خيارات البحث
النتائج 621 - 630 من 2,459
Estuarine macrofauna responses to continuous in situ nutrient addition on a tropical mudflat
2014
Botter-Carvalho, Mônica L. | Carvalho, Paulo V.V.C. | Valença, Ana Paula M.C. | Santos, Paulo J.P.
A field experiment to assess the effects of continuous nutrient addition on the macrobenthic community was carried out on an estuarine mudflat on the northeast coast of Brazil. The experiment began on 5 October 2005 and ended on 8 February 2006. Macrofauna was compared at approximately four-week intervals in triplicate plots with three levels (Control – C, Low Dose – LD and High Dose – HD) of weekly fertilizer additions for 17weeks. Inorganic fertilizer (N–P–K) was applied on nine randomly defined quadrangular plots (4m2 each). All measurements were calculated from species abundances. Multivariate analyses as well as the univariate indices (richness, abundance and Shannon–Wiener index) showed statistically significant differences between the enriched and control areas during the period of the experiment. The expected gradual response based on the succession model of Pearson and Rosenberg was not observed. The nutrient doses used were high enough to cause severe decreases in abundance, richness and evenness, and an increase in dominance.
اظهر المزيد [+] اقل [-]Effect of coastal urbanization on sandy beach coleoptera Phaleria maculata (Kulzer, 1959) in northern Chile
2014
González, Sergio A. | Yáñez-Navea, Katherine | Munoz, Mauricio
The beetle Phaleria maculata is a common inhabitant of the upper intertidal fringe of Chilean beaches. Anthropogenic intervention in coastal areas has increased intensely, leading to changes in the flora and fauna of sandy beaches. To examine the impact of human activities on P. maculata, we studied several beaches along the northern Chilean coast. Beaches were characterized based on morphodynamics and the level of intervention, leading to the estimation of an “Urbanization Index” based on various indicators. The analysis showed a significant inverse correlation between the rate of urbanization and night sky quality. Larval and adult beetles were almost absent on beaches with high levels of urbanization. The results of simple and multiple correlations based on nMDS ordination showed an inverse relationship between increases in urbanization and the abundance of beetles. Because darkling beetles are very sensitive to human interventions on sandy beaches, we suggest that they are ideal indicator organisms for the health of these environments.
اظهر المزيد [+] اقل [-]Informing policy to protect coastal coral reefs: Insight from a global review of reducing agricultural pollution to coastal ecosystems
2014
Kroon, F. J. (Frederieke J.) | Schaffelke, Britta | Bartley, Rebecca
The continuing degradation of coral reefs has serious consequences for the provision of ecosystem goods and services to local and regional communities. While climate change is considered the most serious risk to coral reefs, agricultural pollution threatens approximately 25% of the total global reef area with further increases in sediment and nutrient fluxes projected over the next 50years. Here, we aim to inform coral reef management using insights learned from management examples that were successful in reducing agricultural pollution to coastal ecosystems. We identify multiple examples reporting reduced fluxes of sediment and nutrients at end-of-river, and associated declines in nutrient concentrations and algal biomass in receiving coastal waters. Based on the insights obtained, we recommend that future protection of coral reef ecosystems demands policy focused on desired ecosystem outcomes, targeted regulatory approaches, up-scaling of watershed management, and long-term maintenance of scientifically robust monitoring programs linked with adaptive management.
اظهر المزيد [+] اقل [-]Spatial budgetary evaluation of organochlorine contaminants in the sediments of Cochin Estuary, India
2014
Akhil, P.S. | Sujatha, C.H.
This paper presents the first detailed investigation on the residual levels of organochlorine insecticide (OCI) concentrations in the Cochin estuarine sediment. It aims in elucidate their distribution and ecological impact on the aquatic system. Concentrations of persistent organochlorine compound (OC) were determined for 17 surface sediment samples which were collected from specific sites of Cochin Estuarine System (CES) over a period of November 2009 and November 2011. The contaminant levels in the CES were compared with other worldwide ecosystems. The sites bearing high concentration of organochlorine compounds are well associated with the complexities and low energy environment. Evaluation of ecotoxicological factors suggests that adverse biological effects are expected in certain areas of CES.
