Geochemistry and oxygen and iron isotope ratios of mafic rocks

Recycling of oceanic crust into the deep mantle via subduction is a widely accepted mechanism for creating compositional heterogeneity in the upper mantle and for explaining the distinct geochemistry of mantle plumes. The oxygen isotope ratios (d18O) of some ocean island basalts (OIB) span values both above and below that of unmetasomatised upper mantle (5.5 ± 0.4 per mil) and provide support for this hypothesis, as it is widely assumed that most variations in d18O are produced by near-surface low-temperature processes. Here we show a significant linear relationship between d18O and stable iron isotope ratios (d57Fe) in a suite of pristine eclogite xenoliths. The d18O values of both bulk samples and garnets range from values within error of normal mantle to significantly lighter values. The observed range and correlation between d18O and d57Fe is unlikely to be inherited from oceanic crust, as d57Fe values determined for samples of hydrothermally altered oceanic crust do not differ significantly from the mantle value and show no correlation with d18O. It is proposed that the correlated d57Fe and d18O variations in this particular eclogite suite are predominantly related to isotopic fractionation by disequilibrium partial melting although modification by melt percolation processes cannot be ruled out. Fractionation of Fe and O isotopes by removal of partial melt enriched in isotopically heavy Fe and O is supported by negative correlations between bulk sample d57Fe and Cr content and bulk sample and garnet d18O and Sc contents, as Cr and Sc are elements that become enriched in garnet- and pyroxene-bearing melt residues. Melt extraction could take place either during subduction, where the eclogites represent the residues of melted oceanic lithosphere, or could take place during long-term residence within the lithospheric mantle, in which case the protoliths of the eclogites could be of either crustal or mantle origin. This modification of both d57Fe and d18O by melting processes and specifically the production of low-d18O signatures in mafic rocks implies that some of the isotopically light d18O values observed in OIB and eclogite xenoliths may not necessarily reflect near-surface processes or components.

Chlorophyll fluorescence lifetimes and variable fluorescence parameters from phytoplankton in the global ocean

In situ data was collected between 2008-2014 in upper ocean. This data set includes the date, local time, coordinate, lifetime value, and variable fluorescence values.

Pollen and macroremains from profiles from site Osterholz and Elm

The biostratigraphic classification of the Pleistocene in north-western and central Europe is still insufficiently known, in spite of numerous geological and vegetation-history investigations. The question is not even clear, for example, how often a warm-period vegetation with thermophilous trees such as Quercus, Ulmus, Tilia, Carpinus etc could develop here. In past years, on the basis of several geological and vegetation-history findings, suspicion has often been expressed that some of the classical stages of the Pleistocene could include more warm periods than heretofore assumed, and as a result of recent investigations the period between the Waal and Holstein interglacials seems to include at least two warm periods, of which the Cromer is one. This paper contributes to this problem. The interglacial sediments coming from the Elm-Mountains near Brunswick and from the Osterholz near Elze - both within the limits of the German Mittelgebirge - were investigated by pollen analysis. In both cases a Pinus-Betula zone and a QM zone were found. The vegetation development of the Pinus-Betula zone is characterized in both sequences by the early appearance of Picea. Because of strong local influence at the Osterholz a detailed correlation is difficult. However, vegetation development at the time of the QM zone at both sites was similar; it is especially characterized by the facts that Ulmus clearly migrated to the site earlier than Quercus and was very abundant throughout this time. Furthermore, both diagrams show very low amounts of Corylus. The interglacial of the Osterholz shows in addition to the above; a Carpinus-QM-Picea-zone in which Eucommia reaches a relative high value and in the upper of which Azolla filiculoides was also found. The similarity of vegetation development justifies acceptance of the same age for the occurrences. A comparison of the vegetation development at the Elm and the Osterholz with those of the Eem, Holstein, Waal, and Tegelen warm periods as well as with all the Cromer sites so far investigated shows that only a correlation with the Cromer Complex is possible. This correlation is supported by the geologic relations in the Osterholz (the deposit is overlain by Elster till). Therefore the till-like material with Scandinavian rock fragments underlying the deposit at Elm is of particular interest. The 'Rhume' interglacial beds at Bilshausen, only 60 km south of Osterholz, is also assigned to the Cromer complex, but the two deposits cannot be of the same age because the vegetation development differs. Therefore the Cromer complex must include at least two warm periods. Further conclusions about the relative stratigraphic position of these two occurrences and correlations of other Cromer sites are at this time not possible, however.

