José C. Xavier

José C. Xavier
University of Coimbra | UC

PhD

About

209
Publications
71,170
Reads
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5,115
Citations
Introduction
José Xavier is an Antarctic marine ecologist (Cambridge University, PhD) based at the Marine and Environmental Sciences Centre (MARE-UC) of the University of Coimbra (Portugal) and at the British Antarctic Survey (UK), focusing his research on Southern Ocean ecology, particularly on foraging and feeding behavior of top predators, and ecological links to their prey, to climate change since 1997. José is the youngest scientist to get awarded the prestigious Tinker-Muse Prize for science and policy in Antarctica, and a proud recipient of the APECS international mentorship award.
Additional affiliations
September 2017 - December 2022
University of Coimbra (PT) & British Antarctic Survey (UK)
Position
  • Professor (Assistant)
January 2009 - present
University of Coimbra
Position
  • Researcher
January 1999 - June 2003
University of Cambridge
Position
  • PhD Student
Education
January 1999 - June 2003
University of Cambridge
Field of study
  • Zoology
September 1993 - December 1997
Universidade do Algarve
Field of study
  • Marine Biology

Publications

Publications (209)
Article
Full-text available
Fisheries ecosystem-based management is an important tool for sustainable harvesting of fisheries worldwide. Knowledge of trophic interactions is crucial as changes in trophic balances can induce severe changes in the structure of marine communities. While advocated for deep-sea fisheries, a lack of studies in benthopelagic area persist. The Antarc...
Book
Full-text available
In 2017, the United Nations proclaimed a Decade of Ocean Science for Sustainable Development (hereafter referred to as the UN Ocean Decade) from 2021 until 2030 to support efforts to reverse the cycle of decline in ocean health. To achieve this ambitious goal, this initiative aims to gather ocean stakeholders worldwide behind a common framework tha...
Article
Full-text available
Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become more bioavailable to the Antarctic marine food web (i.e., ice-stored Hg release and higher methylation rates by microorganisms), whose biomagnification processes are poorly documented. Biomagnification of Hg in the food web of the Antarctic Peninsula, o...
Article
Full-text available
Multiple initiatives have called for large-scale representative networks of marine protected areas (MPAs). MPAs should be ecologically representative to be effective, but in large, remote regions this can be difficult to quantify and assess. We present a novel bioregionalization for the Southern Ocean, which uses the modelled circumpolar habitat im...
Article
Ocean circulation connects geographically distinct ecosystems across a wide range of spatial and temporal scales via exchanges of physical and biogeochemical properties. Remote oceanographic processes can be especially important for ecosystems in the Southern Ocean, where the Antarctic Circumpolar Current (ACC) transports properties across ocean ba...
Article
Full-text available
For top consumers in marine environments, trophic discrimination factors (∆¹³C and ∆¹⁵N) between food and consumers’ tissues are expected to be similar among related species. However, few studies conducted in the laboratory indicate a large variability among species, which should be potentially higher in free-ranging animals. Here, we test for diff...
Article
Full-text available
Southern Ocean ecosystems are globally important. Processes in the Antarctic atmosphere, cryosphere, and the Southern Ocean directly influence global atmospheric and oceanic systems. Southern Ocean biogeochemistry has also been shown to have global importance. In contrast, ocean ecological processes are often seen as largely separate from the rest...
Article
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Successful management and mitigation of marine challenges depends on cooperation and knowledge sharing which often occurs across culturally diverse geographic regions. Global ocean science collaboration is therefore essential for developing global solutions. Building effective global research networks that can enable collaboration also need to ensu...
Article
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Cephalopods are an important component of Southern Ocean food webs but studies analysing their habitat and trophic ecology are scarce. Here, we use the Antarctic toothfish Dissostichus mawsoni as a biological sampler of the Southern Ocean's cephalopods in the Ross, Amundsen, and D'Urville Seas. Ten cephalopod taxa were identified in the diet of the...
Article
Full-text available
Southern Ocean ecosystems are globally important and vulnerable to global drivers of change, yet they remain challenging to study. Fish and squid make up a significant portion of the biomass within the Southern Ocean, filling key roles in food webs from forage to mid-trophic species and top predators. They comprise a diverse array of species unique...
