Posts Tagged 'Mediterranean'

« Previous Entries
Next Entries »

Time series in the Mediterranean Sea

Published 15 January 2026 Web sites and blogs Closed
Tags: , ,

13 January 2026/Kiel/Limassol. Today, Expedition M216 set sail for the Mediterranean Sea with the research vessel METEOR. An international research team led by GEOMAR Helmholtz Centre for Ocean Research will assess the state of the Mediterranean over the coming weeks. The research is conducted as part of a time series that was last carried out in 2018. The data collected now are therefore central to assessing current and future changes in the Mediterranean Sea. Among other things, temperature, salinity, nutrients and trace gases are being investigated, as well as the stratification and circulation of the water masses.

Like the Baltic Sea and the Black Sea, the Mediterranean Sea is an inland sea connected to the global ocean only by the Strait of Gibraltar. As a result, it responds more quickly to changes. It warms more rapidly, absorbs more carbon dioxide and acidifies more strongly than the open ocean. At the same time, through its connection with the Atlantic, the Mediterranean Sea also influences the global ocean and additionally plays an important role for the regional climate, fisheries and tourism.

…

Several factors come together in the Mediterranean Sea: it has a very high salinity and pronounced water circulation. The high salt concentration and temperature promotes the uptake of anthropogenic CO2. At the same time, surface water is transported relatively quickly to the depth, where it remains at a temperature of around 12 to 13°C. In addition, the circulation ensures that deep water reaches the surface, which can again absorb CO2. This creates a dynamic cycle that enables the Mediterranean Sea to bind a comparatively large amount of CO2 from the atmosphere,” explains Dr Toste Tanhua, expedition leader and chemical oceanographer at GEOMAR.

Measurements from the surface to the sea floor

The measurements cover the entire water column, i. e. all layers of the Mediterranean Sea from the surface to the sea floor. At its deepest point, the Mediterranean Sea is over five thousand metres deep. “The unique topography of the Mediterranean Sea is challenging for us. There are several basins with different conditions and water depths,” says Toste Tanhua. The expedition focuses on measuring nutrients, salinity, oxygen, alkalinity, dissolved inorganic carbon, organic carbon, CO2 and the degree of ocean acidification. This enables the researchers to deduce how the Mediterranean Sea is faring under the influence of climate change and to estimate further changes. They are also investigating the distribution of water masses, currents and the exchange between surface water and the deep ocean.

“The Med-SHIP programme gives us the opportunity to take a very close look at the individual components of the entire water column. Among other things, we will be investigating inorganic carbon. This refers to carbon that is not found in living organisms, but in rocks, water or in the atmosphere as CO2. Among other things, it is responsible for transporting CO2 between the atmosphere, the surface and deep water. As the water masses in the Mediterranean are in contact with the atmosphere relatively frequent, this is particularly interesting for us,” explains Toste Tanhua.

…

Continue reading ‘Time series in the Mediterranean Sea’

Seasonal and regional dynamics of carbonate chemistry and buffering capacity in contrasting marine systems: the Northeastern Mediterranean and the Sea of Marmara

