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Newly discovered CO2 (carbon dioxide) vent cave drives r-strategy shift in a Mediterranean aphotoendosymbiotic coral

Published 14 November 2025 Science Closed
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Highlights

  • Characterization of an unexplored CO2 vent cave
  • CO2 vents chemical-physical parameters affect ecological traits of calcifiers
  • Aphotoendosymbiotic solitary coral naturally inhabiting a CO2-rich gas environment.
  • Prolonged acidified conditions did not affect C. inornata growth rate
  • Shift towards an r-demographic strategy in response to acidified conditions

Abstract

Submarine CO2 volcanic vents represent peculiar environments with varying seawater chemical-physical parameters that may affect the ecological traits of calcifying organisms, such as growth and demographic characteristics. The present study focused on exploring the growth and population dynamics of a temperate, solitary and aphotoendosymbiotic coral Caryophyllia inornata (Duncan, 1878) living in a CO2 vent cave at 14 m depth. The volcanic emissions in and around the cave led high levels of pCO2, resulting in lower calcium carbonate saturation state (Ωa: 2.1–2.2) values compared to those observed in the ambient seawater of the Mediterranean Sea, not affected by venting activity. Prolonged acidified conditions (pHT: 7.5) did not affect C. inornata growth rate but resulted in a population with higher percentage of juvenile individuals, lower average ages and a lower age at maximum biomass percentage, thus suggesting a transition in its population dynamics towards an r-demographic strategy. This study provides a detailed characterization of a previously unexplored CO2 vent cave, highlighting the importance of these sites as natural laboratories to offer valuable insights into understanding the full ecological impact of aphotoendosymbiotic corals under ocean acidification.

Continue reading ‘Newly discovered CO2 (carbon dioxide) vent cave drives r-strategy shift in a Mediterranean aphotoendosymbiotic coral’

Biogeochemical properties of shallow-water CO2 seeps on Himeshima Island and Showa Iwojima Island, Japan

Published 7 November 2025 Science Closed
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Volcanic gases erupt from the seafloor in several regions around Japan. Volcanological and geochemical gas seep studies have mainly focused on coastal shallow-water areas that are relatively accessible and important to human society. Shallow-water CO2 seeps are thought to foreshadow future marine environments that may develop if CO2 emissions are not drastically reduced. Thus, CO2 seeps provide important insights for assessing and projecting the impacts of ocean acidification on marine ecosystems. This study is the first to investigate two shallow-water CO2 seeps near Japan from the perspective of ocean acidification. We observed biotic transitions and reduced biodiversity around these CO2 seeps, as well as high CO2 concentrations, low pH, and low calcium carbonate saturation—conditions expected to occur by the end of this century unless anthropogenic CO2 emissions are significantly reduced. These results suggest that, from a marine life conservation perspective, it is essential to mitigate ocean acidification through substantial reductions in anthropogenic CO2. Shallow-water CO2 seeps serve as natural experimental sites that illustrate ocean acidification and its effects on marine ecosystems. Given that the shallow-water CO2 seeps examined in this study are both located in geoparks, study tours and ecotourism field trips should utilize these sites to enhance awareness of the consequences of ocean acidification and climate change.

Continue reading ‘Biogeochemical properties of shallow-water CO2 seeps on Himeshima Island and Showa Iwojima Island, Japan’

Elevated carbon dioxide does not increase macroalgal community photosynthesis

Published 4 November 2025 Science Closed
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Ocean acidification, driven by rising atmospheric carbon dioxide levels, has impacts on marine ecosystems. While elevated carbon dioxide concentrations have the potential to enhance Blue Carbon fixation and storage, the response of community photosynthesis in macroalgal-dominated ecosystems remains poorly understood. Here, we investigated the effects of elevated carbon dioxide on macroalgal communities using volcanic carbon dioxide vents as a natural analogue of ocean acidification. Net community photosynthesis was assessed using chambers positioned on the seafloor as well as water mass dynamics monitoring. Despite a shift in algal community composition, only minimal differences in net community photosynthesis were observed between reference and high carbon dioxide sites. The high carbon dioxide site had a lower abundance of algal species with carbon dioxide concentrating mechanisms, based on δ13C isotope measurements. Carbon dioxide concentrating mechanisms facilitate photosynthesis under present-day levels of carbon dioxide in seawater, resulting in a negligible effect of elevated carbon dioxide on macroalgal community photosynthesis. These results challenge the assumption that ocean acidification will enhance Blue Carbon uptake and storage, necessitating a reevaluation of this perspective.

