Slow growth and early sexual maturity: Bane and boon for the red coral Corallium rubrum

This study investigates the size, age and growth of Corallium rubrum which is a key species of the only large reef-like structure in the Mediterranean Sea, the coralligéne. Two populations were studied in the Ligurian Sea at a depth between 36 and 42 m. Basal diameter, colony height and numbers of branches of 230 colonies were measured, and age and growth rates were assessed from 25 colonies. Mean growth rate was 0.2 mm yr⁻¹ of basal diameter growth, corresponding to a mean annual total branch length increase of 5 mm. These results point to a coral growth much slower than assumed in many earlier studies. Additionally, age and size at first reproduction were analysed. Male colonies were shown to become sexually mature at a minimum age of six years (1.2 mm of basal diameter), while female colonies reached maturity when at least 10 years old (2 mm of basal diameter). We further discuss the implications of slow growth and early sexual maturity for red coral management and conservation.     

Magnetic properties of some young basalts from the East Pacific Rise

We report the results of a study of the magnetic properties of basalts recovered from the axis and from 0.7 m.y. old crust at 21° N and 19°30 S on the East Pacific Rise as well as from the 9°03 N overlapping spreading centers. The natural remanent magnetization of the samples from 21° N and 19°30 S decreases from the axis to 0.7 m.y. old crust as a result of low-temperature oxidation. In addition, the magnetic properties of the samples from the 21° N sites indicate that: (1) the magnetic susceptibility and the Koenigsberger ratio decrease with low-temperature alteration, (2) the Curie temperature, the median demagnetizing field and the remanent coercivity increase with maghemitization, (3) the saturation magnetization measured at room temperature does not change significantly with age. The magnetic properties of the basalt samples from the 9°03 N overlapping spreading centers indicate the presence of a high magnetization zone at the tip of the eastern spreading center. This high magnetization zone is the result of the high percentage of unaltered, fine-grained titanomagnetites present in the samples. These measurements are consistent with the results of the three-dimensional inversion of the magnetic field over the 9°03 N overlapping system [Sempere et al., 1984] as well as with detailed tectonic and geochemical investigations of overlapping spreading centers (Sempere and Macdonald, 1986a; Langmuir et al., 1986; Natland et al., 1986). The high magnetization zone appears to be the result of the eruption of highly fractionated basalts enriched in iron associated with the propagation of one of the limbs of the overlapping system into older lithosphere and not just to rapid decay, due to low-temperature oxidation, of the initially high magnetization of pillows extruded in the neovolcanic zone.     

Temporal variability in oxygen and nutrient concentrations in the southern Aegean Sea and the Straits of the Cretan Arc

Nutrient and oxygen data collected in the southern Aegean Sea (Cretan Sea) and the straits of the Cretan Arc, during the four seasonal PELAGOS cruises in 1994–1995, are investigated and compared with data collected from 1987 to 1992 within the same area. During the cruises of the PELAGOS Project, nutrient enrichment of the intermediate layers of the Cretan Sea was observed, as a result of intrusion of ‘nutrient-rich, oxygen-poor’ Transition Mediterranean Water (TMW) compensating the Cretan Deep Water (CDW) outflow. TMW occupied the intermediate layers of the entire Cretan Sea. The concentrations of nutrients within this layer were often two times higher than those observed in the same area during previous studies undertaken before 1992 (increase 2.5 μmol/l of nitrate, 0.05 μmol/l of phosphate and 2.5μmol/l of silicate). The decrease of oxygen in this layer is about 0.8ml/l (35 μmol/l). Outflow of CDW occurs principally through the Antikithira and Kassos Straits (the two deeper straits of the Cretan Arc); it results in an increase of oxygen content but a decrease in the nutrient content of water in the deep and bottom layers outside the Cretan Sea. The major mesoscale features in the area have a major influence of the distributions and exchanges of nutrients and oxygen through the straits of the Cretan Arc. The surface and the intermediate layers were richer in nutrients and poorer in oxygen in spring (March 1994), than in autumn (September 1994).     