Published 12 January 2026 Science Closed
Tags: , , ,

This thesis investigates seasonal and spatial variability in carbonate system dynamics and buffering capacity across two contrasting semi enclosed Turkish seas: the oligotrophic Northeastern Mediterranean and the eutrophic Sea of Marmara. Data were collected in winter and summer on research cruises conducted in 2022–2023. High quality multi-index measurements included total alkalinity (TA), nutrients, and spectrophotometric pH. Derived carbonate system parameters were calculated with PyCO2SYS, and a standardized, layer-based approach was applied to reflect regional hydrography and vertical structure. The Sea of Marmara showed high TA, often above 2700 μmol kg⁻¹, together with elevated dissolved inorganic carbon (DIC) below the halocline due to respiration and weak ventilation. Revelle factors were high, vertical gradients in pH and aragonite saturation state were strong, and hypoxia was present in sub halocline and deep waters. In the Northeastern Mediterranean, TA and DIC were lower and more stable. Revelle factors were lower, and buffering was stronger in surface and intermediate layers, with only modest sensitivity increases at depth. Advanced indices added diagnostic value beyond the Revelle factor. In the Sea of Marmara, βDIC and γDIC were highest below the halocline, identifying where small DIC additions most strongly raise the partial pressure of carbon dioxide (pCO₂) and lower pH. γAlk and ωAlk indicated greater benefit of marginal TA gains at depth. ωDIC isolated saturation state sensitivity to carbon loading in respiration dominated layers. In the Northeastern Mediterranean, the Revelle factor captured first order seasonal shifts in well mixed winter layers, while the advanced indices flagged narrow coastal and subsurface windows of rising sensitivity. These results provide the first multi seasonal, multi-index baseline for Turkish seas. They show that eutrophication, stratification, and ventilation control local acidification risk and that advanced buffer indices sharpen process attribution. The study supports monitoring that couples carbonate chemistry with oxygen and nutrients and guides management toward nutrient reduction and protection of sub halocline habitats where buffering is weakest.

Continue reading ‘Seasonal and regional dynamics of carbonate chemistry and buffering capacity in contrasting marine systems: the Northeastern Mediterranean and the Sea of Marmara’

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 Closed
Tags: , , , , , , ,

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)’

Impact of acidification and ultraviolet radiation on the physiology of Ulva fasciata

Published 19 December 2025 Science Closed
Tags: , , , , , , , , ,

Ocean acidification and increased UVR exposure driven by factors such as global warming, ozone layer depletion and anthropogenic activities are impacting the physiology and ecology of macroalgae in species-specific, diverse and complex ways. This study aims to investigate the individual and combined effects of ocean acidification and ultraviolet radiation (UVR) on the physiological responses of the cosmopolitan macroalgae species Ulva fasciata. The algae samples were cultured under laboratory conditions at two different pH levels (8.2 and 7.7) and under either the presence or absence of UVR. In U. fasciata, the maximum quantum efficiency of photosystem II (Fv/Fm) decreased with low pH and UVR, and a synergistic stress response was observed when these two stressors were applied together. The relative electron transport rate (rETRmax) varied depending on pH, while UVR increased this rate. These findings indicated that U. fasciata samples were under physiological stress. The incubation period significantly affected rETRmax and showed that the organism developed time-dependent adaptation responses. Alpha, a photosynthetic efficiency indicator, was negatively affected by UVR, whereas the light saturation point (Ik) varied as a result of the interaction between incubation time, pH, and UVR. The findings suggest that UVR exerted a more pronounced inhibitory effect on the photosynthetic system and growth of U. fasciata than low pH. Furthermore, combined exposure to UVR and low pH resulted in stronger growth inhibition, and a significant interaction between the two stressors was observed. Low pH and UVR exposure caused increased carbonic anhydrase activity (CA), while high CO2 led to a decrease in nitrate reductase activity (NR). UV-absorbing compounds (UVACs) were significantly affected by low pH and culture duration, whereas the effect of UVR on these compounds became significant only through its interaction with the incubation period. This suggests that the effect of UVR emerges through temporal accumulation. The findings reveal that this species is capable of developing late-phase acclimation strategies in response to environmental stress factors and possesses a potential adaptive capacity to cope with future marine change scenarios.

