细化搜索
结果 2661-2670 的 6,558
Occurrence, antibiotic-resistance and virulence of E. coli strains isolated from mangrove oysters (Crassostrea gasar) farmed in estuaries of Amazonia 全文
2020
Oliveira, Amanda M.S. | Baraúna, Rafael A. | Marcon, Davi J. | Lago, Letícia A.B. | Silva, Artur | Lusio, Joana | Tavares, Rafael D.S. | Tacão, Marta | Henriques, Isabel | Schneider, Maria P.C.
Concentration of bacterial species indicative of fecal contamination in the gut of mangrove oysters (Crassostrea gasar) is a major concern for public health and food surveillance. Our work aimed to determine the occurrence, antibiotic-resistance, phylogenetic profile and virulence of Escherichia coli strains isolated from C. gasar farmed in four estuaries of Amazonia. Santo Antônio de Urindeua was the sampling point with the highest number of E. coli cells in oyster samples (10⁴ per 100 g of sample). Twenty-four isolates (52.2%) showed resistance to cephalotin and 18 to amoxicillin (39.1%). Eighteen clonal populations were determined by rep-PCR and were mainly affiliated to the pathogenic and commensal phylo-groups B1 and D. The presence of elt genes suggests that 10 of these clones belong to the Enterotoxigenic Escherichia coli pathotype. Plasmids, mostly of the F incompatibility group, were detected in the majority of the strains. All isolates were susceptible to last-resort antibiotics.
显示更多 [+] 显示较少 [-]Sediment quality in the semi-enclosed Lumparn Bay, Åland Islands, Baltic Sea 全文
2020
The Lumparn Bay, due to its nature, is prone both to natural and anthropogenic environmental pressures. It is a semi-enclosed rather large, but relatively shallow bay filled with glacial and postglacial sediments. Unlike any other areas in the world the seafloor in this area is filled with gas domes. Comparison with the chemistry of some 2000 surface core samples from the Gulf of Finland revealed that the concentrations of arsenic, cadmium, chromium, copper, mercury, molybdenum, nickel, lead, zinc, and sulphur from the Lumparn Bay were in general on a low level, indicating only minor pressures on the seafloor. However, when compared to established sediment quality guidelines there are a few points of possible concern as some samples exceed the probable effects level for arsenic and quite a few samples exceed the effects range – median level for nickel. Also a few comparably high molybdenum concentrations exceed the lowest effects level.
显示更多 [+] 显示较少 [-]A real time data driven algal bloom risk forecast system for mariculture management 全文
2020
In eutrophic coastal waters, harmful algal blooms (HAB) often occur and present challenges to environmental and fisheries management. Despite decades of research on HAB early warning systems, the field validation of algal bloom forecast models have received scant attention. We propose a daily algal bloom risk forecast system based on: (i) a vertical stability theory verified against 191 past algal bloom events; and (ii) a data-driven artificial neural network (ANN) model that assimilates high frequency data to predict sea surface temperature (SST), vertical temperature and salinity differential with an accuracy of 0.35ᵒC, 0.51ᵒC, and 0.58 psu respectively. The model does not rely on past chlorophyll measurements and has been validated against extensive field data. Operational forecasts are illustrated for representative algal bloom events at a marine fish farm in Tolo Harbour, Hong Kong. The robust model can assist with traditional onsite monitoring as well as artificial-intelligence (AI) based methods.
显示更多 [+] 显示较少 [-]Sediment quality of the Bohai Sea and the northern Yellow Sea indicated by the results of acid-volatile sulfide and simultaneously extracted metals determinations 全文
2020
Gao, Xuelu | Song, Jinming | Li, Xuegang | Yuan, Huamao | Zhao, Jianmin | Xing, Qianguo | Li, Peimiao
The surface sediments from the Bohai Sea (BS) and the northern Yellow Sea (NYS) were analyzed for acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) to assess the sediment quality. The results indicated that >60% of the samples were found to have possible adverse effects on aquatic life in the BS based on the difference between the concentrations of AVS ([AVS]) and SEM ([SEM]), and the corresponding percentage in the NYS was <25%. Nevertheless, there was no indication of adverse effects for all the BS and the NYS samples when the total organic carbon (TOC) concentration was introduced in the sediment quality evaluation with [AVS] and [SEM]. The grain size composition, TOC, water content and pH all had significant influence on the distribution of [SEM] and the [SEM]/[AVS] ratios; while, in contrast, the distribution of [AVS] could be mainly determined by the redox condition of sediment.
显示更多 [+] 显示较少 [-]Beach landscape management as a sustainable tourism resource in Fernando de Noronha Island (Brazil) 全文
2020
Cristiano, Samanta da Costa | Rockett, Gabriela Camboim | Portz, Luana Carla | Souza Filho, José Rodrigues de
The Coastal Scenery Evaluation System was used to analyze the landscape of touristic beaches at the Fernando de Noronha Archipelago, using a checklist with 26 physical and human parameters. The beaches are divided into classes ranging from 1 (extremely attractive natural site) to 5 (unattractive urban areas). The data reflects the natural and anthropogenic characteristics of the coastal Noronha scenery, which have international relevance and are between classes 1–4. Class 3 and 4 beaches are associated with anthropogenic factors/parameters. Seasonal sedimentary stock variation has also contributed to the differences in classes between the seasons at some beaches. The results of this study are useful to create new perspectives for sustainable development based on the singularities of this touristic resource – the landscape. The Fernando de Noronha Archipelago depends on its landscapes for tourism. Therefore, government policies should seek the sustainable management of its beaches, so as to ensure the protection of natural and cultural resources.
