Seawater carbonate chemistry, clearance rates, respiration rates, condition index and cellular turnover (RNA: DNA) of Juvenile King Scallop, Pecten maximus in a laboratory experiment

The decline in ocean water pH and changes in carbonate saturation states through anthropogenically mediated increases in atmospheric CO2 levels may pose a hazard to marine organisms. This may be particularly acute for those species reliant on calcareous structures like shells and exoskeletons. This is of particular concern in the case of valuable commercially exploited species such as the king scallop, Pecten maximus. In this study we investigated the effects on oxygen consumption, clearance rates and cellular turnover in juvenile P. maximus following 3 months laboratory exposure to four pCO2 treatments (290, 380, 750 and 1140 µatm). None of the exposure levels were found to have significant effect on the clearance rates, respiration rates, condition index or cellular turnover (RNA: DNA) of individuals. While it is clear that some life stages of marine bivalves appear susceptible to future levels of ocean acidification, particularly under food limiting conditions, the results from this study suggest that where food is in abundance, bivalves like juvenile P. maximus may display a tolerance to limited changes in seawater chemistry.

Ocean acidification mediates photosynthetic response to UV radiation and temperature increase in the diatom Phaeodactylum tricornutum

Increasing atmospheric CO2 concentration is responsible for progressive ocean acidification, ocean warming as well as decreased thickness of upper mixing layer (UML), thus exposing phytoplankton cells not only to lower pH and higher temperatures but also to higher levels of solar UV radiation. In order to evaluate the combined effects of ocean acidification, UV radiation and temperature, we used the diatom Phaeodactylum tricornutum as a model organism and examined its physiological performance after grown under two CO2 concentrations (390 and 1000 µatm) for more than 20 generations. Compared to the ambient CO2 level (390 µatm), growth at the elevated CO2 concentration increased non-photochemical quenching (NPQ) of cells and partially counteracted the harm to PS II (photosystem II) caused by UV-A and UV-B. Such an effect was less pronounced under increased temperature levels. The ratio of repair to UV-B induced damage decreased with increased NPQ, reflecting induction of NPQ when repair dropped behind the damage, and it was higher under the ocean acidification condition, showing that the increased pCO2 and lowered pH counteracted UV-B induced harm. As for photosynthetic carbon fixation rate which increased with increasing temperature from 15 to 25 °C, the elevated CO2 and temperature levels synergistically interacted to reduce the inhibition caused by UV-B and thus increase the carbon fixation.

Chemical and mineral compositions of sulfide deposits from the Snake Pit hydrothermal field, Mid-Atlantic Ridge rift zone

The Snake Pit hydrothermal field is located on the top of a neovolcanic rise on the Mid-Atlantic Ridge at sea depths between 3460 and 3510 m. It was surveyed during several oceanological expeditions including DSDP Legs. Additional scientific materials were obtained in 2002 and 2003 during expedition onboard R/V Akademik Mstislav Keldysh with two Mir deep-sea manned submersibles. Three eastern hydrothermal mounds (Moose, Beehive, and Fir Tree) are located on the upper part of the eastern slope of the rise over a common fractured pedestal composed of fragments of massive sulfides. The western group of hydrothermal deposits is encountered on the western slope of the axial graben. Within this mature hydrothermal field, which was formed over the past 4000 years, we studied morphology of the hydrothermal mounds, chemistry and mineralogy of hydrothermal deposits, chemistry of sulfide minerals, and isotope composition of sulfur in them.

Mineralogy and geochemistry of altered ash, pelagic clay, and a clay vein in basalt from DSDP Leg 62 Holes

Volcanic ash was recovered from lower Aptian to Albian deposits from DSDP Sites 463, 465, and 466; pelagic clay of the upper Pleistocene to Upper Cretaceous was recovered mainly from Site 464, with minor amounts at Sites 465 and 466. We present X-ray-mineralogy data on pelagic clay and altered volcanic ash recovered from the four Leg 62 sites. In addition, two ash samples from Sites 463 and 465, a pelagic clay from Site 464, and a clay vein from the basaltic basement at Site 464 each were analyzed for major, minor, and trace elements. Our purpose is to describe the mineralogy and chemistry of altered ash and pelagic clays, to determine the sources of their parent material, and to delineate the diagenetic history of these clay-rich deposits. Correlation of chemistry and mineralogy of ash and pelagic clay with volcanic rocks suspected to be their parent material is not always straightforward, because weathering and diagenetic alteration caused depletion or enrichment of many elements.

