Seawater carbonate chemistry, Acropora digitifera growth and skeletal U/Ca ratios during experiments, 2011

The impact of ocean acidification caused by the increasing atmospheric CO2 has been studied in marine calcifiers, including hermatypic corals. However, the effect of elevated pCO2 on the early developmental life-cycle stage of corals has been little studied. In this study, we reared polyps of Acropora digitifera in seawater at pHT 6.55, 7.31, 7.64, 7.77, and 8.03, controlled by CO2 bubbling. We measured the dry weights of polyp skeletons after the 40-d experiment to investigate the relationship between the seawater aragonite saturation state and polyp growth. In addition, we measured skeletal U/Ca ratio to estimate their pH dependence. Skeletal weights of coral polyps increased with the aragonite saturation state and reached an apparent saturation plateau above pH 7.77. U/Ca ratios had a strong inverse relationship with pH and a negligible relationship with skeletal growth rate (polyp weight), suggesting that skeletal U/Ca could be useful for reconstructing paleo-pH.

Radiocarbon dataing, stable oxygen isotopes, and Mg/Ca ratios in surface sediment samples of the tropical eastern Indian Ocean

Shell chemistry of planktic foraminifera and the alkenone unsaturation index in 69 surface sediment samples in the tropical eastern Indian Ocean off West and South Indonesia were studied. Results were compared to modern hydrographic data in order to assess how modern environmental conditions are preserved in sedimentary record, and to determine the best possible proxies to reconstruct seasonality, thermal gradient and upper water column characteristics in this part of the world ocean. Our results imply that alkenone-derived temperatures record annual mean temperatures in the study area. However, this finding might be an artifact due to the temperature limitation of this proxy above 28°C. Combined study of shell stable oxygen isotope and Mg/Ca ratio of planktic foraminifera suggests that Globigerinoides ruber sensu stricto (s.s.), G. ruber sensu lato (s.l.), and G. sacculifer calcify within the mixed-layer between 20 m and 50 m, whereas Globigerina bulloides records mixed-layer conditions at ~50 m depth during boreal summer. Mean calcifications of Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, and Globorotalia tumida occur at the top of the thermocline during boreal summer, at ~75 m, 75-100 m, and 100 m, respectively. Shell Mg/Ca ratios of all species show a significant correlation with temperature at their apparent calcification depths and validate the application of previously published temperature calibrations, except for G. tumida that requires a regional Mg/Ca-temperature calibration (Mg/Ca = 0.41 exp (0.068*T)). We show that the difference in Mg/Ca-temperatures of the mixed-layer species and the thermocline species, particularly between G. ruber s.s. (or s.l.) and P. obliquiloculata, can be applied to track changes in the upper water column stratification. Our results provide critical tools for reconstructing past changes in the hydrography of the study area and their relation to monsoon, El Niño-Southern Oscillation, and the Indian Ocean Dipole Mode.

Uranium contents and isotope ratios of uranium and strontium in sediments, leachates and pore fluids from ODP Hole 162-984A

Bulk dissolution rates for sediment from ODP Site 984A in the North Atlantic are determined using the 234U/238U activity ratios of pore water, bulk sediment, and leachates. Site 984A is one of only several sites where closely spaced pore water samples were obtained from the upper 60 meters of the core; the sedimentation rate is high (11-15 cm/ka), hence the sediments in the upper 60 meters are less than 500 ka old. The sediment is clayey silt and composed mostly of detritus derived from Iceland with a significant component of biogenic carbonate (up to 30%). The pore water 234U/238U activity ratios are higher than seawater values, in the range of 1.2 to 1.6, while the bulk sediment 234U/238U activity ratios are close to 1.0. The 234U/238U of the pore water reflects a balance between the mineral dissolution rate and the supply rate of excess 234U to the pore fluid by a-recoil injection of 234Th. The fraction of 238U decays that result in a-recoil injection of 234U to pore fluid is estimated to be 0.10 to 0.20 based on the 234U/238U of insoluble residue fractions. The calculated bulk dissolution rates, in units of g/g/yr are in the range of 0.0000004 to 0.000002 1/yr. There is significant down-hole variability in pore water 234U/238U activity ratios (and hence dissolution rates) on a scale of ca. 10 m. The inferred bulk dissolution rate constants are 100 to 1000 times slower than laboratory-determined rates, 100 times faster than rates inferred for older sediments based on Sr isotopes, and similar to weathering rates determined for terrestrial soils of similar age. The results of this study suggest that U isotopes can be used to measure in situ dissolution rates in fine-grained clastic materials. The rate estimates for sediments from ODP Site 984 confirm the strong dependence of reactivity on the age of the solid material: the bulk dissolution rate (R_d) of soils and deep-sea sediments can be approximately described by the expression R_d ~ 0.1 1/age for ages spanning 1000 to 500,000,000 yr. The age of the material, which encompasses the grain size, surface area, and other chemical factors that contribute to the rate of dissolution, appears to be a much stronger determinant of dissolution rate than any single physical or chemical property of the system.

