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النتائج 791 - 800 من 1,956
Changes in zooplankton communities along a mercury contamination gradient in a coastal lagoon (Ria de Aveiro, Portugal) النص الكامل
2013
Cardoso, Patrícia Gonçalves | Marques, Sónia Cotrim | D’Ambrosio, Mariaelena | Pereira, Eduarda | Duarte, Armando Costa | Azeiteiro, Ulisses | Pardal, Miguel Ângelo
Changes in zooplankton communities along a mercury contamination gradient in a coastal lagoon (Ria de Aveiro, Portugal) النص الكامل
2013
Cardoso, Patrícia Gonçalves | Marques, Sónia Cotrim | D’Ambrosio, Mariaelena | Pereira, Eduarda | Duarte, Armando Costa | Azeiteiro, Ulisses | Pardal, Miguel Ângelo
The main objective of this paper was to evaluate the impact of mercury on the zooplankton communities’ structure and functioning and their bioaccumulation patterns along a contamination gradient in a temperate coastal lagoon. Our results demonstrated that total abundance was not negatively affected by Hg contamination, since the most contaminated areas presented the highest values, being the copepod Acartia tonsa the dominant species, which means that it is a very well adapted and tolerant species to mercury. Nevertheless, negative effects were observed in terms of species diversity, since the most contaminated areas presented the lowest values of species richness, evenness and heterogeneity. Moreover, the spatial mercury gradient was reflected on the bioaccumulation patterns of the zooplankton communities. This reinforces the idea that zooplankton can be considered as an important vehicle of mercury transfer through the food pelagic web since it constitutes a primordial food resource for several commercial fish species.
اظهر المزيد [+] اقل [-]Changes in zooplankton communities along a mercury contamination gradient in a coastal lagoon (Ria de Aveiro, Portugal)
Changes in zooplankton communities along a mercury contamination gradient in a coastal lagoon (Ria de Aveiro, Portugal) النص الكامل
2013 | 1000
Cardoso, Patrícia Gonçalves | Marques, Sónia Cotrim | D'Ambrosio, Mariaelena | Pereira, Eduarda | Duarte, Armando Costa | Azeiteiro, Ulisses Miranda | Pardal, Miguel Ângelo
The main objective of this paper was to evaluate the impact of mercury on the zooplankton communities' structure and functioning and their bioaccumulation patterns along a contamination gradient in a temperate coastal lagoon. Our results demonstrated that total abundance was not negatively affected by Hg contamination, since the most contaminated areas presented the highest values, being the copepod Acartia tonsa the dominant species, which means that it is a very well adapted and tolerant species to mercury. Nevertheless, negative effects were observed in terms of species diversity, since the most contaminated areas presented the lowest values of species richness, evenness and heterogeneity. Moreover, the spatial mercury gradient was reflected on the bioaccumulation patterns of the zooplankton communities. This reinforces the idea that zooplankton can be considered as an important vehicle of mercury transfer through the food pelagic web since it constitutes a primordial food resource for several commercial fish species.
اظهر المزيد [+] اقل [-]Natural antifouling compounds produced by a novel fungus Aureobasidium pullulans HN isolated from marine biofilm النص الكامل
2013
Gao, Min | Su, Rongguo | Wang, Ke | Li, Xuzhao | Lu, Wei
A fungus, Aureobasidium pullulans, was isolated from marine biofilm and identified. A bioassay-guided fractionation procedure was developed to isolate and purify antifouling compounds from A. pullulans HN. The procedure was: fermentation broth—aeration and addition of sodium thiosulfate–graduated pH and liquid–liquid extraction—SPE purification—GC–MS analysis. Firstly, the fermentation broth was tested for its toxicity. Then it was treated with aeration and addition of sodium thiosulfate, and its toxicity was almost not changed. Lastly, antifouling compounds were extracted at different pH, the extract had high toxicity at pH 2 but almost no toxicity at pH 10, which suggested the toxicants should be fatty acids. The EC50 of the extract against Skeletonema costatum was 90.9μgml−1, and its LC50 against Balanus amphitrete larvae was 22.2μgml−1. After purified by HLB SPE column, the EC50 of the extract against S. costatum was 49.4μgml−1. The myristic and palmitic acids were found as the main toxicants by GC–MS.
اظهر المزيد [+] اقل [-]The growth of coral reef science in the Gulf: A historical perspective النص الكامل
2013
Burt, John A.
