Refine search
Results 1041-1050 of 3,208
Eutrophication effects on phytoplankton size-fractioned biomass and production at a tropical estuary Full text
2015
Guenther, Mariana | Araújo, Moacyr | Flores-Montes, Manuel | Gonzalez-Rodriguez, Eliane | Neumann-Leitão, Sigrid
Size-fractioned phytoplankton (pico, nano and microplankton) biomass and production were estimated throughout a year at Recife harbor (NE Brazil), a shallow well mixed tropical hypereutrophic estuary with short residence times but restricted water renewal. Intense loads of P-PO4 (maximum 14μM) resulted in low N:P ratios (around 2:1), high phytoplankton biomass (B=7.1–72μgchl-aL−1), production (PP=10–2657μgCL−1h−1) and photosynthetic efficiency (PB=0.5–45μgCμgchl-a−1), but no oxygen depletion (average O2 saturation: 109.6%). Nanoplankton dominated phytoplankton biomass (66%) but micro- and nanoplankton performed equivalent primary production rates (47% each). Production-biomass models indicate an export of the exceeding microplankton biomass during most of the year, possibly through grazing. The intense and constant nutrient and organic matter loading at Recife harbor is thus supporting the high microplankton productivity that is not accumulating on the system nor contributing to oxygen depletion, but supporting the whole system’s trophic web.
Show more [+] Less [-]Porous membranes for ballast water treatment from microalgae-rich seawater Full text
2015
Guilbaud, Julie | Massé, Anthony | Wolff, François-Charles | Jaouen, Pascal
The ballast waters from ships pose a major threat to oceans, notably because of the spread of microorganisms. The present study evaluates the techno-economic feasibility of implementing the membrane process to remove microalgae from seawater to be ballasted in a single step during planktonic bloom. The optimal conditions for the microfiltration of complex and reproducible synthetic seawater are a permeate flux and specific filtered volume of 100L.h−1.m−2 and 75L.m−2.cycle−1, respectively. Recovery of the membrane process represents about 76.6% and 62.7% of the annual cost for a cruise ship (5400 passengers) and liquefied natural gas (LNG) carrier (75,000m3 of liquid natural gas), followed by the membrane replacement cost (13.4% and 21.9%, respectively). The treatment costs are competitive with conventional treatments, even when the membrane process is more feasible for cruise ships due to its smaller capital cost and footprint.
Show more [+] Less [-]The detrimental consequences for seagrass of ineffective marine park management related to boat anchoring Full text
2015
La Manna, G. | Donno, Y. | Sarà, G. | Ceccherelli, G.
Posidonia oceanica (L.) Delile meadows are recognized as priority habitat for conservation by the EU Habitats Directive. The La Maddalena Archipelago National Park (Mediterranean Sea) P. oceanica meadow, the dominant coastal habitat of the area, is mostly threatened by boat anchoring. 12years after the establishment of mooring fields and anchoring restrictions, a study was conducted to measure their effectiveness on the conservation of seagrass and the mitigation of anchoring damage. We found that: (i) the condition of P. oceanica was disturbed, both in the mooring fields and in control locations; (ii) mooring fields and anchoring restrictions did not show to be an efficient system for the protection of seagrass, in fact anchor scars increased after the tourist season; (iii) the mooring systems had an impact on the surrounding area of the meadow, probably due to their misuse. On the basis of these results, management recommendations for marine parks are proposed.
