ORCID Profile
0000-0001-9342-669X
Current Organisation
University of Tasmania Institute for Marine and Antarctic Studies
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Marine and Estuarine Ecology (incl. Marine Ichthyology) | Ecology | Physical oceanography | Population Ecology | Biological oceanography | Conservation and Biodiversity | Oceanography | Natural Resource Management | Oceanography | Biological Oceanography | Physical Oceanography | Behavioural Ecology | Global Change Biology
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Antarctic and Sub-Antarctic Flora, Fauna and Biodiversity | Ecosystem Adaptation to Climate Change | Ecosystem Assessment and Management of Antarctic and Sub-Antarctic Environments | Antarctic and Sub-Antarctic Oceanography | Marine Oceanic Processes (excl. climate related) | Ecosystem Assessment and Management of Marine Environments |
Related Links
Publications
Predicting feeding success in a migratory predator: integrating telemetry, environment, and modeling techniques
Publisher: Wiley
Date: 08-2010
DOI: 10.1890/08-2019.1
Abstract: Foraging theory predicts that mobile predators should target high profitability areas with plentiful resources and minimize time spent moving between these areas. This has led to a focus in recent literature on the identification of "hotspots" important for migratory marine predators, i.e., regions where predators spend disproportionate amounts of time ostensibly due to high prey abundance and determination of the environmental features characteristic of such areas. We investigated factors predicting foraging success in southern bluefin tuna (SBT Thunnus maccoyii), by integrating telemetry-based feeding and movement data (n = 19 fish, length to caudal fork [LCF] = 99 +/- 3 cm) with environmental data over the scale of their annual oceanic migrations during 1998-2000. We used widely available statistical modeling techniques, generalized linear models, and generalized linear mixed models, formulated to represent feeding as a Markov process. The results showed increased feeding and predictability of feeding occurs in the coastal waters of southern Australia, providing some evidence that this area represents a fixed foraging "hotspot" for juvenile tuna during the austral summer. However, in oceanic waters southern bluefin tuna did not fit the common model of migration, but rather showed a pattern of relatively high foraging success throughout their migratory range, especially during periods of continuous travel. Interestingly, foraging "coldspots" (prolonged low-feeding periods) as well as "hotspots" were apparent across in idual tracks, predicted most strongly by warm ocean temperatures. These results provide a new perspective on the ecology of large-scale feeding migrations within the context of the heterogeneous ocean environment, where the continuous and opportunistic feeding of generalist predators may be more common, particularly in predatory large pelagic fishes, than is currently documented.
View From Below: Inferring Behavior and Physiology of Southern Ocean Marine Predators From Dive Telemetry
Publisher: Frontiers Media SA
Date: 14-12-2018
Salpa thompsoni in the Indian Sector of the Southern Ocean: Environmental drivers and life history parameters
Publisher: Elsevier BV
Date: 04-2020
Elephant seal foraging success is enhanced in Antarctic coastal polynyas
Publisher: The Royal Society
Date: 26-01-2022
Abstract: Antarctic polynyas are persistent open water areas which enable early and large seasonal phytoplankton blooms. This high primary productivity, boosted by iron supply from coastal glaciers, attracts organisms from all trophic levels to form a rich and erse community. How the ecological benefit of polynya productivity is translated to the highest trophic levels remains poorly resolved. We studied 119 southern elephant seals feeding over the Antarctic shelf and demonstrated that: (i) 96% of seals foraging here used polynyas, with in iduals spending on average 62% of their time there (ii) the seals exhibited more area-restricted search behaviour when in polynyas and (iii) these seals gained more energy (indicated by increased buoyancy from greater fat stores) when inside polynyas. This higher-quality foraging existed even when ice was not present in the study area, indicating that these are important and predictable foraging grounds year-round. Despite these energetic advantages from using polynyas, not all the seals used them extensively. Factors other than food supply may influence an in idual's choice in their use of feeding grounds, such as exposure to predation or the probability of being able to return to distant sub-Antarctic breeding sites.
New insights into prime Southern Ocean forage grounds for thriving Western Australian humpback whales
Publisher: Springer Science and Business Media LLC
Date: 27-09-2019
DOI: 10.1038/S41598-019-50497-2
Abstract: Humpback whale populations migrate extensively between winter breeding grounds and summer feeding grounds, however known links to remote Antarctic feeding grounds remain limited in many cases. New satellite tracks detail humpback whale migration pathways from Western Australia into the Southern Ocean. These highlight a focal feeding area during austral spring and early summer at the southern Kerguelen plateau, in a western boundary current where a sharp northward turn and retroflection of ocean fronts occurs along the eastern plateau edge. The topographic steering of oceanographic features here likely supports a predictable, productive and persistent forage ground. The spatial distribution of whaling catches and Discovery era mark-recaptures confirms the importance of this region to Western Australian humpback whales since at least historical times. Movement modelling discriminates sex-related behaviours, with females moving faster during both transit and resident periods, which may be a consequence of size or indicate differential energetic requirements. Relatively short and directed migratory pathways overall, together with high-quality, reliable forage resources may provide a partial explanation for the ongoing strong recovery demonstrated by this population. The combination of new oceanographic information and movement data provides enhanced understanding of important biological processes, which are relevant within the context of the current spatial management and conservation efforts in the Southern Ocean.
