In this study, researchers analysed two deep-sea fish species from South Georgia: Antimora rostrata (blue antimora), a more pelagic species, and Macrourus holotrachys (bigeye grenadier), a demersal species. In 2020, individuals were collected and four tissues (muscle, brain, liver and gills) were analysed, along with stable isotopes, to determine the habitat and trophic position of each species.

The results showed that:

• Muscle was the tissue with the highest mercury concentrations in both species.
• A. rostrata consistently showed lower concentrations than M. holotrachys.
• Only in M. holotrachys did Hg concentrations increase with body length and weight, suggesting bioaccumulation throughout life
• Differences also reflected habitat use, since the demersal species (M. holotrachys) is more closely associated with benthic food webs, which are generally richer in Hg.
• A. rostrata occupies a lower trophic level than M. holotrachys.

Unexpectedly, the brain showed high Hg concentrations, raising questions about potential neurotoxic effects in these fishes and their predators.

These results reveal that different feeding strategies and habitats shape contaminant accumulation in deep-sea species, with implications for ecosystem health and for top predators that depend on them.

Source: Vaz, D. B., Queirós, J. P., Xavier, J. C., Bustamante, P., Abreu, J., Pereira, E., Hollyman, P. R., Coelho, J. P. & Seco, J. (2025). Mercury Concentrations, Habitat and Trophic Position of Antimora Rostrata and Macrourus Holotrachys from South Georgia (Southern Ocean). Marine Pollution Bulletin. DOI:10.2139/ssrn.5360416

Author: Diana

Because squids are almost impossible to study alive, scientists have to rely on their beaks, hard structures that resist digestion and accumulate in the stomachs of predators to analyse their chemical signatures. In this study, researchers analysed squid beaks collected from the 1970s to the present day to measure mercury concentrations.

The results were remarkable, despite high mercury levels in the first two decades, concentration have been steadily decreasing over the past three decades. This trend suggests that global efforts to reduce mercury emissions, such as the International Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (1972)and improvements in industrial practices, are having measurable positive effects, even in remote ecosystems like the Southern Ocean (Figure 1).

Cephalopods like M. longimana can be valuable bioindicators as they occupy a central position in marine food webs, linking smaller prey such as crustaceans and fish to large predators like seals and whales. Moreover, their short lifespan and rapid make them excellent “record keepers” of environmental conditions giving researchers a unique window into pollutant trends.

By turning squid beaks into environmental archives, scientists have provided evidence that pollution can decline when collective action is taken. These results bring hope, but also serve as a reminder of the need to sustain global commitments to pollution reduction to safeguard ecosystems.

Source: Sara Lopes-Santos, José C. Xavier, José Abreu, José Seco, João P. Coelho, Eduarda Pereira, Richard A. Phillips, José P. Queirós, Decreasing mercury concentrations in beaks of the giant warty squid Moroteuthopsis longimana in the Scotia Sea (Southern Ocean) since the 1970s, Marine Pollution Bulletin, Volume 221, 2025, 118578, ISSN 0025-326X

Author: Lucas

The researchers used stable isotope analyses (δ¹³C and δ¹⁵N) from the muscle tissues of various species collected during fishing seasons in 2020, 2021, and 2022. They identified a food-web with five main trophic levels, with Patagonian (Dissostichus eleginoides) and Antarctic (D. mawsoni) toothfishes as the top predators and noted a potential sixth level when including predators such as seals and whales (Figure 1).

The study found that food chain length varied between years, with the longest chain recorded in 2020 and a shortening of about 0.30 trophic levels by 2022. These changes were linked to shifts in the isotopic signatures of species across multiple trophic levels, suggesting that even mid-trophic level organisms showed significant variability over time.

A major finding is the strong positive linear relationship between food chain length and net primary production. Years with higher net primary production (and related parameters like chlorophyll a concentration) were associated with longer food chains. This supports the productivity hypothesis, which suggests that more productive systems can support a longer chain of energy transfer through more trophic levels. The research highlights the importance of interactions between pelagic (open water) and benthic/demersal (seafloor) components. This coupling occurs primarily between the third and fourth trophic levels, where mobile pelagic species (like squids and crustaceans) interact with demersal fish. Such coupling is key for energy and nutrient fluxes between different ecosystem compartments.