اظهر المزيد [+] اقل [-]Physiological energetics of the fourth instar of Chinese horseshoe crabs (Tachypleus tridentatus) in response to hypoxic stress and re-oxygenation
2014
Shin, Paul K.S. | Chan, Cathy S.K. | Cheung, S.G.
Hypoxia associated with eutrophication is a potential threat to the Chinese horseshoe crab Tachypleus tridentatus which inhabits intertidal sand flats in Asia. This study investigated the effect of dissolved oxygen level (DO) (6, 4 and 2mg O2 l−1) on the physiological energetics in the juvenile T. tridentatus. They were exposed to various oxygen levels for three days and then transferred to normoxia for three days to examine the recovery from low oxygen stress. Feeding rate, respiration rate and scope for growth were reduced at lower DO levels while absorption efficiency and excretion rate were independent of DO levels. Although full recovery of the physiological responses and scope for growth from hypoxis stress was observed when normoxia resumed, their long term survival in suboptimal habitats with frequent occurrence of hypoxia deserves a close monitoring as hypoxia may be even more common in future in a warming world.
اظهر المزيد [+] اقل [-]Assessment of heavy metals/metalloid (As, Pb, Cd, Ni, Zn, Cr, Cu, Mn) concentrations in edible fish species tissue in the Pearl River Delta (PRD), China
2014
Leung, H.M. | Leung, A.O.W. | Wang, H.S. | Ma, K.K. | Liang, Y. | Ho, K.C. | Cheung, K.C. | Tohidi, F. | Yung, K.K.L.
The major aim of this study was to investigate heavy metal content of edible fish in the PRD. Eleven species of fish (consisting of 711 individuals) [catfish (Clarias fuscus), tilapia (Oreochromis mossambicus), grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mandarin fish (Siniperca kneri), snakehead (Channa asiatiea), black bass (Micropterus salmoides), mangrove snapper (Lutjanus griseus), star snapper (Lutjanu stellatus), snubnose pompano (Trachinotus blochii) and orange-spotted grouper (Epinephelus coioides)] were collected for the analyses of heavy metals. Overall concentrations (mg/kg, ww) in the fish muscles were: As (0.03–1.53), Pb (0.03–8.62), Cd (0.02–0.06), Ni (0.44–9.75), Zn (15.7–29.5), Cr (0.22–0.65), Cu (0.79–2.26), Mn (0.82–6.91). Significant level of Pb were found in tilapia at all locations. It is recommended that heavy metal concentrations in different fish species must be determined on a regular basis in the future so as to reduce human health risks from acute and chronic food intoxication.
اظهر المزيد [+] اقل [-]Baseline concentrations of faecal sterols and assessment of sewage input into different inlets of Admiralty Bay, King George Island, Antarctica
2014
Martins, César C. | Aguiar, Sabrina N. | Wisnieski, Edna | Ceschim, Liziane M.M. | Figueira, Rubens C.L. | Montone, Rosalinda C.
The Antarctic region is one of the best preserved environments in the world. However, human activities such as the input of sewage result in the alteration of this pristine site. We report baseline values of faecal sterols in Admiralty Bay, Antarctica. Four sediment cores were collected during the 2006/2007 austral summer at the Ezcurra (THP and BAR), Mackelar (REF) and Martel (BTP) inlets. Concentrations of faecal sterols (coprostanol+epicoprostanol) were <0.16μgg−1, suggesting no sewage contamination and probable “biogenic” contributions for these compounds. Baseline values, calculated using the mean concentration of faecal sterols in core layers for THP, BAR, REF and BTP, were 0.04±0.02, 0.03±0.01, 0.07±0.01 and 0.04±0.02μgg−1, respectively. These results established as natural contributions of faecal sterols, suggesting that these markers can be useful indicators of human-derived faecal input and contributing to monitoring programs to prevent anthropogenic impacts.
