high Pb, Mn V, Cu, Cd and Al concentrations since 1900 due to the urbanization of the site which triggered anthropogenic contamination of the water feeding the speleothems. Surprisingly, these heavy metal concentrations are also high in the oldest part. This early pollution could come from the use of Parisian waste as fertilizers in the orchards and vineyards cultivated above the aqueduct before urbanization. Lead isotopes were measured in these carbonates as well as in lead artifacts from the 17th-18th centuries ((206)Pb/(207)Pb=1.180+/-0.003). The mean (206)Pb/(207)Pb ratio, for one of the speleothems is 1.181+/-0.003 unvarying with time. These lead signatures are close to those of coal and old lead from northern European mines, lower than the natural background signature. It confirms that the high metal concentrations found come from anthropogenic pollution. Conversely, the lead isotopic composition of the second speleothem presents two temporal trends: for the oldest levels, the mean value (1.183+/-0.003) is similar to the first speleothem. For the youngest part, a lower value (1.172+/-0.005) is recorded, evidencing the contribution of a new lead source at the beginning of the industrial revolution. Pb isotopes were also measured in recent samples from a nearby superficial site. The first sample is a recent (AD 1975+/-15 years) deposit ((206)Pb/(207)Pb=1.148+/-0.003), and the second, a thin subactual layer ((206)Pb/(207)Pb=1.181+/-0.002). These data are compatible with the adding of anthropogenic sources (leaded gasoline and industrial lead from Rio Tinto ore).

Development of laser ablation multi-collector inductively coupled plasma mass spectrometry for boron isotopic measurement in marine biocarbonates: new improvements and application to a modern Porites coral†

RATIONALE Laser Ablation coupled to Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICPMS) is a powerful tool for the high-precision measurement of the isotopic ratios of many elements in geological samples, with the isotope ratio ((11) B/(10) B) of boron being used as an indicator of the pH of oceanic waters. Most geological samples or standards are polished and ablation occurs on flat surfaces. However, the shape and the irregularities of marine biocarbonates (e.g., corals, foraminifera) can make precise isotopic measurements of boron difficult. Even after polishing, the porosity properties and the presence of holes or micro-fractures affect the signal and the isotopic ratio when ablating the material, especially in raster mode. METHODS The effect of porosity and of the crater itself on the (11) B signal and the isotopic ratio acquired by LA-MC-ICPMS in both raster and spot mode was studied. Characterization of the craters was then performed with an optical profilometer to determine their shapes and depths. Surface state effects were examined by analyzing the isotopic fractionation of boron in silicate (NIST-SRM 612 and 610 standards) and in carbonate (corals). RESULTS Surface irregularities led to a considerable loss of signal when the crater depth exceeded 20 µm. The stability and precision were degraded when ablation occurred in a deep cavity. The effect of laser focusing and of blank correction was also highlighted and our observations indicate that the accuracy of the boron isotopic ratio does not depend on the shape of the surface. After validation of the analytical protocol for boron isotopes, a raster application on a Porites coral, which grew for 18 months in an aquarium after field sampling, was carried out. CONCLUSIONS This original LA-MC-ICPMS study revealed a well-marked boron isotope ratio temporal variability, probably related to growth rate and density changes, irrespective of the pH of the surrounding seawater. Copyright

Primary Life Stage Boron Isotope and Trace Elements Incorporation in Aposymbiotic Acropora millepora Coral under Ocean Acidification and Warming

