Refinar búsqueda
Resultados 701-710 de 1,956
Coral recruitment and potential recovery of eutrophied and blast fishing impacted reefs in Spermonde Archipelago, Indonesia Texto completo
2013
Sawall, Yvonne | Jompa, Jamaluddin | Litaay, Magdalena | Maddusila, Andi | Richter, Claudio
Coral recruitment and potential recovery of eutrophied and blast fishing impacted reefs in Spermonde Archipelago, Indonesia Texto completo
2013
Sawall, Yvonne | Jompa, Jamaluddin | Litaay, Magdalena | Maddusila, Andi | Richter, Claudio
Coral recruitment was assessed in highly diverse and economically important Spermonde Archipelago, a reef system subjected to land-based sources of siltation/pollution and destructive fishing, over a period of 2years. Recruitment on settlement tiles reached up to 705spatm−2yr−1 and was strongest in the dry season (July–October), except off-shore, where larvae settled earlier. Pocilloporidae dominated near-shore, while a more diverse community of Acroporidae, Poritidae and others settled in the less polluted mid-shelf and off-shore reefs. Non-coral fouling community appeared to hardly influence initial coral settlement on the tiles, although, this does not necessarily infer low coral post-settlement mortality, which may be enhanced at the near- and off-shore reefs as indicated by increased abundances of potential space competitors on natural substrate. Blast fishing showed no local reduction in coral recruitment and live hard coral cover increased in oligotrophic reefs, indicating potential for coral recovery, if managed effectively.
Mostrar más [+] Menos [-]Coral recruitment and potential recovery of eutrophied and blast fishing impacted reefs in Spermonde Archipelago, Indonesia Texto completo
2013
Sawall, Yvonne | Jompa, Jamaluddin | Litaay, Magdalena | Maddusila, Andi | Richter, Claudio
Coral recruitment was assessed in highly diverse and economically important Spermonde Archipelago, a reef system subjected to land-based sources of siltation/pollution and destructive fishing, over a period of 2 years. Recruitment on settlement tiles reached up to 705 spat m�2 yr�1 and was strongest in the dry season (July–October), except off-shore, where larvae settled earlier. Pocilloporidae dominated nearshore, while a more diverse community of Acroporidae, Poritidae and others settled in the less polluted mid-shelf and off-shore reefs. Non-coral fouling community appeared to hardly influence initial coral settlement on the tiles, although, this does not necessarily infer low coral post-settlement mortality, which may be enhanced at the near- and off-shore reefs as indicated by increased abundances of potential space competitors on natural substrate. Blast fishing showed no local reduction in coral recruitment and live hard coral cover increased in oligotrophic reefs, indicating potential for coral recovery, if managed effectively.
Mostrar más [+] Menos [-]A simple technique for counting marine debris at sea reveals steep litter gradients between the Straits of Malacca and the Bay of Bengal Texto completo
2013
Ryan, Peter G.
A size and distance-based technique was used to assess the distribution, abundance and composition of floating marine debris in the northeast Indian Ocean. Densities of floating litter (>1cm) were greater and more variable in the Straits of Malacca (578±219itemskm−2) than in oceanic waters of the Bay of Bengal (8.8±1.4itemskm−2). The density of debris in the Straits was correlated with terrestrial vegetation, and peaked close to urban centres, indicating the predominance of land-based sources. In the Bay of Bengal, debris density increased north of 17°N mainly due to small fragments probably carried in run-off from the Ganges Delta. The low densities in the Bay of Bengal relative to model predictions may result from biofouling-induced sinking and wind-driven export of debris items. Standardised data collection protocols are needed for counts of floating debris, particularly as regards the size classes used, to facilitate comparisons among studies.
Mostrar más [+] Menos [-]Hydrogeochemical variables regionalization – applying cluster analysis for a seasonal evolution model from an estuarine system affected by AMD Texto completo
2013
Grande, J.A. | Carro, B. | Borrego, J. | de la Torre, M.L. | Valente, T. | Santisteban, M.
