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Southern Ocean (southern + ocean)
Selected AbstractsDetermining prey distribution patterns from stomach-contents of satellite-tracked high-predators of the Southern OceanECOGRAPHY, Issue 2 2006J. C. Xavier The distribution of many cephalopod, crustacean and fish species in the Southern Ocean, and adjacent waters, is poorly known, particularly during times of the year when research surveys are rare. Analysing the stomach samples of satellite-tracked higher predators has been advocated as a potential method by which such gaps in knowledge can be filled. We examined the viability of this approach through monitoring wandering albatrosses Diomedea exulans at their colony on Bird Island, South Georgia (54°S, 38°W) over the winters (May,July) of 1999 and 2000. At this time, these birds foraged in up to three different water-masses, the Antarctic zone (AZ), the sub-Antarctic zone (SAZ) and the sub-Tropical zone (STZ), which we defined by contemporaneous satellite images of sea surface temperature. A probabilistic model was applied to the tracking and diet data collected from 38 birds to construct a large-scale map of where various prey were captured. Robustness/sensitivity analyses were used to test model assumptions on the time spent foraging and relative catch efficiencies and to evaluate potential biases associated with the model. We were able to predict the distributions of a wide number of cephalopod, crustacean of fish species. We also discovered some of the limitations to using this type of data and proposed ways to rectify these problems. [source] Penguins as oceanographers unravel hidden mechanisms of marine productivityECOLOGY LETTERS, Issue 3 2002Jean-Benoît Charrassin ABSTRACT A recent concept for investigating marine ecosystems is to employ diving predators as cost-effective, autonomous samplers of environmental parameters (such as sea-temperature). Using king penguins during their foraging trips at sea, we obtained an unprecedented high resolution temperature map at depth off the Kerguelen Islands, Southern Ocean, a poorly sampled but productive area. We found clear evidence of a previously unknown subsurface tongue of cold water, flowing along the eastern shelf break. These new results provide a better understanding of regional water circulation and help explain the high primary productivity above the Kerguelen Plateau. [source] Distribution of Roseobacter RCA and SAR11 lineages and distinct bacterial communities from the subtropics to the Southern OceanENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Helge-Ansgar Giebel Summary We assessed the composition of the bacterioplankton in the Atlantic sector of the Southern Ocean in austral fall and winter and in New Zealand coastal waters in summer. The various water masses between the subtropics/Agulhas,Benguela boundary region and the Antarctic coastal current exhibited distinct bacterioplankton communities with the highest richness in the polar frontal region, as shown by denaturing gradient gel electrophoresis of 16S rRNA gene fragments. The SAR11 clade and the Roseobacter clade-affiliated (RCA) cluster were quantified by real-time quantitative PCR. SAR11 was detected in all samples analysed from subtropical waters to the coastal current and to depths of > 1000 m. In fall and winter, this clade constituted < 3% to 48% and 4,28% of total bacterial 16S rRNA genes respectively, with highest fractions in subtropical to polar frontal regions. The RCA cluster was only present in New Zealand coastal surface waters not exceeding 17°C, in the Agulhas,Benguela boundary region (visited only during the winter cruise), in subantarctic waters and in the Southern Ocean. In fall, this cluster constituted up to 36% of total bacterial 16S rRNA genes with highest fractions in the Antarctic coastal current and outnumbered the SAR11 clade at most stations in the polar frontal region and further south. In winter, the RCA cluster constituted lower proportions than the SAR11 clade and did not exceed 8% of total bacterial 16S rRNA genes. In fall, the RCA cluster exhibited significant positive correlations with latitude and ammonium concentrations and negative correlations with concentrations of nitrate, phosphate, and for near-surface samples also with chlorophyll a, biomass production of heterotrophic prokaryotes and glucose turnover rates. The findings show that the various water masses between the subtropics and the Antarctic coastal current harbour distinct bacterioplankton communities. They further indicate that the RCA cluster, despite the narrow sequence similarity of > 98% of its 16S rRNA gene, is an abundant component of the heterotrophic bacterioplankton in the Southern Ocean, in particular in its coldest regions. [source] Ecological repercussions of historical fish extraction from the Southern OceanFISH AND FISHERIES, Issue 1 2009David G Ainley Abstract A major mid-1980s shift in ecological structure of significant portions of the Southern Ocean was partially due to the serial depletion of fish by intensive industrial fishing, rather than solely to climate factors as previously hypothesized. Over a brief period (1969,1973), several finfish stocks were on average reduced to <50%, and finally (mid-1980s) to <20%, of original size. Despite management actions, few stocks have recovered and some are still declining. Most affected species exhibit K-selected life-history patterns, and before exploitation presumably fluctuated in accordance with infrequent strong year classes, as is true of such fish elsewhere. A climate regime, the Southern Annular Mode, once oscillated between two states, but has remained in its ,positive mode' since the time of the fish extraction. This may have increased finfish vulnerability to exploitation. As breeding stocks decreased, we hypothesize that availability of annually produced juvenile fish fed upon by upper-level predators remained low. Correlations between predator populations and fish biomass in predator foraging areas indicate