Radiocarbon age of bottom sediments from the Atlantic and Pacific Oceans

Procedures for radiocarbon dating of ocean sediments on board the ship using the benzene variant of the method are described. The main features of the benzene synthesis scheme, together with its differences from the method usually used onshore laboratories, are discussed briefly. Parameters of radiometric installation, in which activity of synthesized benzenes is determined are cited. The method was used successfully during Cruise 14 of R/V Dmitry Mendeleev (45 datings) and Cruise 24 of R/V Akademik Kurchatov (81 datings).

Holocene millenial-scale productivity record in the Mediterranean Sea

The calcareous nannofossil assemblages of Ocean Drilling Program Hole 963D from the central Mediterranean Sea have been investigated to document oceanographic changes in surface waters. The studied site is located in an area sensitive to large-scale atmospheric and climatic systems and to high- and low-latitude climate connection. It is characterized by a high sedimentation rate (the achieved mean sampling resolution is <70 years) that allowed the Sicily Channel environmental changes to be examined in great detail over the last 12 ka BP. We focused on the species Florisphaera profunda that lives in the lower photic zone. Its distribution pattern shows repeated abundance fluctuations of about 10-15%. Such variations could be related to different primary production levels, given that the study of the distribution of this species on the Sicily Channel seafloor demonstrates the significant correlation to productivity changes as provided by satellite imagery. Productivity variations were quantitatively estimated and were interpreted on the basis of the relocation of the nutricline within the photic zone, led by the dynamics of the summer thermocline. Productivity changes were compared with oceanographic, atmospheric, and cosmogenic nuclide proxies. The good match with Holocene master records, as with ice-rafted detritus in the subpolar North Atlantic, and the near-1500-year periodicity suggest that the Sicily Channel environment responded to worldwide climate anomalies. Enhanced Northern Hemisphere atmospheric circulation, which has been reported as one of the most important forcing mechanisms for Holocene coolings in previous Mediterranean studies, had a remarkable impact on the water column dynamics of the Sicily Channel.

Concentrations of persistant organic pollutants in Great skua eggs (Stercorarius skua) from Shetland 1980 and 2008

Concentrations of POPs in Great skua eggs from Shetland are among the highest in North Atlantic seabirds, with up to 11,600 µg/kg (ww) DDE and up to 17,900 µg/kg ww SumPCB. Concentrations of legacy POPs were significantly lower in 2008 than 1980. Decreases were greatest for least persistent compounds. Median SumPBDEs increased from 99 µg/kg ww in 1980 to 173 µg/kg ww in 2008. There were changes in Great skua breeding season diet, with more adult Herring and Mackerel and less Sandeel. These changes increase exposure to POPs, since Herring and Mackerel accumulate more POPs than Sandeels. In both years, eggs with higher d15N had higher POP concentrations. In 1980, birds feeding more on demersal discard fish from trawl fisheries and less on Sandeels, had higher POP levels in eggs. In 2008, individuals feeding more on Herring and Mackerel, and less on discards, had higher POP levels in eggs.

Relative abundances of foraminifera and radiocarbon ages of selected cores obtained from the Nordic and Barents Sea

Ocean circulation changes along the continental shelf of the Nordic and Barents Seas have been investigated in order to reconstruct regional changes in the inflow of Atlantic Water (AW) through the last 16,000 calibrated (cal) years (yr) B.P. We have selected five time-slices representing the late glacial (16,000-15,000 cal yr B.P.), the Bølling-Allerød warm interstadials (14,500-13,500 cal yr B.P.), the Younger Dryas cold stadial (12,500-11,500 cal yr B.P.), the early Holocene (9500-7500 cal yr B.P.) and the late Holocene (4000-2000 cal yr B.P.). Twelve previously published records of the distribution of benthic foraminifera faunas and ice-rafted debris have been compiled. The earliest sign of Atlantic Water inflow was recorded at the northern Iceland shelf at 16,000-15,000 cal yr B.P. The inflow of warm AW to the Nordic Seas shelf has been persistent since, but with variable strength and geographic pattern. An apparent zonal seesaw pattern in the strength of the Norwegian Atlantic Current (NwAC) and the Irminger Current (IC) during the late glacial, Bølling-Allerød and Younger Dryas periods was found. During the Holocene, no zonal differences in the inflows of NwAC and IC were found. A strong meridional gradient with warmer conditions at lower latitudes and relatively cold conditions at high northern latitudes existed.

