MAPPING COASTAL AND WETLAND VEGETATION COMMUNITIES USING MULTI-TEMPORAL SENTINEL-2 DATA

Abstract. Operational monitoring of complex vegetation communities, such as the ones growing in coastal and wetland areas, can be effectively supported by satellite remote sensing, providing quantitative spatialized information on vegetation parameters, as well as on their temporal evolution. With this work, we explored and evaluated the potential of Sentinel-2 data for assessing the status and evolution of coastal vegetation as the primary indicator of ecosystem conditions, by mapping the different plant communities of Venice lagoon (Northeast Italy) via a rule-based classification approach exploiting synoptic seasonal features of spectral indices and multispectral reflectance. The results demonstrated that coastal and wetland vegetation community type maps derived for two different years scored a good overall accuracy around 80%, with some misclassification in the coastal areas and overestimation of salt marsh communities coverage, and that virtual collaborative environments can facilitate the use of Sentinel-2 data and products to multidisciplinary users

A kinetic study of gamma-glutamyltransferase (GGT)-mediated S-nitrosoglutathione catabolism.

S-Nitrosoglutathione (GSNO) is a nitric oxide (NO) donor compound which has been postulated to be involved in transport of NO in vivo. It is known that c-glutamyl transpeptidase (GGT) is one of the enzymes involved in the enzyme-mediated decomposition of GSNO, but no kinetics studies of the reaction GSNO-GGT are reported in literature. In this study we directly investigated the kinetics of GGT with respect to GSNO as a substrate and glycyl- glycine (GG) as acceptor co-substrate by spectrophotometry at 334 nm. GGT hydrolyses the c-glutamyl moiety of GSNO to give S-nitroso-cysteinylglycine (CGNO) and c-glutamyl-GG. However, as both the substrate GSNO and the first product CGNO absorb at 334 nm, we optimized an ancillary reaction coupled to the enzymatic reaction, based on the copper-mediated decomposition of CGNO yielding oxidized cysteinyl-glycine and NO. The ancillary reaction allowed us to study directly the GSNO/GGT kinetics by following the decrease of the characteristic absorbance of nitrosothiols at 334 nm. A Km of GGT for GSNO of 0.398 ± 31 mM was thus found, comparable with Km values reported for other c-glutamyl substrates of GGT

T-786→C polymorphism of the endothelial nitric oxide synthase gene is associated with insulin resistance in patients with ischemic or non ischemic cardiomyopathy

Background: Insulin resistance (IR) and endothelial dysfunction are frequently associated in cardiac disease. The T-786→C variant in the promoter region of the endothelial nitric oxide synthase (eNOS) gene has been associated with IR in both non-diabetic and diabetic subjects. Aim of the study was to assess the reciprocal relationships between T-786→C eNOS polymorphism and IR in ischemic and non-ischemic cardiomyopathy.Method: A group of 132 patients (108 males, median age 65 years) with global left ventricular (LV) dysfunction secondary to ischemic or non-ischemic heart disease was enrolled. Genotyping of T-786→C eNOS gene promoter, fasting glucose, insulin, and insulin resistance (defined as HOMA-IR index > 2.5) were determined in all patients.Results: Genotyping analysis yielded 37 patients homozygous for the T allele (TT), 70 heterozygotes (TC) and 25 homozygous for C (CC). Patients with CC genotype had significantly higher systemic arterial pressure, blood glucose, plasma insulin and HOMA index levels than TT. At multivariate logistic analysis, the history of hypertension and the genotype were the only predictors of IR. In particular, CC genotype increased the risk of IR (CI% 1.4-15.0, p < 0.01) 4.5-fold. The only parameter independently associated with the extent of LV dysfunction and the presence of heart failure (HF) was the HOMA index (2.4 CI% 1.1-5.6, p < 0.04).Conclusions: T-786→C eNOS polymorphism was the major independent determinant of IR in a population of patients with ischemic and non-ischemic cardiomyopathy. The results suggest that a condition of primitive eNOS lower expression can predispose to an impairment of glucose homeostasis, which in turn is able to affect the severity of heart disease. © 2012 Vecoli et al.; licensee BioMed Central Ltd

Impaired myocardial metabolic reserve and substrate selection flexibility during stress in patients with idiopathic dilated cardiomyopathy.