that southern elephant seal Mirounga leonina, Antarctic fur seal Arctocephalus gazella, gentoo penguin Pygoscelis papua, macaroni penguin Eudyptes chrysolphus and ,imperial' shag Phalacrocorax spp. , all feeding extensively on these fish, and monitored at Marion, Crozet, Kerguelen, Heard, South Georgia, South Orkney and South Shetland Islands, where fishing was concentrated , declined simultaneously during the two periods of heavy fishing. These patterns indicate the past importance of demersal fish as prey in Antarctic marine systems, but determining these interactions' ecological mechanisms may now be impossible. [source] On the Approximation of Transport Phenomena , a Dynamical Systems ApproachGAMM - MITTEILUNGEN, Issue 1 2009Michael Dellnitz Abstract Transport phenomena are studied in a large variety of dynamical systems with applications ranging from the analysis of fluid flow in the ocean and the predator-prey interaction in jelly-fish to the investigation of blood flow in the cardiovascular system. Our approach to analyze transport is based on the methodology of so-called transfer operators associated with a dynamical system since this is particularly suitable. We describe the approach and illustrate it by two real world applications: the computation of transport for asteroids in the solar system and the approximation of macroscopic structures in the Southern Ocean (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Penguin responses to climate change in the Southern OceanGLOBAL CHANGE BIOLOGY, Issue 7 2009JAUME FORCADA Abstract Penguins are adapted to live in extreme environments, but they can be highly sensitive to climate change, which disrupts penguin life history strategies when it alters the weather, oceanography and critical habitats. For example, in the southwest Atlantic, the distributional range of the ice-obligate emperor and Adélie penguins has shifted poleward and contracted, while the ice-intolerant gentoo and chinstrap penguins have expanded their range southward. In the Southern Ocean, the El Niño-Southern Oscillation and the Southern Annular Mode are the main modes of climate variability that drive changes in the marine ecosystem, ultimately affecting penguins. The interaction between these modes is complex and changes over time, so that penguin responses to climate change are expected to vary accordingly, complicating our understanding of their future population processes. Penguins have long life spans, which slow microevolution, and which is unlikely to increase their tolerance to rapid warming. Therefore, in order that penguins may continue to exploit their transformed ecological niche and maintain their current distributional ranges, they must possess adequate phenotypic plasticity. However, past species-specific adaptations also constrain potential changes in phenology, and are unlikely to be adaptive for altered climatic conditions. Thus, the paleoecological record suggests that penguins are more likely to respond by dispersal rather than adaptation. Ecosystem changes are potentially most important at the borders of current geographic distributions, where penguins operate at the limits of their tolerance; species with low adaptability, particularly the ice-obligates, may therefore be more affected by their need to disperse in response to climate and may struggle to colonize new habitats. While future sea-ice contraction around Antarctica is likely to continue affecting the ice-obligate penguins, understanding the responses of the ice-intolerant penguins also depends on changes in climate mode periodicities and interactions, which to date remain difficult to reproduce in general circulation models. [source] Incursion and excursion of Antarctic biota: past, present and futureGLOBAL ECOLOGY, Issue 2 2006D. K. A. Barnes ABSTRACT Aim, To investigate the major paradigms of intense isolation and little anthropogenic influence around Antarctica and to examine the timings and scales of the modification of the southern polar biota. Location, Antarctica and surrounding regions. Methods, First, mechanisms of and evidence for long-term isolation are reviewed. These include continental drift, the development of a surrounding deep-water channel and the Antarctic Circumpolar Current (ACC). They also include levels of endemism, richness and distinctiveness of assemblages. Secondly, evidence for past and modern opportunities for species transport are investigated. Comparative levels of alien establishments are also examined around the Southern Ocean. Discussion, On a Cenozoic time-scale, it is clear that Gondwana's fragmentation led to increasing geographical isolation of Antarctica and the initiation of the ACC, which restricted biota exchange to low levels while still permitting some movement of biota. On a shorter Quaternary time-scale, the continental ice-sheet, influenced by solar (Milankovitch) cycles, has expanded and contracted periodically, covering and exposing terrestrial and continental shelf habitats. There were probably refugia for organisms during each glacial maxima. It is also likely that new taxa were introduced into Antarctica during cycles of ice sheet and oceanic front movement. The current situation (a glacial minimum) is not ,normal'; full interglacials represent only 10% of the last 430 ka. On short (ecological) time-scales, many natural dispersal processes (airborne, oceanic eddy, rafting and hitch-hiking on migrants) enable the passage of biota to and from Antarctica. In recent years, humans have become influential both directly by transporting organisms and indirectly by increasing survival and establishment prospects via climate change. Main conclusions, Patterns of endemism and alien establishment are very different across taxa, land and sea, and north vs. south of the Polar Frontal Zone. Establishment conditions, as much as transport, are important in limiting alien establishment. Three time-scales emerge as important in the modification of Antarctica's biota. The natural ,interglacial' process of reinvasion of Antarctica