Body mass, flipper length, oxidative balance indices and telomere length of king penguin chicks (A. patagonicus) on Possession Island

One of the reasons for animals not to grow as fast as they potentially could is that fast growth has been shown to be associated with reduced lifespan. However, we are still lacking a clear description of the reality of growth-dependent modulation of ageing mechanisms in wild animals. Using the particular growth trajectory of small king penguin chicks naturally exhibiting higher-than-normal growth rate to compensate for the winter break, we tested whether oxidative stress and telomere shortening are related to growth trajectories. Plasma antioxidant defences, oxidative damage levels and telomere length were measured at the beginning and at the end of the post-winter growth period in three groups of chicks (small chicks, which either passed away or survived the growth period, and large chicks). Small chicks that died early during the growth period had the highest level of oxidative damage and the shortest telomere lengths prior to death. Here, we show that small chicks that grew faster did it at the detriment of body maintenance mechanisms as shown by (i) higher oxidative damage and (ii) accelerated telomere loss. Our study provides the first evidence for a mechanistic link between growth and ageing rates under natural conditions.

Chlorophyll a concentration, and proportion of time in the water column obtained by instrumented bowhead whales

Sixty hours of direct measurements of fluorescence were collected from six bowhead whales (Balaena mysticetus) instrumented with fluorometers in Greenland in April 2005 and 2006. The data were used to (1) characterize the three-dimensional spatial pattern of chlorophyll-a (Chl-a) in the water column, (2) to examine the relationships between whale foraging areas and productive zones, and (3) to examine the correlation between whale-derived in situ values of Chl-a and those from concurrent satellite images using the NASA MODIS (Moderate Resolution Imaging Spectroradiometer) EOS-AQUA satellite (MOD21, SeaWifs analogue OC3M and SST MOD37). Bowhead whales traversed 1600 km**2, providing information on diving, Chl-a structure and temperature profiles to depths below 200 m. Feeding dives frequently passed through surface waters ( >50 m) and targeted depths close to the bottom, and whales did not always target patches of high concentrations of Chl-a in the upper 50 m. Five satellite images were available within the periods whales carried fluorometers. Whales traversed 91 pixels collecting on average 761 s (SD 826) of Chl-a samples per pixel (0-136 m). The depth of the Chl-a maximum ranged widely, from 1 to 66 m. Estimates of Chl-a made from the water-leaving radiance measurements using the OC3M algorithm were highly skewed with most samples estimated as <1 mg/m**3 Chl-a, while data collected from whales had a broad distribution with Chl-a reaching >9 mg/m**3. The correlation between the satellite-derived and whale-derived Chl-a maxima was poor, a linear fit explained only 10% of the variance.

Age determination of hornblende in ODP Site 188-1165 and DSDP Hole 28-268

Sediments from Ocean Drilling Program Site 1165 in the Indian Ocean sector of the Southern Ocean (off Prydz Bay) contain a series of layers that are rich in ice-rafted debris (IRD). Here we present evidence that IRD-rich layers at Site 1165 at 7, 4.8, and 3.5 Ma record short-lived, massive discharges of icebergs from Wilkes Land and Adélie Land, more than 1500 kilometers to the east of the depositional site. This distant source of icebergs is clearly defined by the presence of IRD hornblende grains with 40Ar/39Ar ages of 1200-1100 Ma and 1550-1500 Ma, ages that are not found on the East Antarctic continent in locations closer to Site 1165. This observation requires enormous amounts of detritus-carrying drifting icebergs, most likely in the form of large icebergs. These events probably reflect destabilization, surge, and break-up of ice streams on the Wilkes Land and Adélie Land margins of the East Antarctic Ice Sheet, in the vicinity of the low-lying Aurora and Wilkes Basins. They occurred under warming conditions, but each coast seems to have produced ice-rafting events independently, at different times. The data presented here constitute the first evidence of far-traveled icebergs from specific source areas around the East Antarctic perimeter. Launch of these icebergs may have happened during quite dramatic events, perhaps analogous to "Heinrich Events" in the North Atlantic.

