This paper aims at quantifying current riverine fluxes of microplastics (MPs) in two Mediterranean river catchments, a large one and a small one, namely the Rhône and the Têt, which are discharging ...to the Gulf of Lion in the Northwestern Mediterranean Sea. MP fluxes change markedly through time and space in both river systems. However, no clear relationships between MP concentrations and hydroclimatic conditions have been observed. In the Rhône River a non-linear dilution pattern of MPs in total suspended matter (TSM) during flood conditions could be observed. Although dilution is important, samples during floods exert a strong control on average MP fluxes. Compared to the Rhône River, average MP concentrations in the Têt River were throughout greater and more variable in shape and polymer composition. However, as the study year was exceptionally dry, the average specific MP flux, 76 g km−2 y−1, is only slightly larger than the non-flooding value of the Rhône River. We further monitored MP concentrations in shoreline sediments at the mouth of the Têt River to test whether these sediments can represent MP transport in the river. Besides fibers, which probably are easily washed out and transported offshore, MP concentrations and compositions are in agreement with MP loads upstream the river. We also examined the potential role of atmospheric deposition as a source of MP to the Têt River. The average atmospheric MP deposition of 6 kg km−2 y−1 exceeds by far the river average specific MP flux. Moreover, all MPs in atmospheric deposits were fibers, which in terms of mass are of minor importance in the bulk river fluxes. Atmospheric MP deposits may either have been overestimated and/or may be removed from surface waters by efficient removal processes (such as waste water treatment plants).
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•Under regular conditions, relationships between concentrations and hydroclimatic parameters are difficult to establish.•Flood samples could influence the calculation of average microplastic fluxes.•Accumulations in riverbank sediments could be good indicators for average riverine microplastic loads.•Atmospheric transport of microplastic fibers to the sea is potentially significant.•Microplastics show different shape distributions in the matrices under consideration.
Human activities affect terrestrial and aquatic habitats leading to changes at both individual and population levels in wild animal species. In this study, we investigated the phenotype and ...demographics of the Mediterranean pond turtle Mauremys leprosa (Schweigger, 1812) in contrasted environments of Southern France: two peri-urban rivers receiving effluents from wastewater treatment plants (WWTP), and another one without sewage treatment plant. Our findings revealed the presence of pesticides and pharmaceuticals in the three rivers of investigation, the highest diversities and concentrations of pollutants being found in the river subsections impacted by WWTP effluents. Principal component analysis and hierarchical clustering identified three levels of habitat quality, with different pollutant concentrations, thermal conditions, nutrient, and organic matter levels. The highest turtle densities, growth rates, and body sizes were estimated in the most disturbed habitats, suggesting potential adult benefits derived from harsh environmental conditions induced by pollution and eutrophication. Conversely, juveniles were the most abundant in the least polluted habitats, suggesting adverse effects of pollution on juvenile survival or adult reproduction. This study suggests that turtles living in polluted habitats may benefit from enhanced growth and body size, at the expense of reproductive success.
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•Phenotypes and population structure of Mauremys leprosa are influenced by water quality.•Fast-growing turtles, as well as largest and heaviest males, are associated with the most polluted habitats.•Highest proportions of juveniles are associated with the least polluted habitats.•Eutrophication affects turtle phenotype and may adversely affect reproductive success.
The carbohydrate composition (TDCHO) of dissolved organic matter (DOM) was studied in the Mackenzie margin (southeast Beaufort Sea) in summer 2009 as a part of the MALINA project. Sampling was ...performed in the shelf (bottom depth≤100m), slope (100m<bottom depth≤1000m), and basin (bottom depth>1000m) areas of the Mackenzie margin. Our results showed that sugar concentrations did not follow dissolved organic carbon (DOC) patterns, which decreased from shelf to basin stations (from 115 to 65μM), but instead remained rather constant (965–900nM), indicating an accumulation of carbohydrates in surface waters (0–80m). TDCHO concentrations exhibited their highest values (>1000nM) and higher relative abundance to DOC in the central sector of the studied area, especially in the zone between 130 and 135°W indicating differences in their distribution in the broader area and possible various sources. TDCHO represented 6±2% and 8±3% of DOC (TDCHO-C/DOC) for the shelf and basin stations, respectively. Semi-labile DOC estimated values accounted for 10–40% and 20–50% of DOC in the slope and basin areas and agreed well with the above TDCHO/DOC values suggesting a gradient of carbohydrate freshness from inshore to offshore stations. The high fucose+rhamnose relative abundances (Fuc.+Rha. 15–18%) and high C/N ratios (19–13) recorded in the surface waters of the shelf area are indicative of soil-derived matter delivered by the Mackenzie River, possibly with contributions from mainly gymnosperm terrestrial plants. The high abundance of glucose (up to 50%) suggests that the carbohydrate component of the DOM in the Mackenzie margin appears to have a more pronounced marine autochthonous origin with an important contribution of terrestrial sources, especially for the shelf stations. Overall, these results suggest a largely uniform distribution of TDCHO carbohydrates within the area with occasional patches of lower concentrations.