is being influenced strongly by humans. [source] Variability and trends in the directional wave climate of the Southern HemisphereINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2010Mark A. Hemer Abstract The effect of interannual climate variability and change on the historic, directional wave climate of the Southern Hemisphere is presented. Owing to a lack of in situ wave observations, wave climate in the Southern Hemisphere is determined from satellite altimetry and global ocean wave models. Altimeter data span the period 1985 to present, with the exception of a 2-year gap in 1989,1991. Interannual variability and trends in the significant wave height are determined from the satellite altimeter record (1991 to present), and the dominant modes of variability are identified using an empirical orthogonal function (EOF) analysis. Significant wave heights in the Southern Ocean are observed to show a strong positive correlation with the Southern Annular Mode (SAM), particularly during Austral autumn and winter months. Correlation between altimeter derived significant wave heights and the Southern Oscillation Index is observed in the Pacific basin, which is consistent with several previous studies. Variability and trends of the directional wave climate are determined using the ERA-40 Waves Re-analysis for the period 1980,2001. Significant wave height, mean wave period and mean wave direction data are used to describe the climate of the wave energy flux vector. An EOF analysis of the wave energy flux vector is carried out to determine the dominant modes of variability of the directional seasonal wave energy flux climate. The dominant mode of variability during autumn and winter months is strongly correlated to the SAM. There is an anti-clockwise rotation of wave direction with the southward intensification of the Southern Ocean storm belt associated with the SAM. Clockwise rotation of flux vectors is observed in the Western Pacific Ocean during El-Nino events. Directional variability of the wave energy flux in the Western Pacific Ocean has previously been shown to be of importance to sand transport along the south-eastern Australian margin, and the New Zealand region. The directional variability of the wave energy flux of the Southern Ocean associated with the SAM is expected to be of importance to the wave-driven currents responsible for the transport of sand along coastal margins in the Southern Hemisphere, in particular those on the Southern and Western coastal margins of the Australian continent. Copyright © 2009 Royal Meteorological Society [source] Possible impacts of anthropogenic and natural aerosols on Australian climate: a reviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2009Leon D. Rotstayn Abstract A review is presented of the aerosol,climate interaction with specific focus on the Australian region. The uncertainties associated with this interaction are much larger than those associated with greenhouse gases or other forcing agents, and are currently a major obstacle in climate-change research. However, new research suggests that aerosol effects are of comparable importance to greenhouse gases as a driver of recent climate trends in the Southern Hemisphere, including Australia. A significant new result from climate modelling is that anthropogenic aerosol over Asia affects meridional temperature gradients and atmospheric circulation, and may have caused an increase in rainfall over north-western Australia. Global ocean circulation provides another mechanism whereby aerosol changes in the Northern Hemisphere can affect climate in the Southern Hemisphere, suggesting an urgent need for further targeted studies using coupled ocean-atmosphere global climate models. To better model climate variability and climate change in the Australian region, more research is needed into the sources of aerosol and their precursors, their atmospheric distributions and transformations, and how to incorporate these processes robustly in global climate models (GCMs). The following priorities are suggested for further research in Australia linking aerosol observations and modelling: natural aerosol over the Southern Ocean, tropical biomass-burning aerosol in Indonesia and Australia, secondary organic aerosol (SOA) from volatile organic compounds (VOCs), wind-blown dust and modulation of rainfall by anthropogenic aerosol. Copyright © 2008 Royal Meteorological Society [source] Atmospheric moisture budget over Antarctica and the Southern Ocean based on the ERA-40 reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2008Hanna Tietäväinen Abstract The atmospheric moisture budget over Antarctica and the Southern Ocean was analysed for the period 1979,2001 on the basis of the ERA-40 reanalysis of the European Centre for Medium-Range Weather Forecasts. Meridional transport by transient eddies makes the largest contribution to the southward water vapour transport. The mean meridional circulation contributes to the northward transport in the Antarctic coastal areas, but this effect is compensated by the southward transport by stationary eddies. The convergence of meridional water vapour transport is at its largest at 64,68°S, while the convergence of zonal transport is regionally important in areas of high cyclolysis. Inter-annual variations in water vapour transport are related to the southern annular mode (SAM). The eastward transport has a significant (95% confidence level) positive correlation with the SAM index, while the northward transport has a significant negative correlation with SAM near 60°S. Hydrological balance is well-achieved in the ERA-40 reanalysis: the difference between the water vapour flux convergence (based on analysis) and the net precipitation (precipitation minus evaporation, based on 24-h forecasts) is only 13 mm yr,1 (3%) over the Southern Ocean and , 8 mm yr,1 (5%) over the continental ice sheet. Over the open ocean, the analysis methodology favours the accuracy of the flux convergence. For the whole study region, the annual mean flux