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Physiological and metabolic plasticity in Patella caerulea enables survival in the CO2 vent systems of the Castello Aragonese (Ischia Island)

Published 20 October 2025 Science Closed
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Highlights:

  • OA induced physiological and metabolic adjustment in P. caerulea to allow survival
  • Increased RR at low pH only during summer to potentially boost energy production
  • Reduced ER at low pH during summer and transplant to preserve more energy resources
  • Induction of carnitine metabolism to produce more energy in low pH
  • Increase of osmoregulation, oxidative stress, and nucleic acid metabolites at low pH

Abstract

Ocean acidification (OA) represents a major threat to marine ecosystems, causing detrimental effects mainly on calcifying organisms. However, the limpet Patella caerulea is one of the few calcifiers that can inhabit the naturally acidified areas of the Castello Aragonese vent systems (Ischia Island, Italy). Its presence suggests that this species may have developed tolerance or adaptive strategies to cope with OA.

Nevertheless, the specific biological mechanisms remain largely unknown. To address this gap of knowledge, in our study we conducted physiological and metabolomics analyses on resident limpet populations collected along the acidification gradient of the Castello vent systems. Additionally, we investigated the same mechanisms in specimens transplanted for 30 days from ambient pH conditions to the different pH sites of the vent.

Only during summer, OA increased respiration rates in limpets from the most acidified site and, simultaneously, reduced excretion rates and likely protein catabolism, probably to preserve more energy resources while coping with this environmental stress. Furthermore, the individuals up-regulated carnitine metabolism, potentially enhancing energy production through β-oxidation, and several metabolites involved in osmoregulation, oxidative stress, and nucleic acid mechanisms. Similar results were obtained also in limpets transplanted to low pH sites.

Overall, our results suggest that limpets exposed to acidified conditions may have developed tolerance strategies to maintain energetic reserves and allocate them among metabolic processes, which are fundamental in maintaining biological and ecological traits and distribution when facing environmental disturbance such as OA.

Continue reading ‘Physiological and metabolic plasticity in Patella caerulea enables survival in the CO2 vent systems of the Castello Aragonese (Ischia Island)’

Sibling species differently distributed around a CO2 vent show transplantation proteomic remodelling, while displaying metabolomic signatures associated with their origin

Published 2 October 2025 Science Closed
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The cellular homeostatic response (CHR) and cellular stress response (CSR) work together to maintain homeostasis. Studying phylogenetically closely-related species inhabiting different environments can help investigate the interplay between the CHR and CSR. We conducted reciprocal in situ transplant experiments in a natural CO2 vent (Ischia, Italy), using the sibling annelid species Platynereis cf.. dumerilii and Platynereis cf.. massiliensis which have been shown to have different preferential distributions around the CO2 vent. Following transplantations, we characterised the response of each individual’s proteome, metabolome, and lipidome, to short or long-term exposure to different pCO2 regimes (i.e., high and low), and confirmed its genetic identity. Here we show that different components of the CHR and CSR are utilised at different rates when Platynereis spp. are exposed to different pCO2 regimes, with cellular responses shown to be conserved across species. Metabolome and lipidome responses were dependent on regime of origin, and changed relatively slowly, whereas proteome responses were dependent on transplant type and changed more rapidly. Our results provide new insights to improve our understanding of the interplay between different cellular physiological responses involved in defining the functional phenotype of marine species, and their ability to acclimatise to future projected high pCO2 conditions.

Continue reading ‘Sibling species differently distributed around a CO2 vent show transplantation proteomic remodelling, while displaying metabolomic signatures associated with their origin’

What doesn´t kill you makes you stronger: the sea urchin Arbacia lixula living on volcanic CO2 vents