Interstitial water chemistry of ODP Leg 110 holes

Major-element compositions (Cl-, SO4[2-], Ca2+, Mg2+ , Li+ , K+, Na+ , Sr2+) of interstitial waters obtained from sediment cores along the ODP Leg 110 transect across the Northern Barbados accretionary prism have shown that a complex set of geochemical processes are of importance in this area. In the volcanic ash-rich Pleistocene-Pliocene sediments, alteration reactions involving volcanic ash lead to depletions of Mg2+ and K+. This process is confirmed by the much lower than contemporaneous seawater values of the 87Sr/86Sr ratios of dissolved strontium. In the deeper sediments recovered below the zone of decollement (Sites 671 and 672) large increases in Ca2+ and gradual decreases in Mg2+ , Na+, and d18O (H2O) indicate a potential contribution to the interstitial water chemistry by exchange with underlying basement rocks. This process has been hard to confirm because the drill holes were terminated well short of reaching basement. However, the concentration gradient pattern is consistent with observations in a large number of DSDP drill holes. Finally, but most importantly, low Cl- concentrations in the decollement zone and underlying sand layers, as well as in fault zones at Sites 673 and 674, indicate dilution of interstitial waters. The potential origins of the low Cl- concentrations are discussed, though we are not able to distinguish any mechanism in particular. Our evidence supports the concept of water migration along the decollement and through the underlying sandstones as well as along recent fault zones in the accretionary complex. Interstitial water concentration depth profiles are affected by faulting, thrusting, and overturn processes in the accretionary prism. These processes have caused a diminished diffusive exchange with the overlying ocean, thus explaining increased depletions in Mg2+ and SO4[2-] in sites farther onto the accretionary prism.

(Table 3) Li concentrations and isotopic compositions in foraminiferal shells, carbonate sediments, and associated pore waters from ODP Sites 131-806 and 138-851

An improved procedure for lithium isotope analysis using Li3PO4 as the ion source has been investigated for application to geological samples. The 7Li/6Li ratio is measured using double rhenium filament thermal ionization mass spectrometry in which isotopic fractionation is minimized at high temperatures. The method produces a stable, high intensity Li+ ion beam that allows measurement of nanogram quantities of lithium. This results in a reduction in sample size of up to 1000 times relative to that required for the established Li2BO2+ method while maintaining a comparable precision of better than 1? (1 sigma). Replicate analyses of the NBS L-SVEC Li2CO3 standard yielded a mean value of 12.1047+/-0.0043 (n=21), which is close to the reported absolute value of 12.02+/-0.03. Intercalibration with a wide range of geological samples shows excellent agreement between the Li3PO4 and Li2BO2+ techniques. Replicate analyses of seawater and a fresh submarine basalt display high precision results that agree with previous measurements. Taking advantage of the high ionization efficiency of the phosphate ion source, we have made the first measurements of the lithium concentration (by isotope dilution) and isotopic composition of calcareous foraminiferal tests and other marine carbonates. Preliminary results indicate that substantial lithium exchange occurs between carbonate sediments and their interstitial waters. In addition, a possible link between lithium paleoceanography and paleoclimate during the last 1000 ky may be derived from planktonic foraminiferal tests. This highly sensitive technique can be applied in the examination of low lithium reservoirs and thereby provide insight into some fundamental aspects of lithium geochemistry.

Effects of elevated pCO2 on the post-settlement development of Pocillopora damicornis

Ocean acidification represents a key threat to the recruitment of scleractinian corals. Here, we investigated the effect of increased partial pressure of carbon dioxide (pCO2) on the early development of Pocillopora damicornis by rearing the recruits for 12 days at 3 pCO2 levels (446, 896 and 1681 µatm). Results showed that increased pCO2 exerted minor effects on symbiont density and maximum quantum yield (Fv/Fm), while significantly enhanced the relative electron transport through photosystem II (PSII) of Symbiodinium. Notably, calcification and biomass of recruits decreased sharply by 34% and 24% respectively in 896 µatm, and tended to remain constant as pCO2 was raised from 896 to 1681 µatm. Furthermore, recruits in 1681 ?atm, with comparable surface area as those in 896 µatm, produced fewer buds. These findings indicated that juvenile P. damicornis under high pCO2 would enhance electron transport rate and suppress asexual budding to favor skeletal and tissue growths, which are more critical for their persistence and survival in a high pCO2 environment. This work suggested the physiological plasticity of juvenile corals under short-term exposure to elevated pCO2.