A quantitative, hierarchical approach for detecting drift dives and tracking buoyancy changes in southern elephant seals
Publisher: Springer Science and Business Media LLC
Date: 20-06-2019
DOI: 10.1038/S41598-019-44970-1
Abstract: Foraging behaviour of marine predators inferred from the analysis of horizontal or vertical movements commonly lack quantitative information about foraging success. Several marine mammal species are known to perform es where they passively drift in the water column, termed “drift” es. The drift rate is determined by the animal’s buoyancy, which can be used to make inference regarding body condition. Long term e records retrieved via satellite uplink are often summarized before transmission. This loss of resolution h ers identification of drift es. Here, we develop a flexible, hierarchically structured approach to identify drift es and estimate the drift rate from the summarized time-depth profiles that are increasingly available to the global research community. Based on high-resolution e data from southern elephant seals, we classify es as drift/non-drift and apply a summarization algorithm. We then (i) automatically generate e groups based on inflection point ordering using a ‘Reverse’ Broken-Stick Algorithm, (ii) develop a set of threshold criteria to apply across groups, ensuring non-drift es are most efficiently rejected, and (iii) finally implement a custom Kalman filter to retain the remaining es that are within the seals estimated drifting time series. Validation with independent data sets shows our method retains approximately 3% of all es, of which 88% are true drift es. The drift rate estimates are unbiased, with the upper 95% quantile of the mean squared error between the daily averaged summarized profiles using our method (SDDR) and the observed daily averaged drift rate (ODDR) being only 0.0015. The trend of the drifting time-series match expectations for capital breeders, showing the lowest body condition commencing foraging trips and a progressive improvement as they remain at sea. Our method offers sufficient resolution to track small changes in body condition at a fine temporal scale. This approach overcomes a long-term challenge for large existing and ongoing data collections, with potential application across other drift ing species. Enabling robust identification of foraging success at sea offers a rare and valuable opportunity for monitoring marine ecosystem productivity in space and time by tracking the success of a top predator.
Zooplankton community structure and dominant copepod population structure on the southern Kerguelen Plateau during summer 2016
Publisher: Elsevier BV
Date: 04-2020
Otolith nucleus chemistry distinguishes Electrona antarctica in the westward-flowing Antarctic Slope Current and eastward-flowing Antarctic Circumpolar Current off East Antarctica
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.MARENVRES.2018.09.010
Abstract: Eastward transport in the Southern Ocean is concentrated in jets associated with fronts in the Antarctic Circumpolar Current (ACC), whereas flow along the Antarctic continental slope is strongly westward in the Antarctic Slope Current (ASC). The dominant mesopelagic fish endemic to the Southern Ocean, Electrona antarctica (Günther, 1878), has been linked to Circumpolar Deep Water (CDW) transported by the ACC, and a modified version of CDW associated with the ASC. In conjunction with a regional-scale hydrographic survey south of the Kerguelen Plateau, we s led fish from the ACC and ASC across Princess Elizabeth Trough off East Antarctica, and examined their otolith chemistry. Material laid down in the nucleus during early life showed heterogeneity, arguing against a single homogeneous population. Instead, it suggested exposure to different environments after hatching, consistent with separate transport pathways along the ACC and ASC. Despite clear differences between stations documented in the survey, material laid down along the edge did not show heterogeneity, suggesting instead exposure to similar environments. Seasonal movement northward by ASC fish into the ACC may explain both these results, and potential physical mechanisms include circulation in the Australian-Antarctic Gyre northward movement of slope waters along the eastern margin of Princess Elizabeth Trough and seasonal extension of sea-ice into the ACC. Such meridional movement would expose fish to zonal flow, eastward in the ACC during winter and westward in the ASC during summer, promoting regional retention as well as creating opportunities for mixing with fish transported along the ACC.
Seasonal Transformation and Spatial Variability of Water Masses Within MacKenzie Polynya, Prydz Bay
Publisher: American Geophysical Union (AGU)
Date: 12-2021
DOI: 10.1029/2021JC017748
Abstract: We provide a detailed description of the spatial distribution, seasonality and transformation of the main water masses within MacKenzie Polynya (MP) in Prydz Bay, East Antarctica, using data from instrumented southern elephant seals. Dense Shelf Water (DSW) formation in MP shows large spatial variability that is related to the (a) local bathymetry, (b) water column preconditioning from the presence/absence of different water masses, and (c) proximity to the Amery Ice Shelf meltwater outflow. MP exhibits sustained sea ice production and brine rejection (thus, salinity increase) from April to October. However, new DSW is only formed from June onward, when the mixed layer deepens and convection is strong enough to break the stratification set by Antarctic Surface Water above and Ice Shelf Water below. We found no evidence of DSW export from MP to Darnley polynya, as previously suggested. Rather, our observations suggest some DSW formed in Darnley Polynya may drain toward the western Prydz Bay. Then, DSW is exported offshore from Prydz Bay through the Prydz Channel. The interplay between sea ice formation, meltwater input, and sea floor topography is likely to explain why some coastal polynyas form more DSW than others, as well as the temporal variability in DSW formation within a particular polynya.
