Ocean acidification (OA) is considered a relevant additional threat to marine biodiversity and is linked to the increasing CO2 concentration in the atmosphere. Here, we provide a synthesis on the loss of both taxonomic and functional biodiversity, in the up to date best studied CO2 vents in the world, the Castello Aragonese of Ischia (Tyrrhenian Sea, Italy), analyzing a large data set available at this site and reporting qualitative taxonomic data along a gradient of OA from ambient normal conditions outside the vents (pH 8.1) to low pH conditions (pH 7.8–7.9) and extreme low pH conditions (pH < 7.4). A total of 618 taxa were recorded (micro- and macrophytes, benthic invertebrates, and fishes). A relevant loss of biodiversity (46% of the species) was documented from control/normal pH conditions to low pH, and up to 56% species loss from control of extreme low pH conditions. Functional groups analysis on the fauna (calcification, size, motility, feeding habit, and reproduction/development) allowed us to draw an identikit of the species which is able to better thrive under OA conditions. These are motile forms, small- or medium-sized, generalist feeders, at the low level of the food web (herbivores or detritivores), mainly brooders, or with indirect benthic development, and without calcification or weakly calcified.
Continue reading ‘Syntheses on taxonomic and functional biodiversity related to ocean acidification in a well-studied CO2 vents system: the Castello Aragonese of Ischia (Italy)’Posts Tagged 'vents'
Syntheses on taxonomic and functional biodiversity related to ocean acidification in a well-studied CO2 vents system: the Castello Aragonese of Ischia (Italy)
Published 22 December 2025 Science Leave a CommentTags: biological response, BRcommunity, community composition, field, Mediterranean, otherprocess, review, vents
Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification
Published 10 December 2025 Science Leave a CommentTags: biological response, echinoderms, field, morphology, South Pacific, vents
Ocean acidification can reduce the size of calcified structures produced by marine calcifiers, raising questions about their competitiveness and persistence in future oceans. Yet, size reduction in calcified structures may represent a plastic response to ocean acidification if these structures remain functional. To test this hypothesis and examine whether morphological plasticity can influence the functionality of calcified structures, we assessed the effects of ocean acidification on the morphological, mechanical and chemical properties of the calcified structures of a sea urchin species prevailing at natural CO2 vents. We found that the rigid shells covering sea urchins’ bodies (‘tests’) were thinner and that they had smaller teeth and lower spine density at vents, but the mechanical performance of these calcified structures (mechanical resilience, wear resistance and bending strength) was maintained, possibly mediated by the capacity of sea urchins to sustain acid-base balance for calcification (i.e. increased Na/Ca). Our findings suggest that such morphological shifts in calcified structures may enable sea urchins to maintain structural performance under ocean acidification. Since ocean acidification is a slow process relative to the life cycle of sea urchins, some sea urchin species may acclimate, or even adapt, to ocean acidification so that their populations and ecological functions can persist in a future high-CO2 world.
Continue reading ‘Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification’Posidonia bonsai: dwarf morphotypes of Posidonia oceanica in CO2 vents and non-vents areas suggest a novel growth strategy
Published 10 December 2025 Science Leave a CommentTags: biological response, field, Mediterranean, morphology, phanerogams, vents
Highlights
- Dwarf Posidonia oceanica shoots occur in vents and no-vents areas at Ischia, Palinuro and Ustica.
- Dwarf shoots have a biomass reduced from 82 % to 97 % than normal-sized shoots.
- Bonsai shoots also lack cyclic annual sheath-thickness pattern (lepidochronology).
- Bonsai shoots occur in dead matte areas of the meadows, or behind regular terminal shoots.
- Bonsai shoots suggest a novel growth strategy, likely to favour rapid substrate colonization.