Helium isotope concentrations and ratios in sediments from ODP Hole 130-806B

We have determined the helium abundance and isotopic composition of seafloor carbonate sediments from the flanks of the Ontong Java Plateau, western equatorial Pacific Ocean (ODP Site 806). These results provide a two million year record of the burial flux of extraterrestrial 3He, which we believe is a proxy for the terrestrial accretion rate of interplanetary dust particles. The 3He burial flux prior to ~700 ka was relatively low, ~0.5 pcc/cm**2/kyr, but from 700 ka to the present, the burial flux gradually increased to a value of ~1.0 pcc/cm**2/kyr. 100 kyr periodicity in the 3He burial flux is apparent over the last 700 kyr and correlates with the oxygen isotope record of global climate, with high 3He burial fluxes associated with interglacial periods. This periodicity and phase are consistent with previous 3He measurements in North Atlantic sediments. Although 100 kyr periodicity in 3He burial flux is in agreement with recent predictions of the accretion rate of interplanetary dust based on a model of the orbital evolution of asteroidal debris, the measurements and predictions differ by one half cycle in phase. Nevertheless, our observations suggest the terrestrial accretion rate of interplanetary dust is controlled by orbital eccentricity and/or inclination relative to the solar-system invariable plane. Such control is a necessary but not sufficient condition for the hypothesis of that variations in extraterrestrial dust accretion modulates terrestrial climate with a 100 kyr period. We also identify several brief (<25 kyr) intervals of strongly enhanced 3He burial, possibly related to random and transient fluctuations in the accretion rate of asteroidal or cometary dust particles.

Radionuclide concentrations, ratios, and derived ages of massive sulfides from ODP Leg 139 and Leg 169 sites

Massive sulfide samples from the Bent Hill area were analyzed for 230Th/234U and 231Pa/235U disequilibria. Apparent ages calculated from these ratios are between 8.2 and >300 ka. Concordant ages were found for only three samples that originate near the surface from the clastic sulfide zone and suggest "true" ages of between 8.5 and 16.0 ka (mean of 230Th and 231Pa ages). The uranium vs. depth distribution in the Bent Hill Massive Sulfide deposit suggests an open system for uranium for the deeper part of the deposit, which was probably caused by extensive recrystallization processes inhibiting true age determinations.

Stable carbon and oxygen isotope ratios of benthic and planktic foraminifera from the Atlantic Ocean

Benthonic foraminifera in late Pleistocene deep-sea cores show significant variation in delta 13C with depth in sediment. This, and the report by Sommer et al., (in prep) of delta 13C variations in planktonic foraminifera, indicate that the delta13C in dissolved oceanic CO2 undergoes a significant change in a few thousand years. This is in apparent contradiction to the estimated 300 ka residence time for carbon in the ocean. It is suggested that this is a consequence of changes in the terrestrial plant biomass, which has a delta13C of about -25?. Postulated changes in world vegetation, particularly in tropical rainforests during the Late Pleistocene, were sufficient to produce change of the magnitude observed. Rapid expansions of forests between 13 ka and 8 ka ago may have resulted in the striking accumulation of aragonite pteropods in Atlantic Ocean sediments of the age. Rapid deforestation during an interglacial-glacial transition probably caused the intense carbonate dissolution which is observed in Equatorial Pacific Ocean sediments deposited over this interbal. The current rate of injection of fossil fuel CO2 into the atmosphere is substantially greater than the rate at which it was added during post-interglacial aridification in the tropics.

