Water-sediment partitioning of flumequine and florfenicol, two antibiotics used in salmon aquaculture in Chile.

The water-sediment partitioning of flumequine and florfenicol, two antibiotics used in salmon aquaculture is a critical driver of their fate and environmental impact. Batch experiments, were carried out using pure water or seawater, with or without sediment, and at summer and winter temperatures of Chilean fjords. Log Kd (partition between water and sediment) of florfenicol in seawater varied from 0.62 ± 0.69 to 0.67 ± 0.13, and Log KOC (partition between water and organic fraction of sediment) from 2.15± 0.29 to 2.19 ± 0.13. Difference between KOC and the octanol-water partition constant (KOW) showed that for florfenicol, adsorption onto the surface of particles was more significant than the absorption driven by hydrophobicity whilst hydrophobic absorption was a major driver of flumequine sorption. Flumequine Log Kd (0.92 ± 0.25 to 1.36 ± 0.10) and Log KOC (from 2.44 ± 0.25 to 2.89 ± 0.10) demonstrated its greater affinity than florfenicol to particles and potential accumulation into marine sediments.

Antibiotics florfenicol and flumequine in the water column and sediments of Puyuhuapi Fjord, Chilean Patagonia.

Chile is a major global producer of farmed salmon in the fjords of Patagonia, and therefore a major consumer of antibiotics. We tested whether the antibiotics florfenicol and flumequine persisted in the large Puyuhuapi Fjord after the six months following mandatory concerted treatment by all salmon farms present in the fjord. Antibiotics were detected in 26% of analyzed samples, but only within the particulate phase, with concentrations of florfenicol of up to 23.1 ng L-1, where detected. Flumequine was present in one sample at trace concentration, and neither antibiotic was detected in the dissolved phase nor in surface sediments. A fugacity-based model predicted that flumequine should theoretically remain in surface sediments at the sub-Minimal Inhibiting Concentrations (sub-MIC) previously shown to promote selection for antibiotic resistance in bacteria. Our observations suggest that surface sediments might act as a reservoir for antibiotic resistomes of bacteria, and that bacteria bearing antibiotic resistance genes could eventually become a risk for human health through the consumption of marine products.

PAH transport by sinking particles in the open Mediterranean Sea: a 1 year sediment trap study.

One year time series of sinking particles were collected at two depths in the open Mediterranean Sea and analysed for polycyclic aromatic hydrocarbons (PAH). Average total PAH concentrations were 593+/-284 ng g(-1) at 250 m and 551 +/- 198 ng g(-1) at 2850 m. Total PAH fluxes averaged 73 +/- 58 ng m(-2) d(-1) at 250 m and 53 +/- 39 ng m(-2) d(-1) at 2850 m. Contamination levels and, thus, exposure of marine organisms to PAH are comparable in surface and deep waters. Deep waters appear as a significant, yet overlooked, PAH sink. PAH temporal patterns show noticeable seasonality. This is partly due to varying levels of specific components such as the winter increase of pyrolytic PAH. Downward transport processes and the nature of sinking particles also impact on PAH fluxes, as inferred during periods of increasing productivity. Different phase-associations and interactions with particulate organic carbon for low-MW fossil PAH and high-MW pyrolytic PAH influence their downward transport efficiency.

Spatial and seasonal variabilities of dissolved hydrocarbons in surface waters from the Northwestern Mediterranean Sea: results from one year intensive sampling.

Dissolved aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) were analysed from surface water collected in continental, harbour and off-shore marine sites from Marseilles coastal area (Northwestern Mediterranean Sea) from February 2011 to February 2012. AH and PAH concentrations were in the range of 0.04-0.53 µgl(-1) and 8.1-405 ngl(-1), respectively. They both displayed seasonal and spatial variations in their concentrations and molecular composition. The lowest AH concentrations were found in summer and the highest PAH concentrations in winter. Both natural and anthropogenic (pyrogenic and petrogenic) hydrocarbon sources were identified. In winter, concentrations and composition patterns highlighted an increase in the signature of unburned and combusted fossil fuels, while they suggested an enhancement of weathering processes in summer months. Hydrocarbon inputs to the dissolved phase seemed to originate mainly from the atmosphere and the Rhône River. Hydrocarbon additional sources were identified only at the harbour site, emphasising the intense shipping traffic and industrial activities occurring in one of the most important Mediterranean harbours. This study underscores the strong dynamics of dissolved hydrocarbons and the uncoupling of the sources, transport and removing processes affecting AHs and PAHs. It also demonstrates the pertinence of taking this dynamics into account for the budget assessments of organic pollutants in coastal environments.

Ecodynamics of PAHs at a peri-urban site of the French Mediterranean Sea.

