Changes in lichen diversity and community structure with fur seal population increase on Signy Island, South Orkney Islands

AbstractSigny Island has experienced a dramatic increase in fur seal numbers over recent decades, which has led to the devastation of lowland terrestrial vegetation, with the eradication of moss turfs and carpets being the most prominent feature. Here we demonstrate that fur seals also affect the other major component of this region’s typical cryptogamic vegetation, the lichens, although with a lower decrease in variability and abundance than for bryophytes. Classification (UPGMA) and ordination (Principal Coordinate Analysis) of vegetation data highlight differences in composition and abundance of lichen communities between areas invaded by fur seals and contiguous areas protected from these animals. Multivariate analysis relating lichen communities to environmental parameters, including animal abundance and soil chemistry (Canonical Correspondence Analysis), suggests that fur seal trampling results in the destruction of muscicolous-terricolous lichens, including several cosmopolitan and bipolar fruticose species. In addition, animal excretion favours an increase in nitrophilous crustose species, a group which typically characterizes areas influenced by seabirds and includes several Antarctic endemics. The potential effect of such animal-driven changes in vegetation on the fragile terrestrial ecosystem (e.g. through modification of the ground surface temperature) confirms the importance of indirect environmental processes in Antarctica.

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Changes in the abundance of New Zealand fur seals, Arctocephalus forsteri, in Western Australia

Wildlife Research ◽

10.1071/wr99027 ◽

2000 ◽

Vol 27 (2) ◽

pp. 165 ◽

Cited By ~ 12

Author(s):

N. J. Gales ◽

B. Haberley ◽

P. Collins

Keyword(s):

New Zealand ◽

Western Australia ◽

South Australia ◽

Rate Of Change ◽

Population Increase ◽

Absolute Abundance ◽

Abundance Estimate ◽

Fur Seals ◽

Fur Seal ◽

Rate Of Increase

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.

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Growth of a fur seal population

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1977.0072 ◽

1977 ◽

Vol 279 (963) ◽

pp. 67-79 ◽

Cited By ~ 124

Keyword(s):

Age Groups ◽

Population Increase ◽

South Shetland Islands ◽

First Year ◽

South Georgia ◽

Fur Seals ◽

Fur Seal ◽

Younger Age ◽

Seal Population ◽

Incipient Colonies

The Antarctic fur seal Arctocephalus gazella is a polygynous Otarid in which a single pup is produced annually by cows over the age of 2 years. Following exploitation to the verge of extinction, a small breeding colony was discovered at Bird Island, South Georgia, in the 1930s. Up to 10000 pups a year were produced in the early 1960s and by 1975 the figure had reached an estimated 90000. The rapid population increase has resulted in the colonization of extensive breeding areas on the adjacent mainland of South Georgia with incipient colonies springing up on more distant parts of the island, and also in the South Sandwich, South Orkney and South Shetland Islands. Age determinations from the teeth of 195 breeding cows reveal a low mean age, early first breeding and a predominance of the younger age groups relative to the age structure of a stable population of northern fur seals Callorhinus ursinus . Annual adult cow survival is estimated at 89.8%, while that of first-year animals is about 64.5%. A decline in the rate of population increase is forecast within ten years and an outline for investigating the most likely factors influencing such a change is suggested.

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Reduced resilience of terrestrial ecosystems locally is not reflected on a global scale

Communications Earth & Environment ◽

10.1038/s43247-021-00163-1 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Yuhao Feng ◽

Haojie Su ◽

Zhiyao Tang ◽

Shaopeng Wang ◽

Xia Zhao ◽

...

Keyword(s):

Climate Change ◽

Global Climate Change ◽

Vegetation Index ◽

Global Climate ◽

Terrestrial Ecosystem ◽

Terrestrial Ecosystems ◽

Global Scale ◽

Ecological Resilience ◽

Terrestrial Vegetation ◽

Ecosystem Resilience

AbstractGlobal climate change likely alters the structure and function of vegetation and the stability of terrestrial ecosystems. It is therefore important to assess the factors controlling ecosystem resilience from local to global scales. Here we assess terrestrial vegetation resilience over the past 35 years using early warning indicators calculated from normalized difference vegetation index data. On a local scale we find that climate change reduced the resilience of ecosystems in 64.5% of the global terrestrial vegetated area. Temperature had a greater influence on vegetation resilience than precipitation, while climate mean state had a greater influence than climate variability. However, there is no evidence for decreased ecological resilience on larger scales. Instead, climate warming increased spatial asynchrony of vegetation which buffered the global-scale impacts on resilience. We suggest that the response of terrestrial ecosystem resilience to global climate change is scale-dependent and influenced by spatial asynchrony on the global scale.