Show more [+] Less [-]Effects of oil dispersant on solubilization, sorption and desorption of polycyclic aromatic hydrocarbons in sediment–seawater systems Full text
2015
Zhao, Xiao | Gong, Yanyan | O’Reilly, S.E. | Zhao, Dongye
This work investigated effects of a prototype oil dispersant on solubilization, sorption and desorption of three model PAHs in sediment–seawater systems. Increasing dispersant dosage linearly enhanced solubility for all PAHs. Conversely, the dispersant enhanced the sediment uptake of the PAHs, and induced significant desorption hysteresis. Such contrasting effects (adsolubilization vs. solubilization) of dispersant were found dependent of the dispersant concentration and PAH hydrophobicity. The dual-mode models adequately simulated the sorption kinetics and isotherms, and quantified dispersant-enhanced PAH uptake. Sorption of naphthalene and 1-methylnaphthalene by sediment positively correlated with uptake of the dispersant, while sorption of pyrene dropped sharply when the dispersant exceeded its critical micelle concentration (CMC). The deepwater conditions diminished the dispersant effects on solubilization, but enhanced uptake of the PAHs, albeit sorption of the dispersant was lowered. The information may aid in understanding roles of dispersants on distribution, fate and transport of petroleum PAHs in marine systems.
Show more [+] Less [-]Ingestion of microplastics by commercial fish off the Portuguese coast Full text
2015
Neves, Diogo | Sobral, Paula | Ferreira, Joana Lia | Pereira, Tânia
The digestive tract contents of 263 individuals from 26 species of commercial fish were examined for microplastics. These were found in 17 species, corresponding to 19.8% of the fish of which 32.7% had ingested more than one microplastic. Of all the fish that ingested microplastics, 63.5% was benthic and 36.5% pelagic species. A total of 73 microplastics were recorded, 48 (65.8%) being fibres and 25 (34.2%) being fragments. Polymers were polypropylene, polyethylene, alkyd resin, rayon, polyester, nylon and acrylic. The mean of ingested microplastics was 0.27±0.63 per fish, (n=263). Pelagic fish ingested more particles and benthic fish ingested more fibres, but no significant differences were found. Fish with the highest number of microplastics were from the mouth of the Tagus river.Scomber japonicus registered the highest mean of ingested microplastics, suggesting its potential as indicator species to monitor and investigate trends in ingested litter, in the MSFD marine regions.
Show more [+] Less [-]Micro–scale simulation of atmospheric emissions from power–plant stacks in the Po Valley Full text
2015
Ghermandi, Grazia | Fabbi, Sara | Zaccanti, Marco | Bigi, Alessandro | Teggi, Sergio
The atmospheric dispersion of the NOX plume that will be emitted from a new power–plant, at present under installation, was simulated at micro–scale with Micro–Swift–Spray (MSS) Model. The plant will be constructed in a residential urban area in the town of Modena (Po Valley, Northern Italy), where low wind speeds and thermal inversions are quite frequent. Simulation results point out a different behavior of urban canopy in influencing the 3D dispersion patterns among urban obstacles, according to atmospheric mixing conditions: in case of moderate wind events, urban canyon phenomena may occur with a consequent increasing of NOX concentration gradients among buildings, while with low winds the near–field influence of the buildings emphasizes pollutant accumulation. The MSS simulated NOX concentrations result always much lower than the regulatory limits for air quality. The comparison of simulation results with measured concentration data for NOX shows the importance of micro–scale dispersion modeling to perform an accurate and reliable assessment of meteorological condition effects on pollutant distribution, and the ability of MSS in providing reliable simulations of atmospheric dispersion.
Show more [+] Less [-]Preliminary assessment of size distribution of airborne metals and metalloids in the urban aerosols of Guiyang, southwest China Full text
2015
Zhang, Guoping | Li, Haixia | Wei, Xiaofei | Fu, Zhiping
Size–fractionated (7 fractions from <0.39 up to ≥10.2μm) airborne particulate matter (PM) was collected from Guiyang, southwest China. The concentrations of Al, Ti, Mn, Fe, Cu, Zn, As, Sr, Mo, Cd, Sb, Ba, and Pb in PM and the water–soluble concentrations of these elements were determined by inductively coupled plasma mass spectrometry. Compared to most other large cities in China, the total suspended particulate (TSP), PM10.2, and PM2.1 concentrations in Guiyang were at relatively low levels (59.1–222, 48.6–192, and 33.2–131μg/m3). This is consistent with the small industrial scale of this city. In the winter, coal combustion was proven to be the dominant source of airborne PM, whereas in other seasons, road dust resuspension was considered the primary source. Al, Ti, Fe, Sr, and Ba were highly associated with soil particles in the road dust. Cu and Zn could be associated with vehicle emissions that accumulated in road dust, while As, Mo, Cd, Sb, and Pb (and another portion of Zn) could be associated with main local industrial emissions. Compared to the coarse PM, the fine PM typically exhibited lower concentrations of crustal elements but higher concentrations of anthropogenic elements. The anthropogenic elements exhibited higher water solubility than crustal elements. Almost all of the elements in the PM in the winter exhibited the highest water solubility because of the lowest pH of the PM in this season.