Polarity chron boundaries and foraminiferal 87Sr/86Sr ratios of ODP Sites 162-986 and 162-987

Cores recovered at Sites 986 and 987 comprise glacial fan sedimentation associated with the Svalbard-Barents Sea and Greenland Ice Sheets, respectively. At Site 986, the top 150 m and the basal 250 m yielded interpretable magnetic stratigraphies. The record from the intervening 550 m is compromised by drilling-related core deformation, poor recovery, and numerous debris flows. The uppermost 150 m appears to record the Brunhes/Matuyama boundary and the Jaramillo Subchron. The base of the drilled section (at ~950 meters below seafloor [mbsf]) is interpreted to lie within the Matuyama Chron (age <2.58 Ma) with an apparent normal polarity interval in the ~730-750 mbsf interval. Dinoflagellate cyst biostratigraphy and Sr isotopic ratios are consistent with a Matuyama age for the base of the drilled section and with the normal polarity interval as the Olduvai Subchron. On the other hand, the last occurrence of Neogloboquadrina atlantica (sinistral) and the last common occurrence of the warm-dwelling Globigerina bulloides at 647-650 mbsf in Hole 986D indicate an age for this level of ~2.3 Ma, inconsistent with the designation of the Olduvai Subchron in the ~730-750 mbsf interval. If the age at 647-650 mbsf in Hole 986D is taken as 2.3 Ma and the base of the hole lies within the Matuyama Chron, then the sedimentation rate in the basal 300 m of the cored section averages 1 m/k.y. At Site 987, the magnetic stratigraphy is fairly unambiguous throughout the section and yields an age of 7.5 Ma (Chron 4n) for the base of the drilled section. The paucity of calcareous and siliceous microfossils precludes biostratigraphic corroboration of the magnetostratigraphic interpretation, although dinoflagellate cysts provide general support, particularly at the base of the section. The age model indicates relatively low sedimentation rates (~5 cm/k.y.) at the base of the section with rates at least four to five times greater during intervals of debris flows at ~5-4.6 and ~2.6 Ma.

Effects of phytase supplementation of diets with two tiers of nutrient specifications on growth performance and protein efficiency ratios of broiler chickens

in two feeding experiments male and mixed-sex broiler chicks were offered diets based on sorghum and a wheat-sorghum blend with two tiers of nutrient specifications, without and with microbial phytase (600 and 800 FTU/kg), from 7-25 and 1-42 days post-hatch, respectively. The nutrient specifications for protein, amino acids, energy density and phosphorus (P) of standard diets were reduced to formulate the modified diets on a least-cost basis. Calculated differences in nutrient specifications between standard and modified diets ranged from 14.3 to 17.1 g/kg crude protein, 0.24 to 0.40 MJ/kg apparent metabolisable energy (AME) and 1.06 to 1.20 g/kg available P. In both experiments, reduced nutrient specifications had a negative impact on growth rates and feed efficiency and phytase supplementation had a positive influence on growth performance and protein efficiency ratios (PER). Phytase addition to the less expensive, modified diets either partially or entirely compensated for reduced growth performance and, consequently, feed costs per kg of live weight gain were reduced. In Experiment 1, phytase increased (p<0.001) nitrogen-corrected AME (AMEn) from 15.39 to 15.89 MJ/kg dry matter. For nitrogen (N) retention there was an interaction (p<0.05) between diet type and phytase as the effects of phytase on N retention were more pronounced in the modified diets, with an increase from 0.512 to 0.561. These results demonstrate the positive effects of phytase on protein and energy utilisation, in addition to its established liberation of phytate-bound P and illustrate the feasibility of assigning nutrient replacement values to the feed enzyme for consideration in least-cost ration formulations. Further work is, however, required to define the most appropriate reductions in nutrient specifications in association with phytase supplementation.