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Ontogeny of body size and shape of Antarctic and subantarctic fur seals

Canadian Journal of Zoology ◽

10.1139/z07-092 ◽

2007 ◽

Vol 85 (12) ◽

pp. 1275-1285 ◽

Cited By ~ 6

Author(s):

Sebastián P. Luque ◽

Edward H. Miller ◽

John P.Y. Arnould ◽

Magaly Chambellant ◽

Christophe Guinet

Keyword(s):

Body Size ◽

Body Mass ◽

Morphological Traits ◽

Body Shape ◽

Size And Shape ◽

Fur Seals ◽

Fur Seal ◽

Adult Body ◽

Weaning Age ◽

Lactation Duration

Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic ( Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic ( Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increased over lactation, and A. gazella pups approached adult body shape faster than did A. tropicalis pups. Our results indicate that preweaning growth is associated with significant changes in body shape, involving the acquisition of a longer, more slender body with larger foreflippers in A. gazella. These differences suggest that A. gazella pups are physically more mature at approximately 100 d of age (close to weaning age) than A. tropicalis pups of the same age.

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Deriving SAR Soil Moisture Retrieval Algorithms and Soil Drainage Classification for Boreal Peatlands

10.5194/egusphere-egu21-6503 ◽

2021 ◽

Author(s):

Laura Bourgeau-Chavez ◽

Jeremy Graham ◽

Andrew Poley ◽

Dorthea Leisman ◽

Michael Battaglia

Keyword(s):

Climate Change ◽

Soil Moisture ◽

Land Surface ◽

Ground Surface ◽

Terrestrial Ecosystem ◽

Independent Study ◽

Additive Models ◽

Soil Drainage ◽

Boreal Peatlands ◽

Retrieval Algorithms

Eighty percent of global peatlands are distributed across the boreal and subarctic regions, storing an estimated 30% of earth&#8217;s soil organic carbon (1,016 to 1,105 Gt C) despite representing only about 3% of the global land surface. The accumulation of C in peatlands generally depends on hydrologic conditions that maintain saturated soils and impede rates of decomposition. Boreal Peatlands have provided rich reservoirs of stored C for millennia. However, with climate change, warming and drying patterns across the boreal and arctic are resulting in dramatic changes in ecosystems and putting these systems at risk of changing from a C sink to a source.&#160; Recent changes in climate including earlier springs, longer summers and changes in moisture patterns across the landscape, are affecting wildfire regimes of the boreal region including intensity, severity and frequency of wildfires. This in turn has potential to cause shifts in successional trajectories.&#160; Understanding how these changes in climate are affecting peatlands and their vulnerability to wildfire has been a focus of study of the research team since 2009. &#160;Soil moisture is one variable which can provide information to understand wildfire behavior including the depth of peat consumption in these wildfires but it also has a direct effect on post-fire successional trajectories. Further it is needed to understand methane emissions from peatlands.&#160; To develop the soil moisture retrieval algorithms, we studied a range of boreal peatland sites (bogs and fens) stratified across geographic regions from 2012-2014.&#160; We developed soil moisture retrieval algorithms from polarimetric C-band (5.7 cm wavelength) synthetic aperture radar (SAR) data.&#160; Peatlands have low enough aboveground biomass (<3.0 kg/m2) to allow this shorter wavelength SAR to penetrate the canopy to reach the ground surface.&#160; Data from over 60, 4 ha sites were collected over 3 seasons from Alaska and Michigan USA and Alberta Canada.&#160; Both multi-linear regressions and general additive models (GAM) were developed.&#160; Using both polarimetric SAR parameters that are sensitive to vegetation structure and parameters most sensitive to surface soil moisture in the models provided the best results.&#160; GAM models were tested in an independent study area, Northwest Territories (NWT), Canada.&#160; The sites of NWT were sampled in 2016-2019 coincident to Radarsat-2 polarimetric image collections.&#160; The high accuracy results will be presented as well as methods developed to use multidate C-band data from Sentinel-1 to classify soil drainage (well drained to poorly drained) in recently burned peatlands.&#160; These products are being used in a fire effects and emissions model, CanFIRE, as we parameterize it for peatlands; as well as the Functionally-Assembled Terrestrial Ecosystem Simulator (FATES) to understand the effects of wildfire and hydrology on peatland ecosystems.&#160; Characterization and quantification of boreal peatlands in global C cycling is critical for proper accounting given that peatlands play a significant role in sequestering and releasing large amounts of C. The ability to retrieve soil moisture from C-band SAR, therefore, provides a means to monitor a key variable in scaling C flux estimates as well as understanding the vulnerability and resiliency of boreal peatlands to climate change.&#160;

