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Results for “Oceans and Seas”

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At least 19 recordsLinked to original sources
PubMed2005

Bacterial exopolysaccharides from extreme marine environments with special consideration of the southern ocean, sea ice, and deep-sea hydrothermal vents: a review.

Exopolysaccharides (EPSs) are high molecular weight carbohydrate polymers that make up a substantial component of the extracellular polymers surrounding most microbial cells in the marine environment. EPSs constitute a large fraction of the reduced carbon reservoir in the ocean and enhance the survival of marine bacteria by influencing the physicochemical environment around the bacterial cell. Microbial EPSs are abundant in the Antarctic marine environment, for example, in sea ice and ocean particles, where they may assist microbial communities to endure extremes of temperature, salinity, and nutrient availability. The microbial biodiversity of Antarctic ecosystems is relatively unexplored. Deep-sea hydrothermal vent environments are characterized by high pressure, extreme temperature, and heavy metals. The commercial value of microbial EPSs from these habitats has been established recently. Extreme environments offer novel microbial biodiversity that produces varied and promising EPSs. The biotechnological potential of these biopolymers from hydrothermal vent environments as well as from Antarctic marine ecosystems remains largely untapped.

Antarctic Regions↗
PubMed2001

Freak waves in random oceanic sea states.

Freak waves are very large, rare events in a random ocean wave train. Here we study their generation in a random sea state characterized by the Joint North Sea Wave Project spectrum. We assume, to cubic order in nonlinearity, that the wave dynamics are governed by the nonlinear Schrödinger (NLS) equation. We show from extensive numerical simulations of the NLS equation how freak waves in a random sea state are more likely to occur for large values of the Phillips parameter alpha and the enhancement coefficient gamma. Comparison with linear simulations is also reported.

Journal Article↗
PubMedDate not supplied

[Species of the genus Koellikeria--parasites of Pacific Ocean sea breams].

Rediscriptions and original figures of the trematodes Koellikeria filicollis and K. shimai, parasites of sae breams (Brama brama, B. japonica) from the Pacific with the data on localization and distribution of these species, have been given. K. filicollis is a very polymorphic form, which changes during its development. Didymozoon shimai Pozdnyakov, 1985 is transferred to the genus Koellikeria.

Animals↗
PubMed2003

Lessons learned at sea--ocean sailing as a metaphor for surgical training.

Surgical education is in the process of tumultuous change. Mastering this change will require a new set of competencies and a new understanding of the medical education process. While accreditation agencies are rapidly working to define the new criteria and benchmarks, training programs are quickly pulling together curricula, objectives, and evaluation tools. Yet much has already been learned in other complex, high-risk activities. Blue water sailing, ocean racing, and trans-Atlantic crossing are all activities that require a renewed form of leadership and an understanding of how knowledge, skill, and behavior come together to define the competent sailor. Ideas learned in such endeavors may assist the surgical educator in defining the horizons and the hazards of this uncharted voyage.

Curriculum↗
PubMed1993

Isolation of the nickel-chlorin chelate tunichlorin from the South Pacific ocean sea hare Dolabella auricularia.

The Papua New Guinea shell-less mollusc Dolabella auricularia has been found to contain a series of green to blue-green chlorins. One of these compounds was found to be the nickel chelate tunichlorin [1] which was isolated previously only from the Caribbean tunicate Trididemnum solidum. Discovery of tunichlorin [1] in a sea hare suggests that its occurrence in algae-consuming marine animals may be more common than earlier realized, and it may have a role in electron transfer or other metabolic processes.

Animals↗
PubMed2000

Restricted gene flow and incipient speciation in disjunct Pacific Ocean and Sea of Cortez populations of a reef fish species, Girella nigricans.

Population disjunctions have been proposed to play an important role in speciation processes. In this study, we have examined the possible role of the Pacific Ocean-Sea of Cortez disjunction as a contributing factor to cryptic speciation in a reef fish, the opaleye, Girella nigricans. Mitochondrial control region (D-loop) sequences (380 bp) of 117 individuals completely separated opaleye populations from the Pacific Ocean and the Sea of Cortez. Although opaleye exhibit pelagic larval stages that remain in the water column for several months, gene flow between the Pacific Ocean and the Sea of Cortez was found to be extremely limited (FST = 0.84, Nm = 0.10). Whereas limited gene flow and reciprocal monophyly suggest that the observed physical and genetic disjunction are potentially contributing to the incipient speciation of Pacific and Sea of Cortez opaleye, moderate levels of D-loop sequence divergence (3.3%) and the absence of fixed allozyme markers challenge this idea. Pacific Coast populations also exhibited restricted gene flow levels (FST = 0.25, Nm = 1.49) across Punta Eugenia, a recognized oceanographic boundary along the Baja California coast. Thus, opaleye individuals grouped into three clades: one clade in the Sea of Cortez, one Pacific clade south of Punta Eugenia, and one Pacific clade north of Punta Eugenia. Future work in this region will determine if our results can be generalized to other disjunct populations.

