细化搜索
结果 941-950 的 2,459
Derelict fishing gear in Chesapeake Bay, Virginia: Spatial patterns and implications for marine fauna
2014
Bilkovic, Donna Marie | Havens, Kirk | Stanhope, David | Angstadt, Kory
Derelict fishing gear is a source of mortality for target and non-target marine species. A program employing commercial watermen to remove marine debris provided a novel opportunity to collect extensive spatially-explicit information for four consecutive winters (2008–2012) on the type, distribution, and abundance of derelict fishing gear and bycatch in Virginia waters of Chesapeake Bay. The most abundant form of derelict gear recovered was blue crab pots with almost 32,000 recovered. Derelict pots were widely distributed, but with notable hotspot areas, capturing 40 species and over 31,000 marine organisms. The target species, blue crab, experienced the highest mortality from lost pots with an estimated 900,000 animals killed each year, a potential annual economic loss to the fishery of $300,000. Important fishery species were captured and killed in derelict pots including Atlantic croaker and black sea bass. While some causes of gear loss are unavoidable, others can be managed to minimize loss.
显示更多 [+] 显示较少 [-]Spatio-temporal pattern of community development in dredged material used for habitat enhancement: A study case in a brackish lagoon
2014
Munari, C. | Mistri, M.
Dredged material is a potential resource for beneficial use for create/improve subtidal habitats. In a northwestern Adriatic lagoon, dredged sand was placed in inner areas with the management objective of improving the characteristics of the muddy areas being recharged. With this study we investigated the recolonization dynamics of benthic communities following the placement of dredged sand in a microtidal lagoon. The disposal of dredged sand had an immediate and negative effect on resident fauna. After an initial reduction, benthic communities followed different recovery pathways. One year after disposal, we recorded an almost complete recovery of the benthic invertebrates in terms of univariate parameters. Despite multivariate analyses still showed significantly different community structures, the trajectories of recovery for disposal areas converged towards the same basin of attraction of control areas. The ecological quality of sites, assessed with benthic indices, did not improve, thus no new beneficial habitat was created for macrobenthos.
显示更多 [+] 显示较少 [-]Chemical profiles of urban fugitive dust over Xi'an in the south margin of the Loess Plateau, China
2014
Zhang, Qian | Shen, Zhenxing | Cao, Junji | Ho, KinFai | Zhang, Renjian | Bie, Zengjun | Chang, Hairu | Liu, Suixin
Urban fugitive dust samples were collected to determine the chemical profiles of fugitive dust over Xi'an. Seventy eight samples were collected and divided into categories of paved road dust, construction dust, cement dust, and soil dust. Eighteen elements, including Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Ba, and Pb, and eight water–soluble inorganic ions, including Na+, Mg2−, Ca2−, NH4−, F−, Cl−, NO3− and SO42−, were measured. The most abundant elements in these urban dust samples were Al, Si, Ca, and Fe. Al, Si, K, and Ti and showed strong positive correlations with each other, indicating they are typical dust trace elements. In contrast, elements of Ca, Zn, As, and Pb had negative correlations to crustal elements. Si/Al, K/Al, Ti/Al, Mn/Al, and Fe/Al ratios varied insignificantly among these four samples types; these ratios are similar to the properties of loess, desert, and Gobi soil dust reported in previous studies. A significantly higher Ca/Al ratio was dominant in the chemical profile of the cement samples. In addition, high Pb/Al and Zn/Al ratios were detected in comparison with those in the Gobi soil, desert soil, and loess soil samples, which indicated that Pb/Al and Zn/Al ratios can be considered as markers of urban dust. To t a l water–soluble ions occupied only a small fraction (<5%) in the urban fugitive soil samples indicating that most of the materials in the fugitive dust were insoluble. Ca2+ and SO42− were the most abundant ions in all samples. Most of the Ca and K in the fugitive soil samples were in insoluble phases, which differ significantly in comparison with combustion sources. A strong correlation was observed between Ca2+ and estimated CO32− levels indicating that most of Ca2+ was in the form of CaCO3 rather than other calcium minerals in Xi’an fugitive dust.
