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Результаты 731-740 из 1,953
Microscopic observation of symbiotic and aposymbiotic juvenile corals in nutrient-enriched seawater
2013
Tanaka, Yasuaki | Iguchi, Akira | Inoue, Mayuri | Mori, Chiharu | Sakai, Keinan | Suzuki, Atsushi | Kawahata, Hodaka | Nakamura, Takashi
Symbiotic and aposymbiotic juvenile corals, which were grown in the laboratory from the gametes of the scleractinian coral Acropora digitifera and had settled down onto plastic culture plates, were observed with a microscope under different nutrient conditions. The symbiotic corals successfully removed the surrounding benthic microalgae (BMA), whereas the aposymbiotic corals were in close physical contact with BMA. The areal growth rate of the symbiotic corals was significantly higher than that of the aposymbiotic corals. The addition of nutrients to the culture seawater increased the chlorophyll a content in the symbiotic coral polyps and enhanced the growth of some of the symbiotic corals, however the average growth rate was not significantly affected, most likely because of the competition with BMA. The comparison between the symbiotic and aposymbiotic juvenile corals showed that the establishment of a symbiotic association could be imperative for post-settlement juvenile corals to survive in high-nutrient seawater.
Показать больше [+] Меньше [-]Multiple environmental factors influence the spatial distribution and structure of reef communities in the northeastern Arabian Peninsula
2013
Bauman, Andrew G. | Feary, David A. | Heron, Scott F. | Pratchett, Morgan S. | Burt, John A.
Multivariate analysis revealed distinct sub-regional coral communities among the southern Persian Gulf, Strait of Hormuz, and Gulf of Oman. Differences in community structure among locations were associated with considerable spatial heterogeneity in oceanic conditions, and strong directional environmental gradients. Despite clear community differences, considerable changes to coral community structure have occurred throughout the northeastern Arabian Peninsula as compared with previous studies. The most dramatic of these are the apparent changes from Acropora dominated to poritid and faviid dominated communities, particularly in the southern Persian Gulf and Strait of Hormuz. Although temperature and salinity have previously been cited as the major environmental factors structuring coral communities around the region, additional environmental parameters, including chlorophyll-a, surface currents and winds are shown to be important in structuring reef communities throughout the northeastern Arabian Peninsula.
Показать больше [+] Меньше [-]Entanglement of Antarctic fur seals at Bird Island, South Georgia
2013
Waluda, Claire M. | Staniland, Iain J.
Between November 1989 and March 2013, 1033 Antarctic fur seals Arctocephalus gazella were observed entangled in marine debris at Bird Island, South Georgia. The majority of entanglements involved plastic packaging bands (43%), synthetic line (25%) or fishing net (17%). Juvenile male seals were the most commonly entangled (44%). A piecewise regression analysis showed that a single breakpoint at 1994 gave the best description of inter-annual variability in the data, with higher levels of entanglements prior to 1994 (mean=110±28) followed by persistent lower levels (mean=28±4). Records of entanglements from other sites monitored in the Scotia Sea are also presented. Legislation imposed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has, to a certain extent, been effective, but persistent low levels of seal entanglements are still a cause for concern at South Georgia.
Показать больше [+] Меньше [-]Trace metal enrichments in nearshore sediments and accumulation in mussels (Modiolus capax) along the eastern coast of Baja California, Mexico: Environmental status in 1995
2013
Muñoz-Barbosa, Albino | Huerta-Diaz, Miguel Angel
The biogeochemistry of trace metals in nearshore sediments and mussel was studied at 15 stations along a 1000km long transect paralleling the west coast of the Gulf of California (GOC). Total trace metal (Me) and enrichment factor (EFMe) values in sediments were low due to negligible anthropogenic influence in the region. Past copper mining, however, near Santa Rosalia caused concentrations of Pb, Mn, Co, Zn and Cu which were 10–3.3×103 times greater than the average for the rest of the transect. Mussels also showed relatively high trace metal concentrations at the Santa Rosalia stations, but the variability in the spatial distribution was low and had undefined trends. Our results show that, with the exception of Co and Cu, the contamination caused by the copper mine affected sediments to a greater extent than mussels.
Показать больше [+] Меньше [-]Bacteria associated with sabellids (Polychaeta: Annelida) as a novel source of surface active compounds
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.
Показать больше [+] Меньше [-]Temporal evolution of lead isotope ratios in sediments of the Central Portuguese Margin: A fingerprint of human activities
2013
Stable Pb isotope ratios (206Pb/207Pb, 208Pb/206Pb), 210Pb, Pb, Al, Ca, Fe, Mn and Si concentrations were measured in 7 sediment cores from the west coast of the Iberian Peninsula to assess the Pb contamination throughout the last 200years. Independently of their locations, all cores are characterized by increasing Pb/Al rends not related to grain-size changes. Conversely, decreasing trends of 206Pb/207Pb were found towards the present. This tendency suggest a change in Pb sources reflecting an increased proportion derived from anthropogenic activities. The highest anthropogenic Pb inventories for sediments younger than 1950s were found in the two shallowest cores of Cascais and Lisboa submarine canyons, reflecting the proximity of the Tagus estuary. Lead isotope signatures also help demonstrate that sediments contaminated with Pb are not constrained to estuarine–coastal areas and upper parts of submarine canyons, but are also to transferred to a lesser extent to deeper parts of the Portuguese Margin.
