خيارات البحث
النتائج 701 - 710 من 1,546
Comparison of granulometric methods and sampling strategies used in marine habitat classification and Ecological Status assessment النص الكامل
2012
Forde, James | Collins, Patrick Colman | Patterson, Adrian | Kennedy, Robert
Sediment particle size analysis (PSA) is routinely used to support benthic macrofaunal community distribution data in habitat mapping and Ecological Status (ES) assessment. No optimal PSA Method to explain variability in multivariate macrofaunal distribution has been identified nor have the effects of changing sampling strategy been examined. Here, we use benthic macrofaunal and PSA grabs from two embayments in the south of Ireland. Four frequently used PSA Methods and two common sampling strategies are applied. A combination of laser particle sizing and wet/dry sieving without peroxide pre-treatment to remove organics was identified as the optimal Method for explaining macrofaunal distributions. ES classifications and EUNIS sediment classification were robust to changes in PSA Method. Fauna and PSA samples returned from the same grab sample significantly decreased macrofaunal variance explained by PSA and caused ES to be classified as lower. Employing the optimal PSA Method and sampling strategy will improve benthic monitoring.
اظهر المزيد [+] اقل [-]Metals in sediments and fish from Sea Lots and Point Lisas Harbors, Trinidad and Tobago النص الكامل
2012
Mohammed, Azad | May, Thomas | Echols, Kathy | Walther, Mike | Manoo, Anton | Maraj, Dexter | Agard, John | Orazio, Carl
Concentrations of heavy metals were determined in nearshore marine sediments and fish tissue from Sea Lots area on the west coast, at Caroni Lagoon National Park, and in the Point Lisas harbor, Trinidad. The most dominant metals found in sediments were Al, Fe and Zn with mean concentrations highest at Sea Lots (Al-39420μg/g; Fe-45640μg/g; Zn-245μg/g), when compared to sediments from Point Lisas (Al-11936μg/g; Fe-30171μg/g; Zn-69μg/g) and Caroni (Al-0400μg/g; Fe-19000μg/g; Zn-32μg/g), High concentration of Cu, Al, Fe and Zn were also detected in fish tissue from Point Lisas and Caroni. Metal concentrations in fish tissue showed significant correlation with sediment metals concentration, which suggests that tissue levels are influenced by sediment concentration. Of the metals, only Zn, Hg and Cu had a bioaccumulation factor (BAF) greater than one, which suggests a high bioaccumulation potential for these metals.
اظهر المزيد [+] اقل [-]The use of dinoflagellate cysts to separate human-induced from natural variability in the trophic state of the Po River discharge plume over the last two centuries النص الكامل
2012
Zonneveld, Karin A.F. | Ma, Yukun | Elshanawany, Rehab | Fischer, Helmut W. | Hoins, Mirja | Ibrahim, Mohammed I. | Pittauerova, Daniela | Versteegh, Gerard J.M.
To obtain insight into the natural and/or human-induced changes in the trophic state of the distal portion of the Po River discharge plume over the last two centuries, high temporal resolution dinoflagellate cyst records were established at three sites. Cyst production rates appear to reflect the natural variability in the river’s discharge, whereas cyst associations reflect the trophic state of the upper waters, which in turn can be related to agricultural development. The increased abundances of Lingulodinium machaerophorum and Stelladinium stellatum found as early as 1890 and 1920 correspond to the beginning of the industrial revolution in Italy and the first chemical production and dispersion of ammonia throughout Europe. After 1955, the increased abundances of these species and of Polykrikos schwartzii, Brigantedinium spp. and Pentapharsodinium dalei correspond to agriculturally induced alterations of the hypertrophic conditions. A slight improvement in water quality can be observed from 1987 onward.