Extreme aridity prior to lake expansion deciphered from facies evolution in the Miocene Ili Basin,south‐east Kazakhstan

Central Asia witnessed progressive aridification during the Miocene, commonly related to mountain uplift, the Paratethys retreat and global climate cooling. However, the formation of Miocene lakes in Central Asia seems to oppose drier conditions, suggesting that the precise timing, extent and forcing of the aridification is still not well constrained. This study presents a facies model for the alluvial–lacustrine part of the Middle to Late Miocene of the Ili Basin, obtained from two successions. The model enables the semi‐quantitative assessment of regional water level and salinity, and characterizes the control of water level on evaporite formation and diagenesis. Both the proximal Kendyrlisai and the distal Aktau successions show an overall increase in water availability from dry mudflat deposits to lacustrine sedimentation with a transitional playa phase. Increasing evaporation rates outpaced the water supply and caused groundwater salinization. Subsequent lake expansion coincided with a basin‐wide desalinization and required a shift to a positive water budget. A climatic control of the hydrological evolution is inferred due to abrupt salinization and a minor tectonic influence. The long‐term water accumulation is probably related to the hydrological closure of the basin in the early Middle Miocene (15·3 Ma). Starting at 14·3 Ma, the step‐wise salinization occurred simultaneously with the global cooling of the Miocene Climate Transition. The Miocene Climate Transition led to extreme aridity in the Ili Basin, highlighted by the early diagenetic formation of displacive anhydrite in the basin centre. The expansion of the freshwater lake (12·7 to 11·5 Ma) was possibly promoted by lower evaporation rates due to decreasing air temperatures in the Ili Basin after the Miocene Climate Transition. The extreme aridity in the Ili Basin is interpreted as a continental counterpart to the Badenian Salinity Crisis in the Central Paratethys. This emphasizes the role of atmospheric forcing on evaporite sedimentation across Eurasia during the Middle Miocene.     

Assessment of the geochemical reactivity of Fe-DOM complexes in wetland sediment pore waters using a nitroaromatic probe compound

The reductive capacity of Fe(II) present in anoxic sediment pore waters affects biogeochemically significant processes that occur in these environments, such as metal speciation, mineral solubility, nutrient bioavailability, and the transformation of anthropogenic organic compounds. We studied the reduction of pentachloronitrobenzene (PCNB) in natural pore waters to elucidate the reductive capacity of Fe(II) complexes, and monitored the redox-active species responsible for the observed kinetics. Differential pulse polarography (DPP) scans of sediment pore waters from a coastal Lake Erie wetland (Old Woman Creek National Estuarine Research Reserve, Huron, OH) revealed an increase in both Fe(III)-organic and Fe(II) species to a depth of ∼30 cm below the sediment-water interface. Concentrations of dissolved organic matter (DOM) in pore waters increased while pH decreased with depth. We found that Fe(II) was necessary for rapid PCNB reduction (<24 h), and observed faster reduction with increased pH. PCNB reduction in preserved pore waters (acidified to pH 2.5 after pore water extraction and raised to the native pH (6.7-7.6) prior to reaction) was similar to that observed in a model system containing Fe(II) and fulvic acid isolated from this site. Conversely, PCNB reduction in unaltered pore water was significantly slower than that observed in preserved pore water, indicating that the Fe(II) speciation and its reductive capacity differed. DPP scans of pore waters used for kinetic studies confirmed that pH-adjustment affected Fe_T speciation in the pore waters, as the Fe(III)-DOM peak current was lowered or disappeared completely in the preserved pore water samples. These data show that pH-adjustment of pore waters presumably alters both their complexation chemistry and reactivity towards PCNB, and shows how small changes in Fe complexation can potentially affect redox chemistry in anoxic environments. Our results also show that reactive organic Fe(II) complexes are naturally present in wetland sediment pore waters, and that these species are potentially important mediators of Fe(II)/Fe(III) redox biogeochemistry in anoxic sedimentary environments.     