Under resting conditions, the failing heart shifts fuel use toward greater glucose and lower free fatty acid (FFA) oxidation. We hypothesized that chronic metabolic abnormalities in patients with dilated cardiomyopathy (DCM) are associated with the absence of the normal increase in myocardial glucose uptake and maintenance of cardiac mechanical efficiency in response to pacing stress. In 10 DCM patients and 6 control subjects, we measured coronary flow by intravascular ultrasonometry and sampled arterial and coronary sinus blood. Myocardial metabolism was determined at baseline, during atrial pacing at 130 beats/min, and at 15 min of recovery by infusion of [(3)H]oleate and [(13)C]lactate and measurement of transmyocardial arteriovenous differences of oxygen and metabolites. At baseline, DCM patients showed depressed coronary flow, reduced uptake and oxidation of FFA, and preferential utilization of carbohydrates. During pacing, glucose uptake increased by 106% in control subjects but did not change from baseline in DCM patients. Lactate release increased by 122% in DCM patients but not in control subjects. Cardiac mechanical efficiency in DCM patients was not different compared with control subjects at baseline but was 34% lower during stress. Fatty acid uptake and oxidation did not change with pacing in either group. Our results show that in DCM there is preferential utilization of carbohydrates, which is associated with reduced flow and oxygen consumption at rest and an impaired ability to increase glucose uptake during stress. These metabolic abnormalities might contribute to progressive cardiac deterioration and represent a target for therapeutic strategies aimed at modulating cardiac substrate utilization

The climatic significance of Late Ordovician-early Silurian black

The Ordovician-Silurian transition (455-430 Ma) is characterized by repeated climatic perturbations, concomitant with major changes in the global oceanic redox state best exemplified by the periodic deposition of black shales. The relationship between the climatic evolution and the oceanic redox cycles, however, remains largely debated. Here, using an ocean-atmosphere general circulation model accounting for ocean biogeochemistry (MITgcm), we investigate the mechanisms responsible for the burial of organic carbon immediately before, during and right after the latest Ordovician Hirnantian (445-444 Ma) glacial peak. Our results are compared with recent sedimentological and geochemical data. We show that the late Katian time slice (445 Ma), typified by the deposition of black shales at tropical latitudes, represents an unperturbed oceanic state, with regional organic carbon burial driven by the surface primary productivity. During the Hirnantian, our experiments predict a global oxygenation event, in agreement with the disappearance of the black shales in the sedimentary record. This suggests that deep-water burial of organic matter may not be a tenable triggering factor for the positive carbon excursion reported at that time. Our simulations indicate that the perturbation of the ocean circulation induced by the release of freshwater, in the context of the post-Hirnantian deglaciation, does not sustain over sufficiently long geological periods to cause the Rhuddanian (444 Ma) oceanic anoxic event. Input of nutrients to the ocean, through increased continental weathering and the leaching of newly-exposed glaciogenic sediments, may instead constitute the dominant control on the spread of anoxia in the early Silurian

The end-Ordovician glaciation and the Hirnantian Stage: A global review and questions about Late Ordovician event stratigraphy

This paper proposes a global review of Hirnantian event stratigraphy. The Hirnantian GSSP in south China is tentatively correlated with latest Ordovician strata from the peri-Gondwanan "glacial" regions. Problems of biostratigraphical correlation are highlighted. At a worldwide scale, the major biostratigraphically useful fossil groups (graptolites, chitinozoans, brachiopods, conodonts, acritarchs) are analysed and their limits for global correlation of the uppermost Ordovician are discussed. Palaeobiogeographical disparities are invoked as the primary cause of the difficulty in establishing an effective Late Ordovician global biostratigraphical scheme. As an alternative correlative tool, the HICE (Hirnantian Isotopic Curve Excursion) event is often put forward in the literature. However, carbon isotope chemostratigraphy shows, like biostratigraphy, some limits to the present state of knowledge. No good independent biostratigraphical control of the HICE exists in both shallow carbonate deposits and deeper shaly ones. Recent studies have also demonstrated inconsistencies between carbon isotopic signals obtained from organic (delta(13)C(org)) and inorganic (delta(13)C(carb)) carbon species, further complicating the use of the HICE as an isochronous benchmark. All of these difficulties for Hirnantian event stratigraphy are discussed in detail in order to enable them to be overcome in the future. Precise Late Ordovician and early Silurian event stratigraphies are essential for the understanding of the mechanisms linked to the first of the "Big Five" extinctions. (C) 2009 Elsevier B.V. All rights reserved

