共查询到20条相似文献，搜索用时 62 毫秒
1.
Claudio Campagna Alberto R. Piola Maria Rosa Marin Mirtha Lewis Teresita Fernndez 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1907-1924
This study describes the association between transient, mesoscale hydrographic features along the axis of the Brazil–Malvinas Confluence, in the SW Atlantic, and the foraging behavior of 2–3-year-old (focal) juvenile southern elephant seals, Mirounga leonina, from Península Valdés, Argentina. Departing from the dominant pattern of foraging on predictable bathymetric fronts on the Patagonian shelf and slope, three females out of 12 satellite-tracked juveniles remained at the edge of young warm-core eddies and near the outer core of cold-core eddies, coinciding with the most productive areas of these temperature fronts. Seal trajectories along high-temperature gradients were always consistent with the speed and direction of surface currents inferred from the temperature distribution and confirmed by surface drifters. Movements of foraging seals were compared with those of surface drifters, coinciding in time and space and yielding independent and consistent data on regional water circulation parameters. The diving pattern recorded for one focal seal yielded shallower dives and a loose diel pattern in the eddy, and a marked diurnal cycle compatible with foraging on vertically migrating prey in the cold waters of the Malvinas Current. Pre-reproductive females that use the mesoscale fronts of the Argentine Basin as an alternative foraging area would benefit from lower competition with more experienced seals and with other top predators that reproduce along the coast of Patagonia. 相似文献
2.
《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(10):1792-1814
Elephant seals are wide-ranging, pelagic, deep-diving (average of 400–600 m) predators that typically travel to open waters and continental shelf edges thousands of kilometers from their land breeding colonies. We report a less common pattern of foraging in the shallow waters of a continental shelf. Southern elephant seals, Mirounga leonina, that breed at Península Valdés (Argentina), face an extended (∼1,000,000 km2; 400–700 km-wide, depending on track), shallow (<150 m) and seasonally productive plateau, the Patagonian shelf. Adults of both sexes usually cross it in rapid transit to other potential foraging grounds on the shelf edge or in the Argentine Basin, but 2–4 year-old juveniles spread over the plateau and spent months in shallow waters. This behavior was recorded for 9 seals (5 males and 4 females) of 23 satellite-tracked juveniles (springs of 2004 and 2005) and for 2 subadult males studied in previous seasons. Trips included travel trajectories and time spent in areas where swim speed decreased, suggesting foraging. Preferred locations of juvenile females were in the proximity of the shelf break, where stratified waters had relatively high phytoplankton concentrations, but young and subadult males used the relatively cold (7–8 °C), low-salinity (∼33.3) mid-shelf waters, with depths of 105–120 m and a poorly stratified water column. Three of the latter seals, instrumented with time–depth recorders, showed dives compatible with benthic feeding and no diel pattern of depths distribution. Regions of the mid-shelf were used in different seasons and were associated with low chlorophyll-a concentration at the time of the visit, suggesting that surface productivity does not overlap with putative quality habitat for benthic foragers. Benthic diving on the shallow mid-shelf would be a resource partitioning strategy advantageous for young males prior to greater energetic demands of a high growth rate and a large body size. Later in life, the more predictable, bathymetry-forced, shelf-break front may offer the food resources that explain the uninterrupted increase of this population over several decades. 相似文献
3.
《African Journal of Marine Science》2013,35(3):373-382
Of the four types of terrestrial haulout periods undertaken by southern elephant seals Mirounga leonina, only the purpose of the winter haulout is unknown. Returning to a haulout site from distant pelagic foraging grounds bears significant costs in terms of increased energy expenditure, reduced foraging time and increased exposure to predation; therefore, each haulout must serve a purpose. We examined the hypothesis that the winter haulout serves to maintain familiarity with the natal site, thereby increasing site fidelity. To this end, we analysed a long-term mark-recapture dataset for female southern elephant seals at Marion Island, Southern Ocean. Results indicate that, whereas greater natal site fidelity as primiparous females was associated with recorded presence ashore at the study site during the winter haulout as immatures, this was not the case for multiparous females. Furthermore, recorded presence ashore during both the moult haulouts as immatures, and all haulouts as immatures, irrespective of haulout type, was also associated with increased site fidelity. This suggests that any haulout at the natal island as an immature seal, whether for the moult or winter haulout, assists in maintaining site fidelity. Therefore, while the winter haulout facilitates greater natal site fidelity, whether this is the sole reason for this terrestrial period remains uncertain. 相似文献
4.