convergence exceeded net precipitation by 11 mm yr,1 (3%). The ERA-40 result for the mean precipitation over the Antarctic continental ice sheet in 1979,2001 is 177 ± 8 mm yr,1, while previous estimates range from 173 to 215 mm yr,1. For the period 1979,2001, the ERA-40 data do not show any statistically significant trend in precipitation over the Antarctic grounded ice sheet and ice shelves. From the ERA-40 data, the annual average net evaporation (evaporation minus condensation) is positive over the whole continent. Copyright © 2008 Royal Meteorological Society [source] A simulated reduction in Antarctic sea-ice area since 1750: implications of the long memory of the oceanINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2005Hugues Goosse Abstract Using the three-dimensional coarse-resolution climate model ECBILT-CLIO, 1000-year long ensemble simulations with natural and anthropogenic forcings have been performed to study the long-term variation of the ice cover in the Southern Ocean. Over the last 250 years, the ice area has decreased by about 1 × 106 km2 in its annual mean. A comparison with experiments driven by only natural forcings suggests that this reduction is due to both natural and anthropogenic forcing, the latter playing a larger role than natural forcing over the last 150 years. Despite this contribution from anthropogenic forcing, the simulated ice area at the end of the 20th century is similar to that simulated during the 14th century because of the slow response of the Southern Ocean to radiative forcing. Sensitivity experiments performed with the model show that the model's initial conditions have a large influence on the simulated ice cover and that it is necessary to start simulations at least two centuries before the period of interest in order to remove this influence. Copyright © 2005 Royal Meteorological Society. [source] The role of the oceans in climateINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2003G. R. Bigg Abstract The ocean is increasingly seen as a vital component of the climate system. It exchanges with the atmosphere large quantities of heat, water, gases, particles and momentum. It is an important part of the global redistribution of heat from tropics to polar regions keeping our planet habitable, particularly equatorward of about 30°. In this article we review recent work examining the role of the oceans in climate, focusing on research in the Third Assessment Report of the IPCC and later. We discuss the general nature of oceanic climate variability and the large role played by stochastic variability in the interaction of the atmosphere and ocean. We consider the growing evidence for biogeochemical interaction of climatic significance between ocean and atmosphere. Air,sea exchange of several radiatively important gases, in particular CO2, is a major mechanism for altering their atmospheric concentrations. Some more reactive gases, such as dimethyl sulphide, can alter cloud formation and hence albedo. Particulates containing iron and originating over land can alter ocean primary productivity and hence feedbacks to other biogeochemical exchanges. We show that not only the tropical Pacific Ocean basin can exhibit coupled ocean,atmosphere interaction, but also the tropical Atlantic and Indian Oceans. Longer lived interactions in the North Pacific and Southern Ocean (the circumpolar wave) are also reviewed. The role of the thermohaline circulation in long-term and abrupt climatic change is examined, with the freshwater budget of the ocean being a key factor for the degree, and longevity, of change. The potential for the Mediterranean outflow to contribute to abrupt change is raised. We end by examining the probability of thermohaline changes in a future of global warming. Copyright © 2003 Royal Meteorological Society [source] Estimating food consumption of marine predators: Antarctic fur seals and macaroni penguinsJOURNAL OF APPLIED ECOLOGY, Issue 1 2002I.L. Boyd Summary 1Estimating food consumption is central to defining the ecological role of marine predators. This study developed an algorithm for synthesizing information about physiology, metabolism, growth, diet, life history and the activity budgets of marine predators to estimate population energy requirements and food consumption. 2Two species of marine predators (Antarctic fur seal Arctocephalus gazella and macaroni penguin Eudyptes chrsolophus) that feed on krill in the Southern Ocean were used as examples to test the algorithm. A sensitivity analysis showed that estimates of prey consumed were most sensitive to uncertainty in some demographic variables, particularly the annual survival rate and total offspring production. Uncertainty in the measurement of metabolic rate led to a positive bias in the mean amount of food consumed. Uncertainty in most other variables had little influence on the estimated food consumed. 3Assuming a diet mainly of krill Euphausia superba, annual food consumption by Antarctic fur seals and macaroni penguins at the island of South Georgia was 3·84 [coefficient of variation (CV) = 0·11] and 8·08 (CV = 0·23) million tonnes, respectively. This was equivalent to a total annual carbon consumption of 0·35 (CV = 0·11) and 0·72 (CV = 0·23) G tonnes year,1. Carbon expired as CO2 was 0·26 (CV = 0·06) and 0·65 (CV = 0·19) G tonnes year,1 for fur seals and macaroni penguins, respectively. The per capita food consumption varied depending upon sex and age but, overall, this was 1·7 (CV = 0·22) tonnes year,1 for Antarctic fur seals and 0·45 (CV = 0·22) tonnes year,1 for macaroni penguins. 4The algorithm showed that the seasonal demand for food peaked in both species in the second half of the breeding season and, for macaroni penguins, there was a second peak immediately after moult. Minimum food demand occurred in both species during the first half of the breeding season. 