Refinar búsqueda
Resultados 731-740 de 1,273
Spatial analysis of the invasion of lionfish in the western Atlantic and Caribbean
2011
Johnston, Matthew W. | Purkis, Samuel J.
Pterois volitans and Pterois miles, two sub-species of lionfish, have become the first non-native, invasive marine fish established along the United States Atlantic coast and Caribbean. The route and timing of the invasion is poorly understood, however historical sightings and captures have been robustly documented since their introduction. Herein we analyze these records based on spatial location, dates of arrival, and prevailing physical factors at the capture sights. Using a cellular automata model, we examine the relationship between depth, salinity, temperature, and current, finding the latter as the most influential parameter for transport of lionfish to new areas. The model output is a synthetic validated reproduction of the lionfish invasion, upon which predictive simulations in other locations can be based. This predictive model is simple, highly adaptable, relies entirely on publicly available data, and is applicable to other species.
Mostrar más [+] Menos [-]Organic and inorganic matter in Louisiana coastal waters: Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi regions
2011
Schaeffer, Blake A. | Conmy, Robyn N. | Aukamp, Jessica | Craven, George | Ferer, Erin J.
Chromophoric dissolved organic matter (CDOM) spectral absorption, dissolved organic carbon (DOC) concentration, and the particulate fraction of inorganic (PIM) and organic matter (POM) were measured in Louisiana coastal waters at Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi River locations, in 2007–2008. The range of CDOM was 0.092m⁻¹ at Barataria in June 2008 to 11.225m⁻¹ at Mississippi in February 2008. An indicator of organic matter quality was predicted by the spectral slope of absorption coefficients from 350 to 412nm which was between 0.0087m⁻¹ at Mississippi in May 2008 and 0.0261m⁻¹ at Barataria in June 2008. CDOM was the dominant component of light attenuation at Terrebonne and Barataria. Detritus and CDOM were the primary components of light attenuation at Vermilion, Atchafalaya, and Mississippi. DOC ranged between 65 and 1235μM. PIM ranged between 1.1 and 426.3mgL⁻¹ and POM was between 0.3 and 49.6mgL⁻¹.
Mostrar más [+] Menos [-]Distribution and source differentiation of PAHs and PCBs among size and density fractions in contaminated harbor sediment particles and their implications in toxicological assessment
2011
Huang, Yun-Jie | Lee, Chon-Lin | Fang, Meng-Der
Sediment samples collected from Kaohsiung Harbor (Taiwan) were analyzed for 15 priority polycyclic aromatic hydrocarbons (PAHs) and 118 individual polychlorinated biphenyl (PCB) congeners in various particle size fractions and two density fractions. The PAHs in the low density fraction were a much more sensitive and effective indicator of the PAH source than those in the sediment as a whole. Hierarchical cluster analysis of PAH analytes in the low density sediments revealed significant differences in compositional patterns between locations and among size fractions. In the sediment samples from both study sites, the low density fraction particles had up to 155 and 150 times higher concentrations of PAHs and PCBs, respectively, than those in the corresponding high density fractions. In addition, the total toxic benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzodioxin (TCDD, dioxin) equivalents in the sediment low density fractions were much higher (up to 170 and 273 times, respectively) than the corresponding high density fractions.
Mostrar más [+] Menos [-]The nature of scour development and scour protection at offshore windfarm foundations
2011
Whitehouse, Richard J.S. | Harris, John M. | Sutherland, James | Rees, Jon
Analysis and interpretation of monitoring data for the seabed bathymetry local to offshore windfarm foundations has shown how the scour develops in time and highlighted variations between sites with different seabed sediment characteristics, i.e. sands and clays. Results from European offshore windfarms have generated a unique dataset for comparison with previously published data. Where surficial sediment is underlain by a marine clay the scour (to date) has been limited, whilst those with unconstrained depths of sandy sediments show scour as deep as 1.38 times the monopile diameter. Scour protection has been installed at some sites for structural stability of the foundation or for cable protection. The flow interaction with the protection causes edge scour or secondary scour in the seabed around the protection. In some cases this scour is deeper than the unprotected case. The analysis has resulted in an improved evidence base for scour in the marine environment.
Mostrar más [+] Menos [-]Benthic foraminifera distribution in a tourist lagoon in Rio de Janeiro, Brazil: A response to anthropogenic impacts
2011
Vilela, Claudia Gutterres | Batista, Daniele Silva | Baptista Neto, José Antonio | Ghiselli, Renato Olindo, Jr
Rodrigo de Freitas Lagoon, located in the Rio de Janeiro City, receives several types of polluted discharges. The knowledge of the sediment microfauna correlated with heavy metal and organic matter concentrations could supply important data about the conditions of the lagoon. The benthic foraminiferal assemblage presented larger diversity and more abundant samples in the lagoon entrance than in the inner area. The Ammonia tepida – Elphidiumexcavatum foraminiferal assemblage is characterized by dwarf, corroded and weak organisms. Agglutinated species were found only near the entrance. Low abundance values and sterility of five samples in the inner area (north/northeast) can be caused by high levels of heavy metals and organic matter. A. tepida shows negative correlation with increasing heavy metals values. PAHs and coprostanol high indexes, and the absence or low presence of microfauna in samples around the lagoon margin confirm illegal flows from gas stations and domestic sewage.