Published 1 September 2025 Science Closed
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Anthropogenic CO2 emissions drive ocean acidification (OA), which reduces seawater pH and carbonate ion availability, threatening calcifying organisms such as sea urchins. This study examines the long-term effects of OA on Arbacia lixula using a natural volcanic CO2 vent at Fuencaliente, La Palma (Canary Islands) as an analogue of future conditions. We analyzed the external morphology, skeletal strength, mineralogy, and growth of A. lixula across three sites that differed consistently in mean pH (from 8.14 to 7.65 during low tide). Sea urchins from low pH conditions were smaller, with shorter spines and reduced jaw-to-diameter ratios, yet their tests showed higher fracture resistance than those from ambient conditions. Additionally, individuals from acidified zones showed altered growth dynamics, with fewer growth rings. Skeletal changes and growth alterations are consistent with modified mineralization processes and dietary shifts toward non-calcareous food sources. This study highlighting the morphological plasticity and resilience of A. lixula under persistent natural acidification, offering insight into how sea urchins may respond in a high-CO2 ocean.

Continue reading ‘What doesn´t kill you makes you stronger: the sea urchin Arbacia lixula living on volcanic CO2 vents’

Ocean acidification influences strain selection and metabolism of the benthic diatom Cocconeis neothumensis var. marina

Published 21 August 2025 Science Closed
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The uptake of carbon dioxide (CO2) by oceans is dramatically altering the chemistry of seawater, leading to a continuous decrease of pH over the last century. This phenomenon, called ocean acidification (OA), has raised concerns due to its negative effects on marine biodiversity, including plankton communities and seagrass meadows. The most relevant seagrass in the Mediterranean is Posidonia oceanica, producing complex and stable benthic ecosystems. OA markedly affects the colonization and settlement patterns of epibionts within the leaf communities of P. oceanica. Epiphytic diatoms associated with P. oceanica are influenced by complex chemical and trophic interactions and play a fundamental role in the ecological successions characterizing the leaf stratum. In this study, we isolated two strains of Cocconeis neothumensis var. marina, one of the main epiphyte diatoms associated with P. oceanica, from two sites off the Island of Ischia (Italy) characterized by different pH conditions, i.e., a naturally low pH site (pH 7.6) influenced by volcanic CO2 emissions, and an adjacent location with ambient pH conditions (pH 8.1). We further cultured both strains of C. neothumensis under both pH conditions, resulting in four treatment conditions. Four significantly different growth curves were obtained, and metabolomic studies confirmed that the physiology of the strains differed according to pH conditions. Overall, this study demonstrated that OA is likely to trigger the selection of specific diatom strains, with possible consequences for trophic and chemical relationships among the associated consumers.

Continue reading ‘Ocean acidification influences strain selection and metabolism of the benthic diatom Cocconeis neothumensis var. marina’

Ocean architects at risk from the combined impact of ocean acidification and warming

Published 13 August 2025 Press releases Closed
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Researchers from the Institut de Ciències del Mar (ICM-CSIC) have published a study in Communications Biology showing how ocean acidification and warming — two of the main consequences of global climate change — can simultaneously affect the structure, mineral composition, and microbiome of bryozoans, colonial invertebrates crucial for forming marine habitats. The findings point to potentially serious ecological consequences under a scenario of accelerated climate change.

The “False Coral,” One of the Most Affected Species

The study characterizes for the first time the microbiome of Myriapora truncata, a habitat-forming species known as “false coral” and widely distributed throughout the Mediterranean. It also analyzes the response of this and another encrusting bryozoan species under future environmental conditions. False corals form three-dimensional structures that offer shelter to many species, as do other bryozoans that can even form reef-like systems — although corals usually receive more attention as primary marine habitat builders.

“Despite being a different phylum, very diverse and abundant globally, these small architects of the sea are often overlooked in studies on responses to environmental changes,” explains Blanca Figuerola, ICM-CSIC researcher and lead author of the study. She emphasizes that this work opens a new window to understand better how bryozoans may respond to the ocean’s rapid changes.

The researcher notes that “bryozoans play a very important ecological role,” although little was previously known about their response to the combined effects of ocean acidification and warming. She adds that “their microbiome had been virtually unexplored.”

A Natural Laboratory to Predict Future Scenarios

To conduct the study, the team utilized a “natural laboratory” on the island of Ischia (Italy), where volcanic CO₂ bubbles from the seabed simulate the ocean acidification conditions projected for the end of the century.

“This area offers a unique opportunity to study how marine species respond to acidification under natural conditions,” explains Núria Teixidó, researcher at the Stazione Zoologica Anton Dohrn and last author of the article.