This study describes the spatial evolution of the hydrogeochemical parameters which characterise a strongly affected estuary by Acid Mine Drainage (AMD). The studied estuarine system receives AMD from the Iberian Pyrite Belt (SW Spain) and, simultaneously, is affected by the presence of an industrial chemical complex. Water sampling was performed in the year of 2008, comprising four sampling campaigns, in order to represent seasonality. The results show how the estuary can be divided into three areas of different behaviour in response to hydrogeochemical variables concentrations that define each sampling stations: on one hand, an area dominated by tidal influence; in the opposite end there is a second area including the points located in the two rivers headwaters that are not influenced by seawater; finally there is the area that can be defined as mixing zone. These areas are moved along the hydrological year due to seasonal chemical variations.
Mostrar más [+] Menos [-]Monitoring micropollutants in marine waters, can quality standards be met? Texto completo
2013
Ghekiere, An | Verdonck, Frederik | Claessens, Michiel | Monteyne, Els | Roose, Patrick | Wille, Klaas | Goffin, Annelies | Rappé, Karen | Janssen, Colin R.
The environmental risks of 33 micropollutants occurring in Belgian coastal zone were assessed as single-substances and as mixtures. Water and sediment samples were taken in harbors, coastal waters and the Scheldt estuary during 2007–2009. Measured environmental concentrations were compared to quality standards such as Predicted No Effect Concentrations (PNECs), Environmental Quality Standards (EQSs), and Ecotoxicological Assessment Criteria (EAC). Out of a total of 2547 samples analyzed, 232 and 126 samples exceeded the EQS and EAC, respectively. Highest risks were observed for TBT, PBDEs, PCBs and the PAHs anthracene, indeno(1,2,3-cd)pyrene, benzo(g,h,i)perylene, benzo(k)fluoranthene, and benzo(b)fluoranthene in the water compartment and for TBT and PCBs in the sediment compartment. Samples taken at all stations during the April 2008 campaign indicate a potential risk of the contaminant mixtures to the aquatic environment (except W06 station). This study argues the need to revise quality standards when appropriate and hence the overall regulatory implication of these standards.
Mostrar más [+] Menos [-]Reciprocal experimental transplantations to assess effects of organic enrichment on the recolonization of benthic macrofauna in a subtropical estuary Texto completo
2013
Gern, Fabiana Regina | Lana, Paulo da Cunha
Coastal benthic habitats are usually in a state of continuous recolonization as a consequence of natural disturbances or human activities. Recolonization patterns can be strongly affected by the quality of the sediment. We evaluated herein the macrobenthic recolonization of organically enriched sediments through a manipulative experiment involving reciprocal transplants between contaminated and non-contaminated intertidal areas. Regardless of the experimental treatments, the density of the polychaete Capitella sp. was extremely high in the contaminated area as well as the density of the gastropod Cylichna sp. in the non-contaminated area. We rejected the hypothesis that differences in sediment quality would determine macrofaunal recolonization at least in the considered scales of space in meters and time in weeks. The recolonization process in a subtropical estuarine environment was strongly dependent on the migration of adults present in the sediments adjacent to the experimental units.
Mostrar más [+] Menos [-]Distribution, enrichment and source of heavy metals in surface sediments of the eastern Beibu Bay, South China Sea Texto completo
2013
Dou, Yanguang | Li, Jun | Zhao, Jingtao | Hu, Bangqi | Yang, Shouye
Sixty-nine samples of surface sediments (0∼5 cm) recovered from the eastern Beibu Bay were analyzed for TOC and heavy metals to examine the element distribution pattern and potential pollutant sources. The sediments in the study area are characterized by variable heavy metal concentrations that are comparable with those of the surrounding regions. Obvious positive correlations were observed amongst the concentrations of Zn, Cr, Pb, Cd, Cu and the clay contents, suggesting that fine clay particles are important carriers of trace metals in the sediments. Hg and As show a considerable/low positive correlation with TOC, indicating that organic matter may play a discernible role in the sediment chemistry. Cd contamination was detected in the north of the study area primarily due to the input of phosphate fertilizers carried by rivers. In comparison, Zn, Cr, Pb, and partly Cu are predominantly sourced from lithogenic components, and Hg and As are mainly from organic matter related to anthropogenic input.