Finding mesopelagic prey in a changing Southern Ocean
Publisher: Springer Science and Business Media LLC
Date: 12-12-2019
DOI: 10.1038/S41598-019-55152-4
Abstract: Mesopelagic fish and squid occupy ocean depths extending below the photic zone and their vertical migrations represent a massive pathway moving energy and carbon through the water column. Their spatio-temporal distribution is however, difficult to map across remote regions particularly the vast Southern Ocean. This represents a key gap in understanding biogeochemical processes, marine ecosystem structure, and how changing ocean conditions will affect marine predators, which depend upon mesopelagic prey. We infer mesopelagic prey vertical distribution and relative abundance in the Indian sector of the Southern Ocean (20° to 130°E) with a novel approach using predator-derived indices. Fourteen years of southern elephant seal tracking and e data, from the open ocean between the Antarctic Polar Front and the southern Antarctic Circumpolar Current front, clearly show that the vertical distribution of mesopelagic prey is influenced by the physical hydrographic processes that structure their habitat. Mesopelagic prey have a more restricted vertical migration and higher relative abundance closer to the surface where Circumpolar Deep Water rises to shallower depths. Combining these observations with a future projection of Southern Ocean conditions we show that changes in the coupling of surface and deep waters will potentially redistribute mesopelagic prey. These changes are small overall, but show important spatial variability: prey will increase in relative abundance to the east of the Kerguelen Plateau but decrease to the west. The consequences for deep- ing specialists such as elephant seals and whales over this time scale will likely be minor, but the changes in mesoscale vertical energy flow have implications for predators that forage within the mesopelagic zone as well as the broader pelagic ecosystem.
Modelled mid‐trophic pelagic prey fields improve understanding of marine predator foraging behaviour
Publisher: Wiley
Date: 09-04-2201
DOI: 10.1111/ECOG.04939
Otolith chemistry of Electrona antarctica suggests a potential population marker distinguishing the southern Kerguelen Plateau from the eastward‐flowing Antarctic Circumpolar Current
Publisher: Wiley
Date: 10-10-2020
DOI: 10.1002/LNO.11612
Coastal polynyas: Winter oases for subadult southern elephant seals in East Antarctica
Publisher: Springer Science and Business Media LLC
Date: 16-02-2018
DOI: 10.1038/S41598-018-21388-9
Abstract: Antarctic coastal polynyas are regions of persistent open water and are thought to be key bio-physical features within the sea-ice zone. However, their use by the upper trophic levels of ecosystems remains unclear. A unique bio-physical dataset recorded by southern elephant seals reveals that East Antarctic polynyas are a key winter foraging habitat for male seals. During their post-moult trips from Isles Kerguelen to the Antarctic continental shelf, a total of 18 out of 23 seals visited 9 different polynyas, spending on average 25 ± 20% (up to 75%) of their total trip time inside polynyas. Changes in seal foraging and ing behaviours are observed inside polynyas as compared to outside polynyas. Two polynya usages by seals are observed for the inactive and active polynya phases, pointing to different seasonal peaks in prey abundance. During the active polynya phase, we link seal foraging behaviour to changes in the physical stability of the water-column, which likely impact the seasonal biological dynamics within polynyas.
Plasticity in vertical behaviour of migrating juvenile southern bluefin tuna (Thunnus maccoyii) in relation to oceanography of the south Indian Ocean
Publisher: Wiley
Date: 07-2009
Controls on Dense Shelf Water Formation in Four East Antarctic Polynyas
Publisher: American Geophysical Union (AGU)
Date: 29-11-2022
DOI: 10.1029/2022JC018804
Abstract: Coastal polynyas are key formation regions for dense shelf water (DSW) that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. We examine how the physiographic setting, water‐mass distribution and transformation, water column stratification, and sea‐ice production regulate DSW formation in four East Antarctic coastal polynyas. We use a salt budget to estimate the relative contribution of sea‐ice production and lateral advection to the monthly change in salinity in each polynya. DSW forms in Mackenzie polynya due to a combination of physical features (shallow water depth and a broad continental shelf) and high sea‐ice production. Sea‐ice formation begins early (March) in Mackenzie polynya, counteracting fresh advection and establishing a salty mixed layer in autumn that preconditions the water column for deep convection in winter. Sea‐ice production is moderate in the other three polynyas, but saline DSW is not formed (a fresh variety is formed in the Barrier polynya). In the Shackleton polynya, brine rejection during winter is insufficient to overcome the very fresh autumn mixed layer. In Vincennes Bay, a strong inflow of modified Circumpolar Deep Water stratifies the water column, hindering deep convection and DSW formation. Our study highlights that DSW formation in a given polynya depends on a complex combination of factors, some of which may be strongly altered under a changing climate, with potentially important consequences for the ventilation of the deep ocean, the global meridional overturning circulation, and the transport of ocean heat to Antarctic ice shelves.
