Home About us Contact
|
Home About us Contact | ||
|
|
||
Oceanic Regions (oceanic + regions)
Selected AbstractsAssessing diversity and biogeography of aerobic anoxygenic phototrophic bacteria in surface waters of the Atlantic and Pacific Oceans using the Global Ocean Sampling expedition metagenomesENVIRONMENTAL MICROBIOLOGY, Issue 6 2007Natalya Yutin Summary Aerobic anoxygenic photosynthetic bacteria (AAnP) were recently proposed to be significant contributors to global oceanic carbon and energy cycles. However, AAnP abundance, spatial distribution, diversity and potential ecological importance remain poorly understood. Here we present metagenomic data from the Global Ocean Sampling expedition indicating that AAnP diversity and abundance vary in different oceanic regions. Furthermore, we show for the first time that the composition of AAnP assemblages change between different oceanic regions, with specific bacterial assemblages adapted to open ocean or coastal areas respectively. Our results support the notion that marine AAnP populations are complex and dynamic, and compose an important fraction of bacterioplankton assemblages in certain oceanic areas. [source] Phylogenetic diversity of Synechococcus strains isolated from the East China Sea and the East SeaFEMS MICROBIOLOGY ECOLOGY, Issue 3 2009Dong Han Choi Abstract Phylogenetic relationships among 33 Synechococcus strains isolated from the East China Sea (ECS) and the East Sea (ES) were studied based on 16S rRNA gene sequences and 16S,23S rRNA gene internal transcribed spacer (ITS) sequences. Pigment patterns of the culture strains were also examined. Based on 16S rRNA gene and ITS sequence phylogenies, the Synechococcus isolates were clustered into 10 clades, among which eight were previously identified and two were novel. Half of the culture strains belonged to clade V or VI. All strains that clustered into novel clades exhibited both phycoerythrobilin and phycourobilin. Interestingly, the pigment compositions of isolates belonging to clades V and VI differed from those reported for other oceanic regions. None of the isolates in clade V showed phycourobilin, whereas strains in clade VI exhibited both phycourobilin and phycoerythrobilin, which is in contrast to previous studies. The presence of novel lineages and the different pigment patterns in the ECS and the ES suggests the possibility that some Synechococcus lineages are distributed only in geographically restricted areas and have evolved in these regions. Therefore, further elucidation of the physiological, ecological, and genetic characteristics of the diverse Synechococcus strains is required to understand their spatial and geographical distribution. [source] Ecological effects of regime shifts in the Bering Sea and eastern North Pacific OceanFISH AND FISHERIES, Issue 2 2002Ashleen J Benson Abstract Large-scale shifts occurred in climatic and oceanic conditions in 1925, 1947, 1977, 1989 and possibly 1998. These shifts affected the mix and abundance of suites of coexisting species during each period of relative environmental stability,from primary producers to apex predators. However, the 1989 regime shift was not a simple reversal of the 1977 shift. The regime shifts occurred abruptly and were neither random variations nor simple reversals to the previous conditions. Timing of these anomalous environmental events in the North Pacific Ocean appears to be linked to physical and biological responses in other oceanic regions of the world. Changes in the atmospheric pressure can alter wind patterns that affect oceanic circulation and physical properties such as salinity and depth of the thermocline. This, in turn, affects primary and secondary production. Data from the North Pacific indicate that regime shifts can have opposite effects on species living in different domains, or can affect similar species living within a single domain in opposite ways. Climatic forcing appears to indirectly affect fish and marine mammal populations through changes in the distribution and abundance of their predators and prey. Effects of regime shifts on marine ecosystems are also manifested faster at lower trophic levels. Natural variability in the productivity of fish stocks in association with regime shifts indicates that new approaches to managing fisheries should incorporate climatic as well as fisheries effects. [source] Climate dynamics of atmosphere and ocean in the equatorial zone: a synthesisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2004Stefan Hastenrath Abstract A synopsis is offered of circulation mechanisms in the oceanic regions of the equatorial zone. Over the eastern Atlantic and Pacific, and especially in boreal summer, cross-equatorial flow from the Southern Hemisphere is strong and induces a tongue of cold surface waters, centred to the south of the equator. Upon crossing the equator in these sectors, owing to the Coriolis effect and a kinetic energy imbalance, the airstream speeds up and divergence develops, producing the Intertropical Divergence Zone (ITDZ). Once these processes result in the wind recurving from southeasterly to southwesterly, the flow slows down and becomes convergent, manifest in the Intertropical Convergence Zone, with a maximum to the south of the wind confluence. By contrast, over the western Atlantic and central Pacific and especially in boreal winter, winds in