Refinar búsqueda
Resultados 1051-1060 de 3,208
Short-term impact of deep sand extraction and ecosystem-based landscaping on macrozoobenthos and sediment characteristics Texto completo
2015
de Jong, Maarten F. | Baptist, Martin J. | Lindeboom, Han J. | Hoekstra, Piet
We studied short-term changes in macrozoobenthos in a 20m deep borrow pit. A boxcorer was used to sample macrobenthic infauna and a bottom sledge was used to sample macrobenthic epifauna. Sediment characteristics were determined from the boxcore samples, bed shear stress and near-bed salinity were estimated with a hydrodynamic model. Two years after the cessation of sand extraction, macrozoobenthic biomass increased fivefold in the deepest areas. Species composition changed significantly and white furrow shell (Abra alba) became abundant. Several sediment characteristics also changed significantly in the deepest parts. Macrozoobenthic species composition and biomass significantly correlated with time after cessation of sand extraction, sediment and hydrographical characteristics. Ecosystem-based landscaped sand bars were found to be effective in influencing sediment characteristics and macrozoobenthic assemblage. Significant changes in epifauna occurred in deepest parts in 2012 which coincided with the highest sedimentation rate. We recommend continuing monitoring to investigate medium and long-term impacts.
Mostrar más [+] Menos [-]Ecologically based targets for bioavailable (reactive) nitrogen discharge from the drainage basins of the Wet Tropics region, Great Barrier Reef Texto completo
2015
Wooldridge, Scott A. | Brodie, J. E. (Jon E.) | Kroon, F. J. (Frederieke J.) | Turner, Ryan D.R.
A modelling framework is developed for the Wet Tropics region of the Great Barrier Reef that links a quantitative river discharge parameter (viz. dissolved inorganic nitrogen concentration, DIN) with an eutrophication indicator within the marine environment (viz. chlorophyll-a concentration, chl-a). The model predicts catchment-specific levels of reduction (%) in end-of-river DIN concentrations (as a proxy for total potentially reactive nitrogen, PRN) needed to ensure compliance with chl-a ‘trigger’ guidelines for the ecologically distinct, but PRN-related issues of crown-of-thorns starfish (COTS) outbreaks, reef biodiversity loss, and thermal bleaching sensitivity. The results indicate that even for river basins dominated by agricultural land uses, quite modest reductions in end-of-river PRN concentrations (∼20–40%) may assist in mitigating the risk of primary COTS outbreaks from the mid-shelf reefs of the Wet Tropics. However, more significant reductions (∼60–80%) are required to halt and reverse declines in reef biodiversity, and loss of thermal bleaching resistance.
Mostrar más [+] Menos [-]Trace element and stable isotope analysis of fourteen species of marine invertebrates from the Bay of Fundy, Canada Texto completo
2015
English, Matthew D. | Robertson, Gregory J. | Mallory, Mark L.
The Bay of Fundy, Canada, is a macrotidal bay with a highly productive intertidal zone, hosting a large abundance and diversity of marine invertebrates. We analysed trace element concentrations and stable isotopic values of δ15N and δ13C in 14 species of benthic marine invertebrates from the Bay of Fundy's intertidal zone to investigate bioaccumulation or biodilution of trace elements in the lower level of this marine food web. Barnacles (Balanus balanus) consistently had significantly greater concentrations of trace elements compared to the other species studied, but otherwise we found low concentrations of non-essential trace elements. In the range of trophic levels that we studied, we found limited evidence of bioaccumulation or biodilution of trace elements across species, likely due to the species examined occupying similar trophic levels in different food chains.
Mostrar más [+] Menos [-]Thermophilic biotrickling filtration of gas–phase trimethylamine Texto completo
2015
Wei, Zaishan | Huang, Qianru | Ye, Qihong | Chen, Zhouyang | Li, Baoren | Wang, Jianbin
The objectives of this work were to investigate trimethylamine (TMA) removal by thermophilic biotrickling filtration (TBTF) and to examine the microbial community developed at 56 °C. TMA removal efficiency in the TBTF system was up to 99.9%. At a bed contact time of 25.8s, the elimination capacity at 56 °C in the TBTF was 375.2g TMAm−3 h−1, which was higher than that of mesophilic biotrickling filtration. TBTF was able to quickly recover from a normal temperature shutdown period of a month. The thermophilic bacterial communities in the TBTF which were assessed by polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE), play the dominant role in the thermophilic biological processes of metabolism, ammoxidation, nitrification, denitrification and carbon oxidation. These results show that TBTF is achievable and open new possibilities for applying biotrickling filtration to hot odorous gas streams from sewage sludge drying.