Показать больше [+] Меньше [-]Effects of ocean acidification on the embryos and larvae of red king crab, Paralithodes camtschaticus
2013
Christopher Long, W. | Swiney, Katherine M. | Foy, Robert J.
The effects of the decline in ocean pH, known as ocean acidification, on marine species are not well understood. To test the effects on embryos and larvae of red king crab, Paralithodes camtschaticus, ovigerous crab and their larvae were held in CO2-acidified (pH 7.7) and control (ambient; pH 8.0) seawater during development. Morphometrics, hatch duration, fecundity, survival, mineral content, and condition were measured. Acidified embryos had 4% larger eyes and 5% smaller yolks, while mean hatch duration was 33% longer and female fecundity was unaffected. Acidified embryos also resulted in 4% longer larvae while acidified larvae had lower survival. Calcium content of both larvae and female carapaces after molting increased by 5% and 19%, respectively. Although ocean acidification may increase larval size and calcium content, the implications of this are unclear and decreased survival is likely to harm red king crab populations.
Показать больше [+] Меньше [-]Microbiological composition of native and exotic clams from Tagus estuary: Effect of season and environmental parameters
2013
Anacleto, Patrícia | Pedro, Sónia | Nunes, Maria Leonor | Rosa, Rui | Marques, António
The influence of seasonal and environmental parameters on the occurrence of bacteria was investigated in two clam species (Venerupis pullastra and Ruditapes philippinarum), water and sediment from the Tagus estuary. Total viable counts (TVC), Escherichia coli, Salmonella spp. and Vibrio spp. were evaluated during one-year. Overall, significant seasonal variations were found in both sampling sites, especially for E. coli and Vibrio spp. levels. In summer, significantly higher Vibrio spp. levels were found in R. philippinarum and sediment samples, but not in V. pullastra clams and water samples. In contrast, significantly higher TVC and E. coli levels were observed in winter months in water and sediment samples. Salmonella spp. was generally isolated when higher levels of E. coli were detected, particularly in R. philippinarum. This study is useful for authorities to develop monitoring strategies for coastal contamination and to estimate human health risks associated with the consumption of bivalves.
Показать больше [+] Меньше [-]Metals contamination along the watershed and estuarine areas of southern Bohai Sea, China
2013
Xu, Li | Wang, Tieyu | Ni, Kun | Liu, Shijie | Wang, Pei | Xie, Shuangwei | Meng, Jing | Zheng, Xiaoqi | Lü, Yonglong
Distributions and magnitude of metals in water, sediment and soil collected from the watershed and estuarine areas of southern Bohai Sea, were investigated. The largest dissolved concentrations of As, Cu and Zn in water were 347.70, 2755.00, 2076.00μg/L, respectively, much higher than corresponding drinking water guidelines. The greatest concentrations of Cu, Zn, Cr, Ni, Pb, As and Cd in sediments were 1462.2, 1602.17, 196.43, 67.15, 63.54, 73.86 and 1.41mg/kg, dw, respectively. The mean concentrations of Cu, Ni, Cd, Zn, Cr, Pb and As in soils were 24.67, 24.73, 0.14, 64.75, 56.52, 25.12 and 9.34mg/kg, dw, respectively. Land use was confirmed to be an important factor of influence on soil metal concentrations. Metal contents along the watershed of Jie River were significantly greater than in other locations. The detection of metals in relatively high concentrations from different environmental matrices in this region indicates the necessity of further studies.
Показать больше [+] Меньше [-]Potential acidification impacts on zooplankton in CCS leakage scenarios
2013
Halsband, Claudia | Kurihara, Haruko
Carbon capture and storage (CCS) technologies involve localized acidification of significant volumes of seawater, inhabited mainly by planktonic species. Knowledge on potential impacts of these techniques on the survival and physiology of zooplankton, and subsequent consequences for ecosystem health in targeted areas, is scarce. The recent literature has a focus on anthropogenic greenhouse gas emissions into the atmosphere, leading to enhanced absorption of CO2 by the oceans and a lowered seawater pH, termed ocean acidification. These studies explore the effects of changes in seawater chemistry, as predicted by climate models for the end of this century, on marine biota. Early studies have used unrealistically severe CO2/pH values in this context, but are relevant for CCS leakage scenarios. Little studied meso- and bathypelagic species of the deep sea may be especially vulnerable, as well as vertically migrating zooplankton, which require significant residence times at great depths as part of their life cycle.
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