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  • 1
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    Multifactorial roles of interannual variability, season and sex for foraging patterns in a sexually size monomorphic seabird, the Australasian gannet (Morus serrator) (2018)
    Springer
    In:  Marine Biology, 165 . Art.Nr. 72.
    Details
    Publication Date: 2021-02-08
    Description: Marine top predators forage in environments that show potentially extreme temporal and spatial variation in prey availability, with reproductive success being crucially linked to food supply. Multiple factors of interannual and sexual variation, as well as variation across breeding stages, can shape patterns of spatial use in foraging seabirds, yet studies that address all of these variables simultaneously are rare. We present spatial assessment of foraging patterns by µGPS tracking of a sexually size monomorphic, long-lived species, the Australasian gannet (Morus serrator). The study spanned the incubation and chick-rearing stages in three consecutive breeding seasons. Our findings revealed high interannual variability in foraging distances and trip durations, but no consistent differences between birds across different breeding stages or the sexes. The exception was that core foraging areas were different for female and male Australasian gannets, although trip durations or distances were similar for both sexes. Our results also indicate bimodality in foraging distance and trip duration in this species, while highlighting interannual variability in the extent of bimodality. These findings contribute to a scarcely documented type of foraging behaviour in the seabird family of the Sulidae. Overall, these spatial use patterns provide a baseline for understanding the evolution of sex-specific foraging differences in biparental seabirds, and the extent to which these differences might help in securing breeding success across years of variable food availability.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00227-018-3332-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    First genetic quantification of sex- and stage-specific feeding in the ubiquitous copepod Acartia tonsa (2018)
    Springer
    In:  Marine Biology, 165 (2). Art.No. 25.
    Details
    Publication Date: 2021-02-08
    Description: Marine copepods provide the major food-web link between primary producers and higher trophic levels, and their feeding ecology is of acute interest in light of global change impacts on food-web functioning. Recently, quantitative polymerase chain reaction (qPCR) protocols have been developed, which can complement classic diet quantification methods, such as stable isotope or fatty acid analyses tools. Here, we present first results of feeding experiments assessing sex- and stage-specific food intake by the ubiquitous calanoid copepod Acartia tonsa by 18S targeted qPCR and microscopic grazing assessment. In triplicated mixed-diet feeding treatments, three suitable A. tonsa diets, the cryptophyte Rhodomonas balthica, the haptophyte Isochrysis galbana, and the diatom Thalassiosira weissflogii, were offered in equal biomass proportions under constant conditions. Prey uptake substantially varied between different algal species, as did the extent of sex- and stage-specificity of prey uptake. Male adult copepods had higher R. balthica gut contents than females, and nauplii contained more of this prey source than copepodites or adult copepods in mixed treatments. A trend towards higher amounts of ingested T. weissflogii in adult females than in males and in nauplii than in other stages was detected. Genetic gut content quantifications indicated low feeding on I. galbana, and no consistent sex- or stage-specific differences of I. galbana content in A. tonsa. Our results highlight diet-specific feeding differences between Acartia life stages and sexes, which can have implications on food-web dynamics and specific nutrient transfer to higher trophic levels in copepod populations of varying age composition under changing environmental parameters, such as rising temperatures and increasing ocean acidification.
    Type: Article , PeerReviewed
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    DOI: 10.1007/s00227-017-3281-z
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    A virgin flight across the Tasman Sea? Satellite tracking of post-fledging movement in the Australasian Gannet Morus serrator (2010)
    Springer
    In:  Journal of Ornithology, 151 (3). pp. 755-759.
    Details
    Publication Date: 2020-07-20
    Description: New technologies enable tracking of the route, duration, and destination of previously unassessed long-distance movements. Fledgling Australasian Gannets Morus serrator from breeding populations in New Zealand had been reported to fly across the Tasman Sea to Australia, with this historic knowledge derived from the recovery of banded carcasses and from observations of initial flight direction. We deployed Argos satellite devices on ten M. serrator fledglings at Cape Kidnappers Gannetry, North Island, New Zealand, across 2 years. Birds that were tracked leaving the colony initially appeared to have landed on the sea. A male bird and two female birds were tracked moving along the east coast to the south tip of New Zealand. The two females then crossed the Tasman Sea to eastern Australian coastal waters in 4 and 5 days, respectively. We suggest that, contrary to historic reports, the route via Stewart Island constitutes a realized migration path for fledglings from Cape Kidnappers, which might minimize the distance traveled across the open sea to southeastern Australia or Tasmania. Our results further imply that initial direction of flight needs not be indicative of the subsequent migration route taken by M. serrator. This highlights the importance of direct tracking technology for adequate assessment of dispersal and migration in seabirds and other highly mobile species.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s10336-010-0504-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Brood patch and sex-ratio observations indicate breeding provenance and timing in New Zealand storm petrel (Fregetta maoriana) (2013)
    Marine Ornithology
    In:  Marine Ornithology, 41 . pp. 107-111.