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Low resolution accelerometers can be used to develop time-energy budgets of wild fur seals from captive surrogates

10.7287/peerj.preprints.26570v1 ◽

2018 ◽

Author(s):

Monique A Ladds ◽

Marcus Salton ◽

David P Hocking ◽

Rebecca R McIntosh ◽

Adam P Thompson ◽

...

Keyword(s):

High Resolution ◽

Energy Expenditure ◽

Energetic Cost ◽

Energy Budgets ◽

Gradient Boosting ◽

Low Resolution ◽

Fur Seals ◽

Long Duration ◽

Fur Seal ◽

Significant Difference

Background. Accurate time-energy budgets summarise an animal’s energy expenditure in a given environment and are potentially a sensitive indicator of how an animal responds to changing resources. Deriving accurate time-energy budgets requires a precise measure of time spent in different activities, and an estimate of the energetic cost of that activity. Bio-loggers such as accelerometers may provide a solution for monitoring animals such as fur seals that make long-duration foraging trips over multiple days or weeks. Monitoring such behaviour may require low resolution recording due to the memory constraints of bio-loggers. The aim of this study was to evaluate if accelerometers recording at a low resolution could accurately classify and determine the cost of fur seal activity. Methods. Diving and movement data were collected from nine wild juvenile Australian fur seals equipped with tri-axial accelerometers. To validate time-energy budgets for the fur seals, energy consumption during a range of behaviours was determined from twelve captive surrogates. The time wild fur seals spent in four behavioural states - foraging, grooming, travelling and resting - was quantified with low- and high-resolution data from accelerometers using gradient boosting models (GBM). The daily energy expenditure (DEE) from these four activities was estimated using a relatively simple energetics model developed using their location (land, surface or underwater) and estimates of the energetic cost of each behaviour. Models developed from captive seals were applied to accelerometry data collected from wild juvenile Australian fur seals and their time-energy budgets were reconstructed. Results. Low resolution accelerometery was better at classifying fur seal behaviour over long durations than high resolution accelerometry in captive surrogates. The low resolution model was therefore applied to wild data. This revealed that Juvenile fur seals expended more energy than adults of similar species, but there was no significant difference in DEE across sex or season (winter or summer). Juvenile fur seals used behavioural compensatory techniques to conserve energy during activities that were expected to have high energetic outputs (such as diving). Discussion. Behaviours that are displayed over a long duration can be captured accurately by low-resolution accelerometry and these models can be used to develop time-energy budgets of wild animals. In this study we were able to use such models to monitor juvenile fur seals over multiple foraging trips. This revealed that juvenile fur seals appear to be working energetically harder than their adult counterparts, likely due to the relative novelty of diving and foraging, their smaller body size and the additional cost of growth they sustain. Developing time-energy budgets from accelerometers is an efficient method of estimating energy expenditure from individuals over time.