Hydrographic observations collected by conductivity-temperature-depth(CTD) and instrumented elephant seals on the Prydz Bay continental shelf during 2012 and 2013 are used to characterize the intrusion of modified circumpolar deep water.As a regular occurrence,modified circumpolar deep water(MCDW) intrudes onto the shelf mainly between 150–300 m layer of 73°–75°E and then turns southeast affected by the cyclonic gyre of the Prydz Bay.The southernmost point of the warm water signal is captured on the east front of Amery Ice Shelf during March 2012.In terms of vertical distribution,MCDW occupies the central layer of 200 m with about 100 m thickness in the austral summer,but when to winter transition,the layer of MCDW deepens with time on the central shelf. 相似文献
5.
Dana K. Savidge Julie A. Amft 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1633-1655
Over the past 30 years, shelf circulation on the West Antarctic Peninsula (WAP) has been derived from hydrographic data with a reasonable level of confidence. However, with the exception of a very few drifter tracks and current-meter timeseries from moorings, direct velocity measurements have not previously been available. In this article, shelf and shelf-edge circulation is examined using a new velocity dataset, consisting of several years of acoustic Doppler current profiler transects, routinely collected along the ship tracks of the R/V Gould and the R/V Palmer since the fall of 1997. Initial processing and quality control is performed by Dr. Teresa Chereskin and Dr. Eric Firing, who then place the data in an archive accessible by public website, resulting in the broad availability of the data for a variety of uses. In this study, gridded Eulerian means have been calculated to examine circulation on the shelf and slope off the South Shetland Islands, in Bransfield Strait, and on the shelf and slope south of these regions, including Marguerite Bay and the adjacent shelf and shelf-edge. Shelf-edge flow is northeastward in the study area from the offshore of northern Alexander Island to Smith Island, while a southward flowing shelf-edge feature, probably the shallow component of the polar slope current, appears between Elephant Island and Livingston Island. The shallow polar slope current appears to turn shoreward to pass through Boyd Strait between Smith and Livingston Islands. In Bransfield Strait, there is cyclonic circulation. The previously identified northeastward-flowing South Shetland Island jet is strong and present in all seasons, with a large barotropic component not revealed by the hydrography-based velocities derived in the past. On the shelf seaward of Adelaide, Anvers and Brabant Islands, the strong along-shelf Antarctic Peninsula coastal current flows southwestward, with strongest velocities in winter (June–September) off Anvers and Brabant Islands, but stronger in summer (December–March) off Adelaide Island. Seaward of Marguerite Bay, there is seaward flow in the upper 400 m of the water column over the southwest bank of Marguerite Trough, strongest in summer, and shoreward flow near the northeast bank and adjacent shallower shelf areas. 相似文献
6.
《African Journal of Marine Science》2013,35(1):383-386
During the period April 1991–March 1996, 10 entangled Antarctic fur seals Arctocephalus gazella, 28 entangled Subantarctic fur seals A. tropicalis and one entangled southern elephant seal Mirounga leonina were observed at Marion Island, Southern Ocean. Entanglement of fur seals was estimated at between 0.01 and 0.15% of the combined population of both species. 相似文献
7.
D. S. Roper 《新西兰海洋与淡水研究杂志》2013,47(2):303-307
The distribution of Leptomithrax longipes (Thomson), on the continental shelf east of the Otago Peninsula appears to be affected by females migrating into deeper water at the edge of the shelf. The presence of immature crabs inshore suggests the existence of an onshore current. Nine sexually indeterminate individuals were examined; their combination of male and female characters indicated that they were males undergoing a process of feminisation. Tissue and blood smears contained a bacterium which was possibly causing this feminisation. 相似文献
8.
9.