Using this approach, the researchers compared the morphology, skeleton mineralogy, and microbiome of colonies of two bryozoan species exposed and unexposed to these conditions. Results show that the species exhibit some acclimation capacity, modifying their skeletal mineralogy to become more resistant and maintaining a relatively stable microbiome composition.

“However, we observed a loss in functional microbial diversity, with a decline in genera potentially involved in key processes such as nutrition, defense, or resistance to environmental stress,” Figuerola states.

Continue reading ‘Ocean architects at risk from the combined impact of ocean acidification and warming’

Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans

Published 12 August 2025 Science Closed
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Marine habitat-forming species provide crucial ecosystem functions and services worldwide. Still, the individual and combined long-term effects of ocean acidification and warming on bryozoan populations, structures, and microbiomes remain unexplored. Here, we investigate the skeletal properties, microbiome shifts, and population trends of two bryozoan species living inside and outside a volcanic CO2 vent, a natural analog to future ocean acidification conditions. We show that bryozoans can acclimatize to acidification by adjusting skeletal properties and maintaining stable microbiomes. However, we document a decrease in microbial genera playing essential functions under acidified conditions. Moreover, we show that ocean acidification exacerbates bryozoan cover loss and mortality caused by ocean warming. The observed shifts in the microbiome and cover suggest that, despite their morphological plasticity, bryozoan species will be heavily impacted by future ocean conditions, posing a threat to many benthic ecosystems in which they play a pivotal role.

Continue reading ‘Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans’

Short-term and long-term ocean acidification effects on seagrass performance: evidence from shallow CO2 vents

Published 8 August 2025 Science Closed
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Highlights

  • Cymodocea nodosa performance under in-situ ocean acidification has been evaluated.
  • Morphology of long-term acidified plants does not differ from that of control plants.
  • Higher performance was found in short-term acidified plants.
  • The response of apical shoots was particularly enhanced.

Abstract

Future ocean acidification conditions have the potential to affect seagrasses, although predicting the outcomes remains challenging due to the complexity of ecological interactions. This study aimed at evaluating the effects of ocean acidification on the morphology and physiology of the seagrass Cymodocea nodosa. A field manipulative experiment was conducted (Aeolian Islands, Italy) at a natural low pH site, where shallow submarine CO2 seeps occur, and other control pH sites. The effects of long-term acidification (by comparing untouched plants from control pH to the low pH sites) and a short-term acidification (by comparing transplanted plants from control pH sites to low pH site with translocated control pH plants) were evaluated. The evidence provided suggest that the seagrass may be considered a low pH tolerant seagrass, as the long-term acidification only determined an increase in photopigment concentrations, while the short-term acidification led to the increase in morphology, biomass and pigments, counteracting the negative effects due to cutting manipulation. These enhancements were more pronounced in apical shoots, suggesting a high clonal specialization. Our study provides evidence of morphological and physiological acclimation of C. nodosa in response to acidified conditions, suggesting that future ocean acidification scenarios could also favour this autochthonous seagrass species.

Continue reading ‘Short-term and long-term ocean acidification effects on seagrass performance: evidence from shallow CO2 vents’

Impact of natural CO2 leaks on marine ecosystems

Published 30 July 2025 Web sites and blogs Closed
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Panarea Island, in the Aeolian Archipelago, served as a unique environmental setting for a pilot study on the impact of CO2 on calcifying phytoplankton and zooplankton, in an area characterized by the presence of natural CO2 seeps on the seafloor. 

Patrizia Ziveri a Panarea, les illes Eòlies

This research allowed scientists from ICTA-UAB and the National Institute of Oceanography and Experimental Geophysics (OGS) of Italy to directly address the impact of these CO₂ leaks and ocean acidification on the ecosystems, as well as the species-specific physiological responses, including the calcification processes. 

Oceans absorb a large amount of atmospheric carbon dioxide, which helps mitigate climate change. In certain areas, such as volcanic zones near Sicily, natural CO₂ emissions from the seafloor can be observed. These leaks alter the water chemistry and may have consequences for marine life. 

The study of biodiversity changes resulting from these leaks will deepen the understanding of the role of calcifying plankton in ocean carbon sequestration and will provide valuable insights into their influence on the biogeochemical carbon cycle. This first pilot study greatly benefited from the existing OGS marine laboratory facilities at Panarea.