The influence of dietary sodium chloride, Arginine : Lysine ratio, and methionine source on apparent ileal digestibility of arginine and lysine in acutely heat-stressed broilers

The present study was carried out to determine the ileal digestibility of Arg and Lys in acutely heatstressed broilers using diets varying in Arg:Lys ratio, NaCl concentration, and Met Source. Male broilers were maintained at 22degreesC from 21 to 33 d of age and then at 32degreesC from 33 to 38 d of age. From 28 to 38 d of age, birds were fed a diet with an Arg:Lys ratio of 1.05 and 3 g of supplemental NaCl/kg of diet with or without L-arg free base to increase the Arg:Lys to 1.35, and with or without 3 g/kg of additional NaCl. Methionine was supplied as equimolar amounts of DL-Met or 2-hydroxy-4-(methylthio)-butanoic acid in a 2 x 2 x 2 design. At 38 d of age, digesta were collected from the terminal ileum, and amino acid analyses were conducted on feed and digesta samples and compared with acid-insoluble ash (dietary celite) to calculate the apparent ileal digestibilities of Lys and Arg. Increasing the NaCl concentration and the presence of HMB significantly decreased the digestibility of both Arg and Lys, whereas increasing the Arg:Lys ratio increased the digestibility of only Arg but did increase BW gain (P = 0.08). An interaction between dietary NaCl and Arg:Lys ratio as well as the 3-way interaction suggested that dietary NaCl could affect the apparent ileal digestibility of Arg and Lys at certain Arg:Lys ratios and the response may be influenced by the Met source.

Abnormal retinal vascular reactivity in individuals with impaired glucose tolerance:a preliminary study

To investigate the relationship between vascular function parameters measured at the retinal and systemic level and known markers for cardiovascular risk in patients with impaired glucose tolerance (IGT). Sixty age- and gender- matched White-European adults (30 IGT and 30 normal glucose tolerance -NGT) were recruited for the study. Fasting plasma glucose, lipids and 24-hour blood pressure (BP) was measured in all subjects. Systemic vascular and endothelial function was assessed using carotid-artery intimal media thickness (cIMT) and flow mediated dilation (FMD). Retinal vascular reactivity was assessed by the Dynamic Retinal Vessel Analyser (DVA). Additionally, blood glutathione (GSH, GSSG and tGSH) and plasma von-Willebrand (vWF) factor levels were also measured. Individuals with IGT demonstrated higher BP values (p<0.001), fasting TG and TG:HDL ratios (p<0.001) than NGT subjects. Furthermore, Total:HDL-C ratios and Framingham scores were raised (p=0.010 and p<0.001 respectively). Blood glutathione levels (GSH, GSSG and tGSH) were lower (p<0.001, p=0.039 and p<0.001 respectively) while plasma vWF was increased (p=0.014) in IGT subjects compared to controls. IGT individuals also demonstrated higher IMT in right and left carotid arteries (p=0.017 and p=0.005, respectively) alongside larger brachial artery diameter (p=0.015), lower FMD% (p=0.026) and GTN induced dilation (GID) (p=0.012) than healthy controls. At the retinal arterial level, the IGT subjects showed higher baseline fluctuations (BDF) (p=0.026), longer reaction time (RT) (p=0.032) and reduced baseline-corrected flicker response (bFR) (p=0.045). In IGT subjects retinal BDF correlated with and Total:HDL (p= 0.003) and HDL-C (p= 0.004). Arterial RT also correlated with FMD (p=0.017) in IGT but not NGT subjects. In IGT individuals there is a relationship between macro- and microvascular function, as well as a direct correlation between the observed retinal microcirculatory changes and established plasma markers for CVD. Multifactorial preventive interventions to decrease vascular risk in these individuals should be considered.