Eileen E. Hofmann Yusuf Sinan Hüsrevo
lu 《Deep Sea Research Part II: Topical Studies in Oceanography》2003,50(22-26):3121
A one-dimensional, temperature-dependent model is implemented to simulate the descent–ascent cycle of Antarctic krill (Euphausia superba) embryos and larvae. Inputs to the model are monthly mean climatologies of ambient temperature and density fields obtained from the World Ocean Atlas Database for Southern Ocean waters. Simulations are done with a 1° resolution at a circumpolar scale, south of 60°S, and the results are interpolated to a 5′ grid to match the resolution of the bottom bathymetry data. Simulations of the descent–ascent cycle using environmental conditions corresponding to the Antarctic krill spawning season (December–March) resulted in unconstrained success in completion of the cycle in water deeper than 1000 m. Continental shelf regions favorable to successful hatching of Antarctic krill embryos are limited to areas along the west Antarctic Peninsula, large areas in the Bellingshausen and Amundsen Seas, offshore of Wilkes Land, and to the east and west of Prydz Bay. These are regions where the Southern Antarctic Circumpolar Current Front is along the shelf slope, the Antarctic Slope Front is absent, and Circumpolar Deep Water is present. The effect of seasonal variability in temperature on the descent–ascent cycle tends to enhance the probability of success in regions offshore of Wilkes Land, Queen Maud Land, and the eastern shelf of the Antarctic Peninsula later in the spawning season. The simulations show that success of the descent–ascent cycle is sensitive to initial embryo diameter and larval ascent rate. Initial embryo diameter may provide an additional constraint on success of the descent–ascent cycle, especially in continental shelf waters, where small embryos tend to encounter the bottom before hatching. The circumpolar distributions of simulated embryo hatching depth and larval success show that all regions of the Antarctic are not equal in the ability to support successful completion of the Antarctic krill descent–ascent cycle, which has implications for the overall circum-Antarctic krill distribution and for the development of nutrient and material budgets, especially for Antarctic continental shelf areas. 相似文献
10.
利用美国冰中心和雪冰中心提供的海冰资料和我国南极考察现场的海冰观测资料,对南极海冰的长期变化进行了研究.研究表明20世纪70年代后期是多冰期;80年代是少冰期;90年代南极海冰属于上升趋势,后期偏多,区域性变化差别大,东南极海冰偏多,西南极海冰即南极半岛两侧尤其是威德尔海区和别林斯高晋海的冰明显偏少.东南极和西南极海冰的变化趋势总是反相的.90年代后期普里兹湾的海冰明显偏多,南极大陆陆架冰外缘线总体没有明显的收缩,有崩解也有再生的自然变化现象.西南极威德尔海的龙尼冰架和罗斯海冰架东部崩解和收缩趋势明显,东南极的冰架也有崩解和收缩,但没有西南极明显.陆架冰崩解向海洋输送的冰山对全球海平面升高有一定的影响.目前南极冰盖断裂崩解形成的冰山,向海洋输入的水量可使全球海平面上升约14mm.南极海冰没有随着全球气候温暖化而明显减少,而是按照东南极和西南极反相的变化规律进行周期性的变化、调整和制约. 相似文献
11.
E. Sañé E. Isla A. Grémare J. Gutt G. Vétion D.J. DeMaster 《Journal of Sea Research》2011,65(1):94-102
In March 2002, 3200 km2 of the Larsen B ice shelf collapsed off the Eastern Antarctic Peninsula (EAP). In the austral summer of 2006, sea floor sediment was recovered beneath the extinct Larsen B ice shelf and in a region off the Northern Antarctic Peninsula (NAP), which has been free of ice shelves for more than 1000 yr. To assess changes in the chemical composition of the sediment after ice shelf collapses, chlorophylls and pheophytins were measured in sediment cores at six stations. This is the first time that chlorophyll pigments have been analysed in sediment samples from regions under recently collapsed ice shelves. Five years after the ice shelf collapse, Chla and Chlc concentrations were similar in the interfacial sediment (upper 1 cm) of NAP and EAP regions. However, in EAP Chla and Chlc concentrations decreased more rapidly with depth in the sediment column and were negligible below 2 cm depth. The high Chla to Pheoa ratios indicated that sedimentary pigments found in EAP had undergone limited degradation suggesting that they were locally produced rather than laterally advected. Complementary information from excess 210Pb activity and diatom valve distributions provided further evidence that the pigment fluxes to the seabed in EAP took place only after the ice shelf collapse. 相似文献
12.