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Behavioral responses of Australian fur seals to boat approaches at a breeding colony

Nature Conservation ◽

10.3897/natureconservation.31.26263 ◽

2018 ◽

Vol 31 ◽

pp. 35-52 ◽

Cited By ~ 1

Author(s):

Julia J. Back ◽

Andrew J. Hoskins ◽

Roger Kirkwood ◽

John P.Y. Arnould

Keyword(s):

Time Of Day ◽

Species Variation ◽

Strong Response ◽

Approach Distance ◽

Fur Seals ◽

Increase Energy Expenditure ◽

Fur Seal ◽

Steep Decline ◽

Breeding Seasons ◽

Resting Behavior

In Australia, a multi-million-dollar industry is based on viewing the Australian fur seal (Arctocephaluspusillusdoriferus), predominantly through boat visits to breeding colonies. Regulation of boat approaches varies by site and no systematic investigations have been performed to inform management guidelines. To investigate possible effects of disturbance, experimental boat approaches were made to a colony at Kanowna Island in northern Bass Strait and seal responses were monitored using instantaneous scan sampling. Colony attendance (individuals remaining ashore) was found to be influenced by approach distance and time of day, but was not affected by environmental variables or season, whereas onshore resting behavior was influenced by approach distance, time of day, ambient temperature and wind direction. Onshore resting behavior decreased following experimental boat approaches to 75 m, but changes in abundance of individuals ashore were not observed at this distance. In contrast, approaches to 25 m elicited a strong response, with a steep decline in the number of individuals ashore. This response was strongest when approaches occurred in the morning, with a decline of approximately 47% of individuals, compared to a decline of 21% during afternoon approaches. With regard to onshore resting behavior, afternoon approaches to 75 m led to minimal response. The remaining three combinations of approach distance and time of day had a similar pattern of reductions in the proportion of individuals engaging in onshore resting behavior. The strongest response was again seen during approaches to 25 m conducted in the morning. These behavior changes suggest that unrestricted boat-based ecotourism at Australian fur seal colonies has the potential to increase energy expenditure and reduce the number of seals ashore. Increasing minimum approach distances to ≥75 m and/or restricting visits to afternoons may minimize these impacts at Kanowna Island during the post-molt and non-breeding seasons. As several studies have demonstrated considerable intra-species variation in seal responses to boat approaches, research at other colonies is needed before these findings can be generalized to the remainder of the Australian fur seal population.

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The composition of the milk of antarctic (Arctocephalus gazella) and subantarctic (A. tropicalis) fur seals at Macquarie Island

Australian Journal of Zoology ◽

10.1071/zo98067 ◽

1999 ◽

Vol 47 (6) ◽

pp. 593 ◽

Cited By ~ 10

Author(s):

Simon D. Goldsworthy ◽

Helen M. Crowley

Keyword(s):

Water Content ◽

Energy Content ◽

Post Partum ◽

Milk Composition ◽

Arctocephalus Gazella ◽

Macquarie Island ◽

Fur Seals ◽

Fur Seal ◽

Gross Energy ◽

Subantarctic Fur Seals

The composition of milk collected from 36 antarctic (Arctocephalus gazella) and 17 subantarctic fur seals (A. tropicalis) breeding sympatrically at Macquarie Island was examined over the first 100 days of lactation in the 1990/91 season. The mean composition of milk in A. gazella and A. tropicalis was 41.3% and 44.6% water, 39.8% and 38.6% lipid, 18.1% and 16.1% protein, and the estimated gross energy content of milk was 19.9 and 18.9 kJ g–1, respectively. Neither the composition of milk nor its energy density differed significantly between species, despite a difference of 4–6 months in lactation length. Water content of milk could be used to predict lipid (r2 = 0.67) and protein (r2 = 0.57) content, but was most accurate at predicting gross energy content (r2 = 0.97). These relationships were the same for each species. The water content of milk decreased throughout the first 100 days of lactation in both species, while lipid, protein and energy content all increased. The addition of maternal mass into regression analysis with days post-partum increased the significance of models predicting the content of lipid and proteins in the milk, but not those predicting the water or gross energy content. Milk collected on the first day of 2-day attendance bouts had, on average, 9% greater lipid content, and 5% greater protein content than milk collected on the second day. The growth rates of subantarctic fur seal pups were significantly lower than those of antarctic fur seal pups over the first month of growth, suggesting that (despite similar milk composition, attendance patterns and diet of the two species of fur seal) the overall rates of energy transfer from mother to pup in subantarctic fur seals is lower than in antarctic fur seals.