显示更多 [+] 显示较少 [-]Atmospheric NH3 dynamics at a typical pig farm in China and their implications
2014
Xu, Wen | Zheng, Kun | Liu, Xuejun | Meng, Lingmin | Huaitalla, Roxana M. | Shen, Jianlin | Hartung, Eberhand | Gallmann, Eva | Roelcke, Marco | Zhang, Fusuo
This study investigated NH3 concentrations in and around a large–scale commercial pig farm with the so–called “gan qing fen” manure collection system near Beijing from April 2009 to August 2011. NH3 emissions from the fattening pig houses were calculated based on the heat balance method. Monthly concentrations of time–averaged NH3 in and near the pig house averaged 3 392 and 182μg m−3 and ranged from 1 044 to 7 514μg m−3 and 35.4 to 478μg m−3, respectively. Daily NH3 concentrations varied from 767 to 2 389μg m−3 in the pig house and 184 to 574μg m−3 outside. Time–averaged NH3 concentrations varied from 21.6 to 558μg m−3 within the farm while concentrations outside the farm ranged from 38.4μg m−3 at a distance of 10m to 14.0μg m−3 at a distance of 650m. Calculated average NH3 emission rates per pig were highest in summer and lowest in winter, 8.0±5.5 (average±standard deviation) and 2.0±0.4g day−1 pig−1, respectively. Average NH3 emission rates (normalized to 500kg live weight, expressed as AU) were highest during spring and summer (average 65.4±25.0 and 53.7±35.6 g day−1 AU−1) and lowest in autumn and winter (average 25.4±9.3 and 13.7±2.7g day−1 AU−1). Average NH3 emission per area (m2) from house was almost three times higher in summer (average 3.5±2.4g day−1 m−2) than in winter (average 1.1±0.3g day−1 m−2).
显示更多 [+] 显示较少 [-]Are lionfish set for a Mediterranean invasion? Modelling explains why this is unlikely to occur
2014
Johnston, Matthew W. | Purkis, Sam J.
The Atlantic invasion of Indo-Pacific lionfish (Pterois volitans/P. miles) has been as swift as it has been disastrous. Lionfish are non-native to the Mediterranean, but an invasion is perhaps even more likely than for the Atlantic. First, as for the Atlantic, there are many major cities on the coast of the Mediterranean (where aquarium-keeping is a common practice and chances of accidental and deliberate releases are high), and second, lionfish are native to the Red Sea, to which the Mediterranean is connected via the Suez Canal. Furthermore, there have already been four records of lionfish in the Mediterranean and so the pretext for an invasion is already in place. Up until now, however, it has been difficult to gauge the likelihood of an infestation of lionfish in the Mediterranean as, unlike the Atlantic, this sea has not been examined in terms of its hydrodynamics, ocean climate, and bathymetry, all factors known to be relevant to assessing the possibility of invasion. Motivated by this knowledge-gap, this study used remote sensing and computer modeling to investigate the connectivity between areas along the Mediterranean coastline that fulfill the necessary physical criteria to serve as potential lionfish habitat. Model results from the Mediterranean were compared and contrasted to those from the Atlantic and eastern Pacific. The Atlantic was considered because the lionfish invasion there has been voracious. Meanwhile, the eastern Pacific is interesting as a site without native lionfish, but with plenty of opportunity for their introduction, but no invasion yet recorded. Results indicated that, unlike in the Atlantic, connectivity among potential lionfish habitats in the Mediterranean was low in the study and comparable to that in the eastern Pacific. Although oceanographic conditions in the Mediterranean were found unfavorable for wide dispersion of lionfish larvae, hotspots where numerous lionfish sightings would forewarn an impending invasion were identified. This paper can therefore serve as a guide to the most efficient monitoring of lionfish in the Mediterranean and to where removal efforts should be concentrated, should the species become established.
显示更多 [+] 显示较少 [-]Distribution of cadmium, mercury, and lead in different body parts of Baltic herring (Clupea harengus) and perch (Perca fluviatilis): Implications for environmental status assessments
2014
Boalt, Elin | Miller, Aroha | Dahlgren, Henrik
For heavy metals, quality standards indicating good environmental status are designed to evaluate concentrations in the whole fish body, whereas monitoring of metals is often conducted using muscle or liver tissue. As most metals accumulate at different rates in different parts of fish, data should be adjusted to reflect whole fish body concentrations; however, this requires knowledge on distribution of metal concentrations within fish. Here, concentrations of cadmium, mercury, and lead were analyzed in the liver, muscle and whole fish of herring and perch to create conversion factors for transformation of heavy metal concentrations between these tissues. Species-specific accumulation of metals between muscle, liver, and whole fish were observed. Relationships between different tissues were used to recalculate data from monitoring programs in the Baltic Sea region. Based on whole fish concentrations, environmental status for cadmium and mercury in herring improved compared to assessments based on muscle or liver concentrations alone.