Coral reef science has grown exponentially in recent decades in the Gulf. Analysis of literature from 1950 to 2012 identified 270 publications on coral reefs in the Gulf, half of which were published in just the past decade. This paper summarizes the growth and evolution of coral reef science in the Gulf by examining when, where and how research has been conducted on Gulf reefs, who conducted that research, and what themes and taxa have dominated scientific interest. The results demonstrate that there has been significant growth in our understanding of the valuable coral reefs of the Gulf, but also highlight the fact that we are documenting an increasingly degraded ecosystem. Reef scientists must make a concerted effort to improve dialogue with regional reef management and decision-makers if we are to stem the tide of decline in coral reefs in the Gulf.
اظهر المزيد [+] اقل [-]Distribution of local 137Cs anomalies on the seafloor near the Fukushima Dai-ichi Nuclear Power Plant النص الكامل
2013
Thornton, B. (Blair) | Ohnishi, Seiki | Ura, Tamaki | Odano, Naoteru | Sasaki, Shun | Fujita, Tsuneo | Watanabe, Tomowo | Nakata, Kaoru | Ono, Tsuneo | Ambe, Daisuke
An estimated 3.5±0.7×1015Bq of 137Cs is thought to have been discharged into the ocean following the melt down at Fukushima Dai-ichi Nuclear Power Plant (F1NPP). While efforts have been made to monitor seafloor radiation levels, the sampling techniques used cannot capture the continuous distribution of radionuclides. In this work, we apply in situ measurement techniques using a towed gamma ray spectrometer to map the continuous distribution of 137Cs on the seafloor within 20km of the F1NPP. The results reveal the existence of local 137Cs anomalies, with levels of 137Cs an order of magnitude higher than the surrounding seafloors. The sizes of the anomalies mapped in this work range from a few meters to a few hundreds of meters in length, and it is demonstrated that the distribution of these anomalies is strongly influenced by meter scale features of the terrain.
اظهر المزيد [+] اقل [-]The effects of wastewater effluent and river discharge on benthic heterotrophic production, organic biomass and respiration in marine coastal sediments النص الكامل
2013
Burd, B. | MacDonald, T. | Bertold, S.
We examine effects of high river particulate flux and municipal wastewater effluent on heterotrophic organic carbon cycling in coastal subtidal sediments. Heterotrophic production was a predictable (r2=0.95) proportion (56%) of oxidized OC flux and strongly correlated with organic/inorganic flux. Consistent growth efficiencies (36%) occurred at all stations. Organic biomass was correlated with total, OC and buried OC fluxes, but not oxidized OC flux. Near the river, production was modest and biomass high, resulting in low P/B. Outfall deposition resulted in depleted biomass and high bacterial production, resulting in the highest P/B. These patterns explain why this region is production “saturated”. The δ15N in outfall effluent, sediments and dominant taxa provided insight into where, and which types of organisms feed directly on fresh outfall particulates, on older, refractory material buried in sediments, or utilize chemosynthetic symbiotic bacteria. Results are discussed in the context of declining bottom oxygen conditions along the coast.
اظهر المزيد [+] اقل [-]Factors driving the seasonal distribution of planktonic and epiphytic ciliates in a eutrophicated Mediterranean Lagoon النص الكامل
2013
Dhib, Amel | Brahim, Mounir Ben | Ziadi, Boutheina | Akrout, Fourat | Turki, Souad | Aleya, Lotfi
We studied the distribution of planktonic and epiphytic ciliates coupled with environmental factors and microalgae abundance at five stations in Ghar El Melh Lagoon (Tunisia). Planktonic ciliates were monitored for a year and epiphytic ciliates were sampled during summer 2011 in concordance with the proliferation of the seagrass Ruppia cirrhosa. Ciliate assemblage was largely dominated by Spirotrichea followed respectively by Tintinnida of and Strombidiida. No significant difference was found in the distribution of ciliate species among the stations. Redundancy analysis indicates that abiotic factors (temperature and nutriments) have a significant effect on the dynamics of certain ciliates. For epiphytic ciliates, 4 species were identified: Tintinnopsis campanula, Aspidisca sp., Strombidium acutum and Amphorides amphora. Based on PERMANOVA analyses, ciliates exhibit significant correlations among months and stations. According to ACP, epiphyte distribution follows roughly those of R. cirrhosa and pH. Significant correlations were found between harmful dinoflagellates and both planktonic and epiphytic ciliates.
