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Water soluble phenolic compounds of the marine phanerogam Posidonia oceanica in a Mediterranean area colonised by the introduced chlorophyte Caulerpa taxifolia

Unbound phenolic compounds of leaves of the marine phanerogam Posidonia oceanica (L.) Delile from an area colonised by the introduced chlorophyte Caulerpa taxifolia (Vahl) C. Ag. have been investigated and their concentration assessed using high performance liquid chromatography (HPLC). Leaves of the colonised area exhibited high maximum values of phenolic contents in comparison with a reference area. Nonetheless, because of the high variability of the values, further studies will be needed to confirm that P. oceanica plants are producing unbound phenolic compounds in reaction to growth of C. taxifolia. Ferulic acid, phloridzin, phloroglucinol, p-anisic acid, acetosyringone, sinapic acid, phenol, p-hydroxybenzoic acid, p-coumaric acid and cinnamic acid represent more than 95% of the mean relative concentration of phenolic compounds measured. Several of these compounds had not hitherto been reported in P. oceanica.

Lignin-derived phenolic compounds in the particulate organic matter of a French Mediterranean river: seasonal and spatial variations

Abstract Samples from the Tech river (French Mediterranean river) were analysed for particulate organic carbon (POC) and lignin phenols, to characterise spatial and seasonal variations. A decreasing gradient of lignin phenols (from ca. 0.8 to 0.5 mg 100 mg OC−1) was observed downstream, together with an increase of p-hydroxyl (H) phenols. Seasonal variations in total and lignin–phenols composition were very noticeable and seemed to be connected directly to rainfall variations. Lignin-phenol concentrations were higher in the wet periods (up to 12.1 μg/l) while the dry periods were characterised by the predominance of H phenols over lignin-phenols (Λ) ( H Λ ratios reaching values of 245 during summer). This predominance of H phenols was also associated with high chlorophyll a concentrations, which may indicate an autochthonous (and fresher) source of these phenols to the water column. Mean vanillic acid/vanillin ratios were higher than those of fresh plant material (0.4 for POM against 0.2 for fresh plant tissues), indicating that the lignin component had already been degraded before entering the river. The syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) ratios indicate a predominance of angiosperm+gymnosperm woody material in the lower sector and the presence of some angiosperm non-woody material in the mountain sector, corresponding to alpine and sub-alpine vegetation.

Tracers and constituents indicating the nature of organic fluxes, their origin and the effect of environmental conditions

Abstract The nature of particulate organic matter was studied in suspended material sampled by bottles, particles collected by sediment traps and deposits from deltaic and open sea ecosystems of the northwestern Mediterranean. Elemental analyses were combined with pyrolysis-gas chromatography-mass spectrometry and with analysis of individual compounds such as phenols separated by high-performance liquid chromatography. In the Rhoˆne delta, a multilayered system was observed. The surficial turbid layer was enriched with fresh material of river origin. Organic matter was more altered and richer in phenols in the bottom nepheloid layer. The river regime determined the nature and quantity of suspended material: when in spate, degraded organic matter previously deposited in the river bed was transported to the sea, thereby inducing an increase of pyrolysis derived aromatic hydrocarbons. On the other hand, phenolic aldehydes increased in the bottom nepheloid layer. When water level was low, organic matter seemed to be of more local origin. The content of phenols and nitrogen-containing compounds increased. The influence of the Rhoˆne River decreased off the mouth, when terrestrial markers were diluted by products deriving from phytoplanktonic activity. Compared with suspended material, trapped organic matter was coarser, more degraded and contained more aromatic hydrocarbons. It was different in nature and size, indicating that it was trapped over a longer period. Deposits contained altered organic matter resulting from degrading processes in the water column. Sediments showed a double trend off the mouth of the river; an increase in nitrogen-containing compounds, indicating a more marine character, and a decrease in phenols and carbohydrates deriving from the terrestrial ligno-cellulosic complex. In the southwestern part of the Gulf of Lions, in the Teˆt prodelta, organic matter from sediment traps was fresher than in the Rhoˆne delta. Phenols and some carbohydrates rapidly decreased from the prodelta due to a lower runoff. During the spate, suspended material was rapidly deposited and sediments were enriched in terrestrial phenols. In the open sea environment, in the Lacaze-Duthiers Canyon at 645 m, in summer, the euphotic zone was rich in amino-sugars and contained a large diversity of phenols deriving from fish fecal pellets. In winter/spring, the development of phytoplanktonic blooms in surficial layers led to high contents of nitrogenous compounds. In deeper layers, the nature of organic matter was different from surficial layers in summer and more homogeneous in winter, although a flux of degraded material rich in pyrolysis-derived aromatic hydrocarbons and poor in nitrogenous compounds progressively sank towards the bottom. The two marine prodeltas were compared: organic matter was more degraded in suspended material and sediments collected in the submarine delta of the Rhoˆne River. Organic material originating from the river was transported further offshore, as indicated by a higher content of aromatic hydrocarbons and phenols. In the southwestern part of the Gulf of Lions, the prodelta reflected the influence of local rivers, with lower discharges.