•Dissolved organic carbon (DOC) and dissolved carbohydrate (TDCHO) patterns in the Beaufort Sea Mackenzie margin•TDCHO to DOC ratios and freshness of carbohydrates•Sources and cycling of dissolved carbohydrates in the Beaufort Sea Mackenzie margin
Rationale
Ferulic and p‐coumaric acids are important biological and structural components of plant cell walls and possess antioxidant and antimicrobial properties. These phenolic acids are widespread ...in environmental samples. However, when they are present at very low concentrations or in very complex lipid extracts, their identification and quantification can be challenging.
Methods
The electron ionization mass spectrometry (EI‐MS) fragmentation pathways of ferulic and p‐coumaric acid trimethylsilyl (TMS) derivatives were investigated. These pathways were deduced by (i) low‐energy collision‐induced dissociation (CID) gas chromatography (GC)/EI‐MS/MS, (ii) accurate mass measurement, and (iii) 13C labelling. These compounds were then characterized and quantified in multiple reaction monitoring (MRM) mode in total lipid extracts of deposited atmospheric particles using highly specific transitions based on the main fragmentation pathways elucidated.
Results
Low‐energy CID‐MS/MS analyses, accurate mass measurement and 13C labelling enabled us to elucidate EI‐MS fragmentations of ferulic and p‐coumaric acid TMS derivatives. Some specific fragmentations proved useful for subsequent characterization and quantification of these compounds. As an application of some of the described fragmentations, trace amounts of these phenolic acids were characterized and quantified in MRM mode in wet‐ and dry‐deposited atmospheric particles containing low proportions of organic matter.
Conclusions
EI‐MS fragmentations of ferulic and p‐coumaric acid TMS derivatives exhibit specific fragment ions that can be very useful for the quantification of trace amounts of both phenolic acids in environmental samples.
Atmospheric and in‐water solar radiation, including UVR‐B, UVR‐A and PAR, as well as chromophoric dissolved organic matter absorption aCDOM(λ) in surface waters were monthly measured from November ...2007 to December 2008 at a coastal station in the Northwestern Mediterranean Sea (Bay of Marseilles, France). Our results showed that the UVR‐B/UVR–A ratio followed the same trend in the atmosphere and at 2 m depth in the water (P < 0.0001) with an increase (eight‐fold higher) during summer. The low diffuse attenuation coefficients for downward irradiance Kd(λ) of UVR‐B, UVR‐A and PAR indicated that the waters were highly transparent throughout the year. The relationships between aCDOM(λ) and Kd(λ) in this oligotrophic system suggested that CDOM contributed to UVR attenuation in the UVA domain, but also played a significant role in PAR attenuation. Mean UV doses received in the mixed layer depth were higher by a factor 1.4–33 relative to doses received at fixed depths (5 and 10 m) in summer (stratified period), while the inverse pattern was found in winter (mixing period). This shows the importance of taking into account the vertical mixing in the evaluation of UVR effects on marine organisms.
The wavelengths 305 and 380 nm have been chosen as biologically effective wavelengths for the induction of DNA damages (CPDs) and photorepairs (PERs) respectively. The ratio of the mean doses received within the mixed layer at 305 and 380 nm Q in % = H(m,305)/H(m,380) × 100 along with the mixed layer depth (Zm) are presented. Q ratio can be considered as an indicator of changes in the balance between DNA damages (CPDs) and repairs (PERs). Clearly, Q increased with the stratification of the water column.
•Strong biotic and abiotic degradation of TOM on the Beaufort Shelf observed.•Autoxidation state of TOM appeared to correlate with salinity.•Contact of TOM with seawater induces ...autoxidation.•Photooxidation of TOM on land favors its autoxidation in seawater.•Summary of POM degradation in the Beaufort Sea proposed.