اظهر المزيد [+] اقل [-]A comparison of integrated and discrete depth sampling for monitoring toxic species of Dinophysis النص الكامل
2012
Escalera, Laura | Pazos, Yolanda | Dolores Doval, María | Reguera, Beatriz
Dinophysis acuminata and Dinophysis acuta produce lipophilic toxins that cause most shellfish harvesting closures in the Atlantic coastal waters of Europe. Dinophysis often exhibit patchy distributions and sampling with conventional methods may fail to detect them. A 6-month calibration study in 2006, plus an additional sampling in 2010 were carried out in Galicia to compare Dinophysis counts obtained from weekly high vertical resolution bottle samples with depth-integrated hose samples. Counts with these two methods were comparable at some depth-ranges, but hose maxima were over one order of magnitude lower under thin-layer scenarios. Estimates from hose samplers should be used with caution in programmes using a “Dinophysis index”, either to trigger shellfish sampling or to establish precautionary harvesting closures. In general, hose samplers provide reliable information on the occurrence of Dinophysis except under extreme site-specific hydrodynamic conditions. This study adds new information about the heterogeneous, specific vertical distributions of two Dinophysis spp.
اظهر المزيد [+] اقل [-]Evaluation of the partial renewal of in situ phytoplankton microcosms and application to the impact assessment of bentazon and dimethenamid النص الكامل
2012
de la Broise, Denis | Stachowski-Haberkorn, Sabine
Microcosms, each consisting of 2L natural surface seawater maintained in 2.3-L glass bottles, were immersed at a depth of 6m. The renewal of 10% of microcosm volumes was carried out every other day. Phytoplankton-containing seawater was used for renewal (previously filtered through 25-, 50- or 200-μm cut-off). Phytoplankton community pigment analysis (by HPLC) and flow cytometry analysis were performed. After 13days, data exhibited phytoplankton characteristics in microcosms in the same range as that of the natural surrounding sea water over the same period. Furthermore, in these microcosms, a negative correlation was observed between the filtration cut-off used for renewal water, and the total cell count. Herbicides were tested as commercial mixtures at 1, 10 and 100μgL⁻¹ active substance. Both Frontier® (dimethenamid) and Basamais® (bentazon) induced significant modifications of the phytoplankton populations at every concentration tested. Such results suggest a possible disturbance in polluted coastal areas.
اظهر المزيد [+] اقل [-]Tolerance and accumulation of copper in the salt-marsh shrub Halimione portulacoides النص الكامل
2012
Cambrollé, J. | Mancilla-Leytón, J.M. | Muñoz-Vallés, S. | Luque, T. | Figueroa, M.E.
The present study evaluated the tolerance and accumulation potential in the salt-marsh shrub Halimione portulacoides under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0 to 60mmoll⁻¹) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also determined total copper, nitrogen, phosphorus and sulfur concentrations in the plant tissues. H. portulacoides survived with external Cu concentrations of up to 35mmolCul⁻¹, although the excess of metal resulted in a biomass reduction of 48%. The effects of Cu on growth were linked to a drastic reduction in net photosynthesis. However, H. portulacoides tolerated Cu levels of up to 15mmolCul⁻¹ without suffering adverse physiological effects. Our results indicate that this species could play an important role in the restoration of Cu-contaminated soils.
اظهر المزيد [+] اقل [-]Microbiological and physicochemical analysis of the coastal waters of southern Brazil النص الكامل
2012
Moresco, V. | Viancelli, A. | Nascimento, M.A. | Souza, D.S.M. | Ramos, A.P.D. | Garcia, L.A.T. | Simões, C.M.O. | Barardi, C.R.M.
The aim of this study was to assess the impact of sewage discharge on coastal waters by evaluating the influence of physicochemical parameters on the presence of enteric microorganisms in seawater samples collected from 11 beaches in Florianopolis, Santa Catarina, Brazil, over a one-year period (August 2009 to July 2010). Samples were assessed for the presence of human adenoviruses (HAdV), polyomavirus (JCPyV), hepatitis A virus (HAV), and noroviruses (HuNoV GI and GII). Escherichia coli and physicochemical parameters (salinity, temperature, pH and dissolved oxygen) were also evaluated. From the 132 samples analyzed, 55% were positive for HAdV, 51.5% for HAV, 7.5% for HuNoV GI, 4.5% for HuNoV GII, and 3% for JCPyV. E. coli levels ranged from 8 to 1325CFU/100mL at all sites. The overall results highlight the problem of sewage discharge into coastal waters and confirm that there is no correlation between viral presence and bacterial contamination.