Mostrar más [+] Menos [-]Characterization of epibenthic and demersal megafauna at Mississippi Canyon 252 shortly after the Deepwater Horizon Oil Spill Texto completo
2013
Valentine, Marla M. | Benfield, Mark C.
The Deepwater Horizon Oil Spill resulted in the release of a large quantity of oil and gas into the northern Gulf of Mexico from a bathypelagic source. Due to a lack of pre-spill quantitative data the baseline condition of the communities near the spill site is unknown. This makes it difficult to determine the impact of the spill on deepwater megafauna. Remotely operated vehicles were used to quantify megafauna at five study sites during August and September 2010:2000m north, west, south, and east, and 500m north of the Macondo well. Comparisons of animal abundances indicated that 2000m-N and 2000m-W had the greatest taxonomic richness and highest abundances while 2000m-E had slightly lower values. In contrast 500m-N and 2000m-S had the lowest taxonomic richness and abundances. Our study also suggests that certain taxa were potentially more resistant or sensitive to the spill.
Mostrar más [+] Menos [-]Heavy metals distribution and contamination in surface sediments of the coastal Shandong Peninsula (Yellow Sea) Texto completo
2013
Li, Guogang | Hu, Bangqi | Bi, Jianqiang | Leng, Qinuan | Xiao, Chunqiao | Yang, Zhongcheng
Selected heavy metals (Cr, Cu, Ni, Pb and Zn) in surface sediments from the coastal Shandong Peninsula (Yellow Sea) have been determined to evaluate the spatial distribution and potential ecological risk. Results showed that heavy metal concentrations in the sediments generally met the criteria of China Marine Sediment Quality. However, both the enrichment factor (EF) and geoaccumulation index (Igeo) values suggested the elevation of Pb concentration in the region. Based on the effect-range classification (TEL-PEL SQGs), Cr, Cu and Ni were likely to pose environment risks. Spatial distribution of ecotoxicological index (mean-PEL-quotient) suggested that most of the surface sediments have a 21% probability of being toxic. Similar results were also obtained by pollution load index (PLI). The spatial distribution pattern of heavy metal in surface sediments is a basis for undertaking appropriate action to protect marine sediment quality.
Mostrar más [+] Menos [-]Measuring the effects of stormwater mitigation on beach attendance Texto completo
2013
Atiyah, Perla | Pendleton, Linwood | Vaughn, Ryan | Lessem, Neil
Many studies have used valuation techniques to predict the potential effect of environmental improvements on human use of coastal areas, but there is a lack of post hoc empirical evidence that these policies indeed affect the way people use coastal areas. A panel data approach is developed to statistically determine how storm drain diversions affected attendance at 26 beaches in Southern California. This study uses a 10-year time series of data to conduct a statistical analysis of attendance at beaches with and without diversions and before and after the diversions were installed, while controlling for all observable, confounding factors. Results indicate that beach attendance increased at beaches with diversions compared to those that did not have diversions (between 350,000 and 860,000 visits annually at a 95% confidence interval). Establishing this link between mitigation policies and human use patterns can lead to better management of coastal areas.
Mostrar más [+] Menos [-]Sources and transport of As, Cu, Cd and Pb in the environmental compartments of Deception Island, Antarctica Texto completo
2013
Mão de Ferro, André | Mota, Ana Maria | Canário, João
Sources and transport processes of As, Cu, Cd and Pb were studied in different environmental compartments of Deception Island, an active volcano in the South Shetland Islands, Antarctica. Element concentrations in fresh water samples are consistent with the lowest values reported elsewhere in Antarctica. Interestingly, higher concentration values of As were found in samples collected in or near spring water courses and its transport may be related with processes of lixiviation in underground waters. While in saline waters Cu and Pb had important punctual sources, concentration values for Cd were consistently high pointing to the existence of a natural and diffuse source possibly related with the hydrothermal activity. The high Si/Al ratio, low carbon content, and a non-significant anthropogenic heavy metal input may explain the surprisingly homogeneous heavy metal content found in sediment samples.
Mostrar más [+] Menos [-]