Seawater carbonate chemistry and calcification rate during experiments with coral Stylophora pistillata, 2003

We show here that CO2 partial pressure (pCO2) and temperature significantly interact on coral physiology. The effects of increased pCO2 and temperature on photosynthesis, respiration and calcification rates were investigated in the scleractinian coral Stylophora pistillata. Cuttings were exposed to temperatures of 25°C or 28°C and to pCO2 values of ca. 460 or 760 muatm for 5 weeks. The contents of chlorophyll c2 and protein remained constant throughout the experiment, while the chlorophyll a content was significantly affected by temperature, and was higher under the 'high-temperature-high-pCO2' condition. The cell-specific density was higher at 'high pCO2' than at 'normal pCO2' (1.7 vs. 1.4). The net photosynthesis normalized per unit protein was affected by both temperature and pCO2, whereas respiration was not affected by the treatments. Calcification decreased by 50% when temperature and pCO2 were both elevated. Calcification under normal temperature did not change in response to an increased pCO2. This is not in agreement with numerous published papers that describe a negative relationship between marine calcification and CO2. The confounding effect of temperature has the potential to explain a large portion of the variability of the relationship between calcification and pCO2 reported in the literature, and warrants a re-evaluation of the projected decrease of marine calcification by the year 2100.

Seawater carbonate chemistry and processes during an experiment with coral reef, 2000

The concentration of CO2 in the atmosphere is projected to reach twice the preindustrial level by the middle of the 21st century. This increase will reduce the concentration of [CO3]2- of the surface ocean by 30% relative to the preindustrial level and will reduce the calcium carbonate saturation state of the surface ocean by an equal percentage. Using the large 2650 m3 coral reef mesocosm at the BIOSPHERE-2 facility near Tucson, Arizona, we investigated the effect of the projected changes in seawater carbonate chemistry on the calcification of coral reef organisms at the community scale. Our experimental design was to obtain a long (3.8 years) time series of the net calcification of the complete system and all relevant physical and chemical variables (temperature, salinity, light, nutrients, Ca2+,pCO2, TCO2, and total alkalinity). Periodic additions of NaHCO3, Na2CO3, and/or CaCl2 were made to change the calcium carbonate saturation state of the water. We found that there were consistent and reproducible changes in the rate of calcification in response to our manipulations of the saturation state. We show that the net community calcification rate responds to manipulations in the concentrations of both Ca2+ and [CO3]2- and that the rate is well described as a linear function of the ion concentration product, [Ca2+]0.69[[CO3]2-]. This suggests that saturation state or a closely related quantity is a primary environmental factor that influences calcification on coral reefs at the ecosystem level. We compare the sensitivity of calcification to short-term (days) and long-term (months to years) changes in saturation state and found that the response was not significantly different. This indicates that coral reef organisms do not seem to be able to acclimate to changing saturation state. The predicted decrease in coral reef calcification between the years 1880 and 2065 A.D. based on our long-term results is 40%. Previous small-scale, short-term organismal studies predicted a calcification reduction of 14-30%. This much longer, community-scale study suggests that the impact on coral reefs may be greater than previously suspected. In the next century coral reefs will be less able to cope with rising sea level and other anthropogenic stresses.

Seawater carbonate chemistry and copepod Centropages tenuiremis feeding, filtering and respiration rate during experiments, 2012

Climate change mediates marine chemical and physical environments and therefore influences marine organisms. While increasing atmospheric CO2 level and associated ocean acidification has been predicted to stimulate marine primary productivity and may affect community structure, the processes that impact food chain and biological CO2 pump are less documented. We hypothesized that copepods, as the secondary marine producer, may respond to future changes in seawater carbonate chemistry associated with ocean acidification due to increasing atmospheric CO2 concentration. Here, we show that the copepod, Centropages tenuiremis, was able to perceive the chemical changes in seawater induced under elevated CO2 concentration (>1700 µatm, pH < 7.60) with avoidance strategy. The copepod's respiration increased at the elevated CO2 (1000 µatm), associated acidity (pH 7.83) and its feeding rates also increased correspondingly, except for the initial acclimating period, when it fed less. Our results imply that marine secondary producers increase their respiration and feeding rate in response to ocean acidification to balance the energy cost against increased acidity and CO2 concentration.