Petrology, mineralogy, and chemistry of basaltic rocks at DSDP Leg 81 Holes

We detail the petrography and mineralogy of 145 basaltic rocks from the top, middle, and base of flow units identified on shipboard along with associated pyroclastic samples. Our account includes representative electron microprobe analyses of primary and secondary minerals; 28 whole-rock major-oxide analyses; 135 whole-rock analyses each for 21 trace elements; 7 whole-rock rare-earth analyses; and 77 whole-rock X-ray-diffraction analyses. These data show generally similar petrography, mineralogy, and chemistry for the basalts from all four sites; they are typically subalkaline and consanguineous with limited evolution along the tholeiite trend. Limited fractionation is indicated by immobile trace elements; some xenocrystic incorporation from more basic material also occurred. Secondary alteration products indicate early subaerial weathering followed by prolonged interaction with seawater, most likely below 150°C at Holes 552, 553A, and 554A. At Hole 555, greenschist alteration affected the deepest rocks (olivine-dolerite) penetrated, at 250-300°C.

Geochemistry of Miocene "blue tuff" samples

Distinctive, massive to stratified, pale blue volcaniclastics, initially referred to as the "blue tuff," were encountered at all four sites drilled during ODP Leg 127 in the Japan Sea. Detailed vertical sequence analysis, plagioclase chemistry, plagioclase 87Sr/86Sr isotopic composition, and 40Ar/39Ar age dating indicate that thick sequences of the blue tuff are not genetically related. Blue tuffs at Hole 794B were apparently deposited by density flows at ambient temperature. Deposition was penecontemporaneous with a large submarine phreatomagmatic eruption at 14.9 Ma in bathyal or deeper water depths. The blue tuffs at this location comprise mostly reworked hydroclastic glass shards and lesser amounts of plagioclase crystals. Pyrogenic plagioclase has an average An mole% of 18±3. Comparison of blue tuff plagioclase compositions with the composition of plagioclase from acoustic basement at Site 794 suggests that these rocks are not genetically related. As such, the extrapolation of sediment accumulation rate data in conjunction with this more precise age for the blue tuff corroborates previous minimum age estimates of 16.2 Ma for acoustic basement at Site 794. Blue tuffs at Hole 796B were probably deposited at ambient temperatures by downslope slumping and density flow of reworked pyrogenic debris. This debris includes abundant bubble wall glass shards and plagioclase crystals, with variable admixture of volcanic lithic and intrabasinal fragments. Pyrogenic fragments were produced by subaerial or shallow submarine, magmatic eruptions dated at 7.6 Ma. Blue tuffs contain a heterogeneous mixture of unrelated fragments including a mixed population of plagioclase crystals. The average An mole% of the predominant, probable comagmatic, plagioclase population is 30±4. The two sequences of blue tuff studied are distinct in age, mineral composition, and the eruptive origin of pyroclastic fragments. Preliminary 87Sr/86Sr isotopic compositions of plagioclase, however, indicates that blue tuffs at both locations are the product of typical, subduction-related island arc magmatism. Based on the results of this study, there is no justification for stratigraphic correlation of widespread, Miocene, blue to blue-gray bentonitic tuff and tuffaceous sandstones nor the interpretation that these strata are indicative of regional, explosive submarine volcanism genetically related to rifting and formation of the Japan Sea. Rather, these reworked pyroclastic strata of intermediate composition were deposited over a protracted 6-8 m.y. period in association with widespread, subduction-related submarine to subaerial volcanism in the Japan Sea backarc basin.