the equatorial band are predominantly from the east, upper-ocean Ekman transport is directed away from the equator, and the upwelling and cold tongue are centred on the equator. Cross-equatorial flow is insufficient to produce recurvature, the ITDZ is narrower and weaker, the divergence maximum is at the equator rather than in low northern latitudes, and the convergence maximum straddles the wind confluence. Over the Indian Ocean, the wind field is dominated by the alternation between the predominantly meridional flow of the winter and summer monsoons. Equatorial westerlies are limited to the short monsoon transition seasons. Essential for their origin is an eastward pressure gradient along the equator and weak southern trade winds, allowing recurvature somewhat south of the equator. Because the zonal pressure gradient is strongest in boreal summer and the southern trade winds are weakest in austral summer, the equatorial westerlies peak in spring and autumn. The boreal autumn equatorial westerlies are the surface manifestation of a powerful zonal,vertical circulation cell along the Indian Ocean equator. Equatorial zonal,vertical circulation cells require well-developed zonal flow in the lower troposphere along the equator and, therefore, appear confined to the oceanic longitudes and certain seasons. Thus, they are found over the Atlantic only in boreal winter and over the Indian Ocean only in boreal autumn, whereas over the Pacific they prevail all year round. Copyright © 2004 Royal Meteorological Society [source] The influence of the tropical and subtropical Atlantic and Pacific Oceans on precipitation variability over Southern Central South America on seasonal time scalesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2004Guillermo J. Berri Abstract This paper studies the temporal and spatial patterns of precipitation anomalies over southern central South America (SCSA; 22,40°S and 54,70°W), and their relationship with the sea-surface temperature (SST) variability over the surrounding tropical and subtropical Atlantic and Pacific Oceans. The data include monthly precipitation from 68 weather stations in central,northern Argentina and neighbouring Brazil, Paraguay and Uruguay, and monthly SSTs from the NOAA dataset with a 2° resolution for the period 1961,93. We use the method of canonical correlation analysis (CCA) to study the simultaneous relationship between bi-monthly precipitation and SST variability. Before applying the CCA procedure, standardized anomalies are calculated and a prefiltering is applied by means of an empirical orthogonal function (EOF) analysis. Thus, the CCA input consists of 10 EOF modes of SST and between 9 and 11 modes for precipitation and their corresponding principal components, which are the minimum number of modes necessary to explain at least 80% of the variance of the corresponding field. The results show that November,December presents the most robust association between the SST and SCSA precipitation variability, especially in northeastern Argentina and southern Brazil, followed by March,April and May,June. The period January,February, in contrast, displays a weak relationship with the oceans and represents a temporal minimum of oceanic influence during the summer semester. Based on the CCA maps, we identify the different oceanic and SCSA regions, the regional averages of SST and precipitation are calculated, and linear correlation analysis are conducted. The periods with greater association between the oceans and SCSA precipitation are November,December and May,June. During November,December, every selected region over SCSA reflects the influence of several oceanic regions, whereas during May,June only a few regions show a direct association with the oceans. The Pacific Ocean regions have a greater influence and are more widespread over SCSA; the Atlantic Ocean regions have an influence only over the northwestern and the southeastern parts of SCSA. In general, the relationship with the equatorial and tropical Atlantic and Pacific Oceans is of the type warm,wet/cold,dry, whereas the subtropical regions of both oceans show the opposite relationship, i.e. warm,dry/cold,wet. Copyright © 2004 Royal Meteorological Society [source] COASTAL BOTTLENOSE DOLPHINS FROM SOUTHEASTERN AUSTRALIA ARE TURSIOPS ADUNCUS ACCORDING TO SEQUENCES OF THE MITOCHONDRIAL DNA CONTROL REGIONMARINE MAMMAL SCIENCE, Issue 2 2001Luciana M. Möller Abstract Sequence analysis of the mitochondrial DNA control region was used to clarify the taxonomic status of two coastal bottlenose dolphin populations from southeastern Australia currently classified as Tursiops truncatus. A 368-bp segment of the control region of 57 biopsy-sampled, photo-identified dolphins of Jervis Bay and Port Stephens was compared to published sequences of T. truncatus and T. aduncus from different oceanic regions. Sequence divergence between haplotypes from southeastern Australia and T. aduncus was much lower than that from T. truncatus. Analyses using two different methods of phylogenetic reconstruction unambiguously placed all haplotypes from southeastern Australia in a group composed exclusively of T. aduncus. The results strongly indicated that these two bottlenose dolphin populations belong to T. aduncus, extending the range of the species to subtropical waters of the Western South Pacific Ocean. [source] | |||||||||||||