The authors suggest that as climate change increases productivity in the Southern Ocean, food webs may become longer. This has important implications for energy transfer efficiency, exposure to contaminants (due to biomagnification), and alterations in nutrient cycling, potentially affecting the entire ecosystem’s structure and function.

Overall, the paper demonstrates that deep‐sea food-web structure at the South Sandwich Islands is dynamic and strongly influenced by variations in net primary production. These findings provide crucial insights into how climate-driven changes in productivity could reshape trophic interactions and energy flow in one of the world’s most remote marine ecosystems.

Source: Queirós, J. P., Hollyman, P. R., Bustamante, P., Vaz, D., Belchier, M., & Xavier, J. C. (2025). Deep‐sea food‐web structure at South Sandwich Islands (Southern Ocean): net primary production as a main driver for interannual changes. Ecography.

Author: Sara Santos

But how did they do it? In this study, the scientists turned to eastern rockhopper penguins (Eudyptes chrysocome filholi), from Campbell Island (a sub-Antarctic island of New Zealand) as a biosampler. Researchers collected cephalopods’ beaks from their diet from two breeding seasons (1986–87 and 2012–13) in which they performed stable isotope analysis (SIA), forms of chemical elements that do not undergo radioactive decay. Using this method, they were able to examine the carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic signatures, which provide insights into the habitat and trophic level of organisms. δ¹³C values help to differentiate between inshore and offshore foraging habitats, while δ¹⁵N values indicate the organism’s position in the food web.

What did they find? Using the beaks, scientists were able to pinpoint the differences in cephalopod biodiversity in the diet of penguins between the two breeding seasons. The 1986-87 diet comprised seven cephalopod species while, contrastingly, the 2012-13 diet included only three species: Moroteuthopsis ingens, Nototodarus sloanii, and Octopus campbelli. Moreover, M. ingens and O. campbelli were present in both seasons, but N. sloanii was only found in the 2012-13 season. And what does this mean? Firstly, the overall diversity seemed to decrease, however, this is likely due to the smaller sample size (Nº1986-87= 69 vs Nº 2012-13= 11). Secondly, the identification of N. sloanii may indicate a southward habitat expansion, as this species is more common in the warmer waters of New Zealand.

What about the SIA? These revealed variations in habitat and trophic niches between species. Specifically, M. ingens showed no significant differences in δ¹³C or δ¹⁵N values between years (Figure 1), while for O. campbelli δ¹³C and δ¹⁵N values were significantly lower in 2012-13 compared to 1986-87 (Figure 2), suggesting a shift in foraging location and possibly a move to lower trophic levels. N. sloanii, presented δ¹³C values in accordance with the values of other sub‑Antarctic waters taxa and lower δ¹⁵N values indicative of foraging at lower trophic levels.

What does this mean? The differences in stable isotope values between seasons could be a sign of changes in oceanographic conditions such as warming waters, taking species to new habitats and feeding differently. Additionally, the presence of N. sloanii in diets offers insights into their foraging and possible interactions with New Zealand fisheries, which can affect both the fisheries and the conservation of the eastern rockhopper penguin.

Overall, this study contributes significantly to increasing the knowledge of cephalopod ecology in the Pacific sector of the Southern Ocean. It demonstrates that different cephalopod species exhibit distinct habitat preferences and trophic roles. The findings reinforce the importance of continued monitoring of cephalopod populations, particularly in the face of environmental changes that may alter their distribution and availability to predators like rockhopper penguins.