اظهر المزيد [+] اقل [-]Selected trace metals (As, Cd and Hg) distribution and contamination in the coastal wetland sediment of the northern Beibu Gulf, South China Sea النص الكامل
2013
Gan, Huayang | Lin, Jinqin | Liang, Kai | Xia, Zhen
Contamination with As, Cd and Hg, their spatial and temporal distribution are reported from the coastal wetland sediments of the northern Beibu Gulf, South China Sea. The content of As, Cd, Hg and TOC in surface sediments is 8.1±5.8μgg−1, 0.08±0.14μgg−1, 0.034±0.028μgg−1 and 0.45±0.39%, respectively. The mean sedimentation rates are 0.93–1.37cmyear−1 during 1920s to 2008 determined by 210Pb and 137Cs dating in three cores. The vertical profiles of As, Cd and Hg content in the cores retrieved from Qin and Nanliu River estuaries show increasing trends during 1985–2008 due to anthropogenic impact caused by local economic development. Locally the surface sediments have potential ecological risk of As to benthos according to the NOAA sediment quality guidelines.
اظهر المزيد [+] اقل [-]Anthropogenic marine debris in the coastal environment: A multi-year comparison between coastal waters and local shores النص الكامل
2013
Anthropogenic marine debris (AMD) is frequently studied on sandy beaches and occasionally in coastal waters, but links between these two environments have rarely been studied. High densities of AMD were found in coastal waters and on local shores of a large bay system in northern-central Chile. No seasonal pattern in AMD densities was found, but there was a trend of increasing densities over the entire study period. While plastics and Styrofoam were the most common types of AMD both on shores and in coastal waters, AMD composition differed slightly between the two environments. The results suggest that AMD from coastal waters are deposited on local shores, which over time accumulate all types of AMD. The types and the very low percentages of AMD with epibionts point to mostly local sources. Based on these results, it can be concluded that a reduction of AMD will require local solutions.
اظهر المزيد [+] اقل [-]Twenty years later – Atrazine concentrations in selected coastal waters of the Mediterranean and the Baltic Sea النص الكامل
2013
Despite its EU-wide ban in 2004 the triazine herbicide atrazine (ATR) and its transformation products (TPs) are frequently detected in the aqueous environment. In this study, concentrations of ATR, two of its TPs, and terbuthylazine (TERB) are presented and discussed in coastal waters of the Northern Aegean Sea, the Dardanelles, the Baltic Sea (Germany), the Northern Adriatic Sea (Italy), and the coastline close to Barcelona (Spain). The water samples (n=132) were taken in 2009–2011. Sediment samples (n=7) were taken from Baltic Sea (Germany) and Thermaikos Gulf (Greece). Maximum ATR concentrations (31–41ngL−1) were detected in Istanbul and the Dardanelles. A concentration gradient from East to West in the Aegean Sea was observed, indicating ongoing ATR contamination via the Dardanelles. Low concentrations and detection frequencies were observed at the other locations, indicating the success of the prohibition. However, the presence of TERB in the Northern Adriatic Sea raises concern.
اظهر المزيد [+] اقل [-]Bacteria associated with sabellids (Polychaeta: Annelida) as a novel source of surface active compounds النص الكامل
2013
(Emilio),
A total of 69 bacteria were isolated from crude oil enrichments of the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum, and screened for biosurfactant (BS) production by conventional methods. Potential BS-producers (30 isolates) were primarily selected due to the production of both interesting spots on thin layer chromatography (TLC) plates and highly stable emulsions (E24⩾50%). Only few strains grew on cetyltrimethylammonium bromide and blood agar plates, indicating the probable production of anionic surfactants. The 16S rRNA gene sequencing revealed that selected isolates mainly belonged to the CFB group of Bacteroidetes, followed by Gammaproteobacteria and Alphaproteobacteria.A number of BS-producers belonged to genera (i.e., Cellulophaga, Cobetia, Cohaesibacter, Idiomarina, Pseudovibrio and Thalassospira) that have been never reported as able to produce BSs, even if they have been previously detected in hydrocarbon-enriched samples. Our results suggest that filter-feeding Polychaetes could represent a novel and yet unexplored source of biosurfactant-producing bacteria.
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