Ocean circulation and frontal structure near the southern Kerguelen Plateau: The physical context for the Kerguelen Axis ecosystem study
Publisher: Elsevier BV
Date: 04-2018
Estimation and simulation of foraging trips in land-based marine predators
Publisher: Wiley
Date: 12-06-2017
DOI: 10.1002/ECY.1880
Abstract: The behavior of colony‐based marine predators is the focus of much research globally. Large telemetry and tracking data sets have been collected for this group of animals, and are accompanied by many empirical studies that seek to segment tracks in some useful way, as well as theoretical studies of optimal foraging strategies. However, relatively few studies have detailed statistical methods for inferring behaviors in central place foraging trips. In this paper we describe an approach based on hidden Markov models, which splits foraging trips into segments labeled as “outbound”, “search”, “forage”, and “inbound”. By structuring the hidden Markov model transition matrix appropriately, the model naturally handles the sequence of behaviors within a foraging trip. Additionally, by structuring the model in this way, we are able to develop realistic simulations from the fitted model. We demonstrate our approach on data from southern elephant seals ( Mirounga leonina ) tagged on Kerguelen Island in the Southern Ocean. We discuss the differences between our 4‐state model and the widely used 2‐state model, and the advantages and disadvantages of employing a more complex model.
Movement responses to environment: fast inference of variation among southern elephant seals with a mixed effects model
Publisher: Cold Spring Harbor Laboratory
Date: 04-05-2018
DOI: 10.1101/314690
Abstract: Like many species, movement patterns of southern elephant seals ( Mirounga leonina ) are being influenced by long-term environmental change. These seals migrate up to 4000 km from their breeding colonies, foraging for months in a variety of Southern Ocean habitats. Understanding how movement patterns vary with environmental features and how these relationships differ among in iduals employing different foraging strategies can provide insight into foraging performance at a population level. We apply new fast-estimation tools to fit mixed effects within a random walk movement model, rapidly inferring among-in idual variability in southern elephant seal environment-movement relationships. We found that seals making foraging trips to the sea-ice on or near the Antarctic continental shelf consistently reduced speed and directionality (move persistence) with increasing sea ice coverage and had variable responses to chlorophyll a concentration, whereas seals that foraged pelagically reduced move persistence in regions where circumpolar deep water shoaled. Given future climate scenarios, pelagic foragers may encounter more productive habitat but sea-ice foragers may see reduced habitat availability. Our approach is scalable to large telemetry data sets and allows flexible combinations of mixed effects to be evaluated via model selection, thereby illuminating the ecological context of animal movements that underlie habitat use.
A globally distributed Syndiniales parasite dominates the Southern Ocean micro-eukaryote community near the sea-ice edge
Publisher: Springer Science and Business Media LLC
Date: 26-10-2019
Quality of Sea-ice Habitat Traversed by Antarctic Krill Larvae Influences Recruitment Success
Publisher: Research Square Platform LLC
Date: 02-02-2022
DOI: 10.21203/RS.3.RS-1255733/V1
Abstract: Antarctic krill are a key Southern Ocean species whose success is attributed to their adaption to the extreme polar seasonality. Overwinter sea-ice presence and characteristics exert a strong control on larval survival and subsequent recruitment. Our understanding of the mechanisms through which sea ice influences survival are mainly underpinned by small-scale observations, whereas planktonic larvae may be advected over large scales. Using a state-of-the-art sea-ice model we computed Lagrangian back-trajectories to simulate larval krill advection into three distinct recruitment regions and examined modelled sea-ice habitat characteristics along trajectories. From these results we identify potential overwintering habitats and present a conceptual model for explaining regional variability in sea-ice habitat drivers of recruitment. Crucially, many of these sea-ice habitats are currently under-s led. This work can inform future s ling efforts that will improve our understanding of climate change impacts, and potential interactions with the krill fishery.