Source: Guímaro, H. R., Thompson, D. R., Morrison, K. W., Fragão, J., Matias, R. S., & Xavier, J. C. (2025). Evidence of eastern rockhopper penguin feeding on a key commercial arrow squid species. Polar Biology, 48(1), 1-7

Author: Lucas Bastos

One such squid species, Moroteuhopsis longimana, inhabits the deep waters of the Southern Ocean and can reach more than 2 meters in total length. It bioaccumulates Hg throughout its life and is an important prey item for several top predators such as seabirds, marine mammals and fish, so understanding its role in the transfer of Hg in the food web is crucial. However, there is still a lack of knowledge about the relationship between Hg concentrations in M. longimana beaks and muscle (the main tissue consumed by the predators), which this study aims to analyse.

To do that, 21 buccal masses of M. longimana collected from the stomach of the Antarctic toothfish (Dissostichus mawson). For total Hg analysis, the upper and lower beaks were sectioned into the wing (W) and hood tip (H), and the remainder of the lower (L) and upper (U) beaks (Figure 1). A portion of the buccal mass muscle (M) was also collected for analysis.

Results showed that Hg concentrations in the muscle are ~100 times higher than in the whole beaks (U and L) and ~50 times higher than in the W and H sections (Figure 2). Inter-tissue variability in Hg concentrations confirms that the concentration of Hg in the beak does not reflect directly those in the muscle.

However, a positive relationship was found between Hg concentrations in the wing (W) and muscle (M), translated by the following equation:

Hg_músculo = 34.88 Hg_asa + 0.12

This equation suggests that mercury concentration in the wing can be used as a proxy for Hg concentration in the muscle of M. longimana. However, it should only be used for adult individuals, as this study only used fully chitinized adult beaks.

Future studies can now use this equation to estimate the Hg concentration in the muscle of other M. longimana, through the analysis of the Hg concentration in the beak wing, providing a means of assessing the levels, transport and fate of Hg in within Southern Ocean ecosystem.

Source: Lopes-Santos S, Xavier JC, Seco J, Coelho JP, Hollyman PR, Pereira E, Phillips RA, Queirós JP (2025) Squid beaks as a proxy for mercury concentrations in muscle of the giant warty squid Moroteuthopsis longimana. Marine Environmental Research 204:106841.

Author: Sara Santos

The study measured stable isotope signatures and Hg concentrations in different species, including chinstrap penguins, skuas, gulls, southern giant petrels, and southern elephant seals. Significant differences in δ13C values among species were observed, with considerable overlap between seabird species and seals. Differences in δ15N values reflected variations in diet and trophic position. The lowest Hg concentrations were found in krill (0.007 ± 0.008 μg∙g–1) and the highest in southern giant petrels (12.090 ± 14.177 μg∙g–1).

Results showed a positive relationship between Hg concentrations and trophic levels, with Hg biomagnifying nearly twice at each trophic level. The study suggests that trophic interactions are the major pathways for Hg biomagnification in Southern Ocean ecosystems. The research also highlights that Hg concentrations may increase in marine organisms due to global warming, which enhances Hg methylation and its availability in low-oxygen waters. Long-lived, high trophic level predators, such as some seabirds and seals, are particularly vulnerable to the effects of Hg.

The study concludes that Hg biomagnification in the food webs of the Antarctic Peninsula results in high Hg burdens in top predators. As global temperatures rise, Hg concentrations are expected to increase, potentially causing significant negative effects on Antarctic organisms. The article emphasises the need for further studies to fully understand how taxonomic, geographic, and ecological differences influence Hg dynamics in the marine ecosystems of the Antarctic Peninsula.

Source: Matias, R. S., Guímaro, H. R., Bustamante, P., Seco, J., Chipev, N., Fragão, J., … & Xavier, J. C. (2022). Mercury biomagnification in an Antarctic food web of the Antarctic Peninsula. Environmental Pollution, 304, 119199.

DOI: 10.1016/j.envpol.2022.119199

Author: Laura Lopes

The authors focus on the giant warty squid Moroteuthopsis longimana, which is a major prey for Southern Ocean predators and has been previously studied for its age and growth using different techniques. The study aims to evaluate the feasibility of using beaks collected from predators’ stomachs, such as the Antarctic toothfish (Dissostichus mawsoni) to determine the age and growth of M. longimana and estimate the age and growth patterns of this species in different areas of the Southern Ocean.

