خيارات البحث
النتائج 1961 - 1970 من 5,137
First evidence of microplastic ingestion by fishes from the Amazon River estuary
2018
Pegado, Tamyris de Souza e Silva | Schmid, Kurt | Winemiller, Kirk O. | Chelazzi, David | Cincinelli, Alessandra | Dei, Luigi | Giarrizzo, Tommaso
This study investigated occurrence of microplastic particles in digestive tracts of fishes from the Amazon River estuary. A total of 189 fish specimens representing 46 species from 22 families was sampled from bycatch of the shrimp fishery. Microplastic particles removed from fish gastrointestinal tracts were identified using Attenuated Total Reflectance – Fourier Transform Infrared (ATR-FTIR). In total, 228 microplastic particles were removed from gastrointestinal tracts of 26 specimens representing 14 species (30% of those examined). Microplastic particles were categorized as pellets (97.4%), sheets (1.3%), fragments (0.4%) and threads (0.9%), with size ranging from 0.38 to 4.16 mm. There was a positive correlation between fish standard length and number of particles found in gastrointestinal tracts. The main polymers identified by ATR-FTIR were polyamide, rayon and polyethylene. These findings provide the first evidence of microplastic contamination of biota from the Amazon estuary and northern coast of Brazil.
اظهر المزيد [+] اقل [-]Microplastic analysis in the South Funen Archipelago, Baltic Sea, implementing manta trawling and bulk sampling
2018
Tamminga, Matthias | Hengstmann, Elena | Fischer, Elke Kerstin
Microplastic contamination in surface waters of the South Funen Archipelago in Denmark was assessed. Therefore, ten manta trawls were conducted in June 2015. Moreover, 31 low-volume bulk samples were taken to evaluate, whether consistent results in comparison to the net-based approach can be obtained. Microplastic contamination in the South Funen Archipelago (0.07 ± 0.02 particles/m3) is slightly below values reported before. The sheltered position of the study area, low population pressure on adjacent islands and the absence of any major potential point sources were identified as major factors explaining the low concentration of microplastics. Within the Archipelago, harbors or marinas and the associated vessel traffic are the most probable sources of microplastics. The concentration of microplastics in low-volume bulk samples is not comparable to manta trawl results. This is mainly due to insufficient representativeness of the bulk sample volumes.
اظهر المزيد [+] اقل [-]Marine protected areas and spatial fetishism: A viewpoint on destructive fishing in coastal Tanzania
2018
Raycraft, Justin
This paper focuses on destructive fishing practices in coastal Tanzania. I argue that the dominant conservation narrative that increased capacity and ‘political will’ for enforcement of marine protected areas (MPAs) reflects a form of spatial fetishization, in that it overemphasizes the influence of space over social behaviour. I contend that Tanzanian MPAs offer bandage solutions to underlying structural problems that are contingent upon the inconsistent availability of social and financial resources for monitoring activities. I suggest that a paradigm shift is necessary, involving the de-territorialization of marine conservation discourse in Tanzania, and a movement towards addressing the underlying social, political and economic conditions that influence marine resource use.
اظهر المزيد [+] اقل [-]Major, minor, trace and rare earth elements in sediments of the Bijagós archipelago, Guinea-Bissau
2018
Carvalho, Lina | Figueira, Paula | Monteiro, Rui | Reis, Ana Teresa | Almeida, Joana | Catry, Teresa | Lourenço, Pedro Miguel | Catry, Paulo | Barbosa, Castro | Catry, Inês | Pereira, Eduarda | Granadeiro, José Pedro | Vale, Carlos
Sixty sediment samples from four sites in the Bijagós archipelago were characterized for fine fraction, loss on ignition, major, minor and trace elemental composition (Al, Fe, Ca, Mg, Ti, P, Zr, Mn, Cr, Sr, Ba, B, V, Li, Zn, Ni, Pb, As, Co, U, Cu, Cs and Cd), and the elements of the La–Lu series. Element concentrations were largely explained by the Al content and the proportion of fine fraction content, with the exception of Ca and Sr. Sediments showed enhanced Ti, U, Cr, As and Cd concentrations with respect to estimated upper crust values, most likely mirroring a regional signature. Rare earth elements were in deficit relatively to the North American Shale Composite (NASC), mainly in coarser material. No pronounced Ce-anomaly was observed, while Eu-anomalies were positive in most analyzed sediments.
اظهر المزيد [+] اقل [-]Microplastic in beach sediments of the Isle of Rügen (Baltic Sea) - Implementing a novel glass elutriation column
2018
Hengstmann, Elena | Tamminga, Matthias | vom Bruch, Constantin | Fischer, Elke Kerstin
To extent the understanding on microplastics in the marine environment we performed a case study at four beaches on the Isle of Rügen considering abundance and spatial distribution of microplastics in beach sediments. For the analysis, density separation via a glass elutriation column was implemented. In advance, efficiencies were tested for two polymers, being not buoyant in water. Recovery rates of 80% for PET and 72% for PVC particles in sandy samples were achieved.A median abundance of 88.10 (Q1=55.01/Q3=114.72) microplastic particles per kg dry sediment or 2862.56 (Q1=1787.34/Q3=3727.28) particles per m2 was found at the beaches on Rügen. Fibers were more abundant than fragments at all beaches. In this study, no statistically significant differences but only tendencies were determined between the beaches with different exposition and anthropogenic activity as well as for distribution patterns which showed that microplastic fragments accumulate in topographic depressions, similar to macrolitter items.
