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New Zealand fur seals, Arctocephalus forsteri, have been increasing in abundance in South Australia for at least the past three decades. A survey of New Zealand fur seals during the 1989/90 breeding season determined that about 20...
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New Zealand fur seals, Arctocephalus forsteri, have been increasing in abundance in South Australia for at least the past three decades. A survey of New Zealand fur seals during the 1989/90 breeding season determined that about 20% of the Australian population bred at 16 sites in Western Australia, amounting to 1429 pups and an absolute abundance estimate of 7100 fur seals. A further survey of all fur seal colonies in Western Australia to determine current pup production and abundance estimates, and trends in pup production since the previous survey was undertaken in January 1999. Of the 17 breeding sites now known in Western Australia, 16 were surveyed and pup production had increased at all but one. The rate of change in pup production at the one unsurveyed site (West Island), was estimated as being equivalent to the mean rate of change at other sites. The estimated mean annual, exponential rate of increase (r) for all sites was 0.09, equivalent to a 9.8% annual increase in pup production and an overall increase in pup production in Western Australia of 113.3% between surveys. Total annual pup production has increased to 3090. The estimate of absolute abundance of New Zealand fur seals in Western Australia is now 15 100, in contrast to the 7100 estimated for the 1989/90 season. Mortality of pups at the time of the survey was estimated to be at least 1.3%. It is predicted that New Zealand fur seal populations will continue to increase in Western Australia. This is likely to have important management implications regarding aquaculture and fisheries activities. The increase in fur seal populations appears to be in contrast to populations of Australian sea lions, Neophoca cinerea, for which preliminary data show no evidence for a population increase. It is unknown whether the dynamics affecting these two species are related. [References: 20]
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We have found experimental evidence which shows that the volcanic tremor recorded at Deception Island (South Shetland islands, Antarctica) is a superposition in time of overlapping hybrid events. We studied data from a small apert...
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We have found experimental evidence which shows that the volcanic tremor recorded at Deception Island (South Shetland islands, Antarctica) is a superposition in time of overlapping hybrid events. We studied data from a small aperture seismic array. Data analysis for tremor and hybrids included: (1) spectral analysis; (2) apparent slowness and back-azimuth determination by using the zero-lag cross-correlation method; and (3) polarization analysis. Both types of events share these common features: (a) two dominant spectral bands at frequencies 1-3 Hz (the most energetic) and 4-8 Hz; (b) several coherent phases with the same back-azimuth to the source and apparent slowness along the whole signal; (c) in the high frequency band, the apparent slowness is very low (around 0.17 s/km), indicating the propagation of body waves; (d) in the low frequency band, the apparent slowness is high (around 1.6 s/km), consistent with the presence of surface waves; and (e) clear P-wave onset followed by a complex pattern of Rayleigh waves. Therefore, both types of events are strongly related because they share the same source region, the same wave-propagation properties, and the same wave composition. Moreover, several arrivals, that resemble a single hybrid event, have been found along the tremor signals. Due to these reasons, we hypothesize that volcanic tremor of Deception Island is a superposition of hybrid type events. The source of both types could be the interaction between thaw water and hot materials in a shallow aquifer. [References: 21]
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In addition to protecting species, conservation also includes the maintenance of evolutionary processes, but this aspect is often overlooked. Nesospiza buntings provide a good case study of the need to conserve evolutionary proces...
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In addition to protecting species, conservation also includes the maintenance of evolutionary processes, but this aspect is often overlooked. Nesospiza buntings provide a good case study of the need to conserve evolutionary processes. They are endemic to the South Atlantic Tristan da Cunha archipelago, and traditionally have been treated as two species, with each having different subspecies on Nightingale and Inaccessible Islands. Both species are listed as Vulnerable because of their small ranges (< 20 km(2)) and the threat posed by the possible introduction of alien organisms such as mice or rats. The two species differ markedly in size, especially bill size, related to dietary differences. However, recent research suggests that morphological diversity evolved independently on Nightingale and Inaccessible Islands, necessitating a revision of the taxonomy within the genus. I recommend that five taxa be recognized, with two endemic to Nightingale and three to Inaccessible Island. N. wilkinsi and N. questi on Nightingale are well-defined species, but there is considerable hybridization between taxa on Inaccessible Island. These three taxa may be incipient species, but are perhaps best treated as subspecies: N. acunhae acunhae, N. a. dunnei and N. a. fraseri (nom. nov.). All three species qualify as threatened, with N. acunhae and N. questi Vulnerable and N. wilkinsi Endangered. With fewer than 200 individuals, N. wilkinsi has one of the smallest natural populations of any bird. A reassessment of its population size is a conservation priority, following the 2001 storm that damaged many Phylica trees on Nightingale Island. Improved biosecurity quarantine measures are also needed for Nightingale Island. Care should be taken not to disrupt the natural processes occurring among bunting taxa on Inaccessible Island.