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The Solar-Induced Chlorophyll Fluorescence Imaging Spectrometer (SIFIS) Onboard the First Terrestrial Ecosystem Carbon Inventory Satellite (TECIS-1): Specifications and Prospects

Sensors ◽

10.3390/s20030815 ◽

2020 ◽

Vol 20 (3) ◽

pp. 815 ◽

Cited By ~ 1

Author(s):

Shanshan Du ◽

Liangyun Liu ◽

Xinjie Liu ◽

Xinwei Zhang ◽

Xianlian Gao ◽

...

Keyword(s):

Chlorophyll Fluorescence ◽

Signal To Noise Ratio ◽

Simulated Data ◽

Terrestrial Ecosystem ◽

Global Scale ◽

Terrestrial Vegetation ◽

Atmospheric Transmission ◽

Imaging Spectrometer ◽

Ecosystem Carbon ◽

Carbon Inventory

The global monitoring of solar-induced chlorophyll fluorescence (SIF) using satellite-based observations provides a new way of monitoring the status of terrestrial vegetation photosynthesis on a global scale. Several global SIF products that make use of atmospheric satellite data have been successfully developed in recent decades. The Terrestrial Ecosystem Carbon Inventory Satellite (TECIS-1), the first Chinese terrestrial ecosystem carbon inventory satellite, which is due to be launched in 2021, will carry an imaging spectrometer specifically designed for SIF monitoring. Here, we use an extensive set of simulated data derived from the MODerate resolution atmospheric TRANsmission 5 (MODTRAN 5) and Soil Canopy Observation Photosynthesis and Energy (SCOPE) models to evaluate and optimize the specifications of the SIF Imaging Spectrometer (SIFIS) onboard TECIS for accurate SIF retrievals. The wide spectral range of 670−780 nm was recommended to obtain the SIF at both the red and far-red bands. The results illustrate that the combination of a spectral resolution (SR) of 0.1 nm and a signal-to-noise ratio (SNR) of 127 performs better than an SR of 0.3 nm and SNR of 322 or an SR of 0.5 nm and SNR of 472 nm. The resulting SIF retrievals have a root-mean-squared (RMS) diff* value of 0.15 mW m−2 sr−1 nm−1 at the far-red band and 0.43 mW m−2 sr−1 nm−1 at the red band. This compares with 0.20 and 0.26 mW m−2 sr−1 nm−1 at the far-red band and 0.62 and 1.30 mW m−2 sr−1 nm−1 at the red band for the other two configurations described above. Given an SR of 0.3 nm, the increase in the SNR can also improve the SIF retrieval at both bands. If the SNR is improved to 450, the RMS diff* will be 0.17 mW m−2 sr−1 nm−1 at the far-red band and 0.47 mW m−2 sr−1 nm−1 at the red band. Therefore, the SIFIS onboard TECIS-1 will provide another set of observations dedicated to monitoring SIF at the global scale, which will benefit investigations of terrestrial vegetation photosynthesis from space.

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Oceanographic factors influencing the distribution of South American fur seal, Arctocephalus australis around the Falkland Islands before the breeding season

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315409000770 ◽

2009 ◽

Vol 89 (8) ◽

pp. 1597-1600 ◽

Cited By ~ 3

Author(s):

Vladimir Laptikhovsky

Keyword(s):

Prey Species ◽

Falkland Islands ◽

South American ◽

Important Food ◽

Factors Influencing ◽

South West ◽

Fur Seals ◽

Fur Seal ◽

Important Food Source ◽

Productive Zone

Distribution of fur seals Arctocephalus australis has been studied in October 2007 on the western, southern and eastern Falkland shelves during the survey of spawning grounds of the red cod, Salilota australis. Fur seals presence/absence, numbers and sex were recorded at every oceanographic station. Animals were found foraging on the shelf edge south-west of the islands, in a productive zone with quasi-stationary eddies at a periphery of upwelling. It was also the zone of maximum abundance of lobster-krill, Munida spp.—an important food source of fur seals and aggregations of both red cod and blue whiting, Micromesistius australis. No fur seals were found in waters of the relative cold and saline Falkland Current as well as in the relatively warm, fresh and oxygen-rich waters of Argentine Drift. It allows supposing that position and extension of the foraging grounds are caused by oceanographic features determining distribution of prey species.

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