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Shifts in coral reef holobiont communities in the high-CO2 marine environment of Iōtorishima Island

Published 15 July 2025 Science Closed
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Ocean acidification (OA), driven by rising atmospheric CO2, presents a serious threat to marine biodiversity, especially within coral reef ecosystems. Natural analogue sites, such as the high-pCO2 seep at Iōtorishima Island in Japan, offer insights into future conditions. This study investigated the holobiont communities of Symbiodiniaceae and bacteria in the zoantharian Palythoa tuberculosa at Iōtorishima and compared them to specimens from control sites in Okinawa and Hawaiʻi. Using amplicon sequencing of the dinoflagellate internal transcribed spacer 2 (ITS2) region of ribosomal DNA and microbial 16S rRNA gene, we detected significant shifts in both Symbiodiniaceae and bacterial communities under high-pCO2 conditions at Iōtorishima. Specifically, P. tuberculosa at the seep site had reduced Symbiodiniaceae diversity, predominatly featuring Cladocopium C1 and C3 types. Additionally, its bacterial communities showed lower richness with distinct taxonomic profiles, including increased levels of Mollicutes and Vibrio spp. These results highlight the potentially adverse effects of OA on hexacoral holobionts and emphasize the need for detailed, high-resolution studies across various holobiont species and geographic locations. The shifts observed specifically in Symbiodiniaceae and bacterial communities at the Iōtorishima seep suggest that holobionts may exhibit plasticity in response to environmental stress, which has implications for resilience and adaptation of zoantharians and other reef organisms amid climate change. This research provides crucial baseline data for predicting future coral reef compositions in an OA-affected world.

Continue reading ‘Shifts in coral reef holobiont communities in the high-CO2 marine environment of Iōtorishima Island’

Mollusc epifaunal assemblages are simplified due to habitat shifts under ocean acidification

Published 14 July 2025 Science Closed
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Highlights

  • Ocean acidification can modify the structure of marine communities.
  • The macroalga Halopteris sp. supports a rich community of associated molluscs.
  • Halopteris sp. from an acidified site support fewer and less diverse assemblages.
  • Most abundant species were present both at the acidified and reference sites.
  • Biodiversity of molluscs will be simplified under acidified conditions.

Abstract

Ocean acidification can have profound effects on marine organisms, particularly those that rely on calcium carbonate for shell and skeleton formation, resulting in structural changes to marine ecosystems. Here, we contrast the structure of marine mollusc communities (epifauna) associated with an abundant shallow-water macroalga, Halopteris scoparia, in an area with seawater carbonated by natural CO2 seeps and three reference sites, off the Azores archipelago. Epifaunal mollusc abundance and diversity were significantly lower at the CO2 seep compared to reference sites whilst species accumulation curves and Jaccard multivariate analyses showed that the mollusc assemblage was consistently less diverse at the CO2 seep. Most of the abundant epifaunal species that were present at the CO2 seep were also found at reference sites, but less common or rare species were generally absent from the former. We conclude that while some molluscs are likely to cope with ocean acidification, the overall biodiversity of epifaunal molluscs will be simplified under these conditions in a future ocean.

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Robustness of gametogenesis in the scleractinian coral, Tubastraea aurea, in the shallow-water hydrothermal vent field off Kueishan Island, northeastern Taiwan

Published 8 July 2025 Science Closed
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Highlights

  • Stony corals (Tubastraea aurea) can colonize in acidified shallow-water hydrothermal vent fields.
  • T. aurea is a gynodioecious brooder; mostly females with a low percent of hermaphroditism.
  • HV colonies maintained the similar gametogenic process and seasonal timing of reproduction as NHV colonies.
  • Elevated gametogenic activity of vent T. aurea could facilitate success in extreme conditions.
  • Hydrothermal vents as natural laboratories offer insights on the resiliency of scleractinians.