Article
Indicators of oxidative stress and metabolic capacity are key factors in understanding the fitness of wild populations. In the present study, these factors were evaluated in the pelagic Southern Ocean taxa Antarctic krill (Euphausia superba) and myctophid fish (Electrona antarctica, Gymnoscopelus braueri and G. nicholsi) to establish a baseline rec...
Article
Microplastics (< 5mm in size) is known to be widespread in the marine environment, but it is still poorly studied in Polar Regions, particularly in the Antarctic. As penguins have a wide distribution around Antarctica, three congeneric species, Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarcticus) and gentoo penguin (Pygoscelis papua) wer...
Article
Full-text available
Efforts to model marine food-webs are generally undertaken by small teams working separately on specific regions (<10⁶ km²) and making independent decisions about how to deal with data gaps and uncertainties. Differences in these largely arbitrary decisions (which we call ‘model personality’) can potentially obscure true differences between regiona...
Book
Full-text available
The research in Southern Ocean cephalopods is always an ongoing work. There were three main reasons to publish an updated book on beaks from Southern Ocean cephalopods: Firstly, our motivation is that the guide is used in the future without providing confusion on species taxonomy, Secondly, various mistakes on the original printed version of this b...
Article
Cephalopods play a major role in marine ecosystems, yet very little is known about the dynamics of their habitat use and trophic ecology across the stages of their life cycle, particularly in the Southern Ocean. Here, we used stable isotope analyses of δ13C (a proxy for foraging habitat) and δ15N (a proxy for trophic position) to investigate the ha...
Article
Biomagnification of mercury (Hg) in the Scotia Sea food web of the Southern Ocean was examined using the stable isotope ratios of nitrogen (δ¹⁵N) and carbon (δ¹³C) as proxies for trophic level and feeding habitat, respectively. Total Hg and stable isotopes were measured in samples of particulate organic matter (POM), zooplankton, squid, myctophid f...
Article
Full-text available
In the Southern Ocean and adjacent waters, early stages of cephalopods play an important role in food webs as prey to top predators, but few is known regarding their biology and availability. Snares Penguin, Eudyptes robustus, is a top predator endemic to Snares Islands (New Zealand) that feed on cephalopods. As historical data on diet are rare for...
Article
Full-text available
Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key messages emerged that have stakeholder-relevance and/or a high impact for the scientific community. They address (i) altered biogeochemical cycles, (ii) oc...
Article
Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key messages emerged that have stakeholder-relevance and/or a high impact for the scientific community. They address (i) altered biogeochemical cycles, (ii) oc...
Article
Full-text available
p>Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key messages emerged that have stakeholder-relevance and/or a high impact for the scientific community. They address (i) altered biogeochemical cycles, (ii)...
Article
Full-text available
Trophic niche and diet comparisons among closely sympatric marine species are important to understand complex food webs, particularly in regions most affected by climate change. Using stable isotope analyses, all ontogenetic stages of three sympatric species of Arctic cephalopods (genus Rossia) were studied to assess inter- and intraspecific compet...
Article
Full-text available
Fish morphometric relationships are key tools for fisheries science and studies of food web dynamics and predator foraging behaviour, but parameterisations are lim-ited for Southern Ocean myctophids (Family Myctophidae). New standard length (LS) to total mass (MT) relationships are therefore described for the 12 biomass-dominant myctophid fish spec...
Chapter
Penguins (Family Spheniscidae) are aquatic flightless seabirds breeding in the South Hemisphere, with high diversity in the sub-Antarctic islands (Williams 1995). Some penguins (e.g., Chinstrap penguins Pygoscelis antarcticus, macaroni penguins Eudyptes chrysolophus) breed in vast colonies where food resources are predictable and profitable (Horswi...
Chapter
The continent of Antarctica has an area of c.1.4 million km2 , and the surrounding Southern Ocean (waters south of the Antarctic Polar Front) comprises 9.6% of the world’s oceans, both possessing significant environmental, scientific, historic, educational, and intrinsic values (Burton-Johnson et al. 2016; Hughes et al. 2018; Xavier et al. 2016b)....