    Details
    Publication Date: 2017-10-10
    Description: We used measurements of brood patch and moult status to estimate the breeding phenology of New Zealand Storm-Petrel, using birds caught at sea within the Hauraki Gulf Marine Park near Auckland, New Zealand. Birds caught October–January had completely downy brood patches, whereas birds caught February–April had bare brood patches with an observed male bias in the February sex-ratio, consistent with a female pre-laying exodus typical of petrels and with the existence of an unknown colony in the region. No birds captured exhibited primary moult, which is known to occur in storm-petrels during their non-breeding season. Our data support the conclusion that the New Zealand storm-petrel breeds during January–June in northern New Zealand and that field surveys for the species on offshore islands in this region during this period are warranted
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Mate replacement entails a fitness cost for a socially monogamous seabird (2010)
    Springer
    In:  Naturwissenschaften, 97 (1). pp. 109-113.
    Details
    Publication Date: 2020-06-22
    Description: Studies of the selective advantages of divorce in socially monogamous bird species have unravelled extensive variation among different lineages with diverse ecologies. We quantified the reproductive correlates of mate retention, mate loss and divorce in a highly philopatric, colonially breeding biparental seabird, the Australasian gannet Morus serrator. Estimates of annual divorce rates varied between 40-43% for M. serrator and were high in comparison with both the closely related Morus bassanus and the range of divorce rates reported across monogamous avian breeding systems. Mate retention across seasons was related to consistently higher reproductive success compared with mate replacement, while divorce per se contributed significantly to lower reproductive output only in one of two breeding seasons. Prior reproductive success was not predictive of mate replacement overall or divorce in particular. These patterns are in accordance with the musical chairs hypothesis of adaptive divorce theory, which operates in systems characterised by asynchronous territorial establishment.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00114-009-0618-6
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Climate change affects low trophic level marine consumers: warming decreases copepod size and abundance (2015)
    Springer
    In:  Oecologia, 177 (3). pp. 849-860.
    Details
    Publication Date: 2017-04-13
    Description: Concern about climate change has re-ignited interest in universal ecological responses to temperature variations: (1) biogeographical shifts, (2) phenology changes, and (3) size shifts. In this study we used copepods as model organisms to study size responses to temperature because of their central role in the pelagic food web and because of the ontogenetic length constancy between molts, which facilitates the definition of size of distinct developmental stages. In order to test the expected temperature-induced shifts towards smaller body size and lower abundances under warming conditions, a mesocosm experiment using plankton from the Baltic Sea at three temperature levels (ambient, ambient +4 °C, ambient −4 °C) was performed in summer 2010. Overall copepod and copepodit abundances, copepod size at all life stages, and adult copepod size in particular, showed significant temperature effects. As expected, zooplankton peak abundance was lower in warm than in ambient treatments. Copepod size-at-immature stage significantly increased in cold treatments, while adult size significantly decreased in warm treatments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00442-014-3130-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Evaluating molecular and behavioural sexing methods for the Australasian gannet (Morus serrator) (2007)
    CSIRO
    In:  Australian Journal of Zoology, 55 (6). p. 377.