Oxygen isotope and Mg/Ca record of planktonic foraminifera of sediment core MD01-2390

Changes in the local freshwater budget over the last 22,000 years have been estimated from a sediment core located in the southern South China Sea (SCS) using a combined approach of Mg/Ca and oxygen isotopes on the planktonic foraminifera Globigerinoides ruber (white) sensu stricto (s.s.). Core MD01-2390 (06°28,12N, 113°24,56E; water depth 1591 m) is located near the glacial paleo-river mouths of the Baram, Rajang and North Sunda/Molengraaff Rivers that drained the exposed Sunda Shelf. The delta18Oseawater record reveals lower average values (-0.96±0.18 per mil) during the Last Glacial Maximum (LGM) when compared with modern values (-0.54±0.18 per mil). Low salinity during the LGM is interpreted to reflect a higher freshwater contribution due to a greater proximity of the core site to the mouths of the Baram, Rajang and North Sunda/Molengraaff Rivers at that time. A general deglacial increasing trend in salinity due to the progressive landward displacement of the coastline during deglacial shelf flooding is punctuated by several short-term shifts towards higher and lower salinity that are likely related to abrupt changes in the intensity of the East Asian summer monsoon. Thus, the deglacial delta18Oseawater changes reflect the combined effects of sea-level-induced environmental changes on the shelf (e.g. phases of retreat and breakdown of the shelf drainage systems) and East Asian monsoon climate change. Lower salinity than at present during the Early Holocene may be attributed to an increase in summer monsoonal precipitation that is corroborated by previous marine and terrestrial studies that report a Preboreal-Early Holocene monsoon optimum in the Asian monsoon region.

Pollen record and calculated holocene vegetation and climate dynamics from Sihailongwan Maar Lake, NE China

High-resolution palynological analysis on annually laminated sediments of Sihailongwan Maar Lake (SHL) provides new insights into the Holocene vegetation and climate dynamics of NE China. The robust chronology of the presented record is based on varve counting and AMS radiocarbon dates from terrestrial plant macro-remains. In addition to the qualitative interpretation of the pollen data, we provide quantitative reconstructions of vegetation and climate based on the method of biomization and weighted averaging partial least squares regression (WA-PLS) technique, respectively. Power spectra were computed to investigate the frequency domain distribution of proxy signals and potential natural periodicities. Pollen assemblages, pollen-derived biome scores and climate variables as well as the cyclicity pattern indicate that NE China experienced significant changes in temperature and moisture conditions during the Holocene. Within the earliest phase of the Holocene, a large-scale reorganization of vegetation occurred, reflecting the reconstructed shift towards higher temperatures and precipitation values and the initial Holocene strengthening and northward expansion of the East Asian summer monsoon (EASM). Afterwards, summer temperatures remain at a high level, whereas the reconstructed precipitation shows an increasing trend until approximately 4000 cal. yr BP. Since 3500 cal. yr BP, temperature and precipitation values decline, indicating moderate cooling and weakening of the EASM. A distinct periodicity of 550-600 years and evidence of a Mid-Holocene transition from a temperature-triggered to a predominantly moisture-triggered climate regime are derived from the power spectra analysis. The results obtained from SHL are largely consistent with other palaeoenvironmental records from NE China, substantiating the regional nature of the reconstructed vegetation and climate patterns. However, the reconstructed climate changes contrast with the moisture evolution recorded in S China and the mid-latitude (semi-)arid regions of N China. Whereas a clear insolation-related trend of monsoon intensity over the Holocene is lacking from the SHL record, variations in the coupled atmosphere-Pacific Ocean system can largely explain the reconstructed changes in NE China.

Bryoliths constructed by bryozoans in symbiotic associations with hermit crabs, Golfe d'Arguin, Mauritania

The Golfe d'Arguin offshore of northern Mauritania hosts a rare modern analogue for heterozoan carbonate production in a tropical marine setting. Dominated by ocean upwelling and with additional fertilisation by iron-rich aeolian dust, this naturally eutrophic marine environment lacks typical photozoan communities. A highly productive, tropical cosmopolitan biota dominated by molluscs and suspension-feeders such as bryozoans and balanids characterises the carbonate-rich surface sediments. Overall biodiversity is relatively low and the species present are tolerant against the eutrophic and low-light conditions, the strong hydrodynamic regime governed by ocean upwelling, and the unstable, soft-bottom seafloor with few hard substrata. Here, we describe an ectosymbiosis between the hermit crab Pseudopagurus granulimanus (Miers, 1881) and monospecific assemblages of the encrusting cheilostome bryozoan Acanthodesia commensale (Kirkpatrick and Metzelaar, 1922) that cohabits vacant gastropod shells. Nucleating on an empty gastropod shell, the bryozoan colonies form multilamellar skeletal crusts that produce spherical encrustations and extend the living chamber of the hermit crab through helicospiral tubular growth. This non-obligate mutualistic symbiosis illustrates the adaptive capabilities and benefits from a close partnership in a complex marine environment, driven by trophic conditions, high water energies and instable substratum. Sectioned bryoliths show that between 49 and 97 % of the solid volume of the specimens consists of bryozoan skeleton.