Continue reading ‘Impact of acidification and ultraviolet radiation on the physiology of Ulva fasciata’

Posidonia bonsai: dwarf morphotypes of Posidonia oceanica in CO2 vents and non-vents areas suggest a novel growth strategy

Published 10 December 2025 Science Closed
Tags: , , , , ,

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’

Surface pCO2 and hydrography in the dense water formation area of the southern Adriatic

Published 27 November 2025 Science Closed
Tags: , ,

The rising CO2 concentration in the atmosphere leads to an increase in CO2 uptake in the ocean and to significant changes in seawater chemistry. These changes, in turn, exert profound effects on marine ecosystems across multiple trophic levels. The Mediterranean Sea is considered a hotspot for climate change. Despite such relevance, observations and studies on its carbonate system remain limited, especially in regions that play a crucial role in regulating air-sea CO2 exchange like intermediate and dense water formation areas. The southern Adriatic Sea, a key site for dense water formation in the eastern Mediterranean, hosts the EMSO ERIC and ICOS ERIC South Adriatic observatory (EMSO-E2M3A), operated by the Italian National Institute of Oceanography and Applied Geophysics (OGS). This facility allows the study of physical and biogeochemical dynamics in the deepest area of the Adriatic Sea. The suite of sensors deployed on the surface buoy allows for the characterization of water mass properties, biogeochemical cycles, dense water formation process, and ocean acidification, particularly in relation to carbon sequestration dynamics. Here, time series of meteorological data (e.g., wind speed, wind direction), sea surface physical parameters (e.g., temperature, salinity), dissolved oxygen and partial pressure of CO2 (pCO2sw) and pH from 2014 to 2024 will be presented (https://doi.org/10.13120/y2hw-1j63, Cardin et al., 2025). In particular, quality check and correction and post-processing methods applied to the data will be discussed. The validated surface dataset provides a consistent pCO2sw time series for the Adriatic Sea, with values and seasonal variability in agreement with previous observations across the Mediterranean. Associated temperature, salinity, oxygen, and wind measurements reproduce expected regional patterns, confirming the robustness and suitability of the presented dataset for further biogeochemical and climate-related analyses.

Continue reading ‘Surface pCO2 and hydrography in the dense water formation area of the southern Adriatic’

The multiple responses of Mytilus galloprovincialis in the multi-stressor scenario: impacts of low pH, low dissolved oxygen, and microplastics

Published 18 November 2025 Science Closed
Tags: , , , , , , , ,

Highlights

  • Low pH, low dissolved oxygen (DO), and microplastics (MPs) did not notably affect organismal parameters or ETS activity.
  • Stressors significantly affected hemocytes, genotoxicity, and gill metabolites individually and interactively.
  • Hemolymph phagocytic activity, granulocyte/hyalinocyte ratio, and mantle lipid peroxidation were partly affected.
  • Metabolomic analyses showed that mussel gills are valuable indicators of metabolic status under stress.

Abstract

Along with high temperatures, acidification, deoxygenation, and microplastics (MPs) pollution represent key drivers in coastal marine ecosystems. Sessile invertebrates living in coastal habitats are primarily exposed to the combination of these drivers, often at severe levels. Here, we investigated the individual and combined impacts of low pH (pHT: 7.35), low dissolved oxygen (DO) (1.91 mg L−1), and MP (26 μg L−1) in the Mediterranean mussel Mytilus galloprovincialis by measuring organismal and cellular parameters after a 15-day exposure period. Organismal parameters (respiration rate, ammonia excretion rate, absorption efficiency) as well as electron transport system (ETS) activity were not impacted by the stressors, either individually or combined. At the cellular level, however, we observed significant effects of these stressors individually and interactively on the hemocyte count, hemocyte viability, genotoxicity (comet assay), and gill metabolite profiles. In addition, we observed partial effects on the hemolymph phagocytic activity (PA) and granulocyte/hyalinocyte (G/H) ratio, and mantle lipid peroxidation (LPO). Metabolomics results manifested that the gill of mussels can serve as a valuable indicator of metabolic status under the stress of low pH, low DO and MP. Metabolites involved in osmoregulation, membrane stability, oxidative stress, energy, amino acid and nitrogen metabolism were significantly affected by the stressors, with low DO being the main driver of metabolic changes. We suggest that the individual and variable interactions of these stressors negatively impact M. galloprovincialis, except for the organismal and, to some extent, biochemical parameters.