Mostrar más [+] Menos [-]Bioremediation efficiency of the largest scale artificial Porphyra yezoensis cultivation in the open sea in China Texto completo
2015
Wu, Hailong | Huo, Yuanzi | Zhang, Jianheng | Liu, Yuanyuan | Zhao, Yating | He, Peimin
The bioremediation efficiency of China’s largest scale Porphyra yezoensis cultivation for removing dissolved nutrients and controlling harmful algae was studied in the radial sandbanks waters of Jiangsu Province in the year 2012–2013. Mean nutrient concentration values in the P. yezoensis cultivation area were significantly lower than those in the non-cultivation area, especially during the cultivation season (p<0.05). Tissue nitrogen and phosphorus contents of seaweeds were 5.99–0.80% (dry weight (DW)) and 0.16–0.19% (DW), respectively. Production of P. yezoensis was 58950.87tons DW. Based on these values, 3688.15tons of tissue nitrogen and 105.61tons of tissue phosphorus were removed by harvesting P. yezoensis. The richness index of the red tide species Skeleton emacostatum declined from 0.32 to 0.05 during the P. yezoensis cultivation season. These results indicate that large-scale cultivation of P. yezoensis can be used to efficiently alleviate eutrophication and control harmful algae blooms in open sea.
Mostrar más [+] Menos [-]Bioaccumulation of PCBs in liver tissue of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters Texto completo
2015
Gilbert, Jann M. | Baduel, Christine | Li, Yan | Reichelt-Brushett, Amanda J. | Butcher, Paul A. | McGrath, Shane P. | Peddemors, Victor M. | Hearn, Laurence | Mueller, Jochen | Christidis, Les
Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the marine environment that are known to accumulate in apex predators such as sharks. Liver samples from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters were analysed for the seven indicator PCBs 28, 52, 101, 118, 138, 153 and 180. Median ∑PCBs were significantly higher in white than sandbar sharks (3.35 and 0.36μgg−1 lipid, respectively, p=0.05) but there were no significant differences between dusky sharks (1.31μgg−1 lipid) and the other two species. Congener concentrations were also significantly higher in white sharks. Significant differences in PCB concentrations between mature and immature dusky (3.78 and 0.76μgg−1 lipid, respectively) and sandbar (1.94 and 0.18μgg−1 lipid, respectively) sharks indicated that PCB concentrations in these species increased with age/growth. Higher-chlorinated congeners (hexa and heptachlorobiphenyls) dominated results, accounting for ~90% of ∑PCBs.
Mostrar más [+] Menos [-]Efficient extraction and detection of aromatic toxicants from crude oil and tar balls using multiple cyclodextrin derivatives Texto completo
2015
Serio, Nicole | Levine, Mindy
Herein we report the efficient extraction of aromatic analytes from crude oil and tar balls using multiple cyclodextrin derivatives. The known propensity of the cyclodextrins to bind hydrophobic guests in their hydrophobic interiors enhanced the extraction of aromatic analytes from the oil layer to the aqueous layer, with methyl-β-cyclodextrin and β-cyclodextrin providing the most significant enhancement in extraction efficiencies of aromatic toxicants (69% aromatic toxicants in aqueous layer in the presence of methyl-β-cyclodextrin compared to 47% in cyclodextrin-free solution for tar ball oil extraction), and provide optimal tunability for developing efficient extraction systems. The cyclodextrin derivatives also promoted efficient energy transfer in the aqueous solutions, with up to 86% efficient energy transfer observed in the presence of γ-cyclodextrin compared to 50% in the absence of cyclodextrin for oil spill oil extraction. Together, this dual function extraction followed by detection system has potential in the development of environmental remediation systems.