Feeding ecology of wild migratory tunas revealed by archival tag records of visceral warming
Publisher: Wiley
Date: 14-10-2008
DOI: 10.1111/J.1365-2656.2008.01437.X
Abstract: 1. Seasonal long-distance migrations are often expected to be related to resource distribution, and foraging theory predicts that animals should spend more time in areas with relatively richer resources. Yet for highly migratory marine species, data on feeding success are difficult to obtain. We analysed the temporal feeding patterns of wild juvenile southern bluefin tuna from visceral warming patterns recorded by archival tags implanted within the body cavity. 2. Data collected during 1998-2000 totalled 6221 days, with in idual time series (n = 19) varying from 141 to 496 days. These data span an annual migration circuit including a coastal summer residency within Australian waters and subsequent migration into the temperate south Indian Ocean. 3. In idual fish recommenced feeding between 5 and 38 days after tagging, and feeding events (n = 5194) were subsequently identified on 76.3 +/- 5.8% of days giving a mean estimated daily intake of 0.75 +/- 0.05 kg. 4. The number of feeding events varied significantly with time of day with the greatest number occurring around dawn (58.2 +/- 8.0%). Night feeding, although rare (5.7 +/- 1.3%), was linked to the full moon quarter. Southern bluefin tuna foraged in ambient water temperatures ranging from 4.9 degrees C to 22.9 degrees C and depths ranging from the surface to 672 m, with different targeting strategies evident between seasons. 5. No clear relationship was found between feeding success and time spent within an area. This was primarily due to high in idual variability, with both positive and negative relationships observed at all spatial scales examined (grid ranges of 2 x 2 degrees to 10 x 10 degrees ). Assuming feeding success is proportional to forage density, our data do not support the hypothesis that these predators concentrate their activity in areas of higher resource availability. 6. Multiple-day fasting periods were recorded by most in iduals. The majority of these (87.8%) occurred during periods of apparent residency within warmer waters (sea surface temperature > 15 degrees C) at the northern edge of the observed migratory range. These previously undocumented nonfeeding periods may indicate alternative motivations for residency. 7. Our results demonstrate the importance of obtaining information on feeding when interpreting habitat utilization from in idual animal tracks.
Antarctic pack ice algal distribution: Floe‐scale spatial variability and predictability from physical parameters
Publisher: American Geophysical Union (AGU)
Date: 28-07-2017
DOI: 10.1002/2017GL074346
Determination and precision of otolith growth zone estimates of Electrona antarctica in the Southern Kerguelen Plateau region in the Indian sector of the Southern Ocean
Publisher: Elsevier BV
Date: 04-2020
Feeding ecology of wild migratory tunas revealed by archival tag records of visceral warming
Publisher: Wiley
Date: 14-10-2008
DOI: 10.1111/J.1365-2656.2008.01437.X
Abstract: 1. Seasonal long-distance migrations are often expected to be related to resource distribution, and foraging theory predicts that animals should spend more time in areas with relatively richer resources. Yet for highly migratory marine species, data on feeding success are difficult to obtain. We analysed the temporal feeding patterns of wild juvenile southern bluefin tuna from visceral warming patterns recorded by archival tags implanted within the body cavity. 2. Data collected during 1998-2000 totalled 6221 days, with in idual time series (n = 19) varying from 141 to 496 days. These data span an annual migration circuit including a coastal summer residency within Australian waters and subsequent migration into the temperate south Indian Ocean. 3. In idual fish recommenced feeding between 5 and 38 days after tagging, and feeding events (n = 5194) were subsequently identified on 76.3 +/- 5.8% of days giving a mean estimated daily intake of 0.75 +/- 0.05 kg. 4. The number of feeding events varied significantly with time of day with the greatest number occurring around dawn (58.2 +/- 8.0%). Night feeding, although rare (5.7 +/- 1.3%), was linked to the full moon quarter. Southern bluefin tuna foraged in ambient water temperatures ranging from 4.9 degrees C to 22.9 degrees C and depths ranging from the surface to 672 m, with different targeting strategies evident between seasons. 5. No clear relationship was found between feeding success and time spent within an area. This was primarily due to high in idual variability, with both positive and negative relationships observed at all spatial scales examined (grid ranges of 2 x 2 degrees to 10 x 10 degrees ). Assuming feeding success is proportional to forage density, our data do not support the hypothesis that these predators concentrate their activity in areas of higher resource availability. 6. Multiple-day fasting periods were recorded by most in iduals. The majority of these (87.8%) occurred during periods of apparent residency within warmer waters (sea surface temperature > 15 degrees C) at the northern edge of the observed migratory range. These previously undocumented nonfeeding periods may indicate alternative motivations for residency. 7. Our results demonstrate the importance of obtaining information on feeding when interpreting habitat utilization from in idual animal tracks.
Bio-physical characterisation of polynyas as a key foraging habitat for juvenile male southern elephant seals (Mirounga leonina) in Prydz Bay, East Antarctica
Publisher: Public Library of Science (PLoS)
Date: 13-09-2017
Author Correction: Circumpolar projections of Antarctic krill growth potential
Publisher: Springer Science and Business Media LLC
Date: 10-12-2021
Connective tissue growth factor is a novel pro-depressant.