Abstract

Understanding the reproductive resiliency of scleractinian corals is imperative as ocean acidification and rising sea surface temperatures threaten the foundation of coral reef ecosystems. However, the limited temporal scales of laboratory and transplantation-based methods fail to consider evolutionary time frames offered by natural analogues of future climate conditions, like hydrothermal vents (HV). Accordingly, we characterized the presence of scleractinians surrounding a major shallow-water HV near Kueishan Island in northeastern Taiwan, identified a candidate species, Tubastraea aurea, and investigated its sexual reproductive strategies. Since this was the first study to describe the sexual reproduction of T. aurea, we characterized the gametogenetic process of T. aurea colonies from the HV and three non-HV locations (NHV1, NHV2, NHV3). Oogenesis was similar between HV and NHV sites and mature oocytes reached the same size. The seasonal timing of reproduction was comparable between HV and NHV1 colonies, likely related to the similar seasonal variation of water temperatures. HV colonies showed an even higher gametogenetic activity (100 % of polyps containing developing gametes in HV colonies versus 73.5 % in NHV colonies). As assessed by the presence of larvae, T. aurea is a brooder, with mostly female polyps (97.6 %,) and a low percent of hermaphroditism (2.4 %, as observed in 2 in HV and 1 in NHV colonies). This suggests that parthenogenesis may contribute to larval production. Taken together, we demonstrated the robustness of gametogenesis in T. aurea and propose the heightened reproductive effort of T. aurea at the Kueishan Island HV could be facilitating its success in acidified conditions. Overall, this study exemplified the importance of using unique ecosystems to uncover clues on scleractinian resiliency.

Continue reading ‘Robustness of gametogenesis in the scleractinian coral, Tubastraea aurea, in the shallow-water hydrothermal vent field off Kueishan Island, northeastern Taiwan’

Short and long-term exposure to ocean acidification in limpets from the Castello Aragonese vent systems (Ischia Island, Italy)

Published 12 June 2025 Science Closed
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Highlights

  • First investigation limpet populations collected from the naturally acidified site.
  • Increased dimension and energy endpoints in Patella caerulea from very low pH (<7.4).
  • Induction of antioxidant systems and neurotoxicity in Patella rustica exposed to OA.
  • Transplant of Patella caerulea activated oxidative stress and neurotoxicity endpoints.

Abstract

Ocean acidification (OA) is reported to entail a detrimental impact on calcifying organisms. Nevertheless, patellid limpets – P. caerulea, P. rustica, and P. ulyssiponensis – are able to persist in extremely low pH conditions inside the Castello Aragonese CO2 vent systems (Ischia Island), suggesting that they may have developed tolerance to OA, through plasticity and/or adaptive mechanisms. The aim of this study is to evaluate the long-term strategies adopted by limpets that spent their entire life cycle in naturally acidified conditions and the short-term ones induced by a 30-day in situ transplant experiment.

Regarding native limpet populations, P. caerulea exhibited increasing size and higher energy resources in the extremely acidified site, potentially related to different food availability or to reduction in competition and/or predatory pressure; furthermore, no effects on oxidative stress, biomineralization and neurotoxicity occurred. Similarly, P. ulyssiponensis didn’t exhibit any significant effects among different pH conditions regarding biochemical endpoints. Conversely, P. rustica displayed a significant modulation of almost all biochemical parameters, possibly due to its different position on the rocky shore. The short-term exposure of P. caerulea produced a decrease in protein content and an increase in glycogen content in the extreme acidified site, with an induction of superoxide dismutase and glutathione-S-transferases activities in the intermediate pH site.

Overall, our study revealed that different species of the same genus may have developed distinct responses to OA and suggested different mechanisms to cope with short and long-term exposure to low pH conditions.

Continue reading ‘Short and long-term exposure to ocean acidification in limpets from the Castello Aragonese vent systems (Ischia Island, Italy)’

Hydrothermal vents as observatories for future ocean acidification (OA) scenarios: an in-situ study to unravel the involvement of ATP binding cassette transporters in the adaptation of marine polychaetes Platynereis spp. to OA