Early-life stages of reef-building corals are vital to coral existence and reef maintenance. It is therefore crucial to study juvenile coral response to future climate change pressures. Moreover, corals are known to be reliable recorders of environmental conditions in their skeletal materials. Aposymbiotic Acropora millepora larvae were cultured in different seawater temperature (27 and 29oC) and pCO2 (390 and 750 µatm) conditions to understand the impacts of ‘end of century’ ocean acidification (OA) and ocean warming (OW) conditions on skeletal morphology and geochemistry. The experimental conditions impacted primary polyp juvenile coral skeletal morphology and growth resulting in asymmetric translucent appearances with brittle skeleton features. The impact of OA resulted in microstructure differences with decreased precipitation or lengthening of fasciculi and disorganized aragonite crystals that led to more concentrations of centers of calcifications. The coral skeletal δ11B composition measured by laser ablation MC-ICP-MS was significantly affected by pCO2 (p = 0.0024) and water temperature (p = 1.46 x 10-5). Reconstructed pH of the primary polyp skeleton using the δ11B proxy suggests a difference in coral calcification site and seawater pH consistent with previously observed coral pH up-regulation. Similarly, trace element results measured by laser ablation ICP-MS indicate the impact of pCO2. Primary polyp juvenile Sr/Ca ratio indicates a bias in reconstructed sea surface temperature (SST) under higher pCO2 conditions. Coral microstructure content changes (center of calcification and fasciculi) due to OA possibly contributed to the variability in B/Ca ratios. Our results imply that increasing OA and OW may lead to coral acclimation issues and species-specific inaccuracies of the commonly used Sr/Ca-SST proxy.

Urbanization impact on sulfur content of groundwater revealed by the study of urban speleothem-like deposits: Case study in Paris, France

Speleothem-like deposits that develop underground in urban areas are an archive of the environmental impact of anthropic activities that has been little studied so far. In this paper, the sulfate content in shallow groundwater from northern Paris (France) is compared with the sulfur content in two 300-year-old urban carbonate deposits that grew in a historical underground aqueduct. The present-day waters of the aqueduct have very high sulfur and calcium contents, suggesting pollution from gypsum dissolution. However, geological gypsum levels are located below the water table. Sulfur content was measured by micro-X-ray fluorescence in these very S-rich carbonate deposits (0.5 to 1% of S). A twofold S increase during the second half of the 1800s was found in both samples. These dates correspond to two major periods of urbanization above the site. We discus three possible S sources: anthropic sources (industries, fertilizers…), volcanic eruptions and input within the water through gypsum brought for urbanization above the studied site (backfill with quarry waste) since the middle of the 19th century. For the younger second half of the studied section, S input from gypsum brought during urbanization was confirmed by the study of isotopic sulfur composition (δ34S=+15.2‰ at the top). For the oldest part, several sulfur peaks could be related to early industrial activity in Paris, that caused high local air pollution, as reported in historical archives but also to historical gypsum extraction. This study provides information on the origin and timing of the very high SO42- levels measured nowadays within the shallow groundwater, thus demonstrating the interest in using carbonate deposits in urban areas as a proxy for the history of urbanization or human activities and their impact on water bodies.

Yttrium and rare earth element partitioning in seawaters from the Bay of Bengal

The dissolved yttrium (Y) and rare earth element (REE) concentrations of seawater samples collected along a north-south hydrological transect within the Bay of Bengal (BoB) have been analyzed to estimate contributions of the Ganges and Brahmaputra (G-B) river inputs to the dissolved REE distribution of the Northern Indian Ocean. Surface water masses of the BoB are characterized by Y/Ho ratios (84) intermediate between the G-B river suspended sediment (41) and water mass from the South Indian Ocean (93). Covariation of MREE (middle REE, Sm) and LREE (light REE, La) concentrations suggests that the dissolved REEs in surface waters (upper 100 m depth) of the BoB (Sm/La = 0.21) appear to derive mainly from the freshwater discharge of the G-B river system. In contrast, values obtained in the intermediate and deep waters (Sm/La = 0.14) suggest a mixing of dissolved REEs deriving from the release of G-B river suspended particles (Sm/La = 0.16) and the contribution of Antarctic Bottom Water (AABW) (Sm/La = 0.12). Consequently, we propose that MREE/MREE* ratios in the BoB waters could be an accurate proxy to trace lithogenic inputs from the G-B river system. The dissolved and particle remineralization Nd fluxes from G-B river system are calculated to constitute about 9% and 4% of the global dissolved river discharge and “boundary inputs” flux. Our estimation indicates that the massive G-B river system inputs could greatly alter the dissolved REEs distribution in the BoB and contribute to the dissolved REEs budget in the ocean.