显示更多 [+] 显示较少 [-]Effect of salinity and temperature on the acute and chronic toxicity of arsenic to the marine rotifers Proales similis and Brachionus ibericus 全文
2020
Arreguin Rebolledo, Uriel | Nandini, S. | Sarma, S.S.S. | Escobar-Sánchez, Ofelia
Several abiotic factors influence the ecological responses of aquatic invertebrates to metal toxicity. We examined the effect of salinity (10, 20, and 30 psu) and temperature (25 and 32 °C) on acute and chronic arsenic (As) toxicity to the euryhaline rotifers, Proales similis and Brachionus ibericus. In general, higher salinities and low temperature resulted in lower arsenic toxicity. The population growth studies indicated that P. similis was more sensitive than B. ibericus to As. Arsenic toxicity intensified the vulnerability of P. similis to B. ibericus competition. Life table parameters decreased with increasing As levels in the medium. Chronic toxicity bioassays were more sensitive than acute toxicity tests for determining the adverse effect of As to rotifers. Our findings provide useful insights on the effect of arsenic on rotifer populations exposed to different temperature and salinity scenarios. Proales similis could be an important complement to brachionid rotifers for marine toxicity bioassays.
显示更多 [+] 显示较少 [-]Investigation of submarine groundwater discharge and associated nutrient inputs into Laizhou Bay (China) using radium quartet 全文
2020
Wang, Jerry H. C. | Li, Hailong | Zhang, Yan | Zheng, Chunmiao | Gao, Maosheng
Radium is widely used to estimate flushing time, submarine groundwater discharge (SGD), and submarine fresh groundwater discharge (SFGD), however there are important sources of uncertainty in current methods. Here an improved method is proposed, incorporating all radium quartet information to estimate flushing time, SFGD, SGD, and associated nutrient fluxes during wet and dry seasons in Laizhou Bay, China. Both SGD and SFGD in dry season are comparable to that in wet season, likely due to higher groundwater hydraulic gradients resulting from higher groundwater table and lower mean sea level in dry season. Estimated dry and wet season SFGD are of the same order of magnitude as the annually-averaged Yellow River discharge, highlighting SFGD's importance to the bay environment. Nutrient inputs into Laizhou Bay were estimated for the wet season, suggesting that SGD-derived nutrients are indeed important and significant for coastal environments compared to local river discharge estimates.
显示更多 [+] 显示较少 [-]Investigation on microplastic pollution of Dongting Lake and its affiliated rivers 全文
2020
Hu, Duofei | Zhang, Yaxin | Shen, Maocai
At present, the occurrence and pollution of microplastics have caused widespread concern, but there are still few studies on inland lake and its affiliated rivers. In this study, we monitored the existence and characteristics of microplastics in Dongting Lake and its affiliated rivers. Our sampling site covers almost the entire lake district. A total of 15 surface water samples and 15 sediment samples were collected. The abundance of microplastics achieved 0.62–4.31 items/m² in plankton net samples, with 21–52 items/100 g dw in sediments. The microplastics were dominated by fiber, 0.9–0.333 mm of surface water and ˂0.1 mm of sediments in size. The color of transparent occupied the majority in all microplastics samples. There was no significant difference in the average concentration of microplastics between the four river mouths and the whole lake and the rivers may have important potential contribution to the microplastics pollution in the lake.
显示更多 [+] 显示较少 [-]Coordination of pollution-related MSFD measures in the Mediterranean - Where we stand now and insights for the future 全文
2020
Gorjanc, S. | Klančnik, K. | Murillas-Maza, A. | Uyarra, M.C. | Papadopoulou, N.K. | Paramana, Th | Smith, C. | Chalkiadaki, O. | Dassenakis, M. | Peterlin, M.
Various pollutants keep threatening the environmental status of the Mediterranean Sea, while the Marine Strategy Framework Directive requires that Good Environmental Status needs to be achieved in European Seas by 2020. Previous reviews already established that the ambition levels of national Programmes of Measures (PoMs) are low. This study focuses on the analyses of the levels of coherence and coordination of the proposed PoMs in the Mediterranean, concentrating on nutrient, contaminant, and marine litter pollution, as well as the introduction of non-indigenous species. Coherence and pollinator analyses of the proposed measures of Mediterranean EU Member States (MS) were performed. The results demonstrate that while the current coordination between MS is almost non-existent, several measures are already addressing the same pressures in similar ways and could be easily coordinated on transnational level. Increased coordination and coherence of PoMs in the Mediterranean are vital for achieving good environmental status in future years.
显示更多 [+] 显示较少 [-]Enhancement of phosphorus storage capacity of sediments by coastal wetland restoration, Yellow River Delta, China 全文
2020
Un-restored (R₀) and restored (in 2006 (R₂₀₀₆) and in 2002, (R₂₀₀₂)) coastal wetlands were selected to study phosphorus (P) storage capacity and the risk of P loss in the Yellow River Delta (YRD). The results showed that the maximum P sorption capacity (Qₘₐₓ) in the wetland sediments varied between 201.8–1168.6 mg kg⁻¹; the average value was 576.2 mg kg⁻¹. Qₘₐₓ increased with increasing time since restoration (R₂₀₀₂ > R₂₀₀₆ > R₀). The eutrophication risk index (ERI) ranged between 0.27–2.07% and decreased with increasing time since restoration, but the relationship was not statistically significant (P > 0.05). A correlation analysis demonstrated that Feₒₓ, Mg, and Alₒₓ are the main P sorption agents in wetland sediments, whereas TOC, pH, and clay particles have an important effect on P sorption and release. The analysis suggests that we should restore degraded coastal wetlands to help reduce the P load to offshore waters.
显示更多 [+] 显示较少 [-]