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 models indicate that increasing sea surface temperatures and retreating sea ice (key aspects of ocean warming) are major drivers of changing habitat conditions. Other factors, like chlorophyll concentration (a proxy for primary productivity), also play an important role.

The species-specific responses include potential winners and losers:

Potential Winners: Subtropical and cosmopolitan squid species (e.g., Histioteuthis atlantica, Teuthowenia pellucida, Todarodes filippovae, and Bathyteuthis abyssicola) may gain suitable habitat, particularly at higher latitudes (Figure 1).

Potential Losers: In contrast, Antarctic and many subantarctic species (such as Onykia ingens, Onykia robsoni, Martialia hyadesi, Gonatus antarcticus, Histioteuthis eltaninae, Slosarczykovia circumantarctica, Mesonychoteuthis hamiltoni, Alluroteuthis antarcticus, Galiteuthis glacialis, Psychroteuthis glacialis, and especially Moroteuthopsis longimana) are projected to lose a significant portion of their current habitat (Figure 2).

Additionally, the study found that the northern limits of squid distributions are expected to move southward over time, with a reduction in biodiversity hotspots, which may alter the structure of the pelagic ecosystem. Changes in squid distribution could have cascading effects throughout the Southern Ocean food web, impacting predators such as seabirds, seals, and cetaceans that rely on squid as a major food source.

The authors note uncertainties related to the resolution of environmental data, the lack of trophic interactions in the models, and limited sampling in remote areas. They suggest that future studies incorporate finer-scale data (including depth as a third dimension) and more comprehensive biological information to better inform conservation and marine spatial planning.

Overall, the paper provides essential projections for understanding potential shifts in marine biodiversity due to climate change and highlights the importance of considering these changes in conservation strategies for the Southern Ocean.

Source: Guerreiro, M., Santos, C. P., Borges, F., Santos, C., Xavier, J. C., & Rosa, R. (2025). Projecting future climate change impacts on the distribution of pelagic squid in the Southern Ocean. Marine Ecology Progress Series, 757

Author: Sara Santos

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

These variables may change, for example, the introduction of freshwater by melting sea ice has been recognized as the main driver in the decrease in the dynamism of the water column during the spring-summer seasons. These and other changes can have significant effects on phytoplankton communities [1], communities that play an important role in biogeochemical processes [2] in the ocean.

One of the most important types of phytoplankton in the Antarctic region is the Diatoms, which contribute 75% of primary production in the Antarctic Ocean and support many of the food webs [3] in the region. Within the Diatoms, there are 2 main groups, the pennants and the centrists, these groups present differences in body shape among others thinks. As such, the researchers of this study aimed to describe the distribution of different groups of diatoms in the Ross Sea. For this, they carried out 2 oceanographic cruises during the austral summer of 2014 and 2017.

In 2014 and 2017, the surface distribution of diatoms was dominated in both summers by pennate diatoms (Fragilariopsis and Pseudo-nitzschia), but a temporal variation was analysed, where there was a change in the community, mainly dominated by pennate diatoms to dominated by centric diatoms, in February 2014 and 2017.

In general, the phytoplankton communities were very similar between cruises. However, the concentrations reached were different (Fig.1). A change in the concentrations of groups of Diatoms in surface water agrees with the observation of other authors.

This study was the first description of the diversity of Diatom groups in the Ross Sea, as expected changes in environmental variables affect the distribution of phytoplankton in the water column. The dynamics of the trophic network of the polar regions depend exclusively on the phytoplankton community and its changes, changes that can have effects on the biogeochemical cycles, the authors highlight the lack of studies on this subject and the importance of carrying out more studies to know these communities and its variations.

Smaller organisms are also crucial for balance of our ecosystems!

[1] Phytoplankton: Group of microscopic aquatic organisms that can perform photosynthesis and that live floating along the water column.

[2] Biogeochemical processes: Also known as the cycle of matter, it is therefore the process of passing from the environment (physical-chemical components) to living organisms and from these back to the environment.
[3] Trophic network: Interconnection within an ecosystem of matter and energy transfers between organisms.

Source: Saggiomo, M., Escalera, L., Bolinesi, F., Rivaro, P., Saggiomo, V., & Mangoni, O. (2021). Diatom diversity during two austral summers in the Ross Sea (Antarctica). Marine Micropaleontology, 165. https://doi.org/10.1016/j.marmicro.2021.101993

Author: Graça Sofia Nunes

Defining these Areas is particularly complex, often including international waters, or waters in exclusive economic zones of different countries, or even important areas of marine resources. However, it is crucial that these areas encompass ecologically highly important zones for as many species as possible.

Thus, this study, conducted in the Southern Ocean that surrounds the entire Antarctic continent, sought to identify the most important areas using 17 species of birds and marine mammals that inhabit and/or use this region, from penguins, albatrosses, seals, whales, etc.

This identification was made using data obtained by GPS (placed in the different species), which gives us the location and movements of the animals, in response to more than 15 environmental variables (e.g.: ice concentration, depth, salinity etc.) Finally, with the use of computational models, it was possible to identify ecologically important areas for a large number of species, thus representing crucial areas for their success (Figure 1).

Finally, this knowledge considerably increases our understanding of this region and helps to establish which zones and areas should potentially be protected in the future and included as Marine Protected Areas due to their important ecological function.

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Source:

Reisinger, R. R., Brooks, C. M., Raymond, B., Freer, J. J., Cotté, C., Xavier, J. C.,.. & Hindell, M. (2022). Predator-derived bioregions in the Southern Ocean: Characteristics, drivers and representation in marine protected areas. Biological Conservation, 272, 109630.

Hindell, M.A., Reisinger, R.R., Ropert-Coudert, Y. et al. Tracking of marine predators to protect Southern Ocean ecosystems. Nature 580, 87–92 (2020). https://doi.org/10.1038/s41586-020-2126-y

Author: José Abreu