5As both Antarctic fur seals and macaroni penguins compete for krill with a commercial fishery, these results provide an insight into the seasons and stages of the life cycle in which competition is likely to be greatest. [source] Taxonomic homogenization and differentiation across Southern Ocean Islands differ among insects and vascular plantsJOURNAL OF BIOGEOGRAPHY, Issue 2 2010Justine D. Shaw Abstract Aim, To investigate taxonomic homogenization and/or differentiation of insect and vascular plant assemblages across the Southern Ocean Islands (SOI), and how they differ with changing spatial extent and taxonomic resolution. Location, Twenty-two islands located across the Southern Ocean, further subdivided into five island biogeographical provinces. These islands are used because comprehensive data on both indigenous and non-indigenous insect and plant species are available. Methods, An existing database was updated, using newly published species records, identifying the indigenous and non-indigenous insect and vascular plant species recorded for each island. Homogenization and differentiation were measured using Jaccard's index (JI) of similarity for assemblages across all islands on a pairwise basis, and for island pairs within each of the biogeographical provinces. The effects of taxonomic resolution (species, genus, family) and distance on levels of homogenization or differentiation were examined. To explore further the patterns of similarity among islands for each of the taxa and groupings (indigenous and non-indigenous), islands were clustered based on JI similarity matrices and using group averaging. Results, Across the SOI, insect assemblages have become homogenized (0.7% increase in similarity at species level) while plant assemblages have become differentiated at genus and species levels. Homogenization was recorded only when pairwise distances among islands exceeded 3000 km for insect assemblages, but distances had to exceed 10,000 km for plant assemblages. Widely distributed non-indigenous plant species tend to have wider distributions across the SOI than do their insect counterparts, and this is also true of the indigenous species. Main conclusions, Insect assemblages across the SOI have become homogenized as a consequence of the establishment of non-indigenous species, while plant assemblages have become more differentiated. The likely reason is that indigenous plant assemblages are more similar across the SOI than are insect assemblages, which show greater regionalization. Thus, although a suite of widespread, typically European, weedy, non-indigenous plant species has established on many islands, the outcome has largely been differentiation. Because further introductions of insects and vascular plants are probable as climates warm across the region, the patterns documented here are likely to change through time. [source] Speciation chronology of rockhopper penguins inferred from molecular, geological and palaeoceanographic dataJOURNAL OF BIOGEOGRAPHY, Issue 4 2009Marc De Dinechin Abstract Aim, The Southern Ocean is split into several biogeographical provinces between convergence zones that separate watermasses of different temperatures. Recent molecular phylogenies have uncovered a strong phylogeographic structure among rockhopper penguin populations, Eudyptes chrysocome sensu lato, from different biogeographical provinces. These studies suggested a reclassification as three species in two major clades, corresponding, respectively, to warm, subtropical and cold sub-Antarctic watermasses rather than to geographic proximity. Such a phylogeographic pattern, also observed in plants, invertebrates and fishes of the Southern Ocean, suggests that past changes in the positions of watermasses may have affected the evolutionary history of penguins. We calculated divergence times among various rockhopper penguin clades and calibrated these data with palaeomagmatic and palaeoceanographic events to generate a speciation chronology in rockhopper penguins. Location, Southern Ocean. Methods, Divergence times between populations were calculated using five distinct mitochondrial DNA loci, and assuming a molecular clock model as implemented in mdiv. The molecular evolution rate of rockhopper penguins was calibrated using the radiochronological age of St Paul Island and Amsterdam Island in the southern Indian Ocean. Separations within other clades were correlated with palaeoceanographic data using this calibrated rate. Results, The split between the Atlantic and Indian populations of rockhopper penguins was dated as 0.25 Ma, using the date of emergence of St Paul and Amsterdam islands, and the divergence between sub-Antarctic and subtropical rockhopper penguins was dated as c. 0.9 Ma (i.e. during the mid-Pleistocene transition, a major change in the Earth's climate cycles). Main conclusions, The mid-Pleistocene transition is known to have caused a major southward shift in watermasses in the Southern Ocean, thus changing the environment around the northernmost rockhopper penguin breeding sites. This ecological isolation of northernmost populations may have caused vicariant speciation, splitting the species into two major clades. After the emergence of St Paul and Amsterdam islands in the subtropical Indian Ocean 0.25 Ma, these islands were colonized by penguins from the subtropical Atlantic, 6000 km away, rather than by penguins from the sub-Antarctic Indian Ocean, 5000 km closer. [source] Inter-ocean dispersal is an important mechanism in the zoogeography of hakes (Pisces: Merluccius spp.)JOURNAL OF BIOGEOGRAPHY, Issue 6 2001W. Stewart Grant Aim To present new genetic data and to review available published genetic data that bear on the phylogeny of hakes in the genus Merluccius. To construct a zoogeographical model from a summary phylogenetic tree with dated nodes. To search for an explanation of antitropical distributions in hakes. To assess peripheral isolate, centrifugal and vicariance models of speciation in view of the molecular phylogeny and zoogeography of hakes. Locations Northern and southern Atlantic Ocean, eastern Pacific Ocean, South Pacific Ocean. Methods Electrophoretic analysis of 20 allozyme loci in 10 species of