Published 16 May 2025 Science Closed
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The marine annelid Platynereis dumerilii, is a key model in genetics, evolution, neurobiology, ecology, and ecotoxicology. Along with its sibling species, P. cfr massiliensis, it thrives in both normal and naturally acidified environments. This makes these species ideal candidates for studying mechanisms of tolerance to acidified conditions, resembling future ocean acidification (OA) scenarios. The ATP-binding cassette (ABC) transport proteins help mitigating the adverse impacts of drugs, xenobiotics and physical stressors. There is growing evidence for their involvement to mediate tolerance towards acid-stress in bacteria and tumor cell lines. Such a function may be relevant for the ability of marine species to cope with OA and may be important to consider when predicting future OA scenarios for marine fauna. Here we addressed the question if ABC transporters of Platynereis spp. are involved in compensating adverse effects of low pH by studying ABC transporter transcript levels in marine animals exposed to various pH levels. We firstly examined P. dumerilii whole genome data (version EMBL_pdum_1.0, Genbank assembly: GCA_026936325.1) for the presence of ABC transporter genes, by homology searches, and, using the single-cell atlas database with P. dumerilii gene expression data, we then determined the presence of a potentially relevant subset of ABC transporters from the ABCB, C and G subfamilies in different organs/tissues. Finally, to assess how seawater pH affects ABC transporter expression, we conducted an in-situ reciprocal transplant experiment involving individuals of P. dumerilii/P. cfr massiliensis. Adult specimens were collected inside and outside the CO2 vents off Castello Aragonese (Ischia Island, Italy). Individuals collected from normal pH areas (8.18 ± 0.005) were transplanted to acidified conditions (7.33 ± 0.312), and vice versa, while others were placed in their original areas. We found 81 orthologs from ABC transporter subfamilies A-G, expressed in different organs/tissues including midgut, neurons, body epidermis and ectodermal cells, and somatic and visceral muscle. Following the 30 days transplant experiment, qPCR analyses were performed to examine the expression levels of seven selected genes from the ABCB, ABCC, and ABCG subfamilies (abcb_1, abcb_2, abcb_3, abcc_1, abcc_2, abcc_3, and abcg). Three of these genes were differentially expressed in specimens transplanted from normal pH to low pH areas (abcb_1 and abcg up-regulated while abcb_3 down-regulated). Based on the homology with human ABCB1 and ABCG2, which are crucial in tumor cell adaptation to acidified environments, it seems reasonable to hypothesize that abcb_1, abcb_3 and abcg play a similar role in Platynereis spp. helping in maintaining cellular homeostasis and surviving acid stress.

Continue reading ‘Hydrothermal vents as observatories for future ocean acidification (OA) scenarios: an in-situ study to unravel the involvement of ATP binding cassette transporters in the adaptation of marine polychaetes Platynereis spp. to OA’

Increasing acidification does not affect sexual reproduction of a solitary zooxanthellate coral transplanted at a carbon dioxide vent

Published 8 May 2025 Science Closed
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The absorption of atmospheric carbon dioxide is causing significant changes to the carbonate chemistry of the ocean, in a phenomenon called ocean acidification. The latter makes it potentially more difficult for marine calcifiers like corals, to build their calcium carbonate structures, thus affecting their ability to survive and reproduce. Research on how ocean acidification impacts coral sexual reproduction has focused on tropical species investigated under controlled conditions in aquaria, lacking insights into the intricate natural environment. Here we show that the sexual reproduction of the zooxanthellate solitary scleractinian Balanophyllia europaea transplanted at a CO2 vent off the Island of Panarea (Tyrrhenian Sea, Italy) for up to 5 months is unaffected by decreasing pH (pH range 8.1–7.4). These findings reinforce earlier evidence, suggesting that zooxanthellate corals may exhibit a certain degree of short-term resilience to ocean acidification. However, the interplay between ocean acidification and additional environmental stressors, including warming, will ultimately define the boundaries that distinguish winners and losers amid swift climatic changes.

Continue reading ‘Increasing acidification does not affect sexual reproduction of a solitary zooxanthellate coral transplanted at a carbon dioxide vent’

High heterotrophic capacity favors Mediterranean coral success and resilience in the face of ocean acidification

Published 7 May 2025 Science Closed
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Coral ecosystems support a diverse array of marine life and healthy ecological functioning, yet they are vulnerable to decreases in ocean pH caused by anthropogenic carbon dioxide emissions. In temperate rocky reefs of the Mediterranean, the corals Cladocora caespitosa and Astroides calycularis live at sites with ambient seawater pH and at adjacent submarine volcanic CO2 vent sites with low seawater pH where it is more energetically demanding to grow. We collected corals from distinct ambient pH (average pHT 8.05) and lower pH CO2 vent sites (average pHT 7.74–7.90) and quantified their physiological health and heterotrophic capacity (i.e., feeding capacity). Both species at CO2 vent sites had higher heterotrophic capacity than their ambient site counterparts, enabling them to maintain energy reserves. Our results indicate that high heterotrophic capacity underlies the success of these two temperate corals at CO2 vent sites. Therefore, conservation of CO2 vent coral could be strategically important to maintaining rocky reef ecosystem function and ecological resilience in the Mediterranean.