Clay minerals of the surface sediments of Bransfield Strait, Antarctica, exhibit distinctive geographical distributions: kaolinite has the highest concentration near the shore of the South Shetland Islands in the northern strait (20%); chlorite, near Smith Island in the northwestern strait; illite, on the continental shelf off the Antarctic Peninsula in the southern strait (80%); and smectite, close to the Penguin and Bridgeman islands in the northeastern strait (25%). This distribution pattern, combined with hydrographic and climatic data for the strait, are used to infer clay mineral provenance and dispersal patterns. 相似文献
13.
《African Journal of Marine Science》2013,35(1):549-554
During the period 17–22 December 2001, the onshore distribution and the abundance of Antarctic fur seals Arctocephalus gazella and Subantarctic fur seals A. tropicalis were determined for Prince Edward Island. Two breeding colonies of Antarctic fur seals were located on the south-east coast of the island; the first a mixed (with Subantarctic fur seals) breeding colony with an estimated 24 pups on a vegetated promontory on the northern section of Boggel Beach, and the second, a presumably pure Antarctic fur seal breeding colony with an estimated 380 pups, at Penguin Beach. At a mean intrinsic rate of natural increase of 16.2% per year, Antarctic fur seals appear to be in the rapid recolonization phase of population growth. Breeding colonies of Subantarctic fur seals, largely found on the entire east coast, produced an estimated 15 000 pups, and the population had maintained a mean intrinsic rate of natural increase of some 9.5% per year since 1987/88. 相似文献
14.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(6):987-1010
The Harvard Ocean Prediction System (HOPS) is configured to simulate the circulation of the Scotia Sea and environs. This is part of a study designed to test the hypothesis that Antarctic krill (Euphausia superba) populations at South Georgia in the eastern Scotia Sea are sustained by import of individuals from upstream regions, such as the western Antarctic Peninsula. Comparison of the simulated circulation fields obtained from HOPS with observations showed good agreement. The surface circulation, particularly through the Drake Passage and across the Scotia Sea, matches observations, with its northeastward flow characterized by three high-speed fronts. Also, the Weddell Sea and the Brazil Current, and their associated transports match observations. In addition, mesoscale variability, an important component of the flow in this region, is found in the simulated circulation and the model is overall well suited to model krill transport. Drifter simulations conducted with HOPS showed that krill spawned in areas coinciding with known krill spawning sites along the west Antarctic Peninsula continental shelf can be entrained into the Southern Antarctic Circumpolar Current Front (SACCF). They are transported across the Scotia Sea to South Georgia in 10 months or less. Drifters originating on the continental shelf of the Weddell Sea can reach South Georgia as well; however, transport from this region averages about 20 months. Additional simulations show that such transport is sensitive to changes in wind stress and the location of the SACCF. The results of this study show that krill populations along the Antarctic Peninsula and the Weddell Sea are possible source populations that can provide krill to the South Georgia population. However, successful transport of krill to South Georgia is shown to depend on a multitude of factors, such as the location of the spawning area and timing of spawning, and variations in the location of the SACCF. Therefore, this study provides insight into which environmental factors control the successful transport of krill across the Scotia Sea and with it a better understanding of krill distribution in the region. 相似文献
15.