Mostrar más [+] Menos [-]Bearing the burden of boat harbours: Heavy contaminant and fouling loads in a native habitat-forming alga
2011
Johnston, E.L. | Marzinelli, E.M. | Wood, C.A. | Speranza, D. | Bishop, J.D.D.
Boat harbours are an increasingly common form of artificial habitat. This paper presents a comparative study of contaminants and foulers of a habitat-forming native kelp (Saccharina latissima) in four marinas and four reference locations along the south-west coast of the UK. Fouling of algal laminae was light (<2% cover) in reference locations, while epibiota cover ranged from 25% to 80% of laminae in marinas. Metals associated with antifouling paints were up to six times more concentrated in algal tissues from marinas than from the reference locations. Marinas also carried the greatest cover and diversity of non-indigenous epibiota on the kelp laminae. This indicates not only a potential stress to kelps in these environments, but also the possibility that detached laminae will act as vectors for the dispersal of non-indigenous species. The development of boat harbours creates habitats that are high risk source localities for pollution-tolerant fouling organisms.
Mostrar más [+] Menos [-]Spatial modeling of environmental vulnerability of marine finfish aquaculture using GIS-based neuro-fuzzy techniques
2011
Navas, Juan Moreno | Telfer, Trevor C. | Ross, Lindsay G.
Combining GIS with neuro-fuzzy modeling has the advantage that expert scientific knowledge in coastal aquaculture activities can be incorporated into a geospatial model to classify areas particularly vulnerable to pollutants. Data on the physical environment and its suitability for aquaculture in an Irish fjard, which is host to a number of different aquaculture activities, were derived from a three-dimensional hydrodynamic and GIS models. Subsequent incorporation into environmental vulnerability models, based on neuro-fuzzy techniques, highlighted localities particularly vulnerable to aquaculture development. The models produced an overall classification accuracy of 85.71%, with a Kappa coefficient of agreement of 81%, and were sensitive to different input parameters. A statistical comparison between vulnerability scores and nitrogen concentrations in sediment associated with salmon cages showed good correlation. Neuro-fuzzy techniques within GIS modeling classify vulnerability of coastal regions appropriately and have a role in policy decisions for aquaculture site selection.
Mostrar más [+] Menos [-]Fast and easy method for seagrass monitoring: Application of acoustic telemetry to precision mapping of Posidonia oceanica beds
2011
Descamp, Pierre | Holon, Florian | Ballesta, Laurent | Guilbert, Antonin | Guillot, Marie | Boissery, Pierre | Raimondino, Valérie | Deter, Julie
Posidonia oceanica is an endemic seagrass from the Mediterranean Sea. It is an indicator of water quality and of the ecological state of coastal ecosystems. The aim of this paper is to test acoustic telemetry for monitoring the position of P. oceanica meadow limits with varied types. After evaluating the accuracy of the system, we present results from a spatiotemporal survey of P. oceanica meadows on nine sites located on the French coast. The method has been demonstrated to be highly efficient for high precision underwater mapping regardless of meadow type, with 1cm accuracy for a distance of 40m between the base and the pointer. A temporal survey led at Cerbere–Banyuls shows a weak global progression of 4m² (progression of 26m² - regression of 22m²) between 2006 and 2010. Finally, we discuss the cost and efficiency of this method, and wether it should be generalized for further studies.
Mostrar más [+] Menos [-]Assessment of heavy metal contamination and mineral magnetic characterization of the Asopos River sediments (Central Greece)
2011
Botsou, F. | Karageorgis, A.P. | Dassenakis, E. | Scoullos, M.
The content and distribution of heavy metals in sediments of the intermittent and contaminated Asopos River, located in Central Greece, was assessed by means of total dissolution, dilute acid and sequential extraction procedures. Mineral magnetic properties were used as proxy parameters of transport mechanisms of land-derived material to the sea. The combination of enrichment factors estimated against local background levels and the levels of labile metals revealed that surface sediments are enriched in Cu, Cd, Ni and Cr. The low flow of the system allows particles and organic matter to accumulate in the estuarine shallow “pools” where they undertake a series of redox reactions, authigenic formation, etc. The most fine of these particles, which are metal rich, are transported to relatively long distances off the Asopos River mouth, even under low energy conditions, converting the system to a secondary source of pollution for the adjacent marine environment.
Mostrar más [+] Menos [-]Establishment of numerical beach-litter hindcast/forecast models: An application to Goto Islands, Japan
2011
Kako, Shin’ichiro | Isobe, Atsuhiko | Magome, Shinya | Hinata, Hirofumi | Seino, Satoquo | Kojima, Azusa
This study attempts to establish a system for hindcasting/forecasting the quantity of litter reaching a beach using an ocean circulation model, a two-way particle tracking model (PTM) to find litter sources, and an inverse method to compute litter outflows at each source. Twelve actual beach survey results, and satellite and forecasted wind data were also used. The quantity of beach litter was hindcasted/forecasted using a forward in-time PTM with the surface currents computed in the ocean circulation model driven by satellite-derived/forecasted wind data. Outflows obtained using the inverse method was given for each source in the model. The time series of the hindcasted/forecasted quantity of beach litter were found consistent with the quantity of beach litter determined from sequential webcam images of the actual beach. The accuracy of the model, however, is reduced drastically by intense winds such as typhoons which disturb drifting litter motion.
Mostrar más [+] Menos [-]