The study found that beaks collected from predators’ stomachs can be used to study the age of Southern Ocean squids, specifically M. longimana. The rostrum sagittal section (RSS) of the lower beak was found to be the most reliable section for age estimation (Fig.1), as it had readable micro-increments that could be counted while the upper beaks presented highly compacted increments with many of them being indistinguishable. Also, it was estimated that M. longimana can live up to 820 days and may hatch throughout the year. This species showed a consistent growth rate from hatching to death with at least one period of faster growth. A novel pattern of regular cycles, composed of 7-10 lighter increments followed by a darker one, was found in the medium-anterior region of the RSS (Fig.2b). Differences in growth rate and size reached at the same age were observed between individuals from the Pacific and Atlantic sectors of the Southern Ocean, suggesting the influence of different environmental conditions.

Therefore, beaks collected from predators’ stomachs can be used to study the age and growth of Southern Ocean squid, specifically Moroteuthopsis longimana. However, the authors highlighted the need for future research to validate the periodicity of increment formation in cold-water and deep-sea squid and to consider the impact of environmental conditions on the growth of M. longimana.

Reference: Queirós, J. P., Bartolomé, A., Piatkowski, U., Xavier, J. C., & Perales-Raya, C. (2022). Age and growth estimation of Southern Ocean squid Moroteuthopsis longimana: can we use beaks collected from predators’ stomachs? Marine Biology, 170(1).

https://doi.org/10.1007/s00227-022-04156-2

Author: Diogo Francisco

The Antarctic toothfish (Dissostichus mawsoni), a long-lived top predator in the Southern Ocean, is captured annually in the region. Due to its biological and ecological features, D. mawsoni is susceptible to accumulate high concentrations of trace elements, making it a potential bioindicator for the concentrations of trace and rare earth elements in the deep-sea ecosystem of the Southern Ocean.

Considering the commercial interest of D. mawsoni, in this study the authors discuss how this species can be a good source of nutrients to consumers by also exploring if the different trace elements can be used to determine the origin of the fish. To accomplish this, it was determined for the first time the concentration of 27 trace and rare earth elements in muscle samples of the species D. mawsoni, which was caught in three areas of the Amundsen and Dumont D’Urville Seas in Antarctic (Figure 1).

As expected, the study revealed that major essential elements, particularly potassium (K), exhibited the highest concentrations, while rare earth elements registered the lowest levels in the D. mawsoni muscle. Notable differences were observed between the study areas, indicating that the concentration of these elements in this species varies geographically and within adjacent fishing areas, with highest levels identified in fish from the Amundsen Sea slope. The authors suggested that these disparities may be linked to dietary variations, differences in Southern Ocean water composition and contrasting trends in environmental changes that influence the input of some elements into the environment.

Additionally, by using otolith [1] lengths as a proxy for fish size and δ15N [2] values as an indicator of trophic position, the study found no evidence of bioaccumulation of those elements in the muscle of D. mawsoni. Instead, concentrations tended to decrease with fish size, suggesting potential influences from a growth dilution effect, metabolic and lipid content variations between younger and older fish, or habitat-related factors. Moreover, the absence of significant correlations with δ15N values indicates no biomagnification [3] potential within these food webs.

The later evaluation of the potential detoxification role of selenium (Se) for Mercury (Hg) in D. mawsoni was significant, specifically when mercury concentrations reach levels that could be harmful to the organism. This implies that selenium might play a crucial role in protecting the Antarctic toothfish from the adverse effects of elevated levels of Hg.

Thereby, according to these findings, D. mawsoni not only stands out as a bioindicator for the concentrations of the different trace and rare earth elements in the Southern Ocean, but also reveals itself as a good source of major essential elements to humans with concentrations of major essential elements above some of other marine fish worldwide.

Definitions:

[1] Otholits: Hard, calcium carbonate structures located directly behind the brain of bony fishes.

[2] δ15N: Nitrogen stable isotope, which allows for an estimation of the trophic position of consumers in a diet chain.