《Marine Geology》2007,236(1-2):1-13
The direct record of Late Miocene–Early Pliocene Antarctic Peninsula Ice Sheet expansions from a previously published seismostratigraphic study of the outer shelf at Ocean Drilling Program Site 1097 is compared to the glacial history we deduced from published proxy evidence within coeval sections on the adjacent continental rise. The proxies are sedimentary structures (laminated vs. massive/bioturbated facies) and clay minerals (predominantly smectite and chlorite contents) from Ocean Drilling Program Site 1095 located on the distal part of a large drift. The comparison shows that more sedimentary cycles are evident on the continental rise for three of the four diatom biozones we considered. This indicates that the continental-rise sedimentology may indeed be related to local or regional paleoenvironmental variability, including Antarctic Peninsula Ice Sheet grounding events on the adjacent outer continental shelf. If correct, this would be a promising result because unlike the outer continental shelf sequences drilled thus far, the continental rise record is relatively continuous and can be dated using paleomagnetic and biostratigraphic data. However, our study also shows that no objective criteria provide direct linkages between the glacial history we deduced from the two continental rise proxies and that previously derived from the continental-shelf seismic stratigraphy. Furthermore, the two sedimentologic proxies on the continental rise do not always provide a consistent picture of glacial history when compared against each other. 相似文献
16.
Productivity, trophic levels and size spectra of zooplankton in northern Norwegian shelf regions 总被引：1，自引：0，他引：1
Meng Zhou Kurt S. Tande Yiwu Zhu Sünnje Basedow 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1934
Many studies have been conducted in northern Norwegian shelf regions to assess distributions and abundances of zooplankton in the last decade using towed Scanfish-conductivity, temperature and depth sensors (CTD)–optical plankton counter (OPC), and plankton nets. Significant progresses have been made in understanding dominant species, life histories and behavior, and in using size-structured data to identify dominant species in a certain size range. Using these Scanfish–CTD–OPC data, the analysis of zooplankton community size structures, compositions and their relationships with water types is made along the shelf region from Lofoten, North Cape to Varangerfjorden. From the relationships between the water types and zooplankton communities, the transports and exchanges of zooplankton communities between the Norwegian Coastal and Norwegian Atlantic Waters in regions near Malangsgrunnen and Nordvestbanken are examined. The biovolume (biomass) spectra are further analyzed for the productivity, trophic levels and seasonality of communities in these regions, indicating a steeper slope of the biovolume spectrum for a community dominated by herbivorous species in spring and a flatter slope for a community dominated by carnivorous–omnivorous species in winter. The comparison with the zooplankton biovolume spectra obtained in areas west of Antarctic Peninsula is made to examine and understand the differences in the zooplankton biovolume spectra, their trophic dynamics and potential human impacts between different regions. 相似文献
17.
Antoni Quetglas Francesc Ordines María González Ignacio Franco 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1379-1390
The life cycle of the deep-sea octopus Pteroctopus tetracirrhus was studied from monthly samples obtained throughout the year in different areas of the western Mediterranean (mainly around the Balearic Islands and along the coast of the Iberian Peninsula). A total of 373 individuals (205 females, 168 males) were analyzed; females ranged from 4.5 to 14.0 cm mantle length (ML) and males from 4.5 to 11.5 cm ML. There were few small-sized octopuses (<7 cm ML) in the samples, which might indicate that these individuals inhabit rocky grounds that are not accessible to trawlers or waters deeper than the maximum depth sampled (800 m). The species occurred more frequently around the Balearic Islands than along the Iberian Peninsula as they appeared in 20% and 7%, respectively, of the hauls in these areas. The octopus inhabits the lower continental shelf and upper slope in both areas, primarily between 200 and 500 m depth. Modal lengths were followed from autumn, when recruits were caught by trawlers, to summer, when reproduction took place. Females grew from 8 to 10 cm ML from winter to spring, but this modal size did not increase further in summer; males grew from 7 to 9 cm ML from winter to spring. The total disappearance of large individuals after summer suggests a life cycle lasting a single year. The evolution of the monthly mean sizes showed that the growth was best described by log-linear functions in both sexes. The length at first maturity was clearly higher in females (12 cm ML) than in males (8 cm ML). A total of 30 different prey items, belonging to four major taxonomic groups (crustaceans, osteichthyes, cephalopods and gastropods), were identified in the stomach contents. The diet of the octopus was based on crustaceans and teleosts, which accounted for 75% and 23% of the prey items, respectively. Cephalopods and gastropods were accessory prey as they only represented 1.6% and 0.7%, respectively, of the total. The octopus showed a marked preference for the benthic fish Symphurus nigrescens and the endobenthic crustacean Alpheus glaber. The bathymetric distribution of P. tetracirrhus coincides with those of these two main prey, which suggests that the distribution of the octopus might be strongly linked to its trophic resources. 相似文献
18.