Diamond precipitation from ascending reduced fluids in the Kaapvaal lithosphere: Thermodynamic constraints

Previous research has shown that the Kaapvaal lithospheric mantle is generally reduced and characterised by a decreasing redox state with increasing depth. As a consequence, C-O-H fluids in the Kaapvaal lithospheric mantle are dominated by H₂O, CH₄, and C₂H₆. Thermodynamic calculations demonstrate that diamond precipitation from such a fluid during ascend is possible as it is exposed to a more oxidised environment and both CH₄ and C₂H₆ are oxidised. However, the calculations also demonstrate that the diamond precipitation potential from such a fluid decreases when: (1) the mantle is either more reduced or oxidised compared to the Kaapvaal mantle, or (2) the change in temperature with pressure is smaller compared to that of the Kaapvaal mantle. Therefore, the presence of reduced mantle fluid species and a generally decreasing oxygen fugacity with increasing depth do not necessarily warrant diamond precipitation from a rising reduced fluid.     

Capitalising the farm family entrepreneur: negotiating private equity partnerships in Australia

ABSTRACT

Research on the financialisation of land and agribusiness has highlighted major shifts in agri-food systems globally. Yet these accounts tend to focus on the activities of financial actors, and few take seriously the role of farmers in negotiating investments in land and agribusiness. Farmers in the global North may be well placed to benefit from partnerships with financial investors, although little is known about the way that such partnerships are formed. Australian studies of farmer agency have been productive in examining farm family entrepreneurs and globally engaged farmers who work beyond the farm gate to organise supply chains. This paper adds to these studies by providing insights about a capitalising farm family entrepreneur, who successfully negotiated and entered into a direct equity partnership with a large foreign pension fund. Several observations are significant: the exceptional skill, time and expense required to negotiate these partnerships; the role of consultants and non-human actors in structuring them; and the spatially- and temporally divergent farm development practices that are enabled by a shift from debt to equity financing. These observations are indicative of a new adaptive strategy of family farmers to shifting financial landscapes and of emergent family, corporate, and financial farm hybridity.     

The SCUBA HAlf Degree Extragalactic Survey – VI. 350-μm mapping of submillimetre galaxies

A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich  ( M _dust≃ 9 × 10⁸ M_⊙)  , luminous  ( L _FIR≃ 2 × 10¹² L_⊙)  star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of  ≃400 M_⊙ yr⁻¹  . We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N ₃₅₀(>25 mJy) ∼ 200–500 deg⁻².     

Testing variations within the Tagish Lake meteorite—II: Whole‐rock geochemistry of pristine samples

Four pristine specimens of the Tagish Lake C2 chondrite meteorite were previously determined through mineralogy, petrology, and organic chemistry to have been affected by aqueous alteration in the order (from least to most altered) TL5b < TL11h < TL11i, and TL11v as a mixture of the other specimens (Herd et al. 2011 ; Blinova et al. 2014 ). Here, we report the whole‐rock data for a total of 65 elements for the same four Tagish Lake samples as determined by ICP‐MS and ICP‐AES (utilizing the Parr bomb digestion method on small samples, approximately 50 mg), and by INAA. Our data demonstrate that the determined aqueous alteration sequence has a positive correlation with trace elements, such as K and Br that are mobile during aqueous alteration, which appear to be controlled by an increase of phyllosilicates from least to most altered samples. Yet, the homogeneity of other elements suggests that elemental mass transfer occurred on a localized scale and aqueous alteration was isochemical for these elements, similar to other primitive carbonaceous chondrites. By plotting data from three samples (TL5b, TL11h, and TL11i) on a Zn/Mn versus Sc/Mn diagram, we also confirm that the Tagish Lake meteorite is not a simple mixture of CI and CM material.