خيارات البحث
النتائج 451 - 460 من 1,539
Analysis of Pacific oyster larval proteome and its response to high-CO₂
2012
Dineshram, R. | Wong, Kelvin K.W. | Xiao, Shu | Yu, Ziniu | Qian, Pei Yuan | Thiyagarajan, Vengatesen
Most calcifying organisms show depressed metabolic, growth and calcification rates as symptoms to high-CO₂ due to ocean acidification (OA) process. Analysis of the global expression pattern of proteins (proteome analysis) represents a powerful tool to examine these physiological symptoms at molecular level, but its applications are inadequate. To address this knowledge gap, 2-DE coupled with mass spectrophotometer was used to compare the global protein expression pattern of oyster larvae exposed to ambient and to high-CO₂. Exposure to OA resulted in marked reduction of global protein expression with a decrease or loss of 71 proteins (18% of the expressed proteins in control), indicating a wide-spread depression of metabolic genes expression in larvae reared under OA. This is, to our knowledge, the first proteome analysis that provides insights into the link between physiological suppression and protein down-regulation under OA in oyster larvae.
اظهر المزيد [+] اقل [-]GhostNet marine debris survey in the Gulf of Alaska – Satellite guidance and aircraft observations
2012
Pichel, William G. | Veenstra, Timothy S. | Churnside, James H. | Arabini, Elena | Friedman, Karen S. | Foley, David G. | Brainard, Russell E. | Kiefer, Dale | Ogle, Simeon | Clemente-Colon, Pablo | Li, Xiaofeng
Marine debris, particularly debris that is composed of lost or abandoned fishing gear, is recognized as a serious threat to marine life, vessels, and coral reefs. The goal of the GhostNet project is the detection of derelict nets at sea through the use of weather and ocean models, drifting buoys and satellite imagery to locate convergent areas where nets are likely to collect, followed by airborne surveys with trained observers and remote sensing instruments to spot individual derelict nets. These components of GhostNet were first tested together in the field during a 14-day marine debris survey of the Gulf of Alaska in July and August 2003. Model, buoy, and satellite data were used in flight planning. A manned aircraft survey with visible and IR cameras and a LIDAR instrument located debris in the targeted locations, including 102 individual pieces of debris of anthropogenic or terrestrial origin.
اظهر المزيد [+] اقل [-]Quantifying potential propagule pressure of aquatic invasive species from the commercial shipping industry in Canada
2012
Lo, Veronica B. | Levings, Colin D. | Chan, Kai M.A.
We quantify and compare different measures of potential propagule pressure (PPP) of aquatic invasive species (AIS) from commercial vessels in Canada. We used ship arrivals and ballast water discharge volumes as proxies for PPP from ballast water organisms, and wetted surface area (WSA) as a proxy for hull fouling PPP, to determine their relative contributions to total PPP. For three regions studied, PPP proxies correlated significantly across ports and some vessel categories. Relative contributions of ship arrivals, ballast discharge, and WSAs to PPP, evidenced by non-significant correlations across these measures, varied across regions, ports, vessel types, and seasons. Flow-through (dominant on east and west coasts) and empty-refill (in Great Lakes-St. Lawrence region) were the major ballast water exchange methods employed by the vessels surveyed. These methods have different biological efficacy for AIS removal, influencing PPP. Our study illustrates benefits and limitations of using different PPP proxies to estimate invasion risk.
اظهر المزيد [+] اقل [-]Airborne sensors for detecting large marine debris at sea
2012
Veenstra, Timothy S. | Churnside, James H.
The human eye is an excellent, general-purpose airborne sensor for detecting marine debris larger than 10cm on or near the surface of the water. Coupled with the human brain, it can adjust for light conditions and sea-surface roughness, track persistence, differentiate color and texture, detect change in movement, and combine all of the available information to detect and identify marine debris. Matching this performance with computers and sensors is difficult at best. However, there are distinct advantages over the human eye and brain that sensors and computers can offer such as the ability to use finer spectral resolution, to work outside the spectral range of human vision, to control the illumination, to process the information in ways unavailable to the human vision system, to provide a more objective and reproducible result, to operate from unmanned aircraft, and to provide a permanent record that can be used for later analysis.
اظهر المزيد [+] اقل [-]Spatial distribution and temporal trends of persistent organochlorine pollutants in sediments from Lake Maryut, Alexandria, Egypt
2012
Barakat, Assem O. | Mostafa, Alaa | Wade, Terry L. | Sweet, Stephen T. | El Sayed, Nadia B.
Organochlorine compounds (OCs) in surface and core sediments collected from Lake Maryut, Egypt, were examined to elucidate their distribution, ecological risk and historical trend. To our knowledge, this is the first study on residue levels of OCs in sediments from Lake Maryut. Concentrations of PCBs and DDTs were higher than other OCs, ranging from 3.06 to 388 and from 0.07 to 106ng/g dry wt., respectively. The highest concentrations of OCs were found at stations near the discharge point of sewage and close to industrial areas. The distribution of DDT and its metabolites suggest no recent inputs into the lake environment. Contamination levels of sedimentary PCBs and DDTs, can be categorized moderate to high compared to other urbanized regions worldwide. Temporal trends in OCs levels were influenced by input pathways at two sites. Evaluation of ecotoxicological risks suggests that adverse biological effects are expected mainly in the main basin area.