《African Journal of Marine Science》2013,35(3):451-455
The onshore distributions and the abundances of Antarctic fur seals Arctocephalus gazella and Subantarctic fur seals A. tropicalis were determined at Prince Edward Island during 16-20 December 2008. This repeats a survey conducted in December 2001 and extends the area surveyed to include the entire south-west coast of Prince Edward Island. Of the two colonies of Antarctic fur seals, the colony among Subantarctic fur seals north of Boggel Beach remained small, with increased numbers of Subantarctic fur seals and putative hybrids. The other Antarctic fur seal breeding colony at Penguin Beach remained free of Subantarctic fur seals and had expanded at a mean intrinsic rate of natural increase of 11.4% per year from 2001. With an estimated 810 pups, the Antarctic fur seal is still in the rapid recolonisation phase of population growth. The distribution of the more widespread and abundant Subantarctic fur seals also had increased, with several new breeding colonies along the east coast and one at Kent Crater on the west coast. The annual pup production was conservatively estimated at 14 130 pups. The mean intrinsic rate of natural increase has declined to ?0.3% per year over the last seven years, compared to the 9.3% per year between 1987/1988 and 2001/2002, and the population is in the mature phase of population growth. 相似文献
19.
《African Journal of Marine Science》2013,35(1):75-86
Systematic recording of elephant-seal sightings, including 92 hitherto unpublished records, has increased the number of records on the coast of southern Africa to 130. The data set is now the largest on record for any southern continent other than Antarctica. It provides an opportunity to examine the biological significance of such matters as seasonality, possible causes of haul-out, their possible origins and implications for interpretation of elephant-seal dispersal around their breeding colonies. The number of sightings has increased recently. The overall sex ratio is 52,4 per cent male to 21 per cent female, 26,6 per cent being of indeterminate sex. The seals haul out mainly from November to February, and indications are that males and females disperse straight after the breeding season and a few months later reach the coast of southern Africa. The most likely primary cause of haul-out for immature seals is to moult. It is postulated that the seals originated mainly from South Georgia. It is not clear if the seals recorded are true vagrants or the outer fringe of a normal dispersal. Of the sightings, 24 were tagged after arrival, and of these, 13 were sighted more than once and 6 showed a regular pattern of movement. There were 19 sightings of elephant seals at local fur-seal rookeries and, with one exception, the two species co-existed peacefully. There are three confirmed and two unconfirmed births on the coast. The ability to develop a preference for unfamiliar places and to pup outside their natal colonies could explain how they colonize new areas. 相似文献
20.
The seasonal cycle of circulation and transport in the Antarctic Peninsula shelf region is investigated using a high-resolution (∼2 km) regional model based on the Regional Oceanic Modeling System (ROMS). The model also includes a naturally occurring tracer with a strong source over the shelf (radium isotope 228Ra, t1/2=5.8 years) to investigate the sediment Fe input and its transport. The model is spun-up for three years using climatological boundary and surface forcing and then run for the 2004–2006 period using realistic forcing. Model results suggest a persistent and coherent circulation system throughout the year consisting of several major components that converge water masses from various sources toward Elephant Island. These currents are largely in geostrophic balance, driven by surface winds, topographic steering, and large-scale forcing. Strong off-shelf transport of the Fe-rich shelf waters takes place over the northeastern shelf/slope of Elephant Island, driven by a combination of topographic steering, extension of shelf currents, and strong horizontal mixing between the ACC and shelf waters. These results are generally consistent with recent and historical observational studies. Both the shelf circulation and off-shelf transport show a significant seasonality, mainly due to the seasonal changes of surface winds and large-scale circulation. Modeled and observed distributions of 228Ra suggest that a majority of Fe-rich upper layer waters exported off-shelf around Elephant Island are carried by the shelfbreak current and the Bransfield Strait Current from the shallow sills between Gerlache Strait and Livingston Island, and northern shelf of the South Shetland Islands, where strong winter mixing supplies much of the sediment derived nutrients (including Fe) input to the surface layer. 相似文献