Eric J. Woehler

Ocean circulation off east Antarctica affects ecosystem structure and sea-ice extent

Sea ice and oceanic boundaries have a dominant effect in structuring Antarctic marine ecosystems. Satellite imagery and historical data have identified the southern boundary of the Antarctic Circumpolar Current as a site of enhanced biological productivity. Meso-scale surveys off the Antarctic peninsula have related the abundances of Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) to inter-annual variations in sea-ice extent. Here we have examined the ecosystem structure and oceanography spanning 3,500 km of the east Antarctic coastline, linking the scales of local surveys and global observations. Between 80° and 150° E there is a threefold variation in the extent of annual sea-ice cover, enabling us to examine the regional effects of sea ice and ocean circulation on biological productivity. Phytoplankton, primary productivity, Antarctic krill, whales and seabirds were concentrated where winter sea-ice extent is maximal, whereas salps were located where the sea-ice extent is minimal. We found enhanced biological activity south of the southern boundary of the Antarctic Circumpolar Current rather than in association with it. We propose that along this coastline ocean circulation determines both the sea-ice conditions and the level of biological productivity at all trophic levels.

Phenological changes in the southern hemisphere.

Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand), South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias), although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa) and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially and logistically supported.

Shearwater Foraging in the Southern Ocean: The Roles of Prey Availability and Winds

Background Sooty (Puffinus griseus) and short-tailed (P. tenuirostris) shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. Methodology/Principal Findings Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140°E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. Conclusions/Significance The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.

Observed and predicted effects of climate on Australian seabirds

Abstract Although there is growing evidence of climate warming, for many regions the broader effects of climate variation on marine top predators remains unknown owing to the difficulty in obtaining, for synthesis, long-term and short-term datasets on multiple species. In the Australian region, climatic and oceanographic variability and change have been shown to affect marine species, often with profound consequences. Many seabirds are apex predators for which changes in climatic and oceanic dynamics have driven range movements poleward, reduced breeding success and altered breeding timing for some species. Here we review the literature to assess and determine the vulnerability of Australian seabirds to variation and change in climate and identify which species and ecosystems may be more resilient to future climate warming. It is clear from this synthesis that not all Australian seabirds are affected similarly, with responses varying by species and location. In addition, the paucity of information on the distribution and biology of seabird prey, foraging patterns and movements of seabirds, and the ability of seabirds to switch between prey species or adjust timing of life-cycles make generalisations about potential effects of future climate change and adaptive capacity in seabirds difficult. This applies both within Australia and elsewhere, where data are similarly sparse.

Impacts of human visitors on breeding success and long-term population trends in Adélie Penguins at Casey, Antarctica

Breeding populations of Aélie Penguins Pygoscelis adeliae have been counted at two localities near Casey Station in Wilkes Land, East Antarctica since 1959/60 and 1968/69. At Whitney Point, the breeding population increased from 1122 pairs in 14 colonies in 1959/60 to 4714 pairs in 36 colonies in 1992/93. All new colonies at Whitney Point established on relict colony sites identified in 1959/60. On Shirley Island, the total breeding population has remained at 7770 pairs ±10% between 1968/69 and 1992/93, except in 1990/91 when the population peaked at 8719 pairs. An association between the age of a colony and its rate of increase was observed at Whitney Point, with new colonies (those established since 1971/72) increasing more rapidly than colonies extant in 1959/60. At Shirley Island, where most of the colonies extant in 1968/69 have decreased in population, the establishment and growth of 13 colonies has offset this decrease; these new colonies also exhibited the association between age and rate of increase. Breeding success (chicks fledged per nest) was significantly lower for Shirley Island colonies than for those at Whitney Point. Human visitors to Shirley Island from Casey station are believed to be responsible for the observed changes in the distribution and abundance of breeding pairs and for maintaining the stable population by reducing overall breeding success through the disturbance associated with visits.

A 9000-year record of Adélie penguin occupation and diet in the Windmill Islands, East Antarctica

We investigated 17 abandoned Adélie penguin (Pygoscelis adeliae) colonies in the Windmill Islands, East Antarctica, in summer 2002/03. Forty radiocarbon dates on penguin bones and eggshells from 13 of these sites indicate a near continuous occupation by breeding penguins in this region for over 9000 years. These dates refine the recent geological record in this region and indicate that deglaciation of the northern islands occurred much earlier than previously suggested. Dietary remains from these sites include at least 23 taxa of cephalopods and teleost fish. Quantification of these remains indicates significant fluctuations in the relative abundance of two of the more common major prey taxa. The Antarctic silverfish (Pleuragramma antarcticum Boulenger) was the most common teleost prey during all time periods represented by the ages of the sites, but preservational factors may explain a gradual decrease in the remains of this species in increasingly older sites. The most common cephalopod in the sediments was the squid, Psychroteuthis glacialis Thiele, which occurred in low numbers in most sites except one (Site 75). An unusually high number of squid beaks preserved in Site 75, dating to approximately 5700–6100 cal. yr BP, does not correlate with a decrease in fish prey at that time. The high number of abandoned penguin colonies (> 200) in the Windmill Islands may be due to population cycles in the past in association with low nest-site fidelity and movement by breeding penguins to new sites within this region.