Article
Yellowfin tuna are the mainstay of the traditional tuna fisheries in St Helena waters, but there is limited knowledge of their ecology and feeding behaviour in the area. In this study yellowfin tuna stomach contents were used to assess spatio‐temporal changes in feeding strategy and consider the role of tuna in the local ecosystem. Comparisons of t...
Article
Full-text available
Long-term studies of pelagic nekton in the Southern ocean and their responses to ongoing environmental change are rare. Using stable isotope ratios measured in squid beaks recovered from diet samples of wandering albatrosses Diomedea exulans, we assessed decadal variation (from 1976 to 2016) in the habitat (δ 13C) and trophic level (δ 15N) of five...
Article
As the role of mercury is poorly known in Southern Ocean biota, the total mercury (T-Hg) concentrations were evaluated in upper/lower beaks, digestive gland, gills and mantle muscle of Adelieledone polymorpha and Pareledone turqueti, two of the most abundant octopod species around South Georgia. Beaks had the lowest T-Hg concentrations (A. polymorp...
Article
Cephalopods represent an important pathway for mercury transfer through food webs. Due to the general difficulties in capturing oceanic squid, beaks found in the diet of top predators can be used to study their life-cycles and ecological role. Using upper beaks of the giant warty squid Moroteuthopsis longimana (major prey in the Southern Ocean), we...
Book
Full-text available
Crustaceans are an important component in the diet of numerous predators of the Southern Ocean (water masses located south of the Subtropical Front). As identifying crustaceans from food samples using conventional methods is not easy, a crustacean guide was written to aid scientists working on trophic relationships within the Southern Ocean. Having...
Article
Mercury is a bioaccumulating toxic pollutant which can reach humans through the consumption of contaminated food (e.g. marine fish). Although the Southern Ocean is often portrayed as a pristine ecosystem, its fishery products are not immune to mercury contamination. We analysed mercury concentration (organic and inorganic forms – T-Hg) in the muscl...
Article
Myctophids are the most abundant fish group in the Southern Ocean pelagic ecosystem and are an important link in the Antarctic marine food web. Due to their major ecological role, evaluating the level of mercury (Hg) contamination in myctophids is important as a step towards understanding the trophic pathway of this contaminant. The concentrations...
Poster
The Southern Ocean (SO) includes some of the most rapidly warming areas on the planet, but the ecological effects of climate change are likely to be mediated by regional differences in ecosystems, including differences in food web structure. Here we compare the structure and response to change of four food web models from different SO regions: the...
Article
Full-text available
The giant Antarctic Octopus Megaleledone setebos is the largest Southern Ocean octopod whose ecology is poorly known. Here, we study ontogenetic shifts of habitat and trophic ecology of M. setebos throughout its life cycle by stable isotopic analysis of δ13C and δ15N on its beaks collected from the diet of Antarctic toothfish in Amundsen and Ross S...
Article
Full-text available
Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally...
Article
Full-text available
The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for mul...
Article
The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for mul...
Article
Full-text available
Diet analyses can reveal important changes in seabird foraging ecology and, by inference, resource availability and predator–prey dynamics within the wider marine ecosystem. Here, we analysed stomach contents of 1544 grey-headed albatross Thalassarche chrysostoma (GHA) and black-browed albatross T. melanophris (BBA) chicks from Bird Island, South G...
Article
This study examines age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni from the Scotia Sea in the Southern Ocean, through the analysis of annual growth increments deposited on sagittal otoliths. Otolith pairs from 177 G. braueri and 118 K. anderssoni were collected in different seasons from...
Article
Full-text available
Understanding the underlying ecological factors that affect the distribution patterns of organisms is vital for their conservation. Cephalopods such as giant warty squids Moroteuthopsis longimana are important in the diets of marine predators, including grey-headed albatrosses Thalassarche chrysostoma , yet our understanding of their habitat and tr...
Article
Full-text available
Vampyroteuthis infernalis Chun, 1903, is a widely distributed deepwater cephalopod with unique morphology and phylogenetic position. We assessed its habitat and trophic ecology on a global scale via stable isotope analyses of a unique collection of beaks from 104 specimens from the Atlantic, Pacific and Indian Oceans. Cephalopods typically are acti...