hakes. Phylogenetic tree construction with parsimony and bootstrap methods. Reanalysis of previous genetic data. Analysis of zoogeographical patterns with geographical distributions of molecular genetic markers. Results Phylogenetic analyses of new and previous allozyme data and previous mitochondrial DNA data indicate a deep genetic partition between Old- and New-World hakes with genetic distances corresponding to 10,15 Myr of separation. This time marks a widening rift between Europe and North America and a rapid drop in ocean temperatures that subdivided an ancestral population of North Atlantic hake. Two Old-World clades spanning the equator include pairs of sister taxa separated by tropical waters. Divergence times between these pairs of sister-taxa variously date to the early Pliocene and late Pleistocene. Amongst New-World hakes, pairs of sister taxa are separated by equatorial waters, by the Southern Ocean, and by the Panama Isthmus. These genetic separations reflect isolation by the rise of the Isthmus 3,4 Ma and by Pliocene and Pleistocene dispersals. Pairs of species occurring in sympatry or parapatry in six regions do not reflect sister-species relationships, but appear to reflect allopatric divergence and back dispersals of descendent species. Some geographically isolated regional populations originating within the last few hundreds of thousands of years merit subspecies designations. Conclusions Vicariance from tectonic movement of continental plates or ridge formation cannot account for the disjunct distributions of most hake sister taxa. Molecular genetic divergences place the origin of most hake species diversity in the last 2,3 Myr, a period of negligible tectonic activity. Distributions of many hake species appear to have resulted from dispersals and back dispersals across both warm equatorial waters and cool waters in the Southern Ocean, driven by oscillations in climate and ocean temperatures. Genetic and ecological divergence prevents hybridization and competitive exclusion between sympatric species pairs in six regions. Sister-taxa relationships and estimates of divergence are consistent with the modified peripheral isolate model of speciation in which vicariances, range expansions and contractions, dispersals and founder events lead to isolated populations that subsequently diverge to form new species. [source] Shedding new light on the life cycle of mackerel icefish in the Southern OceanJOURNAL OF FISH BIOLOGY, Issue 1 2003K.-H. Kock Mackerel icefish have a widespread distribution in the Atlantic and Indian Ocean sectors of the low-Antarctic region. Biological characteristics differ considerably between populations in the southern Scotia Arc and those living further to the north. Fish living in the north mature 1 year earlier than in the south. They have a much shorter life span and die after they have spawned two to three times. The number of eggs produced per gram of body mass is higher in the north. Stocks have declined in most parts of the distributional range due to the impact of fishing and due to natural causes. Increases in populations of Antarctic fur seals at South Georgia and parts of the Indian Ocean appear to have led to increased predation on stocks of icefish. Shifts in hydrological regimes in the northern part of the distributional range have either started to lead or will lead to deteriorating living conditions for mackerel icefish in the near future. Fish stock assessment needs to take these constraints into consideration when providing advice on total allowable catches for fisheries management. [source] A SYSTEMATIC STUDY OF GIGAR-TINACEAE FROM PACIFIC NORTH AMERICA BASED ON MOLECULAR AND MORPHOLOGICAL EVIDENCEJOURNAL OF PHYCOLOGY, Issue 2000J.R. Hughey Greater than 50 species of Gigartinaceae have been described from Pacific North America, about half of which are currently recognized. Although the family is treated extensively in the taxonomic literature, many of the species are still confused and a comprehensive revision is required. We sequenced the rbcL (RuBisCO) gene and ITS (Internal Transcribed Spacer) 1, 2, and 5.8S regions from a large number of recent collections and identified a discrete of number data sets. These were analysed in comparison with the morphological evidence for each of the taxa. Uncertain of the possibility that our operational taxonomic units may not correspond to the types, we developed a protocol for isolating PCR-friendly DNA from herbarium specimens, some reaching back as far as 1670. The DNA profiles of types and historically important specimens were compared to those for recently collected silica gel-dried and formalin-fixed material and assigned correct names. Species studied ranged from Alaska to Mexico and the Gulf of California and were compared to outgroup taxa from Pacific South America and the Southern Ocean. Particular attention was paid to variations in morphology as they relate to habitat with emphasis on the presence or absence of different morphological forms among sympatric and allopatric populations. We recognize 10 species in Chondracanthus (including one new combination and one new species) and 16 species in Mazzaella (including two new combinations and two new species). Finally, we tested a phylogenetic hypothesis inferred for the Gigartinaceae from rbcL sequences for congruence with one generated from ITS sequences. [source] Holocene bipolar climate seesaw: possible subtle evidence from the deep North East Atlantic Ocean?,JOURNAL OF QUATERNARY SCIENCE, Issue 3 2010Mark A. Maslin Abstract The occurrence of a millennial-scale bipolar climate seesaw has been documented in detail for the last glacial period and Termination. There is, however, debate whether it occurs during interglacials and if it does what influence it could have on future climate. We present here new evidence from a North East Atlantic Ocean deep-sea core which supports the hypothesis for a Holocene bipolar climate seesaw. BENGAL Site 13078#16, from the Porcupine Abyssal Plain, is 4844,m deep and situated at