Animals↗
PubMed2001

Distribution of viral haemorrhagic septicaemia virus in wild fish species of the North Sea, north east Atlantic Ocean and Irish Sea.

A surveillance programme was initiated on the occurrence and distribution of viral haemorrhagic septicaemia virus (VHSV) in wild marine fish. Six research cruises were undertaken in an 18 mo period during 1997 and 1998, covering the North Sea, the Atlantic waters off the north and west coasts of Scotland and the Irish Sea. A total of 19,293 fish were sampled from 23 different species including cod, haddock, Norway pout, herring and sprat. Individual fish lengths were recorded and the fish were checked for lesions, haemorrhaging and other signs of disease. Pools of organ samples were taken for virus assay. The majority of fish sampled did not display clinical signs indicative of viral haemorrhagic septicaemia. A small number of cod were found with skin lesions and haddock with skin haemorrhaging. Of the 2081 organ and skin sample pools collected, 21 tested positive for VHSV by tissue culture and enzyme-linked immunosorbent assay. Seventeen of the isolates originated from Norway pout Trisopterus esmarkii, one from cod Gadus morhua (skin lesion), one from herring Clupea harengus, one from whiting Merlangius merlangus, and one from a previously unreported host species, poor cod Trisopterus minutus.

Animals↗
PubMed2006

Southern Ocean sea-ice extent, productivity and iron flux over the past eight glacial cycles.

Sea ice and dust flux increased greatly in the Southern Ocean during the last glacial period. Palaeorecords provide contradictory evidence about marine productivity in this region, but beyond one glacial cycle, data were sparse. Here we present continuous chemical proxy data spanning the last eight glacial cycles (740,000 years) from the Dome C Antarctic ice core. These data constrain winter sea-ice extent in the Indian Ocean, Southern Ocean biogenic productivity and Patagonian climatic conditions. We found that maximum sea-ice extent is closely tied to Antarctic temperature on multi-millennial timescales, but less so on shorter timescales. Biological dimethylsulphide emissions south of the polar front seem to have changed little with climate, suggesting that sulphur compounds were not active in climate regulation. We observe large glacial-interglacial contrasts in iron deposition, which we infer reflects strongly changing Patagonian conditions. During glacial terminations, changes in Patagonia apparently preceded sea-ice reduction, indicating that multiple mechanisms may be responsible for different phases of CO2 increase during glacial terminations. We observe no changes in internal climatic feedbacks that could have caused the change in amplitude of Antarctic temperature variations observed 440,000 years ago.

Calcium↗
PubMedDate not supplied

[Application of the method of capillary microscopy to determing the total population and biomass of microorganisms in seas and oceans].

The total number and biomass of microorganisms in samples of sea water were determined by direct counting in capillaries by Perfiliev and Gabe after preliminary concentration of water by filtering it through membrane filters. Reliability of the figures obtained upon concentration of diluted bacterial suspensions (10(3) to 10(5) cells/ml) was checked with dilutions of the cell suspension of Bacterium parvulum. The total number of the microorganisms was determined in 22 samples of sea water fixed with 4 to 5 per cent formalin, and deviations for each capillary were calculated.

Bacteriological Techniques↗
PubMed2006

Diversity of piezophilic microorganisms in the closed ocean Japan Sea.

Deep-sea sediment samples were collected at a depth of 3,064 m in the Japan Sea. Microorganisms in the sediment sample were cultivated under several pressure conditions, and the high-pressure adapted microbes were isolated. Two of the isolates exhibited piezophilic growth profiles. This is the first report to show the presence of piezophiles in the Japan Sea.

Biodiversity↗
PubMed2003

Aplanochytrium stocchinoi: a new Labyrinthulomycota from the southern ocean (Ross Sea, Antarctica).

Aplanochytrium stocchinoi, a new species of Labyrinthulomycota, is described from samples collected in Antarctica. Ultrastructural, life cycle and molecular data characterizing the new taxon are provided and compared with the features of other species included in the genus Aplanochytrium. The phylogenetic position of A. stocchinoi is investigated using the 18S rDNA as molecular marker and applying maximum parsimony, minimum evolution and maximum likelihood methods.

Animals↗
PubMed2005

The relationship between Indian Ocean sea-surface temperature and East African rainfall.

Knowledge of the processes that control East African rainfall is essential for the development of seasonal forecasting systems, which may mitigate the effects of flood and drought. This study uses observational data to unravel the relationship between the Indian Ocean Dipole (IOD), the El Nino Southern Oscillation (ENSO) and rainy autumns in East Africa. Analysis of sea-surface temperature data shows that strong East African rainfall is associated with warming in the Pacific and Western Indian Oceans and cooling in the Eastern Indian Ocean. The resemblance of this pattern to that which develops during IOD events implies a link between the IOD and strong East African rainfall. Further investigation suggests that the observed teleconnection between East African rainfall and ENSO is a manifestation of a link between ENSO and the IOD.

Journal Article↗