Publisher: Elsevier BV
Date: 10-2018
Predicting krill swarm characteristics important for marine predators foraging off East Antarctica
Publisher: Wiley
Date: 27-09-2018
DOI: 10.1111/ECOG.03080
Iron Limitation Drives the Globally Extreme Fluorescence/Chlorophyll Ratios of the Southern Ocean
Publisher: American Geophysical Union (AGU)
Date: 13-06-2022
DOI: 10.1029/2021GL097616
Abstract: The ratio between fluorescence (F) and chlorophyll‐a (Chl)—where fluorescence is measured with a saturating fluorometer—is variable in the world's oceans, with the highest ratios and highest variability observed in the Southern Ocean. While species composition and Chl packaging per cell are strong drivers for the observed variability, additional factors, including iron limitation, have to this date not specifically been evaluated. Radiometers on biogeochemical (BGC)‐Argo floats allow for an independent estimate of Chl concentration that is based on the light attenuation coefficient, K d . Making use of 4,000 radiometry profiles from BGC‐Argo floats in the Southern Ocean, we estimate Chl based on K d and investigate the variability in F/Chl. Our analysis reveals a positive correlation between F/Chl and a proxy for iron limitation based on non‐photochemical quenching dynamics. The strong influence of iron limitation on F/Chl is further corroborated by data from Southern Ocean phytoplankton cultures.
Spruce giga‐genomes: structurally similar yet distinctive with differentially expanding gene families and rapidly evolving genes
Publisher: Wiley
Date: 16-07-2022
DOI: 10.1111/TPJ.15889
Abstract: Spruces ( Picea spp.) are coniferous trees widespread in boreal and mountainous forests of the northern hemisphere, with large economic significance and enormous contributions to global carbon sequestration. Spruces harbor very large genomes with high repetitiveness, h ering their comparative analysis. Here, we present and compare the genomes of four different North American spruces: the genome assemblies for Engelmann spruce ( Picea engelmannii ) and Sitka spruce ( Picea sitchensis ) together with improved and more contiguous genome assemblies for white spruce ( Picea glauca ) and for a naturally occurring introgress of these three species known as interior spruce ( P. engelmannii × glauca × sitchensis ). The genomes were structurally similar, and a large part of scaffolds could be anchored to a genetic map. The composition of the interior spruce genome indicated asymmetric contributions from the three ancestral genomes. Phylogenetic analysis of the nuclear and organelle genomes revealed a topology indicative of ancient reticulation. Different patterns of expansion of gene families among genomes were observed and related with presumed ersifying ecological adaptations. We identified rapidly evolving genes that harbored high rates of non‐synonymous polymorphisms relative to synonymous ones, indicative of positive selection and its hitchhiking effects. These gene sets were mostly distinct between the genomes of ecologically contrasted species, and signatures of convergent balancing selection were detected. Stress and stimulus response was identified as the most frequent function assigned to expanding gene families and rapidly evolving genes. These two aspects of genomic evolution were complementary in their contribution to ergent evolution of presumed adaptive nature. These more contiguous spruce giga‐genome sequences should strengthen our understanding of conifer genome structure and evolution, as their comparison offers clues into the genetic basis of adaptation and ecology of conifers at the genomic level. They will also provide tools to better monitor natural genetic ersity and improve the management of conifer forests. The genomes of four closely related North American spruces indicate that their high similarity at the morphological level is paralleled by the high conservation of their physical genome structure. Yet, the evidence of ergent evolution is apparent in their rapidly evolving genomes, supported by differential expansion of key gene families and large sets of genes under positive selection, largely in relation to stimulus and environmental stress response.
Bacterial epibiont communities of panmictic Antarctic krill are spatially structured
Publisher: Wiley
Date: 15-01-2021
DOI: 10.1111/MEC.15771
Taking animal tracking to new depths
Publisher: Wiley
Date: 02-2015
DOI: 10.1890/14-0469.1
Abstract: In animal ecology, a question of key interest for aquatic species is how changes in movement behavior are related in the horizontal and vertical dimensions when in iduals forage. Alternative theoretical models and inconsistent empirical findings mean that this question remains unresolved. Here we tested expectations by incorporating the vertical dimension ( e information) when predicting switching between movement states ("resident" or "directed") within a state-space model. We integrated telemetry-based tracking and ing data available for four seal species (southern elephant, Weddell, antarctic fur, and crabeater) in East Antarctica. Where possible, we included e variables derived from the relationships between (1) e duration and depth (as a measure of effort), and (2) e duration and the post e surface interval (as a physiological measure of cost). Our results varied within and across species, but there was a general tendency for the probability of switching into "resident" state to be positively associated with shorter e durations (for a given depth) and longer post e surface intervals (for a given e duration). Our results add to a growing body of literature suggesting that simplistic interpretations of optimal foraging theory based only on horizontal movements do not directly translate into the vertical dimension in dynamic marine environments. Analyses that incorporate at least two dimensions can test more sophisticated models of foraging behavior.