Abstract
Dwarf shoots of the Mediterranean seagrass Posidonia oceanica, referred to as “Posidonia bonsai”, described in shallow hydrothermal vents, showed markedly reduced size and altered phenology, that were attributed to the extreme environmental conditions associated with ocean acidification and H2S emissions of these vent systems. Here we report new records of Posidonia “bonsai” from CO2 vent off the Ischia Island and non-vent areas with normal pH conditions at Ischia, and Ustica islands and at Palinuro. At Ustica and Palinuro, bonsai shoots we found exclusively on rocky bottoms, while at Ischia they occurred on the dead P. oceanica matte, both within vent systems and in control areas. Bonsai shoots exhibited a reduced number of leaves, significantly shorter leaf length and width, resulting in a drastic reduction of total leaf surface area (84–95 % lower) and biomass (82–97 % lower) compared to nearby regular-sized shoots. In addition, bonsai shoots lacked the typical annual cycle of leaf sheath thickness observed in normal shoots (lepidochronological cycle), as previously observed in bonsai from other sites. The high number of sheaths recorded per rhizome length, suggests high leaf production and turnover. The occurrence of bonsai shoots on dead matte at the meadow margins and in small clearings, or behind regular terminal shoots on creeping rhizomes in hard bottoms, leads to hypothesize that Posidonia bonsai represents a novel growth and colonization strategy, probably trigged by stressful conditions, not limited to ocean acidification, and point out the remarkable phenotypic plasticity of this seagrass.
Continue reading ‘Posidonia bonsai: dwarf morphotypes of Posidonia oceanica in CO2 vents and non-vents areas suggest a novel growth strategy’Volcanic bubbles in Papua New Guinea a window into coral’s future
Published 9 December 2025 Press releases Leave a CommentTags: corals, South Pacific, vents
By the end of this century, coral reefs in Australia and around the world could be slower to recover, structurally simpler, and increasingly dominated by fleshy algae as rising carbon dioxide reshapes ocean chemistry.
These are the predictions that new international research – published this week in Communications Biology – is warning against, as scientists present a volley of stark new findings about the current and long-term impact of a process known as ocean acidification.
As the oceans absorb more carbon dioxide from the atmosphere, they are becoming increasingly acidic – eroding the very calcium carbonate skeletons that build coral reefs. Yet despite decades of laboratory studies and ecosystem models, scientists have lacked real-world systems that reflect how entire reef communities respond to these long-term chemical shifts.
Researchers from the Australian Institute of Marine Science (AIMS) have now filled that gap by studying shallow-water reefs naturally bathed in volcanic CO₂. These reefs, located near remote submarine vents in Papua New Guinea’s Milne Bay Province, experience chronic exposure to elevated carbon dioxide, offering scientists a rare preview of the seascapes expected under future emissions scenarios.
Continue reading ‘Volcanic bubbles in Papua New Guinea a window into coral’s future’Progressive changes in coral reef communities with increasing ocean acidification
Published 8 December 2025 Science ClosedTags: algae, BRcommunity, chemistry, community composition, corals, field, otherprocess, vents
Ocean acidification from increasing atmospheric CO2 is progressively affecting seawater chemistry, but predicting ongoing and near-future consequences for marine ecosystems is challenging without empirical field data. Here we quantify tropical coral reef benthic communities at 37 stations with varying exposure to submarine volcanic CO2 seeping, and determine the aragonite saturation state (ΩAr) where significant changes occur in situ. With declining ΩAr, reef communities displayed progressive retractions of most reef-building taxa and a proliferation in the biomass and cover of non-calcareous brown and red algae, without clear tipping points. The percent cover of all complex habitat-forming corals, crustose coralline algae (CCA) and articulate coralline Rhodophyta declined by over 50% as ΩAr levels declined from present-day to 2, and importantly, the cover of some of these groups was already significantly altered at an ΩAr of 3.2. The diversity of adult and juvenile coral also rapidly declined. We further quantitatively predict coral reef community metrics for the year 2100 for a range of emissions scenarios, especially shared socio-economic pathways SSP2-4.5 and SSP3-7.0. The response curves show that due to ocean acidification alone, reef states will directly depend on CO2 emissions, with higher emissions causing larger deviations from the reefs of today.
Continue reading ‘Progressive changes in coral reef communities with increasing ocean acidification’Distinct biochemical profiles in Antarctic seaweeds reflect acclimation to polar and hydrothermal environments with implications for biomass nutritional value
Published 1 December 2025 Science ClosedTags: algae, Antarctic, biological response, chemistry, field, physiology, vents
Highlights
- Chlorophyll a content in some seaweed species increased with latitude along the Antarctic Peninsula.