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Euromarine summer school: PulseOcean

Published 28 April 2025 Events Closed
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Dates: September 14-20, 2025
Venue: Ischia Marine Center- Stazione Zoologica Anton Dohrn, Ischia, Italy
Application deadline: May 26, 2025

More information:
https://drive.google.com/file/d/1bCfxPO2SMxCUUIZ2d7PfCKTijObZIbBj/view?usp=sharing
Application Form (A Google account is required to complete the form due to file upload
fields): https://forms.gle/bb8QitenPPmzdsJfA

We are thrilled to announce that the Euromarine Summer School PulseOcean is now open for applications! Tailored for PhD students and early-career researchers, this course combines lectures, fieldwork at the submarine CO2 vents in Ischia, and lab-based projects to provide a unique hands-on learning experience. You will learn and discuss topics including seawater chemistry and ecological methods, insights into blue carbon, AI-based image analysis, drone surveys and photogrammetry, and data science tools such as R and GitHub.

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Microbe-host associations as drivers of benthic carbon and nitrogen cycling in a changing Mediterranean Sea

Published 14 April 2025 Science Closed
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Seagrasses, such as the endemic Mediterranean species Posidonia oceanica, are critical components of coastal marine ecosystems, providing essential ecosystem services, including carbon sequestration, nutrient cycling, and habitat formation. P. oceanica forms extensive meadows that serve as biodiversity hotspots and play a crucial role in mitigating climate change through long-term carbon storage. Despite their ecological significance, the interactions between P. oceanica and associated organisms, as well as their combined contributions to biogeochemical cycling, remain poorly understood, particularly under changing environmental conditions. This thesis explores the carbon and nitrogen cycling processes within the P. oceanica holobiont, focusing on the epiphytic and microbial communities, microbial driven metabolic processes, and the interaction between P. oceanica and larger associated invertebrates, such as the sponge Chondrilla nucula. Through field and laboratory experiments, this work demonstrates the significant role of epiphytic algae in the primary production of the seagrass holobiont, contributing a substantial portion of net primary production. Nitrogen cycling processes such as N₂ fixation, nitrification, and denitrification in the seagrass phyllosphere were quantified, revealing their importance in meeting the N demands of the seagrass holobiont, especially under natural ocean acidification conditions. Experiments near marine CO₂ vents indicated that ocean acidification accelerates net primary production and nitrogen cycling, while the structure of the microbial community associated with P. oceanica leaves remains largely stable. The facultative mutualism between P. oceanica and the sponge C. nucula further highlights the complexity of the seagrass holobiont. P. oceanica releases dissolved organic carbon, which meets a portion of the sponge’s respiratory carbon demand. Conversely, C. nucula releases dissolved inorganic nitrogen, including ammonium and nitrate generated by microbial nitrification, which supports seagrass growth. Stable isotope analysis suggests that the association facilitates nutrient exchange, with P. oceanica preferentially absorbing sponge-derived ammonium, while epiphytes may benefit from sponge-produced nitrate. This dynamic reduces seasonal fluctuations in productivity, stabilizing the seagrass ecosystem during periods of senescence. Sponge-associated nitrification contributes to the nitrogen budget of the seagrass holobiont, potentially reducing nutrient limitations in oligotrophic Mediterranean waters. The microbiome of C. nucula plays a key role in these processes, harboring nitrifiers that mediate the production of nitrate. High-throughput sequencing revealed taxonomic diversity among microbes associated with both the sponge and seagrass, including microorganisms involved in carbon and nitrogen cycling processes. These microbial communities not only mediate nutrient exchange within the seagrass-sponge association but also contribute to the overall resilience and productivity of the ecosystem. This thesis highlights the intricate interactions within the P. oceanica holobiont and its nested ecosystem with C. nucula. These findings underscore the importance of microbial and epiphytic communities in maintaining the resilience and productivity of seagrass meadows, particularly in nutrient-poor environments like the Mediterranean Sea. This research enhances our understanding of the biogeochemical processes that support seagrass ecosystem stability and provides valuable insights to guide conservation efforts in the face of climate change and anthropogenic pressures.

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