Characterisation of riverine particulate organic matter by pyrolysis-gas chromatography-mass spectrometry.

Particulate matter samples were collected in the mountainous section and river mouth at the Tech River basin, south France, during flood (December 1996) and summer (September 1997) periods. Suspended material was analysed by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and 23 identified pyrolysis products were divided into five main fractions: aminosugars, aromatic hydrocarbons, polysaccharides, phenols and nitrogenous compounds. Analysis of relative amounts of these fractions revealed neither significant spatial nor temporal changes in the particulate organic matter composition. Nevertheless, their specific composition showed that during flooding there is a certain homogeneity in the composition of the riverine particulate organic matter, with more degraded material of pedogenic (allochthonous) character, and during the summer the results suggest the presence of two components, allochthonous and autochthonous.

Neutral sugars as biomarkers in the particulate organic matter of a French Mediterranean river

Abstract Neutral sugars (arabinose, glucose, galactose, fucose, mannose, rhamnose, xylose and lyxose) in riverine POM and adjacent soil samples were analysed by gas chromatography over a period of 18 months in a small Mediterranean river basin. Total neutral sugars or TCHO, and individual neutral sugar abundance were highly variable, with TCHO yields varying from 0.04 to 94 mgTCHO/100 mgOC and concentrations from 0.04 to 78 μg/l. The most abundant neutral sugars were arabinose (ARA) in riverine POM and fucose (FUC) in soil samples. Temporal fluctuations in relative neutral sugar abundance (wt.%) and ratios indicated a mainly allochthonous and transformed POM source during autumn and winter while the dry season (from Dec-97 to Jul-98) was characterised by a fresher, phytoplanktonic component. Comparison of %FUC+RHA, %GLU, %GLU+GAL and (FUC+RHA)/(ARA+XYL) ratios with other parameters such as chlorophyll a and lignin-phenols enhanced the conclusions concerning the neutral sugar sources (terrestrial and phytoplanktonic) of riverine POM.

Dosage des acides et aldéhydes phénoliques par chromatographie liquide haute-performance: analyse comparative des sols de haute montagne et de leur végétation

Abstract Analysis of phenolic acids and aldehydes by high-performance liquid chromatography: a comparative analysis of high mountain soils and their vegetation. A method is described for the analysis of phenolic acids and aldehydes by reversed-phase high-performance liquid chromatography with a ternary isocratic elution system. It is applied to the separation and the estimation of phenolic compounds issued from: (1) pyrenean soils at high altitude (Pyrenees-Orientales, France, 2500 m), and (2) the main plant growing there. Phenolic extracts of soil and plant are isolated exactly in the same way by the procedure described.

Nature and distribution of phenolic compounds in water and sediments from Mediterranean deltaic and lagunal environments

The nature and distribution of phenolic compounds were studied in suspended particles, sediment trap material and deposits in deltaic, marine and lagunal environments of the northwestern Mediterranean sea (Gulf of Lions).In deltaic environments (Rhône delta), the river flow controlled amounts of terrestrial run-off offshore as characterized by the abundance of phenolic compounds. A clear distinction appeared between surface water layers and deep layers. In the former, organic matter was less degraded and richer in phenolic acids than in the latter, where an abundant lithogenic phase was associated with degraded organic material rich in phenolic aldehydes, partly due to anthropogenic pollution. During the spate period, some compounds, such as phenolic aldehydes, were good indicators of hydrodynamic conditions, as they were carried down from the river bed to the prodelta. There, associated with the organo-mineral complex, they sank down to reach the benthic nepheloïd layer and flowed out offshore.Considering the chemical nature of phenolics, suspended material contained more labile phenolic compounds such as syringyl phenols. In contrast, vanillyl phenols, which are rather refractory components, were more concentrated in sediments.In the Lacaze-Duthiers Canyon (south of the Gulf of Lions), trapped material from the euphotic zone was relatively rich in phenols of marine origin. Similarities in phenolic composition appeared between trapped organic material in bottom layers of the Têt prodelta and of the side of the Canyon, reflecting a transfer of particles by advective currents from the shelf to the deep sea.In deposits containing relatively abundant phenols, humic acids were richer in phenols than fulvic acids.In lagunal environments, phenol contents in suspended material and deposits were relatively high, resulting from the abundant vegetal cover. Highest dissolved phenol contents occurred in water at the end of summer and early autumn on the edges of the Canet lagoon where abundant debris of decaying plants accumulated. Their nature depended essentially on the extent of phanerogam populations (Ruppia maritima, Phragmites australis), which are their major sources. In this area, fine deposits contained humic fractions richer in phenols than coarse sediments were.