Major and minor element concentrations in the livers of polar bears (Ursus maritimus) from Greenland, Canada and Alaska

To assess geographic distributions of elements in the Arctic we compared essential and non-essential elements in the livers of polar bears (Ursus maritimus) collected from five regions within Canada in 2002, in Alaska between 1994 and 1999 and from the northwest and east coasts of Greenland between 1988 and 2000. As, Hg, Pb and Se varied with age, and Co and Zn with gender, which limited spatial comparisons across all populations to Cd, which was highest in Greenland bears. Collectively, geographic relationships appeared similar to past studies with little change in concentration over time in Canada and Greenland for most elements; Hg and Se were higher in some Canadian populations in 2002 as compared to 1982 and 1984. Concentrations of most elements in the polar bears did not exceed toxicity thresholds, although Cd and Hg exceeded levels correlated with the formation of hepatic lesions in laboratory animals.

Total length, and lipid and toxaphene content in blubber of minke whales (B. acutorostrata) from the North Atlantic

Toxaphene contamination of minke whales (Balaenoptera acutorostrata) from North Atlantic waters was examined for the first time. Total toxaphene and SumCHB (sum of 11 chlorobornanes) concentrations in blubber samples ranged from 170 ± 110 and 41 ± 39 ng/g lipid weight (l.w.) for female minke whales from southeastern Greenland to 5800 ± 4100 and 1100 ± 780 ng/g l.w. for males from the North Sea, respectively. Very large variations in toxaphene concentrations among sampling areas were observed suggesting a spatial segregation of minke whales. However, much of the apparent geographical discrimination was explained by the seasonal fluctuation of animal fat mass. Patterns of CHBs in males revealed that recalcitrant CHBs were in higher proportions in animals from the more easterly areas than in animals from the more westerly areas. This trend may be influenced by the predominance of the US, over the European, input of toxaphene to North Atlantic waters.

Amino acid geochronology of foraminifera test from north Queensland margin

In this study, we demonstrate the utility of amino acid geochronology based on single-foraminiferal tests in Quaternary sediment cores from the Queensland margin, Australia. The large planktonic foraminifer Pulleniatina obliquiloculata is ubiquitous in shelf, slope, and basin sediments of north Queensland as well as pantropical oceans. Fossil tests are resistant to dissolution, and retain substantial concentrations of amino acids (2-4 nmol/mg of shell) over hundreds of thousands of years. Amino acid D and L isomers of aspartic acid (Asp) and glutamic acid (Glu) were separated using reverse phase chromatography, which is sensitive enough to analyze individual foraminifera tests. In all, 462 Pulleniatina tests from 80 horizons in 11 cores exhibit a systematic increase in D/L ratios down core. D/L ratios were determined in 32 samples whose ages are known from AMS 14C analyses. In all cases, the Asp and Glu D/L ratios are concordant with 14C age. D/L ratios of equal-age samples are slightly lower for cores taken from deeper water sites, reflecting the sensitivity of the rate of racemization to bottom water temperature. Beyond the range of 14C dating, previously identified marine oxygen-isotope stage boundaries provide approximate ages of the sediments up to about 500,000 years. For this longer time frame, D/L ratios also vary systematically with isotope-correlated ages. The rate of racemization for Glu and Asp was modeled using power functions. These equations can be used to estimate ages of samples from the Queensland margin extending back at least 500,000 years. This analytical approach provides new opportunities for geochronological control necessary to understand fundamental sedimentary processes affecting a wide range of marine environments.