اظهر المزيد [+] اقل [-]Organochlorine pesticide content and distribution in coastal seafoods in Zhoushan, Zhejiang Province
2014
Wang, Jie-yu | Yu, Xin-wei | Fang, Li
Thirteen types of seafoods were collected from four counties (districts) of Zhoushan, Zhejiang Province, China and analyzed for organochlorine pesticides (OCPs). The average concentrations of OCPs in seafoods ranged from 258.3ngg−1 (lw) to 3459.6ngg−1 (lw). Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the most abundant compounds in these environments and in total accounted for 8.2–62.2% and 32.1–89.0% of the total OCPs in seafoods, respectively. The total OCP contents were higher in seafoods from Shengsi and Putuo and lower in those from Dinghai and Daishan. The ratios of (DDE+DDD)/DDTs reflected a mixed input of accumulated and fresh DDTs in Shengsi, Putuo. The ratios of o,p′-DDT/p,p′-DDT in seafoods of Shengsi ranged 0.10–0.60 (mean 0.33), indicating that DDTs in seafoods of Shengsi may partly contain dicofol products and other pollutants accumulated in Yangtze Estuary. DDTs are a greater concern for ecotoxicological risk in the study area.
اظهر المزيد [+] اقل [-]Widespread distribution of microplastics in subsurface seawater in the NE Pacific Ocean
2014
Desforges, Jean-Pierre W. | Galbraith, Moira | Dangerfield, Neil | Ross, Peter S.
We document the abundance, composition and distribution of microplastics in sub-surface seawaters of the northeastern Pacific Ocean and coastal British Columbia. Samples were acid-digested and plastics were characterized using light microscopy by type (fibres or fragments) and size (<100, 100–500, 500–100 and >1000μm). Microplastics concentrations ranged from 8 to 9200particles/m3; lowest concentrations were in offshore Pacific waters, and increased 6, 12 and 27-fold in west coast Vancouver Island, Strait of Georgia, and Queen Charlotte Sound, respectively. Fibres accounted for ∼75% of particles on average, although nearshore samples had more fibre content than offshore (p<0.05). While elevated microplastic concentrations near urban areas are consistent with land-based sources, the high levels in Queen Charlotte Sound appeared to be the result of oceanographic conditions that trap and concentrate debris. This assessment of microplastics in the NE Pacific is of interest in light of the on-coming debris from the 2011 Tohoku Tsunami.
اظهر المزيد [+] اقل [-]The PAH level, distribution and composition in surface sediments from a Mediterranean Lagoon: The Marano and Grado Lagoon (Northern Adriatic Sea, Italy)
2014
Acquavita, Alessandro | Falomo, Jari | Predonzani, Sergio | Tamberlich, Francesco | Bettoso, Nicola | Mattassi, Giorgio
The Marano and Grado Lagoon is one of the best conserved transitional environment in the whole Mediterranean area. On the other hand, it suffers from industrial, agricultural and fisheries activities, which could have an important impact on its environmental quality. With the application of the WFD, the sediment chemical status was investigated. In this work, 16 polycyclic aromatic hydrocarbons included by the US EPA within the priority pollutants were considered. PAHs values ranged from non-detectable to 1056ngg−1 showing the highest contamination close to the Aussa-Corno River mouth, which received the industrial inputs. The contamination level was comparable to that observed in low contaminated sites of the Mediterranean region, and lower than the adjacent Gulf of Trieste. The ratios of selected PAHs congeners pointed out the prevalence of pyrolitic sources. Moreover, the application of the ERL/ERM displayed an environment, which should not have a potential biological impact.
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