Occurrence and type of dolomite in ODP Site 124-768 samples (Table 1)

Occurrence of deep-sea dolomites has been reported from numerous settings (for discussion see Lumsden, 1988). Different authors agree that dolomite formation in the pelagic realm is a relatively early diagenetic process (e.g., Jorgensen, 1983; Shimmield and Price, 1984; Kablanow et al., 1984; Kulm et al., 1984). Baker and Burns (1985) suggest that most of the pelagic dolomites formed within a few tens of meters below the seafloor within the zone of microbial sulfate reduction. According to Fuechtbauer and Richter (1988), dolomite can form in the deep-sea at a minimum temperature of 10°C. Other deep-sea dolomites are products of fluids derived from underlying evaporites or submarine weathering of basalts (Garrison, 1981). In some cases (Mullins et al., 1985; Dix and Mullins, 1988; Mullins et al., 1988), the existence of dolomite is linked to disconformities and its formation may have resulted from circulation of seawater through the sediment during prolonged exposure (Dix and Mullins, 1988, p. 287). At Site 768 (Fig. 1), lithified carbonate layers, some containing variable amounts of dolomite, occur below 201 mbsf (Miocene). These beds alternate with unconsolidated or semi-lithified marl layers interbedded in clays and siliciclastic turbidites. The irregular depth distribution of the limestone beds and the variation in preservation and recrystallization of the calcareous microfaunas suggest that lithification of carbonates at Site 768 not only reflects burial diagenesis as described by Garrison (1981) and others, but in part may be a selective, early diagenetic process. The different types and distribution of the dolomite additionally seem to support this assumption. The purpose of this report is to document the occurrence and textural nature of the dolomite at Site 768. Methods used were analyses of stained thin sections (Alizarin S and Ferrocyanide) and studies with the scanning electron microscope. No geochemical analyses (e.g., stable isotopes) were carried out; they will be the subject of further investigations.

Primary production of phytoplankton and chlorophyll a in the southeast Barents Sea in August-September 1998

A study was performed from August 11 to September 3, 1998 in the Pechora Sea, which covered the shallow-water southeastern Barents Sea. Chlorophyll a concentration in the surface layer (C_chls) ranged from 0.08 to 1.15 mg/m**3, while primary production in the water column (C_phs) Varied from 17 to 170 mg C/m**2/day, aver. 75 mg C/m**2/day. Transition from central deep-water (60-190 m) parts of the sea to coastal shallow-water (15-30 m) parts was accompanied by increase of average C_chls values 2.4 times (from 0.21 to 0.51 mg/m**3) and decrease in average C_phs 1.6 times (from 95 to 58 mg C/m**2/day); the latter, in turn, resulted from decrease in thickness of the photosynthetic layer (H_ph) from 55 to 12 m and its relative transparency (H) from 17 to 4 m. This sharp change in H value and absence of a positive feedback between C_chls and C_phs were most probably related to rapid increase in the role of yellow substance and suspended matter in absorption of solar radiation in coastal waters. In sea areas with depths greater than 30 m a deep chlorophyll maximum was observed; at most of stations it located in the 20-35 m deep layer during illumination in photosynthetic active radiation range comprising 0.8-1.5% of its surface value. Parameters of photosynthetic light curves in these regions indicate participation of shade-adapted flora in formation of the deep chlorophyll maximum. In coastal waters characterized by a relatively uniform chlorophyll distribution over the water column no light adaptation of phytoplankton to efficient utilization of low irradiation for photosynthesis was encountered. Thus, a conclusion was made that combination of extremely low values of C_phs and H_ph makes the pelagic ecosystem of the Pechora Sea coastal regions very sensitive to anthropogenic impacts that may increase water turbidity.

Effect of simulated ocean acidification on the acute toxicity of Cu and Cd to Tigriopus japonicus

Heavy metals pollution in marine environments has caused great damage to marine biological and ecological systems. Heavy metals accumulate in marine creatures, after which they are delivered to higher trophic levels of marine organisms through the marine food chain, which causes serious harm to marine biological systems and human health. Additionally, excess carbon dioxide in the atmosphere has caused ocean acidification. Indeed, about one third of the CO2 released into the atmosphere by anthropogenic activities since the beginning of the industrial revolution has been absorbed by the world's oceans, which play a key role in moderating climate change. Modeling has shown that, if current trends in CO2 emissions continue, the average pH of the ocean will reach 7.8 by the end of this century, corresponding to 0.5 units below the pre-industrial level, or a three-fold increase in H+ concentration. The ocean pH has not been at this level for several millions of years. Additionally, these changes are occurring at speeds 100 times greater than ever previously observed. As a result, several marine species, communities and ecosystems might not have time to acclimate or adapt to these fast changes in ocean chemistry. In addition, decreasing ocean pH has the potential to seriously affect the growth, development and reproduction reproductive processes of marine organisms, as well as threaten normal development of the marine ecosystem. Copepods are an important part of the meiofauna that play an important role in the marine ecosystem. Pollution of the marine environment can influence their growth and development, as well as the ecological processes they are involved in. Accordingly, there is important scientific value to investigation of the response of copepods to ocean acidification and heavy metals pollution. In the present study, we evaluated the effects of simulated future ocean acidification and the toxicological interaction between ocean acidity and heavy metals of Cu and Cd on T. japonicus. To accomplish this, harpacticoids were exposed to Cu and Cd concentration gradient seawater that had been equilibrated with CO2 and air to reach pH 8.0, 7.7, 7.3 and 6.5 for 96 h. Survival was not significantly suppressed under single sea water acidification, and the final survival rates were greater than 93% in both the experimental groups and the controls. The toxicity of Cu to T. japonicus was significantly affected by sea water acidification, with the 96h LC50 decreasing by nearly threefold from 1.98 to 0.64 mg/L with decreasing pH. The 96 h LC50 of Cd decreased with decreasing pH, but there was no significant difference in mortality among pH treatments. The results of the present study demonstrated that the predicted future ocean acidification has the potential to negatively affect survival of T. japonicus by exacerbating the toxicity of Cu. The calculated safe concentrations of Cu were 11.9 (pH 7.7) and 10.5 (pH 7.3) µg/L, which were below the class I value and very close to the class II level of the China National Quality Standard for Sea Water. Overall, these results indicate that the Chinese coastal sea will face a