The PAH contamination level and biochemical composition of sinking particles and surficial sediments (0-0.5 cm layer) were assessed at a rural coastal site in the northwestern Mediterranean Sea. Surficial sediment contamination (≈20 ng g(-1)) was considerably lower than at other Mediterranean sites, yet particles collected in sediment traps had 6-8 times more PAH. Contaminated particles were mostly marine in origin. Temporal variation of contamination levels correlated with organic content of the particles, but some of the observed variability could be attributed to seasonal changes in pyrolytic PAH production. Sinking organic particles were potentially as readily digestible as surficial sediments for prospective consumers however, transfer of PAHs along the benthic food chain is probably enhanced because of the particles' higher nutritional value.

Can UV radiation affect benthic deposit-feeders through biochemical alteration of food resources? An experimental study with juveniles of the benthic polychaete Eupolymnia nebulosa.

The growth, tentacle development and feeding activity of the benthic polychaete Eupolymnia nebulosa were examined to determine whether UV might affect marine deposit-feeders indirectly through the modification of the nutritional quality of their resources. Since marine invertebrates have higher nutritional requirements during the period following settlement, we tested the effect of UV-altered phytodetritus on freshly settled juveniles of E. nebulosa. Phytodetritus was prepared from cultures of the diatom Skeletonema costatum either grown under or sheltered from UVB radiation. Sterol content of phytodetritus was unmodified by UV radiation. Conversely, phytodetritus was noticeably depleted in polyunsaturated fatty acids. Growth and tentacle development of juveniles fed on altered phytodetritus were reduced by 35% and 15% respectively, suggesting potential deficiencies in essential nutrients. In response to the lower quality of the phytodetritus, juveniles explored a wider area as they search for food, a strategy that could compensate for low food quality.

Vertical fluxes of aromatic and aliphatic hydrocarbons in the Northwestern Mediterranean Sea.

Aliphatic and aromatic hydrocarbon fluxes were measured in time series sediment trap samples at 200 m and at 1000 m depths in the open Northwestern Mediterranean Sea, from December 2000 to July 2002. Averaged fluxes of n-alkanes, UCM and T-PAH(35) were 2.96 ± 2.60 µg m(-2) d(-1), 64 ± 60 µg m(-2) d(-1) and 0.68 ± 0.59 µg m(-2) d(-1), respectively. Molecular compositions of both hydrocarbon classes showed a contamination in petrogenic hydrocarbons well above the background levels of such an open site, whereas pyrolytic hydrocarbons stand in the range of other open Mediterranean locations. Fluxes displayed ample interannual and seasonal variabilities, mainly related to mass flux variation while concentration evolutions trigger secondary changes in pollutant fluxes. High lithogenic flux events exported particles with a larger pollutant load than biogenic particles formed during the spring bloom and during the summer. Sinking hydrocarbons were efficiently transported from 200 m to 1000 m.

Salt-induced changes in lipid composition and membrane fluidity of halophilic yeast-like melanized fungi.

The halophilic melanized yeast-like fungi Hortaea werneckii, Phaeotheca triangularis, and the halotolerant Aureobasidium pullulans, isolated from salterns as their natural environment, were grown at different NaCl concentrations and their membrane lipid composition and fluidity were examined. Among sterols, besides ergosterol, which was the predominant one, 23 additional sterols were identified. Their total content did not change consistently or significantly in response to raised NaCl concentrations in studied melanized fungi. The major phospholipid classes were phosphatidylcholine and phosphatidylethanolamine, followed by anionic phospholipids. The most abundant fatty acids in phospholipids contained C16 and C18 chain lengths with a high percentage of C18:2Delta9,12. Salt stress caused an increase in the fatty acid unsaturation in the halophilic H. werneckii and halotolerant A. pullulans but a slight decrease in halophilic P. triangularis. All the halophilic fungi maintained their sterol-to-phospholipid ratio at a significantly lower level than did the salt-sensitive Saccharomyces cerevisiae and halotolerant A. pullulans. Electron paramagnetic resonance (EPR) spectroscopy measurements showed that the membranes of all halophilic fungi were more fluid than those of the halotolerant A. pullulans and salt-sensitive S. cerevisiae, which is in good agreement with the lipid composition observed in this study.

Oceanic biogeochemical controls on global dynamics of persistent organic pollutants.

Understanding and quantifying the global dynamics and sinks of persistent organic pollutants (POPs) is important to assess their environmental impact and fate. Air-surface exchange processes, where temperature plays a central role in controlling volatilization and deposition, are of key importance in controlling global POP dynamics. The present study is an assessment of the role of oceanic biogeochemical processes, notably phytoplankton uptake and vertical fluxes of particles, on the global dynamics of POPs. Field measurements of atmospheric polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), and furans (PCDFs) are combined with remote sensing estimations of oceanic temperature, wind speed, and chlorophyll, to model the interactions between air-water exchange, phytoplankton uptake, and export of organic matter and POPs out of the mixed surface ocean layer. Deposition is enhanced in the mid-high latitudes and is driven by sinking marine particulate matter, rather than by a cold condensation effect. However, the relative contribution of the biological pump is a function of the physical-chemical properties of POPs. It is concluded that oceanic biogeochemical processes play a critical role in controlling the global dynamics and the ultimate sink of POPs.