اظهر المزيد [+] اقل [-]Diagnostic tool to ascertain marine phytoplankton exposure to chemically enhanced water accommodated fraction of oil using Fourier Transform Infrared spectroscopy
2018
Kamalanathan, Manoj | Schwehr, Kathleen A. | Bretherton, Laura | Genzer, Jennifer | Hillhouse, Jessica | Xu, Chen | Williams, Alicia | Santschi, Peter | Quigg, Antonietta
Phytoplankton alter their macromolecule composition in response to changing environmental conditions. Often these changes are consistent and can be used as indicators to predict their exposure to a given condition. FTIR-spectroscopy is a powerful tool that provides rapid snapshot of microbial samples. We used FTIR to develop signature macromolecular composition profiles of three cultures: Skeletonema costatum, Emiliania huxleyi, and Navicula sp., exposed to chemically enhanced water accommodated oil fraction (CEWAF) in artificial seawater and control. Using a multivariate model created with a Partial Least Square Discriminant Analysis of the FTIR-spectra, classification of CEWAF exposed versus control samples was possible. This model was validated using aggregate samples from a mesocosm study. Analysis of spectra and PCA-loadings plot showed changes to carbohydrates and proteins in response to CEWAF. Overall we developed a robust multivariate model that can be used to identify if a phytoplankton sample has been exposed to oil with dispersant.
اظهر المزيد [+] اقل [-]The distribution and seasonal variations of sedimentary organic matter in the East China Sea shelf
2018
Zhou, Fengxia | Gao, Xuelu | Yuan, Huamao | Song, Jinming | Chen, Fajin
We sampled the surface sediments of the East China Sea shelf (ECSS) in spring and autumn, 2014, and analyzed the biogenic element concentrations and stable carbon (δ13C) and nitrogen (δ15N) isotopic compositions to study the distribution and seasonal variations of sedimentary organic matter (OM). The average concentrations of TOC, TN and OP in autumn decreased obviously compared with those in spring. The increase of δ15N values in autumn indicated the priority utilization of 14N by bacterial decomposition activity. The values of δ13C were used to trace organic matter sources. The estimated percentages for terrestrial OM were in the range of 0–34.6%. They generally decreased seaward in nearshore areas, indicating the decrease of terrigenous influence. There was an obvious tongue-shaped region with relatively low percentages of terrestrial OM (<12%) in the northern part of the ECSS, which may be a reflection of the intrusion pathway of the outer seawater.
اظهر المزيد [+] اقل [-]Bioaccumulation of mercury and other trace elements in bottom-dwelling omnivorous fishes: The case of Diplodus sargus (L.) (Osteichthyes: Sparidae)
2018
Merciai, Roberto | Rodríguez-Prieto, Conxi | Torres, Jordi | Casadevall, Margarida
The presence of toxic elements in fish represents a hazard for human health, especially in Mediterranean countries and other regions with high per-capita fish consumption. The present research, carried out along the northern Catalan coast (NW Mediterranean), aimed to determine the levels of trace metals and arsenic in the muscle of white seabream Diplodus sargus (L.), a common demersal species of growing interest for fisheries and aquaculture. Average mercury concentrations widely exceeded the limits imposed by EU despite the low contamination levels previously reported for the study area, stressing the potential risk associated to the consumption of medium-sized, non-predatory fishes. The other analyzed elements fell within the recommended limits. Preliminary results about the feeding habits of D. sargus are reported, in order to determine feeding habitat and items of the analyzed specimens.
اظهر المزيد [+] اقل [-]Tolerance and bioaccumulation of combined copper, zinc, and cadmium in Sesuvium portulacastrum
2018
Feng, Jianxiang | Lin, Yanyan | Yang, Yao | Shen, Qianqian | Huang, Jianrong | Wang, Shugong | Zhu, Xiaoshan | Li, Zufu
Sesuvium portulacastrum was treated with mixture of copper, zinc, and cadmium for 60 days, with the concentration of each metal ranging from 0 to 20 mg/L. The tolerance of plants and bioaccumulation of heavy metals were then investigated. The height of S. portulacastrum decreased significantly with increasing heavy metal concentrations from 1 to 20 mg/L. The biomass was adversely impacted when the concentration exceeded 5 mg/L. There were no significant differences in malondialdehyde (MDA) concentration among different treatment groups, while the soluble protein content and superoxide dismutase (SOD) activity decreased with increasing heavy metal concentration. However, the BCF values of the three metals were all higher than 10 and the tolerance in root was up to 1000 mg/kg without causing significant growth inhibition, suggesting that S. portulacastrum should be a potential candidate for phytostabilization for the phytoremediation of polymetallic contaminations in coastal environments.
اظهر المزيد [+] اقل [-]Mangrove clearing impacts on macrofaunal assemblages and benthic food webs in a tropical estuary
2018
Bernardino, Angelo Fraga | Gomes, Luiz Eduardo de Oliveira | Hadlich, Heliatrice Louise | Andrades, Ryan | Correa, Lucas Barreto
Despite over 21,000ha of mangrove forests being removed per year in Brazil, ecological changes following mangrove deforestation have been overlooked. Here we evaluated changes in benthic macrofaunal assemblages and food-webs at a mangrove removal and natural sites in a tropical estuary in Eastern Brazil. The impacted site had coarser sediment particle sizes suggesting significant changes in sedimentation processes after forest clearing. Spatial differences in macrofaunal abundance, biomass and diversity were not directly associated with the removal of mangrove forests, supporting recolonization of impacted areas by estuarine fauna. However, benthic assemblage composition, infaunal δ13C signatures and food-web diversity markedly differed at the impacted site being strongly related to sedimentary changes. The loss of infaunal trophic diversity that followed mangrove removal suggests that large-scale forest clearing may impact estuarine food webs, with potential consequences to nearby coastal ecosystems given the high clearing rate of mangrove forests in Brazil.
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