[3] Biomagnification: Increase in concentration of a substance in the tissues of organisms at successively higher levels in a food chain.

Reference: Queirós, J. P., Machado, J. F., Pereira, E., Bustamante, P., Carvalho, L., Soares, E., Stevens, D. W., & Xavier, J. C. (2023). Antarctic toothfish Dissostichus mawsoni as a bioindicator of trace and rare earth elements in the Southern Ocean. Chemosphere, 321, 138134. https://doi.org/10.1016/j.chemosphere.2023.138134

Author: Maria Soares

Seabirds, as top predators, reflect the Hg contamination that is present in their marine food web, through biomagnification processes. Their main form of Hg excretion is through moulting. Within seabirds, the Adelie penguin (Pygoscelis adeliae) (Figure 1) has a set of ideal characteristics to be used as a bioindicator for Hg concentrations in Antarctic food webs, since it has a circumpolar distribution and is the most common and abundant penguin species on the Antarctic continent.

For the circumpolar assessment of Hg concentrations, feather samples were collected from 538 individuals (490 adults of reproductive age and 48 pre-fledging chicks) between 2005 and 2021 in 24 colonies around the continent. Total mercury (T-Hg) concentrations were evaluated for each sample. Values of the isotopes δ¹³C and δ¹⁵N were also determined on the feathers and used as proxies for the feeding habitat and trophic position of the penguins, respectively.

At the circumpolar level, Hg contamination proved to be relatively homogeneous between the different regions assessed. However, a Hg hotspot was observed in the Ross Sea (Figure 2), associated with a higher trophic position of Adélie penguins, likely due to a higher proportion of fish in their diets.

It is essential to continue monitoring Hg concentrations to assess the effectiveness of the Minamata Convention on Mercury. Large-scale assessments are extremely important to monitor the contamination status of Antarctic food webs over time, and also to assess global trends, taking into account the climate change context.

Author: Sara Santos

Source: Cusset, F., Bustamante, P., Carravieri, A. et al. Circumpolar assessment of mercury contamination: the Adélie penguin as a bioindicator of Antarctic marine ecosystems. Ecotoxicology 32, 1024–1049 (2023). https://doi.org/10.1007/s10646-023-02709-9

DOI: https://doi.org/10.1007/s10646-023-02709-9

The reduction of ice in certain regions not only generates instability, putting the lives of those looking for food at risk, but also triggers changes in ecosystems. Another critical factor in the loss of ecosystems is related to the acidification of the Arctic Ocean (Fig.1). This phenomenon occurs due to the influx of melting river waters, causing the displacement of some fish species. It is important to note that, on the other hand, other species may benefit from acidification. Understanding the consequences of these changes encompasses cultural, identity and community issues, including the sharing of traditional and ancestral knowledge that is being lost.

As we delve deeper into the study, we see that the health of these populations and communities is at risk, both nutritionally, due to the loss of access to certain foods, and mentally. However, it is necessary to bear in mind that the other side of climate change verified in that region allows an increase in resource extraction, tourism and economic development. Everything is interconnected.

The authors of the report present seven case studies to show the situation in different areas of the Arctic region and in different communities that have found ways to adapt resiliently to the new circumstances (Fig.2). This new reality is no longer restricted to the Arctic or indigenous populations

Author: Céline Rodrigues

Reference: Arctic Council, Protection of the Arctic Marine Environment (PAME). (2021). Indigenous Food Security in the Arctic, Implications of a Changing Ocean. Information Brief.

https://pame.is/doclink/mpa-information-brief-indigenous-food-security-in-the-arctic/eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJtcGEtaW5mb3JtYXRpb24tYnJpZWYtaW5kaWdlbm91cy1mb29kLXNlY3VyaXR5LWluLXRoZS1hcmN0aWMiLCJpYXQiOjE2MjE0OTg0MTEsImV4cCI6MTYyMTU4NDgxMX0.OiJzl0OyRDTdvq1faMQhUvEgmSxn2wEeQuL0RLVupA8