Local biomass control on the composition and reactivity of particulate organic matter in aquatic environments

Freshwater ecosystems have been recognized as important components of the global carbon cycle, and the flux of organic matter (OM) from freshwater to marine environments can significantly affect estuarine and coastal productivity. The focus of this study was the assessment of carbon dynamics in two aquatic environments, namely the Florida Everglades and small prairie streams in Kansas, with the aim of characterizing the biogeochemistry of OM. In the Everglades, particulate OM (POM) is mostly found as a layer of flocculent material (floc). While floc is believed to be the main energy source driving trophic dynamics in this oligotrophic wetland, not much is known about its biogeochemistry. The objective of this study was to determine the origin/sources of OM in floc using biomarkers and pigment-based chemotaxonomy to assess specific biomass contributions to this material, on a spatial (freshwater marshes vs. mangrove fringe) and seasonal (wet vs. dry) scales. It was found that floc OM is derived from the local vegetation (mainly algal components and macrophyte litter) and its composition is controlled by seasonal drivers of hydrology and local biomass productivity. Photo-reactivity experiments showed that light exposure on floc resulted in photo-dissolution of POC with the generation of significant amounts of both dissolved OM (DOM) and nutrients (N & P), potentially influencing nutrient dynamics in this ecosystem. The bio-reactivity experiments determined as the amount and rate of CO2 evolution during incubation were found to vary on seasonal and spatial scales and were highly influenced by phosphorus limitation. Not much is known on OM dynamics in small headwater streams. The objective of this study was to determine carbon dynamics in sediments from intermittent prairie streams, characterized by different vegetation cover for their watershed (C4 grasses) vs. riparian zone (C3 plants). In this study sedimentary OM was characterized using a biomarker and compound specific carbon stable isotope approach. It was found that the biomarker composition of these sediments is dominated by higher plant inputs from the riparian zone, although inputs from adjacent prairie grasses were also apparent. Conflicting to some extent with the River Continuum Concept, sediments of the upper reaches contained more degraded OM, while the lower reaches were enriched in fresh material deriving from higher plants and plankton sources as a result of hydrological regimes and particle sorting.

Stable oxygen isotope and Mg/Ca ratios on Globorotalia inflata

We present a species-specific Mg/Ca-calcification temperature calibration for Globorotalia inflata from a suite of 38 core top samples from the South Atlantic (from 8° to 49°S). G. inflata is a deep-dwelling planktonic foraminifer commonly occurring in subtropical to subpolar conditions, which qualifies it for reconstructions of the permanent thermocline. Apparent calcification depths and calcification temperatures were determined by comparing measured d18O with equilibrium d18O of calcite based on water column properties. Based on our core top samples, G. inflata apparent calcification depth is constant throughout the South Atlantic mid-latitudes with a depth of 350-400 m within the permanent thermocline. The resulting Mg/Ca-calcification temperature calibration is Mg/Ca = 0.72 +/-0.045/0.042 exp (0.076 +0.006 calcification 2 temperature) (r2 = 0.81) and covers the temperature range 3.1-16.5°C. We applied our Mg/Ca calibration to gravity core PS2495-3 from the Mid-Atlantic Ridge at ca. 41°S to test its validity by reconstructing a low-resolution record covering the last two glacial-interglacial cycles. Our paleotemperature record reveals large changes in temperature for Terminations I and II, when permanent thermocline temperature increased by as much as 8°C. The G. inflata paleotemperature record suggests that oceanic fronts repeatedly migrated over the location of site PS2495-3 during the last 160 kyr. This study shows the potential of G. inflata Mg/Ca to reconstruct paleotemperatures in the permanent thermocline.

(Table 1) Helium isotope ratios of sediment core TT013_114

We present a helium isotope record for core TT013-114PC from the central equatorial Pacific (140°W, 4°N, 4432 m water depth) spanning a period of 1 million years. We focus on the time interval from 560 to 800 kyr, largely coinciding with the mid-Pleistocene climate transition (MPT) when the dominant period of the Earth's climate variability shifted from 41 kyr to 100 kyr. The terrigenous 4He concentrations from our study correlate very well with published titanium concentrations in this core strongly supporting the use of terrigenous 4He as a monitor of continental dust. Normalizing titanium and terrigenous 4He concentrations to 3He suggests that the dust supply during the MPT was approximately 30% lower compared to the subsequent period (560-100 kyr). The 3He-normalized barium, aluminum and phosphorus concentrations, trace elements with a predominantly biogenic source in these sediments, are relatively constant. This is in contrast to previous studies that reported an apparent rise of titanium-normalized productivity proxies. Rather than a significant increase in productivity during the MPT, we conclude that the dust flux to the central equatorial Pacific was reduced and that the export productivity was approximately constant during this period of climate reorganization.