Sterols and their biotic and abiotic degradation products were quantified in suspended particulate matter (SPM) from surface waters in the Mackenzie River mouth to the Beaufort Sea shelf (Canadian Arctic). 24-Ethylcholesterol (sitosterol) and 24-methylcholesterol (campesterol) appeared to be extensively degraded by bacterial and especially autoxidative degradation in the samples. Degradation was most extensive in some samples from the outer boundaries of the plume, which exhibited much higher sitosterol/campesterol ratio values than previously observed in studies of the Beaufort Sea. The lack of reactivity of specific planktonic sterols such as cholesterol, 24-methylcholesta-5,22E-dien-3β-ol (epi-brassicasterol) and 24-methylenecholesterol and the good correlation between the abundances of sitosterol, campesterol and dehydroabietic acid (DHAA, a biomarker of Pinaceae resin) oxidation products allowed us to attribute the main origin of these two sterols to terrigenous vascular plants. A good correlation was observed between the extent of autoxidation and salinity, suggesting that the free radical oxidation is enhanced via contact with seawater. Laboratory incubation of Mackenzie River SPM in Milli-Q water and seawater confirmed this proposal. To explain the specific induction of autoxidation on vascular plant-derived material, a mechanism involving homolytic cleavage of photochemically produced hydroperoxides resulting from the senescence of higher plants on land is proposed. Cleavage could be catalyzed by redox-active metal ions released from SPM in the mixing zone of riverine water and marine water. The greatest extent of degradation observed at outer boundaries of the plume is attributed to preferential settling of lithic material relative to less dense higher plant debris increasing the proportion of highly degraded vascular plant material in the SPM. The results are important for this ecologically vulnerable region, where destabilization of permafrost by global warming is expected to increase the input of terrigenous C to coastal seas. Autoxidation, which until now has received little attention, plays a key role in the degradation of vascular plant-derived lipids in surface waters and should be taken into consideration during future studies of terrigenous organic matter degradation.
The distribution of bifunctional carboxylic acids (BCAs) is largely reported as primary or secondary organic aerosols. However, sparse studies describe the distribution of these organic compounds in ...fluvial and marine environments. In the context of a global warming, we present the first results of a study of the distribution of BCAs in a surface Arctic coastal area near the mouth of the Mackenzie River. These results showed that the Beaufort Sea is an area with elevated BCA content among which glyoxylic acid is predominant, in contrast to low concentrations and predominance of oxalic acid in aerosols reported elsewhere. The carbon fraction of BCAs represents 1.8% to 4.5% of dissolved organic carbon pool in Arctic Ocean. This study reinforces the hypothesis that aquatic biological processes govern the molecular distribution of BCA in marine/river waters, whereas photochemical oxidation reactions regulate their molecular distribution in rain and aerosols. Our results indicate that the Mackenzie River is an important source of BCAs in the Arctic Ocean during July–October period, with a first estimate of 35 × 103 tons of BCAs including 12 × 103 tons of diacids and 23 × 103 tons of oxoacids.
Key Points
Here we present the first results of a study of the distribution of BCAs (including dicarboxylic and oxoacids) in a surface Arctic Ocean
Arctic Rivers provide large amount of BCA to the Arctic Ocean, a process that might be increased with global warming
BCAs have been recognized as major water soluble organic compounds that potentially may act for a part as cloud condensation nuclei (CCN)
•α, ω –dicarboxylic acids and ω-oxoacids (BCAs) were analyzed for the first time in the Rhone River.•Glyoxilic oxalic and fumaric acids were the most abundant among the pool of BCAs.•BCA molecular ...distribution is controlled by biological processes in aquatic systems.•BCA molecular distribution is controlled by photochemistry in the atmosphere.