Hollow-using vertebrate fauna of Tasmania: distribution, hollow requirements and conservation status

In Tasmania, a considerable proportion of the forested landscape is available for land clearance and production forestry, which has and will continue to result in a decline in hollow availability unless managed appropriately. All hollow-using species are listed as having priority status under the Tasmanian Regional Forest Agreement. To ensure the habitat for hollow-using fauna is managed effectively, we first have to understand the requirements of the species involved. This paper is a review of the distribution, hollow requirements and conservation status of the five species of arboreal marsupials, eight species of bats and 29 bird species that use hollows in Tasmania. The number of species that use hollows is lower than in many other areas of Australia, but these species represent a large proportion of the vertebrate fauna of Tasmania. Three of these species and nine subspecies are endemic to Tasmania and seven are exotic. Four bird species are listed as Threatened at the state and/or national level. Twenty-five of Tasmania’s hollow-using species are capable of using small hollows, 14 can use medium-sized hollows and three bird species are limited to using large hollows. Current records indicate that the highest diversity of hollow-using species is associated with dry forest areas.

Distribution and abundance of the antarctic petrel

-Published and unpublished information on the distribution and abundance of the Antarctic Petrel (Thalassoica antarctica) is reviewed. Currently 35 colonies with approximately half a million breeding pairs are known. All but one of these known colonies are situated in East Antarctica. However, an estimate derived from at sea studies in three of four apparent centers of oceanic occurrence suggests a population as high as four to seven million breeding pairs (10 to 20 million individuals). In spite of the tentative nature of such an estimate, the difference with the colony-derived figure strongly suggests the existence of large, currently undiscovered colonies, particularly in western Antarctica and Victoria Land, where a complete mismatch exists between bird observations at sea and known colonies. In eastern Antarctica, in addition to undiscovered colonies, some known ones could be considerably larger than currently documented. Received 16June 1998, accepted 15 December 1998.

Consumption of marine resources by seabirds and seals at Heard Island and the McDonald Islands

SummaryThe seabird and seal community at Heard Island and the McDonald Islands comprised an estimated total biomass of 27893 tonnes of which the 15 breeding species of seabirds made up 70%. The total annual consumption of marine resources was estimated to be approximately 521 000 t, of which 81% was consumed by seabirds Approximately 165 000 t of fish, 41 600 t of squid and 312 000 t of crustaceans are consumed annually by this seabird and seal community. The annual energy flux to this community was estimated to be 2.17·1012 kJ and approximately 56 000 t of carbon are consumed annually. Breeding populations of King Penguins and Antarctic Fur Seals are increasing, that of the Southern Elephant Seal is decreasing; there are no data on the population trend for Macaroni Penguins, the predominant consumer species. Commercial fisheries are presently operating at the nearby Iles Kerguelen, and similar activities may prove to be commercially viable at Heard Island. The fishery is for Champsocephalus gunnari, a major prey species of penguins and Antarctic Fur Seals at Heard Island during the summer breeding season.

Population trends of Adélie penguin (Pygoscelis adeliae) breeding colonies: a spatial analysis of the effects of snow accumulation and human activities

Many of the Adélie penguin colonies used for long-term demographic studies are located near research stations, and there is a need to disentangle the effects of human activities and environmental variability on Adélie penguin population trends. This study used Geographic Information Systems and decision trees to examine whether potential changes in snow cover and/or proximity to human activities were able to explain the varying population trends of colonies at two breeding localities near Casey, East Antarctica. At the less visited site, Whitney Pt, wind exposure and snow accumulation correctly predicted the broad trends of colonies in most (84%) instances, whereas at Shirley I their predictive accuracy fell to 58%. At Shirley I, proximity to human activity correctly predicted the broad trends for 84% of colonies. While snow accumulation patterns are a primary driver of variation in population trends among colonies, the effect of snow accumulation is outweighed by proximity to human activities near Casey.