Decadal changes in habitat characteristics influence population trajectories of southern elephant seals
Publisher: Wiley
Date: 12-07-2017
DOI: 10.1111/GCB.13776
Abstract: Understanding ergent biological responses to climate change is important for predicting ecosystem level consequences. We use species habitat models to predict the winter foraging habitats of female southern elephant seals and investigate how changes in environmental variables within these habitats may be related to observed decreases in the Macquarie Island population. There were three main groups of seals that specialized in different ocean realms (the sub-Antarctic, the Ross Sea and the Victoria Land Coast). The physical and climate attributes (e.g. wind strength, sea surface height, ocean current strength) varied amongst the realms and also displayed different temporal trends over the last two to four decades. Most notably, sea ice extent increased on average in the Victoria Land realm while it decreased overall in the Ross Sea realm. Using a species distribution model relating mean residence times (time spent in each 50 × 50 km grid cell) to 9 climate and physical co-variates, we developed spatial predictions of residence time to identify the core regions used by the seals across the Southern Ocean from 120°E to 120°W. Population size at Macquarie Island was negatively correlated with ice concentration within the core habitat of seals using the Victoria Land Coast and the Ross Sea. Sea ice extent and concentration is predicted to continue to change in the Southern Ocean, having unknown consequences for the biota of the region. The proportion of Macquarie Island females (40%) utilizing the relatively stable sub-Antarctic region, may buffer this population against longer-term regional changes in habitat quality, but the Macquarie Island population has persistently decreased (-1.45% per annum) over seven decades indicating that environmental changes in the Antarctic are acting on the remaining 60% of the population to impose a long-term population decline in a top Southern Ocean predator.
From trips to bouts to dives: temporal patterns in the diving behaviour of chick-rearing Adelie penguins, East Antarctica
Publisher: Inter-Research Science Center
Date: 12-11-2020
DOI: 10.3354/MEPS13519
Abstract: Breeding Adélie penguins forage at sea and return to land to provision their chicks, adjusting their foraging behaviour in response to environmental fluctuations over time. At Béchervaise Island, a nesting site in an East Antarctic population, Adélie penguin ing behaviour remains undocumented. This represents a key area of uncertainty in efforts to understand and predict foraging success at this colony. We compiled a multi-year telemetry dataset from time-depth recorders deployed from 1992 to 2004 on 64 birds at Béchervaise Island. We examined ing activity at multiple scales, ranging from foraging trips (n = 125) to e bouts (n = 3461) to in idual es (n = 84521), and then characterised the stage- and sex-specific variation in ing behaviour of chick-rearing Adélie penguins using linear mixed effect models. Total foraging trip effort (trip duration, number of es, vertical distance travelled and number of wiggles [a proxy for prey ingestion]) substantially increased as the chick-rearing period progressed (guard through crèche), consistent with increasing chick provisioning and self-maintenance requirements over time. Foraging activity was predominantly structured in periods of sustained ing bouts, indicating sustained foraging effort over the course of the foraging trip. Diving behaviour ( e-level depth, duration, bottom time and attempts of catch per unit effort) varied in relation to sex and chick-rearing stage. Dives were performed more frequently during high and low levels of solar light, which is likely linked to visual predation strategies or prey activity. Our findings advance our understanding of this population’s foraging behaviour, which is ultimately required to underpin the conservation and management of this breeding colony.
Sustained Upwelling of Subsurface Iron Supplies Seasonally Persistent Phytoplankton Blooms Around the Southern Kerguelen Plateau, Southern Ocean
Publisher: American Geophysical Union (AGU)
Date: 08-2018
DOI: 10.1029/2018JC013932
Marine ecosystem assessment for the Southern Ocean: birds and marine mammals in a changing climate
Publisher: Frontiers Media SA
Date: 04-11-2020
Modeling Antarctic Krill Circumpolar Spawning Habitat Quality to Identify Regions With Potential to Support High Larval Production
Publisher: American Geophysical Union (AGU)
Date: 19-06-2021
DOI: 10.1029/2020GL091206
Abstract: Antarctic krill (krill) are important within Southern Ocean ecosystems and support an expanding fishery. Toward understanding krill's response to environmental change, it is necessary to identify regions that support high krill larval production (spawning habitat). We develop a mechanistic model combining thermal and food requirements for krill egg production, with predation pressure post‐spawning, to predict regions of high‐quality spawning habitat. We optimize our model regionally and generate circumpolar predictions of spawning habitat quality. Our results indicate the southwest Atlantic accounts for almost half of all predicted high‐quality spawning habitat. Small‐scale management units (SSMUs) around the Antarctic Peninsula had high coverage of high‐quality spawning habitat. In contrast, the remaining SSMUs (except around South Georgia) were poorly covered, suggestive of population sinks reliant on input from external sources upstream. This implies strong potential for downstream impacts of fishing in key spawning areas, with implications for management of SSMUs and the krill fishery.
