José C. Xavier

University of Coimbra | UC

Patagonian toothfish (Dissostichus eleginoides) supports valuable fisheries across the Southern Ocean under the management of the Commission for the Conservation of Antarctic Marine Living Resources. The fishery at South Georgia accounts for 26 % of the catch of this species in the Southern Ocean in the last 25 years. This study assesses the effect...

Background Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. Howeve...

Comprehensive spatial planning in international waters is key to achieving ocean sustainability

Understanding and managing the response of marine ecosystems to human pressures including climate change requires reliable large-scale and multi-decadal information on the state of key populations. These populations include the pelagic animals that support ecosystem services including carbon export and fisheries. The use of research vessels to coll...

Cephalopods play an important role in the Southern Ocean marine ecosystem connecting top predators and mid-trophic organisms. However, there is a lack of knowledge of the ecology of cephalopod fauna in the Pacific sector of the Southern Ocean. Stable isotope analysis (SIA) was applied to study the habitat and trophic ecology of cephalopods in the d...

Understanding the biodiversity of an ecosystem is crucial to determine its structure and resistance to climate change. The South Sandwich Islands (SSI) are located in the Scotia Sea (Southern Ocean), within the South Georgia and the South Sandwich Islands Marine Protected Area. However, the biodiversity of the archipelago remains poorly studied, wh...

Climate change is expected to have major negative effects on marine life across phylogenetic groups. Cephalopods, however, have life history characteristics that suggest they may benefit from certain climate change scenarios. Of all cephalopods, squids reach the greatest biomasses; as a result, they are of substantial importance for human and preda...

Numerous terrestrial and marine organisms, including cephalopods, are capable of light emission. In addition to communication, bioluminescence is used for attraction and defense mechanisms. The present review aims to: (i) present updated information on the taxonomic diversity of luminous cephalopods and morphological features, (ii) describe large-s...

Animal tracking has afforded insights into patterns of space use in numerous species and thereby informed area-based conservation planning. A crucial consideration when estimating spatial distributions from tracking data is whether the sample of tracked animals is representative of the wider population. However, it may also be important to track an...

The Antarctic toothfish Dissostichus mawsoni is a Southern Ocean long-lived top predator, regularly captured on an annual fishery operating in the region. By its biological and ecological characteristics, it is a potential bioindicator for the concentrations of trace and rare earth elements in the Antarctic. As these elements are mainly transferred...

[This corrects the article DOI: 10.3389/fphys.2022.1038064.].

Climate change is expected to produce major effects across marine life, and cephalopods seem to benefit from these effects. Of these animals, squids exhibit the greatest levels of biomass and of a substantial importance for human consumption. To test the hypothesis that effects of climate change are beneficial for commercial squid, we used species...

Squid play a major role in the Southern Ocean food web. However, their age and growth remain poorly studied. Here, using upper and lower beaks of Moroteuthopsis longimana collected from the diet of Dissostichus mawsoni from Pacific and Atlantic sectors of the Southern Ocean, we studied: (1) Feasibility of using beaks collected from predators' stoma...

Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gon...

Supplementary file for the following paper: https://www.mdpi.com/2076-2615/12/24/3548

The use of cephalopod beaks in ecological and population dynamics studies has allowed major advances of our knowledge on the role of cephalopods in marine ecosystems in the last 60 years. Since the 1960’s, with the pioneering research by Malcolm Clarke and colleagues, cephalopod beaks (also named jaws or mandibles) have been described to species le...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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)...

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...

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...

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...

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)....

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...