Show more [+] Less [-]Variations in macrobenthic community structures in relation to environmental variables in the Seto Inland Sea, Japan Full text
2015
Nishijima, Wataru | Umehara, Akira | Okuda, Tetsuji | Nakai, Satoshi
A data set of 425 sites investigated by the Ministry of the Environment in 2001–2005 was used to evaluate the current sediment situation and its effect on macrobenthic community structure in the Seto Inland Sea, Japan. Cluster analysis and principle component analysis of sediments using physico-chemical parameters revealed that total organic carbon, mud, sulfide contents, and oxidation–reduction potential were important parameters influencing macrobenthic population size and biodiversity. A total organic carbon of 1mgg−1 interval was highly negatively correlated with two biodiversity indices in the range of 1–20mgg−1. Overall, 42% of total sites were organically enriched with much lower macrobenthic population sizes and biodiversity, while 26% were characterized by sandy sediment with a high population size and high proportion of Arthropoda. Nemertea sp., Glycera sp., Notomastus sp. and Ophiophragmus japonicus were common macrobenthos, while Theora fragilis and Ptychoderidae were typical macrobenthos in organically enriched sediments.
Show more [+] Less [-]An almost completed pollution-recovery cycle reflected by sediment geochemistry and benthic foraminiferal assemblages in a Swedish–Norwegian Skagerrak fjord Full text
2015
Polovodova Asteman, Irina | Hanslik, Daniela | Nordberg, Kjell
During the 20th century Idefjord was considered one of the most polluted marine areas in Scandinavia. For decades it received high discharges from paper/pulp industry, which made it anoxic and extremely polluted by heavy metals and organic contaminants. Today the fjord is close to fulfil a complete pollution-recovery cycle, which is recorded in its sediment archives. Here we report results from five sediment cores studied for TC, C/N, heavy metals and benthic foraminifera. All of the cores have laminations deposited during 1940–1980s and indicative of long-lasting anoxia; high TC and heavy metal content, poor foraminiferal faunas and lack of macrofauna. The upper part of the cores deposited since 1980s shows a gradual pollutant decrease and partial foraminiferal recovery. The majority of foraminiferal species in Idefjord are agglutinated opportunistic and stress-tolerant taxa, which to some extent tolerate hypoxia and are early colonisers of previously disturbed environments. The current study demonstrates a value of benthic foraminiferal stratigraphy as a useful tool in understanding processes driving environmental degradation and recovery of coastal ecosystems.
Show more [+] Less [-]Screening for microplastic particles in plankton samples: How to integrate marine litter assessment into existing monitoring programs? Full text
2015
Gorokhova, Elena
Microplastics (MPs) are a newly recognized type of environmental pollution in aquatic systems; however no monitoring of these contaminants is conducted, mostly due to the lack of routine quantification. In the net samples collected with a 90-μm WP2 net, pelagic MP abundance was quantified by light microscopy and evaluated as a function of inshore–offshore gradient, depth, and season; the same samples were used for zooplankton analysis. The MP abundance was ∼102–104particlesm−3, with no significant inshore–offshore gradient during summer but increasing offshore in winter. MP abundance in deeper layers was positively affected by zooplankton abundance in the upper layers and significantly lower during winter compared to summer. These findings indicate heterogeneity of MP distribution due to biotic and abiotic factors and suggest that samples collected for other purposes can be used for quantification of MPs in the Baltic Sea, thus facilitating integration of MP assessment into existing monitoring schemes.
Show more [+] Less [-]