the North Atlantic Deep Water and Antarctic Bottom Water (AABW) interface. Planktic foraminiferal fragment accumulation rate data at this site is an indicator of coarse carbonate dissolution, which is highly sensitive to the incursion of under-saturated AABW. Five dissolution peaks have been identified, which seem to occur approximately 500 a after each of the North Atlantic 'Bond' ice rafting pulses, suggesting a subsequent subtle shallowing of AABW. This indicates a possible lagged climatic link between North East Atlantic surface water conditions and AABW production in the Southern Ocean during the Holocene. This provides the first tentative evidence that there was a Holocene bipolar climate seesaw and that the deep ocean was involved. This study also suggests that extremely sensitive locations need to be sought as the Holocene bipolar climate seesaw seems to be very subtle compared with its glacial counterparts. Copyright © 2009 John Wiley & Sons, Ltd. [source] Population in the UN Environment Programme's Global Environment Outlook 2000POPULATION AND DEVELOPMENT REVIEW, Issue 3 2000Article first published online: 27 JAN 200 Most specialized agencies in the United Nations system have taken to compiling a periodic status report on their field. The UN Environment Programme (UNEP) issued the first in a proposed biennial series in 1998, titled Global Environment Outlook-1 or GEO-1. The second in the series, Global Environment Outlook 2000, was published in 1999. GEO-2000 is described by the UNEP's Executive Director, Klaus Töpfer, in the foreword as "a comprehensive integrated assessment of the global environment at the turn of the millennium, [and] a forward-looking document, providing a vision into the 21st century." Its status, however, is rendered uncertain by the printed caution that "The contents of this volume do not necessarily reflect the views or policies of UNEP or contributory organizations." GEO-2000 paints a generally bleak picture of environmental trends. It evidences a wide array of particulars ("In the Southern Ocean, the Patagonian toothfish is being over-fished and there is a large accidental mortality of seabirds caught up in fishing equipment"), but perhaps of more import are its statements about the root causes of environmental problems and what must be done. The excerpts below reflect some of these general views as they pertain to population. They are taken from the section entitled "Areas of danger and opportunity" in Chapter 1 of the report, and from the section "Tackling root causes" in Chapter 5. High resource consumption, fueled by affluent, Western lifestyles, is seen as a basic cause of environmental degradation. Cutting back this consumption will be required, freeing up resources for development elsewhere. Materialist values associated with urban living are part of the problem, given the concentration of future population growth in cities. And "genuine globalization" will entail free movement of people as well as capital and goods, thus optimizing "the population to environmental carrying capacity." Some of these positions are at least questionable: the supposed "innate environmental sensitivity of people raised on the land or close to nature," or the aim of "globalization of population movements." The latter does not appear in the recommendations, perhaps because of an implicit assumption that the effect of open borders on environmental trends is unlikely to be favorable. (For an earlier statement of the same sentiment,from 1927,see the comments by Albert Thomas, first director of the ILO, reproduced in the Archives section of PDR 9, no. 4.) [source] The global response to tropical heating in the Madden,Julian oscillation during the northern winterTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 601 2004Adrian J. Matthews Abstract A life cycle of the Madden,Julian oscillation (MJO) was constructed, based on 21 years of outgoing long-wave radiation data. Regression maps of NCEP,NCAR reanalysis data for the northern winter show statistically significant upper-tropospheric equatorial wave patterns linked to the tropical convection anomalies, and extratropical wave patterns over the North Pacific, North America, the Atlantic, the Southern Ocean and South America. To assess the cause of the circulation anomalies, a global primitive-equation model was initialized with the observed three-dimensional (3D) winter climatological mean flow and forced with a time-dependent heat source derived from the observed MJO anomalies. A model MJO cycle was constructed from the global response to the heating, and both the tropical and extratropical circulation anomalies generally matched the observations well. The equatorial wave patterns are established in a few days, while it takes approximately two weeks for the extratropical patterns to appear. The model response is robust and insensitive to realistic changes in damping and basic state. The model tropical anomalies are consistent with a forced equatorial Rossby,Kelvin wave response to the tropical MJO heating, although it is shifted westward by approximately 20° longitude relative to observations. This may be due to a lack of damping processes (cumulus friction) in the regions of convective heating. Once this shift is accounted for, the extratropical response is consistent with theories of Rossby wave forcing and dispersion on the climatological flow, and the pattern correlation between the observed and modelled extratropical flow is up to 0.85. The observed tropical and extratropical wave patterns account for a significant fraction of the intraseasonal circulation variance, and this reproducibility as a response to tropical MJO convection has implications for global medium-range weather prediction. Copyright © 2004 Royal Meteorological Society [source] The whaling war: Conflicting cultural perspectives (Respond to this article at http://www.therai.org.uk/at/debate)ANTHROPOLOGY TODAY, Issue 3 2010Adrian Peace The political ritual generated by Japanese whaling in the Southern Ocean annually captures the Australian imagination and at least the attention of international audiences. This article examines how Australia has become the self-appointed guardian of Antarctic whales whilst Japan remains resolutely pro-whaling. [source] Foraging areas of black-browed and grey-headed albatrosses breeding on Macquarie Island in relation to marine protected areasAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2006Aleks Terauds Abstract 1.Although marine protected areas (MPAs) are often established to protect threatened top-order predators, there is a paucity of data that can be used to evaluate their efficacy in achieving this purpose. 