Behaviour of suspended and sedimentary organic matter in the deltaic areas of the Gulf of Lions (Mediterranean Sea)

The behaviour of organic matter has been approached in two fluvio-marine areas of the Gulf of Lions in the Northwestern Mediterranean Sea: deltas of the Rhône and Têt rivers. Elemental analysis, pyrolysis-gas chromatography-mass spectrometry (main classes of organic compounds) and high performance liquid chromatography (phenolic compounds) enabled to show the fractioning processes and the differentiation of water layers from the river mouth to the open sea. Transitory horizontal and vertical geochemical gradients appeared in the water column. They were more marked in surficial sediments. They underlined the effects of the river inputs which were characterized by high phenol contents. The increase of the marine character towards the open sea was shown by increasing nitrogen-containing compounds. In the Rhône delta, the distribution of the suspended material and organic compounds emphasized the occurrence of a multi-layered water system. In the surficial layers the suspended organic matter was in a little degraded state. On the contrary, the bottom nepheloid contained altered organo-mineral complexes enriched in resistant organic compounds. In the deeper areas of the Lacaze-Duthiers Canyon, in front of the Têt prodelta, the abundance of phytoplanktonic material in the euphotic zone was emphasized by the increase of both nitrogen-containing compounds and aminosugars. In the deeper layers, the suspended material transported by advective currents showed a detrital characteri.e. enriched in clays and in degraded organic matter. The observations carried out in the Rhône delta, the Têt prodelta and the Lacaze-Duthiers Canyon underlined the importance of the general transfer system of suspended material from East to West enhanced by the Liguro-Provençal current.

Organic matter transport across a macrotidal estuary grandient: the Seine estuary, Fance

The macrotidal Seine estuary receives mineral and organic fluxes from a strongly industrialized basin. Upstream-downstream analysis of POC, polysaccharides and phenolic compounds in the particulate fraction indicated clearly the continental inflow. Within the maximum turbidity zone, the organic matter/suspended particulate matter ratio is lower than elsewhere which results from the dilution effect. Particulate tracers were quantified using grain size analysis and S.E.M. techniques. These sedimentary data defined the ratio of marine to continental particulate flux and mechanisms controlling the suspended particulate matter load within the estuarine mixing zone (resuspension, frontal enrichment and turbulent mixing processes). Organic parameters confirm the data on the mineral matter and were used to distinguish between the marine and continental inputs, from the upstream and downstream samples. Between the two endmembers, variations in organic parameters were controlled mainly by the hydrodynamics in the estuarine zone, rather than by salinity changes.

Spatio-temporal variations of fluorescence properties of dissolved organic matter along the River Têt (Pyrénées-Orientales, France)

Fluorescence excitation-emission matrices showed the spectral signature of dissolved organic matter (DOM) downstream in the River Têt at all seasons corresponding to humic substances with maximum fluorescence emission λem=420–460 nm for excitations of λex=340–360 nm and the occasional presence of tryptophan, tracer of anthropogenic pressure, spectroscopically identified by λex/λem=310/350 nm. A factorial discriminant analysis, performed using the parameters selected (λex/λem pairs of wavelength), succeeded in a better discrimination of seasons than stations, and clearly showed the presence of two fluorophores. Fluorophore 1, with two absorption bands: λex=260–320 nm and 330–390 nm for λem=440–500 nm, and Fluorophore 2, with one absorption band: λex=300–360 nm for λem=410 nm, which are attributed to humic acid (HA) and fulvic acid (FA), respectively. Variations of DOM relative contents downstream in the River Têt, according to seasons and stations, showed high amounts of DOM (pedogenic character) along the river in the humid period, with the highest value obtained in the mountain section. In contrast, in summer, the DOM contents were low (aquagenic character). Moreover, DOM presents a relatively constant composition with a percentage of FA ranging from 40% at the mountain station to 48% at the mouth river, whatever the season.