اظهر المزيد [+] اقل [-]Water column characterisation on the Azores platform and at the sea mounts south of the archipelago النص الكامل
2012
Palma, Carla | Lillebø, Ana I. | Borges, Carlos | Souto, Miguel | Pereira, Eduarda | Duarte, Armando C. | Abreu, Manuel Pinto de
This study provides data concerning the hydrography and water chemistry of the Atlantic region between 29–38° N and 27–31° W, and establishes background values for dissolved Cu, Cd, Pb and As. Three water masses were identified: the Eastern North Atlantic Central Water (ENACW), the Mediterranean Water (MW) and the North Atlantic Deep Water (NADW). The ENACW exhibits a clear meridional gradient of temperature and salinity, with comparatively high values at the southern sites and lower values on the Azores platform. The ENACW, which includes the euphotic zone, also had comparatively high concentrations of oxygen and lower concentrations of nutrients and metals. The Cu, Cd and Pb results suggest that new background concentrations for OSPAR Region V (the Wider Atlantic) should be established as follows: 0.15–13nM for Cu, 0.05–1.4nM for Cd and 0.03–5nM for Pb. The background concentrations of As for OSPAR Region V should be 7–28nM.
اظهر المزيد [+] اقل [-]Metazooplankton communities in the Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia): Spatiotemporal variations and trophic relationships النص الكامل
2012
Pagano, Marc | Sagarra, Pascual-Boi | Champalbert, Gisèle | Bouvy, Marc | Dupuy, Christine | Thomas, Yoann | Charpy, Loïc
Metazooplankton abundance, biomass (<80μm, 200–500μm and >500μm) and community structure in the Ahe atoll were studied together with their relationships with environmental factors (temperature, salinity, wind) and trophic factors (phytoplankton, bacteria, heterotrophic nanoflagellates (HNF) and ciliates) during three periods in 2008–2009. Meroplankton, mainly bivalve and gastropod larvae, was dominant. Holoplankton was dominated by copepods, the main species being Oithona spp., Paracalanus parvus, Clausocalanus spp., Corycaeus spp., Acartia fossae and Undinula vulgaris. The results suggest a clear wind influence on the structure and horizontal distribution of the zooplankton communities. The metazooplankton appeared to be controlled mainly by food resources, suggesting a bottom-up control. The low nanophytoplankton biomass in contrast to the high abundance of picophytoplankton, HNF and nano-particle grazers (mainly Oithona spp., Paracalanus and bivalve larvae) highlighted the importance of the microbial loop in the food web.
اظهر المزيد [+] اقل [-]The impact of coastal urbanization on the structure of phytobenthic communities in southern Brazil النص الكامل
2012
Martins, Cintia D.L. | Arantes, Noele | Faveri, Caroline | Batista, Manuela B. | Oliveira, Eurico C. | Pagliosa, Paulo R. | Fonseca, Alessandra L. | Nunes, José Marcos C. | Chow, Fungyi | Pereira, Sonia B. | Horta, Paulo A.
The anthropogenic pressures on coastal areas represent important factors affecting local, regional, and even global patterns of distribution and abundance of benthic organisms. This report undertakes a comparative analysis of the community structure of rocky shore intertidal phytobenthos in both pristine like environments (PLE) and urbanized environments (UBE) in southern Brazil, characterizing variations on different spatial scales. Multivariate analysis of variance indicated that the PLE is characterized by a larger number of taxa and an increased occurrence of Rhodophyta species in relation to UBE. In contrast, UBE were dominated by opportunistic algae, such as Cladophora and Ulva spp. Significance tests further indicated higher species richness and Shannon–Wiener diversity on the PLE in relation to UBE. Here we provide data showing the magnitude of seaweed biodiversity loss and discuss direct and indirect consequences of unplanned urbanization on these communities.
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