اظهر المزيد [+] اقل [-]Algal δ¹⁵N values detect a wastewater effluent plume in nearshore and offshore surface waters and three-dimensionally model the plume across a coral reef on Maui, Hawai‘i, USA
2012
Dailer, Meghan L. | Ramey, Hailey L. | Saephan, Stephanie | Smith, Celia M.
The coral reef at Kahekili, Maui is located ∼300m south of the Lahaina Wastewater Reclamation Facility which uses four Class V injection wells to dispose of 3–5million gallons of wastewater effluent daily. Prior research documented that the wastewater effluent percolates into the nearshore region of Kahekili. To determine if the wastewater effluent was detectable in the surface waters offshore, we used algal bioassays from the nearshore region to 100m offshore and throughout the water column from the surface to the benthos. These algal bioassays documented that significantly more wastewater effluent was detected in the surface rather than the benthic waters and allowed us to generate a three-dimensional model of the wastewater plume in the Kahekili coastal region. Samples located over freshwater seeps had the highest δ¹⁵N values (∼30–35‰) and the effluent was detected in surface samples 500m south and 100m offshore of the freshwater seeps (∼8–11‰).
اظهر المزيد [+] اقل [-]Plastic pellets as oviposition site and means of dispersal for the ocean-skater insect Halobates
2012
Majer, A.P. | Vedolin, M.C. | Turra, A.
Microplastics are omnipresent in the oceans and generally have negative impacts on the biota. However, flotsam may increase the availability of hard substrates, which are considered a limiting resource for some oceanic species, e.g. as oviposition sites for the ocean insect Halobates. This study describes the use of plastic pellets as an oviposition site for Halobates micans and discusses possible effects on its abundance and dispersion. Inspection of egg masses on stranded particles on beaches revealed that a mean of 24% (from 0% to 62%) of the pellets bore eggs (mean of 5 and max. of 48 eggs per pellet). Most eggs (63%) contained embryos, while 37% were empty egg shells. This shows that even small plastic particles are used as oviposition site by H. micans, and that marine litter may have a positive effect over the abundance and dispersion of this species.
اظهر المزيد [+] اقل [-]Occurrence of DDA in DDT-contaminated sediments of the Southern California Bight
2012
Chen, Zhenshan | Chen, Li | Liu, Yu | Cui, Li | Tang, Chi-Li | Vega, Helen | Krieger, Robert I.
DDT, DDE and some additional lipophilic derivatives are recognized contaminants in sediments of Southern California Bight (SCB). Only about 10% of total DDTs discharged into the SCB are accounted for using available monitoring data (sediment, water, and biota). DDA represented up to 0.03% DDTs (DDT/DDE/DDD) in SCB surface sediments (top 2cm) in amounts up to 76μgDDA/kg dry weight. Highest DDA levels were found where DDT and DDD levels were maximal at the primary wastewater outfall indicating a natural precursor-product relationship for DDT and DDA. Still culture of SCB sediment revealed limited DDA formation following DDT fortification. DDA residues have also been found in contaminated Long Island, NY sediments provided by USGS. The formation of DDA and its potential release from sediments may be significant in resolution of uncertainties concerning the natural recovery of sediments in DDT-contaminated environments.
اظهر المزيد [+] اقل [-]Links between bacterial communities in marine sediments and trace metal geochemistry as measured by in situ DET/DGT approaches
2012
Gillan, David C. | Baeyens, Willy | Bechara, Rafeh | Billon, Gabriel | Denis, Kevin | Grosjean, Philippe | Leermakers, Martine | Lesven, Ludovic | Pede, Annelies | Sabbe, Koen | Gao, Yue
Our current view about the relationship between metals and bacteria in marine sediments might be biased because most studies only use ex situ approaches to quantify metals. The aim of the present research was to compare ex situ and in situ methods of metal measurement (DET and DGT – diffusive equilibration or diffusive gradients in thin-films) and relate the results with two commonly used microbiological variables (bacterial biomass and bacterial diversity as revealed by DGGE). No previous studies have used such in situ approaches in microbial ecology. For biomass and most of the investigated trace metals (Ag, Cd, Sn, Cr, Ni, Cu, Pb, and Al) no significant correlations were found. The exceptions were Fe, Mn, Co, and As which behave like micronutrients. For bacterial diversity, no relevant relationships were found. We conclude that in situ methods are more adapted tools for microbial ecologists but that ex situ approaches are still necessary.
اظهر المزيد [+] اقل [-]Tidal flushing and wind driven circulation of Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia) from in situ observations and numerical modelling
2012
Dumas, F. | Le Gendre, R. | Thomas, Y. | Andréfouët, S.
Hydrodynamic functioning and water circulation of the semi-closed deep lagoon of Ahe atoll (Tuamotu Archipelago, French Polynesia) were investigated using 1year of field data and a 3D hydrodynamical model. Tidal amplitude averaged less than 30cm, but tide generated very strong currents (2ms⁻¹) in the pass, creating a jet-like circulation that partitioned the lagoon into three residual circulation cells. The pass entirely flushed excess water brought by waves-induced radiation stress. Circulation patterns were computed for climatological meteorological conditions and summarized with stream function and flushing time. Lagoon hydrodynamics and general overturning circulation was driven by wind. Renewal time was 250days, whereas the e-flushing time yielded a lagoon-wide 80-days average. Tide-driven flush through the pass and wind-driven overturning circulation designate Ahe as a wind-driven, tidally and weakly wave-flushed deep lagoon. The 3D model allows studying pearl oyster larvae dispersal in both realistic and climatological conditions for aquaculture applications.
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