Mostrar más [+] Menos [-]The emerging threats of climate change on tropical coastal ecosystem services, public health, local economies and livelihood sustainability of small islands: Cumulative impacts and synergies Texto completo
2015
Hernández-Delgado, E.A.
Climate change has significantly impacted tropical ecosystems critical for sustaining local economies and community livelihoods at global scales. Coastal ecosystems have largely declined, threatening the principal source of protein, building materials, tourism-based revenue, and the first line of defense against storm swells and sea level rise (SLR) for small tropical islands. Climate change has also impacted public health (i.e., altered distribution and increased prevalence of allergies, water-borne, and vector-borne diseases). Rapid human population growth has exacerbated pressure over coupled social–ecological systems, with concomitant non-sustainable impacts on natural resources, water availability, food security and sovereignty, public health, and quality of life, which should increase vulnerability and erode adaptation and mitigation capacity. This paper examines cumulative and synergistic impacts of climate change in the challenging context of highly vulnerable small tropical islands. Multiple adaptive strategies of coupled social–ecological ecosystems are discussed. Multi-level, multi-sectorial responses are necessary for adaptation to be successful.
Mostrar más [+] Menos [-]Microplastic in a macro filter feeder: Humpback whale Megaptera novaeangliae Texto completo
2015
Besseling, E. | Foekema, E.M. | Van Franeker, J.A. | Leopold, M.F. | Kühn, S. | Bravo Rebolledo, E.L. | Heße, E. | Mielke, L. | IJzer, J. | Kamminga, P. | Koelmans, A.A.
Marine filter feeders are exposed to microplastic because of their selection of small particles as food source. Baleen whales feed by filtering small particles from large water volumes. Macroplastic was found in baleen whales before. This study is the first to show the presence of microplastic in intestines of a baleen whale (Megaptera novaeangliae). Contents of its gastrointestinal tract were sieved, dissolved in 10% potassium hydroxide and washed. From the remaining dried material, potential synthetic polymer particles were selected based on density and appearance, and analysed by Fourier transform infrared (FTIR) spectroscopy. Several polymer types (polyethylene, polypropylene, polyvinylchloride, polyethylene terephthalate, nylon) were found, in varying particle shapes: sheets, fragments and threads with a size of 1mm to 17cm. This diversity in polymer types and particle shapes, can be interpreted as a representation of the varying characteristics of marine plastic and the unselective way of ingestion by M. novaeangliae.
Mostrar más [+] Menos [-]Impact of intertidal oyster trestle cultivation on the Ecological Status of benthic habitats Texto completo
2015
Forde, James | O’Beirn, Francis X. | O’Carroll, Jack PJ. | Patterson, Adrian | Kennedy, Robert
A considerable number of Ireland’s shellfish production areas co-occur with or are adjacent to Natura 2000 sites which are protected under European legislation. To investigate the general interaction between trestle oyster cultivation and the surrounding intertidal environment, six sites were selected within designated Natura 2000 sites. At each trestle site three Treatment areas were sampled. One Treatment area corresponded to potential impacts associated with cultivation activities occurring at trestle structures (designated the Trestle Treatment) while one Treatment area corresponded to potential impacts due to cultivation activities occurring along access routes (the Access Treatment). An area not subject to any known anthropogenic activity was used as a control (the Control Treatment). Potential impacts associated with Trestle Treatment areas included changes in sediment total organic matter (TOM) levels underneath trestles due to the bio-deposition of faecal/pseudofaecal material while the predominant impact associated with Access Treatment areas was compaction of sediments due to heavy vehicle traffic. In this study, macrobenthic communities at the sites were highly variable and exhibited low levels of diversity which prevented the detection of general effects of cultivation activity on community structure, diversity and secondary production. To overcome this variability, the Infaunal Quality Index (IQI) was used to assess impacts on Ecological Status (ES) of benthic communities (sensu Water Framework Directive). Relative to Control and Trestle Treatment areas, activities occurring at Access Treatment areas had a significant negative impact on ES. This study highlights the potential of the IQI for the management of aquaculture activity and provides validation for the use of the IQI in Irish intertidal environments. This study also highlights the IQI as a potential tool for assessing the conservation status of designated habitats in Natura 2000 sites.
Mostrar más [+] Menos [-]