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Darwin described as an 'abominable mystery' the abrupt origin of angiosperms in the mid-Cretaceous and the high diversification rates in their early history. The father of evolutionary theory could not fathom this rapid diversific...
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Darwin described as an 'abominable mystery' the abrupt origin of angiosperms in the mid-Cretaceous and the high diversification rates in their early history. The father of evolutionary theory could not fathom this rapid diversification and rather invoked that 'there was during long ages a small isolated continent in the S. hemisphere, which served as the birthplace of the higher plants'. In this essay, we comment on the spatial origin of angiosperms, but focus primarily on understanding the abiotic factors that promoted the early diversification of angiosperms by reviewing palaeobotanical, palaeogeographical, phylogenetics and biogeographical evidence. We argue that islands located in the region today occupied by South-East Asia played a major role in angiosperm diversification during the Late Jurassic and Early Cretaceous
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Aim Networks of connected marine protected areas (MPAn) are recognized as the key area-based management tool to preserve biodiversity, moderate exploitation of marine resources and increase ecological resilience to climate change....
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Aim Networks of connected marine protected areas (MPAn) are recognized as the key area-based management tool to preserve biodiversity, moderate exploitation of marine resources and increase ecological resilience to climate change. Although population genetic studies could greatly benefit connectivity assessments between MPAs, genetic data are rarely used in MPAn planning. Here, we aim to illustrate the use of a multispecies and multilocus approach to provide recommendations for MPAn design, highlighting the importance of the species selected and the analyses performed. Our study is focused on the Southern Ocean, an area of keen multinational interest given its scientific significance, economic importance and its unique, shared legal status. Location South Georgia and South Sandwich Islands MPA (SGSSI MPA), the South Orkney Islands and the Western Antarctic Peninsula (WAP)—where an MPA was proposed in 2018 (Domain 1 MPA) but has not been approved by the Commission for the Conservation of the Antarctic Marine Living Resources (CCAMLR). Methods Our datasets include 819 individuals from five different species with contrasting life-history strategies: two nemerteans ( Antarctonemertes valida and A. riesgoae ), two annelids ( Pterocirrus giribeti and Neanthes kerguelensis ) and one sponge ( Mycale [Oxymycale] acerata ). To identify genetic connectivity patterns in our study area, spanning roughly 2500?km, we used the COI mitochondrial marker and genome-wide ddRADseq-derived SNPs. Results A consistent lack of connectivity between SGSSI MPA and the WAP was found for all studied species. Additionally, our data indicated a stepping-stone role for the South Orkney Islands between these two genetically differentiated regions. Main conclusions Our results reveal how the application of comparative phylogeography and population genomics can guide policymakers in their decision-making process during MPAn design. We detected priority areas for conservation in Antarctica, including the South Orkney Islands and the WAP, providing strong evidence for the implementation of the Domain 1 MPA.
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Detrital zircon populations from two sandstone samples from the lower member (Johnsons Dock Member) of the Miers Bluff Formation at Hurd Peninsula have been dated by the Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb metho...
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Detrital zircon populations from two sandstone samples from the lower member (Johnsons Dock Member) of the Miers Bluff Formation at Hurd Peninsula have been dated by the Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb method. In one of the samples, zircons as young as early Middle Jurassic (Bajocian) age are present. In the second sample, the youngest detrital zircons are Middle Triassic in age. The detrital zircon age spectra indicate that Permian, early Palaeozoic and Meso- to Neoproterozoic zircon bearing rocks were present in the source areas of the Miers Bluff Formation. The sedimentary rocks are intruded by the Hesperides Point Intrusive diorite stock which yielded a U-Pb zircon crystallization age of 137.7 +/- 1.4 Ma (Early Cretaceous, Valanginian). These results indicate that sedimentation of the Johnsons Dock Member of the Miers Bluff Formation is bracketed in time between the Bajocian and the Valanginian. The Miers Bluff Formation has been correlated with the Trinity Peninsula Group from the Antarctic Peninsula, based on sedimentological and structural similarity. Since the Trinity Peninsula Group is older than Middle Jurassic a direct chronological correlation is not supported by our new U-Pb zircon data. However, we suggest that the tectonic setting may have migrated in time with deposition of the pre-Middle Jurassic TPG on the peninsula, to Livingston Island where the maximum age for deposition of the MBF is Bajocian (about 170 Ma).
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This paper presents horizontal and seasonal differences in the concentrations of nitrogen and phosphorus in the surface waters of Admiralty Bay. The average annual concentrations of total nitrogen and total phosphorus were found t...