2.We assessed the effectiveness of a network of MPAs around Macquarie Island in the Southern Ocean by examining the foraging areas of breeding black-browed Thalassarche melanophrys and grey-headed albatrosses T. chrysostoma. 3.During late incubation and brood periods over 90% of time spent foraging by black-browed albatrosses was contained within MPAs, principally the Economic Exclusion Zone (EEZ) around Macquarie Island. In contrast, grey-headed albatrosses spent only 34% of their time foraging in MPAs. 4.Black-browed and grey-headed albatrosses spent 30% and 15% of their respective foraging times in the Marine Park around Macquarie Island. 5.Both black-browed and grey-headed albatrosses foraged in Antarctic waters under the jurisdiction of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), accounting for 5% and 12% of the total foraging times respectively. 6.The spatial extent of MPAs around Macquarie Island appear to adequately cover much of the foraging distribution of breeding black-browed albatrosses from Macquarie Island. 7.Breeding grey-headed albatrosses spend significantly more time in waters outside the spatial extent of the surrounding MPAs and are at higher risk from fisheries activities and other threats. 8.Further information on the foraging movements both of albatrosses outside the breeding season and of juvenile albatrosses is required to more fully assess the efficacy of MPAs in protecting foraging habitats of these species. Copyright © 2005 John Wiley & Sons, Ltd. [source] Climatic variability and the evolution of insect freeze toleranceBIOLOGICAL REVIEWS, Issue 2 2003BRENT J. SINCLAIR ABSTRACT Insects may survive subzero temperatures by two general strategies: Freeze-tolerant insects withstand the formation of internal ice, while freeze-avoiding insects die upon freezing. While it is widely recognized that these represent alternative strategies to survive low temperatures, and mechanistic understanding of the physical and molecular process of cold tolerance are becoming well elucidated, the reasons why one strategy or the other is adopted remain unclear. Freeze avoidance is clearly basal within the arthropod lineages, and it seems that freeze tolerance has evolved convergently at least six times among the insects (in the Blattaria, Orthoptera, Coleoptera, Hymenoptera, Diptera and Lepidoptera). Of the pterygote insect species whose cold-tolerance strategy has been reported in the literature, 29% (69 of 241 species studied) of those in the Northern Hemisphere, whereas 85%(11 of 13 species) in the Southern Hemisphere exhibit freeze tolerance. A randomization test indicates that this predominance of freeze tolerance in the Southern Hemisphere is too great to be due to chance, and there is no evidence of a recent publication bias in favour of new reports of freeze-tolerant species. We conclude from this that the specific nature of cold insect habitats in the Southern Hemisphere, which are characterized by oceanic influence and climate variability must lead to strong selection in favour of freeze tolerance in this hemisphere. We envisage two main scenarios where it would prove advantageous for insects to be freeze tolerant. In the first, characteristic of cold continental habitats of the Northern Hemisphere, freeze tolerance allows insects to survive very low temperatures for long periods of time, and to avoid desiccation. These responses tend to be strongly seasonal, and insects in these habitats are only freeze tolerant for the overwintering period. By contrast, in mild and unpredictable environments, characteristic of habitats influenced by the Southern Ocean, freeze tolerance allows insects which habitually have ice nucleators in their guts to survive summer cold snaps, and to take advantage of mild winter periods without the need for extensive seasonal cold hardening. Thus, we conclude that the climates of the two hemispheres have led to the parallel evolution of freeze tolerance for very different reasons, and that this hemispheric difference is symptomatic of many wide-scale disparities in Northern and Southern ecological processes. [source] The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopusesCLADISTICS, Issue 6 2008Jan M. Strugnell Understanding how environmental forcing has generated and maintained large-scale patterns of biodiversity is a key goal of evolutionary research and critical to predicting the impacts of global climate change. We suggest that the initiation of the global thermohaline circulation provided a mechanism for the radiation of Southern Ocean fauna into the deep sea. We test this hypothesis using a relaxed phylogenetic approach to coestimate phylogeny and divergence times for a lineage of octopuses with Antarctic and deep-sea representatives. We show that the deep-sea lineage had their evolutionary origins in Antarctica, and estimate that this lineage diverged around 33 million years ago (Ma) and subsequently radiated at 15 Ma. Both of these dates are critical in development of the thermohaline circulation and we suggest that this has acted as an evolutionary driver enabling the Southern Ocean to become a centre of origin for deep-sea fauna. This is the first unequivocal molecular evidence that deep-sea fauna from other ocean basins originated from Southern Ocean taxa and this is the first evidence to be dated. © The Willi Hennig Society 2008. [source] | ||||||||||||||||