Distribution of larval and juvenile pelagic squids in the Kerguelen Axis region: Oceanographic influence on size structure and evidence of spawning locations
Publisher: Elsevier BV
Date: 04-2020
Supplementary material from Elephant seal foraging success is enhanced in Antarctic coastal polynyas
Publisher: The Royal Society
Date: 2021
Integrative modelling of animal movement: Incorporating in situ habitat and behavioural information for a migratory marine predator
Publisher: The Royal Society
Date: 07-01-2013
Abstract: A fundamental goal in animal ecology is to quantify how environmental (and other) factors influence in idual movement, as this is key to understanding responsiveness of populations to future change. However, quantitative interpretation of in idual-based telemetry data is h ered by the complexity of, and error within, these multi-dimensional data. Here, we present an integrative hierarchical Bayesian state-space modelling approach where, for the first time, the mechanistic process model for the movement state of animals directly incorporates both environmental and other behavioural information, and observation and process model parameters are estimated within a single model. When applied to a migratory marine predator, the southern elephant seal ( Mirounga leonina ), we find the switch from directed to resident movement state was associated with colder water temperatures, relatively short e bottom time and rapid descent rates. The approach presented here can have widespread utility for quantifying movement–behaviour ( ing or other)–environment relationships across species and systems.
Humpback whale migrations to Antarctic summer foraging grounds through the southwest Pacific Ocean
Publisher: Springer Science and Business Media LLC
Date: 17-08-2018
DOI: 10.1038/S41598-018-30748-4
Abstract: Humpback whale ( Megaptera novaeangliae ) populations typically undertake seasonal migrations, spending winters in low latitude breeding grounds and summers foraging in high latitude feeding grounds. Until recently, a broad scale understanding of whale movement has been derived from whaling records, Discovery marks, photo identification and genetic analyses. However, with advances in satellite tagging technology and concurrent development of analytical methodologies we can now detail finer scale humpback whale movement, infer behavioural context and examine how these animals interact with their physical environment. Here we describe the temporal and spatial characteristics of migration along the east Australian seaboard and into the Southern Ocean by 30 humpback whales satellite tagged over three consecutive austral summers. We characterise the putative Antarctic feeding grounds and identify supplemental foraging within temperate, migratory corridors. We demonstrate that Antarctic foraging habitat is associated with the marginal ice zone, with key predictors of inferred foraging behaviour including distance from the ice edge, ice melt rate and variability in ice concentration two months prior to arrival. We discuss the highly variable ice season within the putative foraging habitat and the implications that this and other environmental factors may have on the continued strong recovery of this humpback whale population.
Circumpolar projections of Antarctic krill growth potential
Publisher: Springer Science and Business Media LLC
Date: 18-05-2020
Stomach content analysis of mesopelagic fish from the southern Kerguelen Axis
Publisher: Elsevier BV
Date: 04-2020
SI Appendix 2. Supplementary material (Figures and Tables) for Arce et al doi:10.1098/rspb.2021.2452 from Elephant seal foraging success is enhanced in Antarctic coastal polynyas
Publisher: The Royal Society
Date: 2021
Putting the behavior into animal movement modeling: Improved activity budgets from use of ancillary tag information
Publisher: Wiley
Date: 20-10-2016
DOI: 10.1002/ECE3.2530
State-space models for bio-loggers
Publisher: Elsevier BV
Date: 04-2013
Movement responses to environment: fast inference of variation among southern elephant seals with a mixed effects model
Publisher: Wiley
Date: 24-12-2018
DOI: 10.1002/ECY.2566
Abstract: Like many species, movement patterns of southern elephant seals ( Mirounga leonina ) are being influenced by long‐term environmental change. These seals migrate up to 4,000 km from their breeding colonies, foraging for months in a variety of Southern Ocean habitats. Understanding how movement patterns vary with environmental features and how these relationships differ among in iduals employing different foraging strategies can provide insight into foraging performance at a population level. We apply new fast‐estimation tools to fit mixed effects within a random walk movement model, rapidly inferring among‐in idual variability in southern elephant seal environment–movement relationships. We found that seals making foraging trips to the sea ice on or near the Antarctic continental shelf consistently reduced speed and directionality (move persistence) with increasing sea‐ice coverage but had variable responses to chlorophyll a concentration, whereas seals foraging in the open ocean reduced move persistence in regions where circumpolar deep water shoaled. Given future climate scenarios, open‐ocean foragers may encounter more productive habitat but sea‐ice foragers may see reduced habitat availability. Our approach is scalable to large telemetry data sets and allows flexible combinations of mixed effects to be evaluated via model selection, thereby illuminating the ecological context of animal movements that underlie habitat usage.
Related Organisations
University Of Tasmania Institute For Marine And Antarctic Studies
Location: Australia
Related Funding Activities
Mathematical Models For Antarctic Animal Migrations In A Changing Climate
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End Date: 2020
Funder: Australian Research Council
View Funded ActivityThe Role Of Eastern Antarctic Polynyas In Global Ocean Circulation
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End Date: 2021
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View Funded ActivityDiscovery Projects - Grant ID: DP230101368
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End Date: 04-2026
Amount: $807,639.00
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View Funded ActivitySuper Science Fellowships - Grant ID: FS110200057
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View Funded ActivityDiscovery Early Career Researcher Award - Grant ID: DE180100828
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View Funded ActivityDiscovery Projects - Grant ID: DP180101667
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