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This paper presents horizontal and seasonal differences in the concentrations of nitrogen and phosphorus in the surface waters of Admiralty Bay. The average annual concentrations of total nitrogen and total phosphorus were found to be 1. 054 and 0. 129 mg dm(-3) respectively. Organic nitrogen constituted 59% of total nitrogen on average, while N-NO3- was substantially higher than N-NH4+ (0.362 and 0.062 mgN dm(-3), respectively). Organic phosphorus constituted 34% of total phosphorus on average, and the mean annual concentration of reactive phosphorus was 0.085 mgP dm(-3). The observed concentrations of N and P were higher in the nearshore area and lower in the central part of the Admiralty Bay basin. In explaining this account was taken of surface runoff into the bay, the decay of marine macroalgae in the tidal area and the excretion of N and P by marine animals. The concentrations of total nitrogen and total phosphorus in freshwater streams varied from 0.528-5.698 mgN dm(-3) and from 0.088-1.709 mgP dm(-3). In laboratory experiments, 24-hour loads of total nitrogen and total phosphorus released from the remains of macroalgae into the waters of the bay were estimated at about 6.2 N and 10.3 tP, while the approximate quantities excreted by macrozoobenthos were 482 kgN and 48 kgP. The availability of N-NH4+ was seen to be greater in the waters of the bay than has been reported for open water in this part of the ocean and water from the Bransfield Strait had a diluting effect on the concentrations of nitrogen and phosphorus in the bay. The role of the wind in carrying mineral salts from waters of the Bay to the inland environment was also discussed.
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During the summer, a northward, wind-driven current dominates the Rottnest Island region in southwestern Australia. Field studies have shown that the interaction between Rottnest Island and the northward current generates upwellin...
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During the summer, a northward, wind-driven current dominates the Rottnest Island region in southwestern Australia. Field studies have shown that the interaction between Rottnest Island and the northward current generates upwelling at the western end of the island, which is advected downstream, resulting in isotherm doming in the wake region. Flow curvature-induced secondary circulation has been proposed as the dominant mechanism responsible for this upwelling. Here, a three-dimensional numerical model, together with field observations, was used to undertake a detailed investigation of the three-dimensional flow structure in the wake region. Comparison of the observed upwelling pattern and the simulated flows revealed the island's dominant role in generating upwelling. This result was confirmed with the use of idealized numerical experiments. The modeling results confirmed the presence of secondary circulation, generated as a result of flow curvature at the western end of the island, which caused strong upwelling and extended downstream.
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At Laurie Island, South Orkney Islands, there are some breeding areas where two Pygoscelid species (Pygoscelis adeliae and P. antarctica) breed at the same sites, competing for the available space. To study the effects of this com...
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At Laurie Island, South Orkney Islands, there are some breeding areas where two Pygoscelid species (Pygoscelis adeliae and P. antarctica) breed at the same sites, competing for the available space. To study the effects of this competition on the breeding performance of the Adelie penguin, data on breeding chronology, population size and reproductive success were collected from the 1995/96 to 1997/98 breeding seasons in areas of competition (mixed groups) and areas where only Adelie penguins breed (single groups). The numbers of Adelie breeding pairs increased by 54% in single groups while they dropped by 14% in mixed groups. The number of chicks in creches followed a similar overall trend in mixed and single groups throughout the study period. However, while the chicks in creches in mixed groups represented 64% of the total number in 1995, they only amounted to 56% in the 1997 season. On average, 32% of the Adelie nests were usurped by P. antarctica. The peak of Adelie nest losses to chinstraps occurred from 6-20 November in 1995 and 1996, while in 1997 the peak of nest site takeovers took place between 20 November and 6 December due to the later arrival of chinstraps. In areas of competition, the overall breeding success of Adelie penguins was significantly depressed, this depression being due mainly to egg losses. We suggest that the presence of chinstraps had not only direct adverse effects on the breeding success of Adelie penguins in mixed sites, but also a possible long-term effect by negatively impacting on the recruitment of pre-breeding birds.
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In the summer 2000-01, thermal monitoring of the permafrost active layer within various terrestrial sites covered by lichen, moss or grasses was undertaken at Jubany (King George Island) and Signy Island in the Maritime Antarctic....
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In the summer 2000-01, thermal monitoring of the permafrost active layer within various terrestrial sites covered by lichen, moss or grasses was undertaken at Jubany (King George Island) and Signy Island in the Maritime Antarctic. The results demonstrated the buffering effect of vegetation on ground surface temperature (GST) and the relationship between vegetation and active layer thickness. Vegetation type and coverage influenced the GST in both locations with highest variations and values in the Deschampsia and Usnea sites and the lowest variations and values in the Jubany moss site. Active layer thickness ranged from 57 cm (Jubany moss site) to 227 cm (Signy Deschampsia site). Active layer thickness data from Signy were compared with data collected at the same location four decades earlier. Using a regression equation for air temperature versus ground surface temperatures the patterns of changing air temperature over time suggest that the active layer thickness increased c. 30 cm between 1963 and 1990 and then decreased 30 cm between 1990 and 2000. The documented increased rate of warming (2 degrees C +/- 1) since 1950 for air temperatures recorded in the South Orkney Islands suggests that the overall trend of active layer thickness increase will be around 1 cm year(-1).
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