    Details
    Publication Date: 2020-06-16
    Description: The availability of molecular methods for avian sex identification has revolutionised the study of sexual differences in behaviour, morphology, life-history traits and conservation management. We implemented the recommendations of a recent review of DNA-based sex-identification by (1) verifying the sex-specificity and (2) estimating the accuracy of different sex-assignment methods in an apparently monomorphic seabird, the Australasian gannet (Morus serrator). The polymerase chain reaction (PCR) method based on the amplification of the sex-linked chromodomainhelicase-DNA binding gene (CHD) repeatedly assigned the same sex in 96% (n = 27 replicates) and correctly sexed all individuals with known gonadal anatomy (n = 6). PCR and sex-specific restriction fragment length polymorphism (RFLPs) showed agreement for 99.5% of individuals (n = 201). DNA-sexed pairs known to be social mates consisted of a male and a female in 96% of pairs sexed by PCR (n = 77) and 98% of pairs sexed by RFLP (n = 65). DNA-sexed females were in the bottom and males in the top copulatory position in 86% of observed copulations (n = 43 individuals). These results validate assumptions that both membership in social pairs and different copulatory positions can serve as reliable behavioural proxies for field-based sex identification in this colonial and obligately biparental seabird.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1071/ZO07073
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Evaluating on-land capture methods for monitoring a recently rediscovered seabird, the New Zealand Storm-Petrel Fregetta maoriana (2015)
    Marine Ornithology
    In:  Marine Ornithology, 43 (2). pp. 255-258.
    Details
    Publication Date: 2017-10-10
    Description: We provide a first assessment of various on-land capture methods for a procellarid seabird, the New Zealand Storm-Petrel Fregetta maoriana, which had been presumed extinct but for which a breeding site has just been discovered on Little Barrier Island. In the vicinity of an active breeding site, playback only, also involving a newly isolated call from in situ deployed sound-recording devices, could efficiently be employed for capture, while light attraction in combination with playback achieved comparable capture success further afield. We consider that these findings can be relevant for breeding ground searches and capture operations in other storm-petrel species, and more generally in seabirds that visit their breeding sites at night.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Is the chemical composition of biomass the agent by which ocean acidification impacts on zooplankton ecology? (2017)
    Springer
    In:  Aquatic Sciences, 79 (3). pp. 733-748.
    Details
    Publication Date: 2020-02-06
    Description: Climate change impacts prevail on marine pelagic systems and food webs, including zooplankton, the key link between primary producers and fish. Several metabolic, physiological, and ecological responses of zooplankton species and communities to global stressors have recently been tested, with an emerging field in assessing effects of combined climate-related factors. Yet, integrative studies are needed to understand how ocean acidification interacts with global warming, mediating zooplankton body chemistry and ecology. Here, we tested the combined effects of global warming and ocean acidification, predicted for the year 2100, on a community of calanoid copepods, a ubiquitously important mesozooplankton compartment. Warming combined with tested pCO2 increase affected metabolism, altered stable isotope composition and fatty acid contents, and reduced zooplankton fitness, leading to lower copepodite abundances and decreased body sizes, and ultimately reduced survival. These interactive effects of temperature and acidification indicate that metabolism-driven chemical responses may be the underlying correlates of ecological effects observed in zooplankton communities, and highlight the importance of testing combined stressors with a regression approach when identifying possible effects on higher trophic levels.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00027-017-0532-5
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Effect of food concentration and type of diet on Acartia survival and naupliar development (2008)
    Springer
    In:  Marine Biology, 154 . pp. 335-343.
    Details
    Publication Date: 2018-06-07
    Description: We have performed life table experiments to investigate the effects of different food types and concentrations on the larval development and survival up to adulthood of Acartia tonsa. The food species offered comprised a wide taxonomic spectrum: the pigmented flagellates Isochrysis galbana, Emiliania huxleyi, Rhodomonas sp., Prorocentrum minimum, the diatom Thalassiosira weissflogii, grown on medium offering enriched macronutrient concentrations and the ciliate Euplotes sp. initially cultured on Rhodomonas. For the ciliate species, also the functional response was studied. In order to avoid limitation by mineral nutrients, food algae have been taken from the exponential growth phase of the nutrient replete cultures. The suitability of Rhodomonas as a food source throughout the entire life cycle was not a surprise. However, in contrast to much of the recent literature about the inadequacy or even toxicity of diatoms, we found that also Thalassiosira could support Acartia-development through the entire life cycle. On the other hand, Acartia could not complete its life cycle when fed with the other food items, Prorocentrum having adverse effects even when mixed with Rhodomonas and Thalassiosira. Isochrysis well supported naupliar survival and development, but was insufficient to support further development until reproduction. With Emiliania and Euplotes, nauplii died off before most of them could reach the first copepodite stages. Acartia-nauplii showed a behavioral preference for Euplotes-feeding over diatom feeding, but nevertheless Euplotes was an insufficient diet to complete development beyond the naupliar stages.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00227-008-0928-9
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