Palynostratigraphy and vegetational changes in the Siluro-Devonian of the Ghadamis Basin, North Africa

This study. based chiefly on cryptospores and trilete spores from North Africa (MG-1 borehole, Ghadamis Basin, southern Tunisia). contributes to the understanding of the terrestrialization process. its timing and its palaeoenvironmental consequences across the Silurian-Devonian transition in Western Gondwana The investigated section comprises. in ascending stratigraphic order. the Tanezzuft, Acacus and Tadrart formations. Four well preserved and diversified miospore assemblages are recognized and attributed respectively to the late Gorstian-Ludfordian, Lufordian-early Pridoli, Pridoli and early Lochkovian, based on correlation with previously established palynozonations. and independent age evidence from chitmozoan faunas The lithostratigraphical boundary between the Acacus and the Tradart fms. corresponds to the Silurian-Devonian transition. In this time span, the Ghadamis Basin was the site of an extensive regression The middle Silurian-Lochkovian Tunisian miospore assemblages do not differ significantly from coeval associations both from Gondwanan and Laurussian localities. hence they do not provide evidence for a pronounced palaeobiogeographical differentiation This similarity could reflect: a) palaeogeographical proximity of the two palaeocontments and b) the low diversity of primitive vegetation in its early stages of evolutionary development. Minor but distinct variations in taxonomic composition of assemblages belonging to the same palaeogeographic domain. are thought to reflect varying environmental or physiographic conditions at regional and/or local scale. (C) 2009 Elsevier B.V. All rights reserve

Palynology, organic geochemistry and carbon isotope analysis of a latest Ordovician through Silurian clastic succession from borehole Tt1, Ghadamis Basin, southern Tunisia, North Africa: Palaeoenvironmental interpretation

Palynological and palynofacies analyses combined with organic carbon isotope measurements have been performed on terminal Ordovician through Silurian clastic sediments from the North African margin of Gondwana (southern Tunisia). A first carbon isotopic signal (delta(13)C(org)) from Gondwanan Silurian sedimentary sequences is presented, showing interesting correlation with existing coeval isotopic curves from other areas. Changes in lithology, palynofacies characteristics, palynomorph diversity, carbon isotope developments, and organic geochemistry parameters appear to be all causally linked, and to reflect changes in palaeoceano-graphic conditions. In particular, the detailed chronostratigraphic correlation and the observed similarities in patterns of carbon isotopic developments and (palyno- and litho-) facies changes through the study section has permitted to identify the supposedly global earliest Wenlock ("Ireviken Event") and late Ludlow ("Lau Event") isotopic excursions for the first time in high-latitude Gondwana. This confirms that these excursions were linked to global changes in the oceanic system. The present results suggest that from Rhuddanian to early Wenlock times, an extended period of black shale deposition occurred over the North African Gondwanan margin, progressively transgressing from basin palaeodepressions to basin palaeohighs. Palynofacies and organic geochemistry support a coastal upwelling-promoted productivity increase during this interval, associated to a decrease in diversity of the marine microplanktonic communities. The earliest Wenlock strong positive isotopic shift appears associated with this protracted period of massive black shale deposition, and thus of organic carbon burial, on continental platforms located in high-latitude settings. This could well explain the apparent paradox between excessive carbonate deposition simultaneous to a carbon isotopic shift towards lighter values observed in low palaeolatitude localities (Laurentia and Baltica). the strong, distinct isotope excursion occurring in late Ludlow times is possibly linked to the well know Lau Event. Evidence for extensive organic carbon burial is lacking to explain this strong excursion. Some significant changes in the marine palynomorph communities are recorded in connection to the increase in stable isotope values (delta(13)C(org)). Additionally, a strong correlation between abundance of terrestrially derived palynomorphs (miospores) and delta(13)C(org) development is recorded which seems to support increased clastic input from a terrestrial source. (C) 2008 Elsevier B.V. All rights reserved