- Seaweeds from fumarole vent sites revealed variations in fatty acids and pigments.
- Lower nutritional value in Antarctic seaweeds from fumarole sites suggests potential responses to ocean warming and acidification.
- Species-specific biochemical shifts in Antarctic seaweeds are anticipated under global change scenarios.
Abstract
Global change is driving ocean warming (OW) and acidification (OA), impacting marine ecosystems worldwide, including polar regions. Seaweeds, as key primary producers in coastal ecosystems, synthesize a wide range of biochemical compounds that support higher trophic levels. Their biochemical composition is conditioned by local environmental factors, including seawater temperature, pH, and nutrient availability. However, how polar seaweeds respond to ongoing global change remains poorly understood. In this study, we examined the influence of local environmental changes on the biochemical composition – including fatty acids (FA), pigments, carbon, and nitrogen – of nine Antarctic brown and red seaweed species. Specifically, we considered a latitudinal gradient from the South Shetland Islands (⁓62°S) to Yalour Island (⁓65°S), and the presence of active fumarole vents at Deception Island. Our results reveal species-specific and location-dependent biochemical shifts in most species. While chlorophyll a concentrations tended to increase with latitude, specimens collected from fumarole vents exhibited a reduction in total FA content, PUFA:SFA (polyunsaturated to saturated fatty acid) ratios, PUFA omega-3, and pigment concentrations. These shifts under hydrothermal influence are likely driven by elevated seawater temperatures and acidic conditions, suggesting a potential decline in nutritional value under future global change scenarios. Additionally, higher magnesium content was found in the skeletons of crustose coralline algae from shallow waters than in those at 22 m depth. Our results highlight the species-specific nature of biochemical responses to environmental stressors, underlining the complexity of predicting the impacts of global change on seaweed physiology and the potential cascading effects on Antarctic food webs.
Continue reading ‘Distinct biochemical profiles in Antarctic seaweeds reflect acclimation to polar and hydrothermal environments with implications for biomass nutritional value’Newly discovered CO2 (carbon dioxide) vent cave drives r-strategy shift in a Mediterranean aphotoendosymbiotic coral
Published 14 November 2025 Science ClosedTags: abundance, biological response, chemistry, corals, field, growth, Mediterranean, morphology, reproduction, vents
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 ClosedTags: algae, biological response, BRcommunity, chemistry, community composition, field, North Pacific, otherprocess, vents
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 ClosedTags: algae, biological response, community composition, field, North Pacific, otherprocess, photosynthesis, vents
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.
Continue reading ‘Elevated carbon dioxide does not increase macroalgal community photosynthesis’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 ClosedTags: adaptation, biological response, field, Mediterranean, mollusks, otherprocess, physiology, respiration, vents
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 ClosedTags: adaptation, annelids, biological response, BRcommunity, field, Mediterranean, otherprocess, physiology, vents
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 ClosedTags: adaptation, biological response, echinoderms, field, morphology, North Atlantic, otherprocess, vents
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 ClosedTags: biological response, growth, laboratory, Mediterranean, physiology, phytoplankton, vents
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 ClosedTags: bryozoa, Mediterranean, vents
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 ClosedTags: abundance, adaptation, biological response, BRcommunity, bryozoa, community composition, communitymodeling, field, Mediterranean, modeling, molecular biology, morphology, mortality, otherprocess, prokaryotes, vents
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 ClosedTags: biological response, field, Mediterranean, morphology, phanerogams, physiology, vents
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.
Impact of natural CO2 leaks on marine ecosystems
Published 30 July 2025 Web sites and blogs ClosedTags: vents
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.
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.
Continue reading ‘Impact of natural CO2 leaks on marine ecosystems’Shifts in coral reef holobiont communities in the high-CO2 marine environment of Iōtorishima Island
Published 15 July 2025 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, corals, field, molecular biology, North Pacific, otherprocess, phytoplankton, prokaryotes, vents
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 ClosedTags: abundance, biological response, BRcommunity, community composition, field, mollusks, North Atlantic, otherprocess, vents
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.
Continue reading ‘Mollusc epifaunal assemblages are simplified due to habitat shifts under ocean acidification’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 ClosedTags: biological response, corals, field, North Pacific, reproduction, vents
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’