The Mediterranean Sea is a semi-enclosed marine environment surrounded by densely populated areas. This ecosystem is under strong anthropogenic pressure at present. Riverine waters are important input pathways of water-soluble organic compounds that potentially contribute to the dissolved organic carbon (DOC) pool. Here, we report the first ever measurements of bi-functional carboxylic acids such as α, ω -dicarboxylic acids (or diacids) and related polar compounds ω -oxoacids (or ketoacids) (BCAs=α, ω-dicarboxylic acids+ω -oxoacids), along with the DOC levels in Rhone River waters. Surface water samples were collected from February 2006 to June 2009 approximately 50km above the Rhone River mouth, which is the main supplier of freshwater to the Mediterranean Sea. The BCA concentrations averaged 32.4±15.3µgl−1, and exhibited a wide range of values from 13.2µgl−1 (Spring 2008) to 71.2µgl−1 (winter 2007). The contribution of carbon from BCAs to the DOC pool (BCA-C) accounted for 0.28 to 1.42% of the DOC. Although no seasonal trend was evident in the studied period, our results showed that the highest BCA concentrations did not always follow high water discharges. α,ω -dicarboxylic acids are the most abundant compound class (20.7±10.6µgl−1), which is followed by ω -oxoacids (11.7±6.2µgl−1). The Rhone River was estimated to deliver between 1.37 and 16.4 t d−1 of BCA to the Gulf of Lions. Assuming a mean water discharge of ∼1790m3s−1, a broad estimate suggests a loading of 750–4000 t yr−1 BCAs to the northwestern Mediterranean Sea. Our results indicated that glyoxylic acid (ωC2) was the most abundant BCA followed by oxalic acid (C2di) and fumaric acid (trans configuration of unsaturated C4 diacid). This result indicates that there is a different molecular distribution between the aquatic and atmospheric compartments, including rainwaters and aerosols, for which previous studies highlighted a predominance of oxalic acid, which was followed by malonic and/or succinic acid. Runoff and riverine biological process (rather than photochemical oxidation reactions) are hypothesized to control the BCA occurrence and molecular distribution in the Rhone River and thus their inputs to the coastal NW Mediterranean Sea, although the environmental implications of this stock of BCA are still unknown.
•Increasing salinity favored lipoxygenase induction in terrestrial higher plant debris.•Lipoxygenases initiated autoxidative degradation of terrestrial POM in estuaries.•Autoxidative degradation of ...terrestrial POM enhanced at low and high latitude.•In temperate zones autoxidative damage of terrestrial POM more limited.
There exists a substantial amount of research on abiotic (e.g. photochemical) degradation pertaining to organic matter (OM) in the marine realm. While recent research has shown its importance in the degradation of terrestrial particulate OM (TPOM), the mechanisms involved in the induction of autoxidation in estuaries remain unclear. In this study, we propose for the first time the involvement of lipoxygenase (LOX) activity in the induction of autoxidation in mixed waters. The observation of unusual profiles of palmitoleic acid oxidation products and the presence of jasmonic acid in suspended particulate matter (SPM) collected close to the Rhône River, as well as in samples from the Mackenzie and Amazon rivers, is attributed to strong LOX activity. We show the role played by salinity in the induction of this LOX activity and provide an explanation for the differences in estuarine autoxidation level. At high latitude, lower temperatures and irradiance favor photooxidative damage to higher plant debris and, consequently, hydroperoxide production. High hydroperoxide content strongly contributes to LOX activation in mixed waters. The high resulting LOX activity enhances alkoxyl radical production and thus autoxidation. On the contrary, at low latitude, photooxidative effects are limited, and riverine autoxidation is favored. The higher hydroperoxide content of TPOM may, as a consequence, thereby also contribute to a high level of LOX activity and autoxidation in estuaries. In temperate zones, land and riverine photooxidative and autoxidative damage is limited, unlike estuaries where we observed significant LOX-induced and autoxidative damage.
Most of the ocean is deep with the majority of its volume (> 80%) lying under a depth greater than 1000 m. Deep-ocean substrates input is mainly supplied as organic matter (in particulate and/or ...dissolved forms) by physical and biological processes. Bioavailable dissolved organic carbon (DOC) is mainly consumed in surface water by prokaryotes, while most of DOC in the deep ocean is recalcitrant. Deep-sea prokaryotes are known to be adapted to degrade complex substrates. In this study, we investigate the utilization of HMW-DOC on the short temporal scale (10–15 days) by deep-sea prokaryotes maintained at in situ high-pressure conditions. Deep-sea prokaryotic natural assemblages were collected in the Mediterranean Sea in two contrasting hydrological conditions (water column stratification and deep-water formation period conditions). The experimental results were coupled with a cell-quota model, in order to quantify the kinetics of HMW-DOC degradation and its impact on the prokaryotic assemblages under these two contrasting hydrological conditions. The results show that under stratified water conditions autochthonous deep prokaryotic assemblages are able to degrade up to 46.6% of DOC on the timescales of the incubation, when maintained under in situ sampling high-pressure conditions. By contrast, during deep-water convection period condition, DOC is weakly degraded on the timescales of the incubation under in situ high-pressure conditions. This study shows that the remineralization rates of DOC are controlled by the prokaryotic communities, which are further driven by the hydrological conditions of the water column.
•Dissolved Organic Carbon (DOC) degradation rates in deep ocean depend on hydrological conditions and microbial community.•In situ high-pressure incubations give a better estimation of prokaryotic activity.•Deep-water convection has a direct influence on the DOC input and its degradation.•Autochthonous deep-sea prokaryotes have the capacity to degrade HMW DOC.
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