Biogeochemical processes at the sediment-water interface in a Northeastern Atlantic abyssal locality (Porcupine Abyssal Plain)

Abstract Temporal and spatial variability in the composition of suspended particulate material (SPM) was found at a Northeastern Atlantic abyssal locality on the Porcupine Abyssal Plain at a depth of 4850 m. Total SPM was distinctly higher in July 1997 than in March-April 1997 and October 1996. The 20 m of water immediately overlying the seabed was strongly influenced by resuspension and the suspended particulate matter was enriched with iron and manganese. Two water distinct layers, which were characterized by being enriched with SPM, Fe p , Mn p and Al p , were encountered during all sampling periods at depths of 4000 m and 4800 m. The enrichment of SPM with biogenic elements such as Ba, Ca and Sr implies it has a high biogenic content. Increases were observed in the concentrations of these biogenic elements throughout the sampling period, which indicates that the biogenic content of the SPM was steadily increased. SPM content and element/aluminum ratios increased in the spring and summer of 1997 compared to autumn 1996, probably as a result of increases in primary productivity, coincidental increases in near-bottom current velocities and possibly other processes such as increases in bacterial activity and bioturbation. Authigenic formation of solid phases of Fe and Mn were also influencing the spatial variability. Chemical reactions involving organic carbon and oxygen, which lead to the incorporation of iron and manganese in various forms into sediments were deduced. It is proposed that there was formation of lepidocrocite (γ-FeOOH) in the presence of organic carbon and oxygen, and also that iron may also have been transformed into Fe 2 O 3 . Re-precipitation of Fe and Mn is strongly enhanced by their enrichment in the SPM in the bottom waters. The sediments predominantly consist of biogenic carbonates and can be characterized as foraminiferal ooze. The proportion of these biogenic carbonates proved to be higher in the more recent sediments, either as result of recent increases in total primary productivity or because of carbonate dissolution within the subsurface sediments. Parallel increases of Mn, Fe and carbonates in the sediment layers supports the idea that the metallic ions are being adsorbed on to calcite surfaces, rather than being co-precipitated in the carbonate phases. Reprecipitation of iron and manganese in other solid phases with the involvement of organic carbon (C org ) in the oxygen penetration zone is suggested

Endothelin-B Receptors and Left Ventricular Dysfunction after Regional versus Global Ischaemia-Reperfusion in Rat Hearts

Background. Endothelin-1 (ET-1) is implicated in left ventricular dysfunction after ischaemia-reperfusion. ETA and ETB receptors mediate diverse actions, but it is unknown whether these actions depend on ischaemia type and duration. We investigated the role of ETB receptors after four ischaemia-reperfusion protocols in isolated rat hearts. Methods. Left ventricular haemodynamic variables were measured in the Langendorff-perfused model after 40-and 20-minute regional or global ischaemia, followed by 30-minute reperfusion. Wild-type (n = 39) and ETB-deficient (n = 41) rats were compared. Infarct size was measured using fluorescent microspheres after regional ischaemia-reperfusion. Results. Left ventricular dysfunction was more prominent in ETBdeficient rats, particularly after regional ischaemia. Infarct size was smaller (P = 0.006) in wild-type (31.5 ± 4.4%) than ETBdeficient (45.0 ± 7.3%) rats after 40 minutes of regional ischaemia-reperfusion. Although the recovery of left ventricular function was poorer after 40-minute ischaemia-reperfusion, end-diastolic pressure in ETB-deficient rats was higher after 20 than after 40 minutes of regional ischaemia-reperfusion. Conclusion. ETB receptors exert cytoprotective effects in the rat heart, mainly after regional ischaemia-reperfusion. Longer periods of ischaemia suppress the recovery of left ventricular function after reperfusion, but the role of ETB receptors may be more important during the early phases

Bioavailability of iodine in the UK-Peak District environment and its human bioaccessibility: an assessment of the causes of historical goitre in this area

Iodine is an essential micronutrient for human health. Its deficiency causes a number of functional and developmental abnormalities such as goitre. The limestone region of Derbyshire, UK was goitre-endemic until it declined from the 1930s and the reason for this has escaped a conclusive explanation. The present study investigates the cause(s) of goitre in the UK-Peak District area through an assessment of iodine in terms of its environmental mobility, bioavailability, uptake into the food chain and human bioaccessibility. The goitre-endemic limestone area is compared with the background millstone grit area of the UK-Peak District. The findings of this study show that ‘total’ environmental iodine is not linked to goitre in the limestone area, but the governing factors include iodine mobility, bioavailability and bioaccessibility. Compared with the millstone grit area, higher soil pH and calcium content of the limestone area restrict iodine mobility in this area, also soil organic carbon in the limestone area is influential in binding the iodine to the soil. Higher calcium content in the limestone area is an important factor in terms of strongly fixing the iodine to the soil. Higher iodine bioaccessibility in the millstone grit than the limestone area suggests that its oral bioaccessibility is restricted in the limestone area. Iodine taken up by plant roots is transported freely into the aerial plant parts in the millstone grit area unlike the limestone area, thus providing higher iodine into the human food chain in the millstone grit area through grazing animals unlike the goitre-prevalent limestone area

Characteristics of the Mesophotic Megabenthic Assemblages of the Vercelli Seamount (North Tyrrhenian Sea)

The biodiversity of the megabenthic assemblages of the mesophotic zone of a Tyrrhenian seamount (Vercelli Seamount) is described using Remotely Operated Vehicle (ROV) video imaging from 100 m depth to the top of the mount around 61 m depth. This pinnacle hosts a rich coralligenous community characterized by three different assemblages: (i) the top shows a dense covering of the kelp Laminaria rodriguezii; (ii) the southern side biocoenosis is mainly dominated by the octocorals Paramuricea clavata and Eunicella cavolinii; while (iii) the northern side of the seamount assemblage is colonized by active filter-feeding organisms such as sponges (sometimes covering 100% of the surface) with numerous colonies of the ascidian Diazona violacea, and the polychaete Sabella pavonina. This study highlights, also for a Mediterranean seamount, the potential role of an isolated rocky peak penetrating the euphotic zone, to work as an aggregating structure, hosting abundant benthic communities dominated by suspension feeders, whose distribution may vary in accordance to the geomorphology of the area and the different local hydrodynamic conditions

Genetic Basis of Myocarditis: Myth or Reality?

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Geochemical investigations on sediments from the Eastern Pacific

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