Discharge measurements and storm event chemistry at the San Francisco River station (Planta) in 2007-2008

To improve our knowledge of the influence of land-use on solute behaviour and export rates in neotropical montane catchments we investigated total organic carbon (TOC), Ca, Mg, Na, K, NO3 and SO4 concentrations during April 2007-May 2008 at different flow conditions and over time in six forested and pasture-dominated headwaters (0.7-76 km2) in Ecuador. NO3 and SO4 concentrations decreased during the study period, with a continual decrease in NO3 and an abrupt decrease in February 2008 for SO4. We attribute this to changing weather regimes connected to a weakening La Niña event. Stream Na concentration decreased in all catchments, and Mg and Ca concentration decreased in all but the forested catchments during storm flow. Under all land-uses TOC increased at high flows. The differences in solute behaviour during storm flow might be attributed to largely shallow subsurface and surface flow paths in pasture streams on the one hand, and a predominant origin of storm flow from the organic layer in the forested streams on the other hand. Nutrient export rates in the forested streams were comparable to the values found in literature for tropical streams. They amounted to 6-8 kg/ha/y for Ca, 7-8 kg/ha/y for K, 4-5 kg/ha/y for Mg, 11-14 kg/ha/y for Na, 19-22 kg/ha/y for NO3 (i.e. 4.3-5.0 kg/ha/y NO3-N) and 17 kg/ha/y for SO4. Our data contradict the assumption that nutrient export increases with the loss of forest cover. For NO3 we observed a positive correlation of export value and percentage forest cover.

(Table 1) Boron concentration and d11B values of interstitial water from IODP Holes 308-U1319A, U1320A, U1322B and U1324B

The Integrated Ocean Drilling Program Expedition 308 (IODP308) drilled normal-pressured sediments from the Brazos-Trinity Basin IV and over-pressured sediments from the Ursa Basin on the northern slope of the Gulf of Mexico. The interstitial water samples from the normal-pressured basin show B concentrations and B isotopic compositions ranging from 255 to 631 µM (0.6 to 1.5 times of seawater value) and from +29.1 to +42.7 per mil (relative to NIST SRM 951), respectively. A wider range is observed both for B concentrations (292 to 865 µM, 0.7 to 2.1 times of seawater value) and d11B values (+25.5 to +43.2 per mil) of the interstitial water in the over-pressured basin. The down-core distribution of B concentrations and d11B values in the interstitial waters are sensitive tracers for assessing various processes occurring in the sediment column, including boron adsorption/desorption reactions involving clay minerals and organic matter in sediments as well as fluid migration and mixing in certain horizons and in the sediment column. In the normal-pressured basin adsorption/desorption reactions in shallow sediments play the major role in controlling the B content and B isotopic composition of the interstitial water. In contrast, multiple processes affect the B content and d11B of the interstitial water in the over-pressured Ursa Basin. There, the stratigraphic level of the maxima of B and d11B correspond to seismic reflectors. The intruded fluids along the seismic reflector boundary from high to low-topography mix with local interstitial water. Fluid flow is inferred in the Blue Unit (a coarse sandstone layer, connecting the high- to low-pressured region) from the freshening of interstitial water in Ursa Basin Site U1322, and upward flow by the overpressure expels fluid from the overburden above the Blue Unit.

Seawater carbonate chemistry and net photosynthesis, C/N ratio, growth rate, size of Ostreococcus tauri in a laboratory experiment

Phytoplankton are the basis of marine food webs, and affect biogeochemical cycles. As CO2 levels increase, shifts in the frequencies and physiology of ecotypes within phytoplankton groups will affect their nutritional value and biogeochemical function. However, studies so far are based on a few representative genotypes from key species. Here, we measure changes in cellular function and growth rate at atmospheric CO2 concentrations predicted for the year 2100 in 16 ecotypes of the marine picoplankton Ostreococcus. We find that variation in plastic responses among ecotypes is on par with published between-genera variation, so the responses of one or a few ecotypes cannot estimate changes to the physiology or composition of a species under CO2 enrichment. We show that ecotypes best at taking advantage of CO2 enrichment by changing their photosynthesis rates most should increase in relative fitness, and so in frequency in a high-CO2 environment. Finally, information on sampling location, and not phylogenetic relatedness, is a good predictor of ecotypes likely to increase in frequency in this system.