Article
Illex argentinus is an ecologically and economically important species, assumed to be restricted to the Patagonian Shelf and around the subtropical convergence. Beaks found in diet samples from black-browed albatrosses Thalassarche melanophris during chick rearing initially suggested that it may also inhabit Antarctic waters until it was appreciate...
Article
Rossia palpebrosa (Sepiolida) is the most abundant nekto-benthic cephalopod in the Arctic; however, its feeding and trophic ecology are largely unknown. This work aims to assess the role of this species in Arctic ecosystems based on the contents of its stomachs and analyses of δ13C and δ15N stable isotopes in its beaks. The main taxa identified in...
Article
Understanding how changes in oceanographic conditions affect predators and their prey is fundamental for interpreting variability in natural marine ecosystems. At South Georgia, Antarctic fur seals Arctocephalus gazella are known cephalopod predators and potential indicators of changes in regional environment conditions and prey availability. The c...
Article
Full-text available
There is growing evidence that microplastic pollution (<5 mm in size) is now present in virtually all marine ecosystems, even in remote areas, such as the Arctic and the Antarctic. Microplastics have been found in water and sediments of the Antarctic but little is known of their ingestion by higher predators and mechanisms of their entry into Antar...
Article
he concentrations of total and proportions of organic mercury were measured in tissues of 355 in- dividuals of 8 species of Southern Ocean squid (Alluroteuthis antarcticus, Bathyteuthis abyssicola, Filippovia knipovitchi, Galiteuthis glacialis, Gonatus antarcticus, Kondakovia longimana, Psychroteuthis glacialis and Slosarczykovia circumantarctica)....
Article
Full-text available
Within the context of global climate change and overfishing of fish stocks, there is some evidence that cephalopod populations are benefiting from this changing setting. These invertebrates show enhanced phenotypic flexibility and are found from polar regions to the tropics. Yet, the global patterns of species richness in coastal cephalopods are no...
Article
The Humboldt Current System presents high interannual variability, influenced by the El Niño Southern Oscillation (ENSO), whose implications in wildlife are not fully understood. We studied the isotopic niche of wild Humboldt penguins at Punta San Juan (Peru) during the pre-moult foraging trip in 4 consecutive years (2008–2011) under known oceanogr...
Article
Sympatry can lead to higher competition under climate change and other environmental pressures, including in South Georgia, Antarctica, where the two most common octopod species, Adelieledone polymorpha and Pareledone turqueti, occur side by side. Since cephalopods are typically elusive animals, the ecology of both species is poorly known. As beaks...
Article
Cephalopods are important prey in the diet of top predators, such as marine mammals and seabirds. However, detailed information on their trophic relationships in the Patagonian marine ecosystem is scarce, including those cephalopod species with commercial interest. The aims of this study were to evaluate the composition of the cephalopod component...
Article
Polar Educators International (PEI) is a volunteer-based organization designed to build collaborative relationships between educators and polar researchers. Founded in 2012, PEI was created out of the networks formed during the International Polar Year 2007–2008. This paper explores PEI’s first five years (2012–17) of successes, challenges and oppo...
Article
Full-text available
International Polar Week is an educational activity that has been carried out since the International Polar Year 2007–2008 (known then as International Polar Days). This event, which brings together educators and polar scientists to promote polar science, is generally organised by the Association of Polar Early Career Scientists and Polar Educators...
Article
Total and organic mercury concentrations were determined for males, females and juveniles of Euphausia superba collected at three discrete locations in the Scotia Sea (South Orkney Islands, South Georgia and Antarctic Polar Front) to assess spatial mercury variability in Antarctic krill. There was clear geographic differentiation in mercury concent...
Article
The development of formal discourse about education and outreach within the Antarctic Treaty Consultative Meetings (ATCM), and the influence of major international activities in this field, are described. This study reflects on the ATCM Parties’ approach to implementing the ambition of the Protocol on Environmental Protection to the Antarctic Treat...
Article
Full-text available
The life histories of cephalopods are still not well described. Stable isotopic analysis of cephalopod beaks is an effective method to study of habitat and trophic ecology of this group of organisms. As beaks grow continuously throughout squid's life without replacement, we hypothesised that analysing different sections along the beak will provide...