显示更多 [+] 显示较少 [-]Monitoring plant response to phenanthrene using the red edge of canopy hyperspectral reflectance
2014
Zhu, Linhai | Chen, Zhongxin | Wang, Jianjian | Ding, Jinzhi | Yu, Yunjiang | Li, Junsheng | Xiao, Nengwen | Jiang, Lianhe | Zheng, Yuanrun | Rimmington, Glyn M.
To investigate the mechanisms and potential for the remote sensing of phenanthrene-induced vegetation stress, we measured field canopy spectra, and associated plant and soil parameters in the field controlled experiment in the Yellow River Delta of China. Two widely distributed plant communities, separately dominated by reed (Phragmites australis) and glaucous seepweed (Suaeda salsa), were treated with different doses of phenanthrene. The canopy spectral changes of plant community resulted from the decreases of biomass and foliar projective coverage, while leaf photosynthetic pigment concentrations showed no significance difference among treatments. The spectral response to phenanthrene included a flattened red edge, with decreased first derivative of reflectance. The red edge slope and area consistently responded to phenanthrene, showing a strong relationship with aboveground biomass, coverage and canopy pigments density. These results suggest the potential of remote sensing and the importance of field validation to correctly interpret the causes of the spectral changes.
显示更多 [+] 显示较少 [-]Maternal-to-fetal transfer and concentration profiles of PCB congeners for Steller sea lions (Eumetopias jubatus) from Hokkaido, Japan
2014
Kubo, Keiko | Yamaguchi, Katsuyuki | Ishinazaka, Tsuyoshi | Yamada, Wakana | Hattori, Kaoru | Tanaka, Shunitz
The concentrations of PCB congeners in the blubber and liver of mother Steller sea lions (Eumetopias jubatus; SSLs) and their fetuses from the coast of Hokkaido, Japan in 2008, 2010 and 2012 were analyzed by HRGC–HRMS, in order to elucidate PCB congener profiles and maternal-to-fetal transfer of PCBs in SSLs. ΣPCBs in the fetuses were 1400±660 (the mean±SD) ng/g-fat in the blubber and 570±320ng/g-fat in the liver, respectively. There was a concern that SSLs had been contaminated by PCBs during the fetal period. The concentrations of the major congeners in the blubber and liver were a correlation between the fetus and mother (blubber: r=0.9934, liver: r=0.9160; P≦0.05). The results indicated that PCBs in the fetuses came from the mothers. #177 and #199 showed no correlations between the fetus and the mother in the blubber and liver. This indicated a selective capture by some natural protector such as the placenta.
显示更多 [+] 显示较少 [-]Monitoring red tide with satellite imagery and numerical models: A case study in the Arabian Gulf
2014
Zhao, Jun | Ghedira, Hosni
A red tide event that occurred in August 2008 in the Arabian Gulf was monitored and assessed using satellite observations and numerical models. Satellite observations revealed the bloom extent and evolution from August 2008 to August 2009. Flow patterns of the bloom patch were confirmed by results from a HYCOM model. HYCOM data and satellite-derived sea surface temperature data further suggested that the bloom could have been initiated offshore and advected onshore by bottom Ekman layer. Analysis indicated that nutrient sources supporting the bloom included upwelling, Trichodesmium, and dust deposition while other potential sources of nutrient supply should also be considered. In order to monitor and detect red tide effectively and provide insights into its initiation and maintenance mechanisms, the integration of multiple platforms is required. The case study presented here demonstrated the benefit of combing satellite observations and numerical models for studying red tide outbreaks and dynamics.
显示更多 [+] 显示较少 [-]Macrobenthic diversity in protected, disturbed, and newly formed intertidal wetlands of a subtropical estuary in China
2014
Lv, Weiwei | Ma, Chang-an | Huang, Youhui | Yang, Yang | Yu, Ji | Zhang, Mingqing | Zhao, Yunlong
In this study, intertidal macrobenthic diversity in protected, disturbed, and newly formed wetlands of Yangtze estuary was assessed using PRIMER 5.2 based on species diversity and species relatedness. We observed high diversity in nature reserves and low diversity in adjacent disturbed and newly formed wetlands. These diversity data were then integrated with historical data to detect the variation in macrobenthic diversity over the past two decades. The integrated data indicated that the intertidal macrobenthic diversity sharply decreased in heavy reclamation tidal flats whereas markedly increased in non-disturbed nature reserve and newly formed wetland. Benthic health was observed with the departure degree of average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) from the simulated 95% confidence funnel. All the habitats were subjected to different levels of human interference, except Jiuduansha and Beigangbeisha. The degradation of intertidal wetland in Yangtze estuary was mainly attributed to land reclamation, overgrazing, and overfishing.
显示更多 [+] 显示较少 [-]