The potential of ocean acidifi cation on suppressing larval development in the Pacifi c oyster Crassostrea gigas and blood cockle Arca infl ata Reeve

We evaluated the effect of pH on larval development in larval Pacific oyster (Crassostrea gigas) and blood cockle ( Arca inflata Reeve). The larvae were reared at pH 8.2 (control), 7.9, 7.6, or 7.3 beginning 30 min or 24 h post fertilization. Exposure to lower pH during early embryonic development inhibited larval shell formation in both species. Compared with the control, larvae took longer to reach the D-veliger stage when reared under pH 7.6 and 7.3. Exposure to lower pH immediately after fertilization resulted in significantly delayed shell formation in the Pacific oyster larvae at pH 7.3 and blood cockle larvae at pH 7.6 and 7.3. However, when exposure was delayed until 24 h post fertilization, shell formation was only inhibited in blood cockle larvae reared at pH 7.3. Thus, the early embryonic stages were more sensitive to acidified conditions. Our results suggest that ocean acidification will have an adverse effect on embryonic development in bivalves. Although the effects appear subtle, they may accumulate and lead to subsequent issues during later larval development.

Interactive effects of light, nitrogen source, and carbon dioxide on energy metabolism in the diatom Thalassiosira pseudonana

Due to the ongoing effects of climate change, phytoplankton are likely to experience enhanced irradiance, more reduced nitrogen, and increased water acidity in the future ocean. Here, we used Thalassiosira pseudonana as a model organism to examine how phytoplankton adjust energy production and expenditure to cope with these multiple, interrelated environmental factors. Following acclimation to a matrix of irradiance, nitrogen source, and CO2 levels, the diatom's energy production and expenditures were quantified and incorporated into an energetic budget to predict how photosynthesis was affected by growth conditions. Increased light intensity and a shift from inline image to inline image led to increased energy generation, through higher rates of light capture at high light and greater investment in photosynthetic proteins when grown on inline image. Secondary energetic expenditures were adjusted modestly at different culture conditions, except that inline image utilization was systematically reduced by increasing pCO2. The subsequent changes in element stoichiometry, biochemical composition, and release of dissolved organic compounds may have important implications for marine biogeochemical cycles. The predicted effects of changing environmental conditions on photosynthesis, made using an energetic budget, were in good agreement with observations at low light, when energy is clearly limiting, but the energetic budget over-predicts the response to inline image at high light, which might be due to relief of energetic limitations and/or increased percentage of inactive photosystem II at high light. Taken together, our study demonstrates that energetic budgets offered significant insight into the response of phytoplankton energy metabolism to the changing environment and did a reasonable job predicting them.

Introducción al estudio de las mineralizaciones del Señorío y Tierra de Molina de Aragón (Guadalajara, España)

In this communication it's efected an introduction to the study of the mineralizations placed in the Señorio and Tierra de Molina de Aragón an historical demarcation of Guadalajara situated in the Sistema Ibérico. In this comunication, we will introduce the Study Castilian mineralizations between them, C/Ag are present as well as stratiform iron and copper mineralization.

Li & Pb MD Sinulations

Pb17Li is today a reference breeder material in diverse fusion R&D programs worldwide. Extracting dynamic and structural properties of liquid LiPb mixtures via molecular dynamics simulations, represent a crucial step for multiscale modeling efforts in order to understand the suitability of this compound for future Nuclear Fusion technologies. At present a Li-Pb cross potential is not available in the literature. Here we present our first results on the validation of two semi-empirical potentials for Li and Pb in liquid phase. Our results represent the establishment of a solid base as a previous but crucial step to implement a LiPb cross potential. Structural and thermodynamical analyses confirm that the implemented potentials for Li and Pb are realistic to simulate both elements in the liquid phase.

One dimensional exciton luminescence induced by extended defects in nonpolar (Al,Ga)N/GaN quantum wells

In this study, we present the optical properties of nonpolar GaN/(Al,Ga)N single quantum wells (QWs) grown on either a- or m-plane GaN templates for Al contents set below 15%. In order to reduce the density of extended defects, the templates have been processed using the epitaxial lateral overgrowth technique. As expected for polarization-free heterostructures, the larger the QW width for a given Al content, the narrower the QW emission line. In structures with an Al content set to 5 or 10%, we also observe emission from excitons bound to the intersection of I1-type basal plane stacking faults (BSFs) with the QW. Similarly to what is seen in bulk material, the temperature dependence of BSF-bound QW exciton luminescence reveals intra-BSF localization. A qualitative model evidences the large spatial extension of the wavefunction of these BSF-bound QW excitons, making them extremely sensitive to potential fluctuations located in and away from BSF. Finally, polarization-dependent measurements show a strong emission anisotropy for BSF-bound QW excitons, which is related to their one-dimensional character and that confirms that the intersection between a BSF and a GaN/(Al,Ga)N QW can be described as a quantum wire.