Continue reading ‘The multiple responses of Mytilus galloprovincialis in the multi-stressor scenario: impacts of low pH, low dissolved oxygen, and microplastics’

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

Published 14 November 2025 Science Closed
Tags: , , , , , , , , ,

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’

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
Tags: , , , , , , , ,

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)’

Low pH does not impact reproductive success but leads to negative carry-over effects between parents and larvae in a Mediterranean gastropod

Published 15 October 2025 Science Closed
Tags: , , , , ,

Understanding how marine organisms respond to ocean acidification across all life stages is essential for assessing the future resilience of ecosystems. We investigated the effects of long-term exposure to low pH conditions (pHT ranging from 7.95 to 7.22) on the reproductive traits and intracapsular development of Hexaplex trunculus, a predatory Mediterranean gastropod. Spawning success, fecundity, and capsule morphology were not affected by pH. However, larval development was significantly impaired at pHT lower than 7.51, with observed delayed development and fewer larvae developing successfully to the hatchling stage. Cross-transplantation of spawns between pHs indicated a negative carryover effect of parental exposure to low pH on larval development, although this was partially reversible when spawns were transferred back to the ambient pH. Notably, we observed inter-individual variability in larval growth, suggesting that phenotypic plasticity or genotype-specific tolerance may play a role in moderating sensitivity to future ocean acidification. Our study highlights the importance of considering parental exposure, natural pH variability, and within-population variation when assessing species responses to global drivers

Continue reading ‘Low pH does not impact reproductive success but leads to negative carry-over effects between parents and larvae in a Mediterranean gastropod’

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
Tags: , , , , , , , ,

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 climate change means for the Mediterranean Sea

Published 11 September 2025 Press releases Closed
Tags:

Temperatures in the Mediterranean are currently rising to record levels. Instead of a refreshing dip, holidaymakers in places like Greece, Italy, and Spain, among other places, are now facing water temperatures up to 28° C or even higher. With an average water temperature of 26.9° C, July 2025 was the warmest since records began for the Mediterranean Sea, according to the Copernicus Earth Observation Service.

Warming caused by climate change is considered—alongside stressors such as overfishing, pollution, and habitat destruction—a major factor threatening marine and coastal habitats.

“The consequences of warming are not only projections for the future, but very real damages we are witnessing now. The continuing rise in temperatures, sea level and ocean acidification cause severe risks for the environment in and around the Mediterranean Sea,” says Dr. Abed El Rahman Hassoun, Biogeochemical Oceanographer at the Helmholtz Center for Ocean Research Kiel.

Meta-study on climate change scenarios

Dr. Hassoun and Prof. Dr. Meryem Mojtahid, Professor of Paleo-Oceanography at the University of Angers and at the Laboratory of Planetology and Geosciences (France), working with colleagues, have investigated the effects of climate change on marine and coastal ecosystems in the Mediterranean region. Their paper is published in the journal Scientific Reports.

The projections of the meta-study are based on recognized climate scenarios of the IPCC (Intergovernmental Panel on Climate Change). The research team analyzed 131 scientific studies on the Mediterranean published up to August 2023. For the first time, this resulted in a so-called “burning ember” diagram for Mediterranean marine and coastal ecosystems—a risk assessment tool originally developed by the IPCC.

“The diagram clearly shows how strongly climate change threatens key ecosystems. I hope our results will help raise awareness and inspire real action to protect these unique ecosystems,” says Mojtahid. The study also draws on the Research Initiative on Climate Change and Environmental Degradation in the Mediterranean Region (MedECC). In 2020, the initiative published the first Mediterranean Assessment Report under the name MAR1, thus playing a key role in consolidating knowledge on climate and environmental changes in the Mediterranean area.

Continue reading ‘What climate change means for the Mediterranean Sea’

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

Published 21 August 2025 Science Closed
Tags: , , , , , ,

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’

When time reveals the cost: effects of long-term exposure to low pH on a predatory gastropod

Published 13 August 2025 Science Closed
Tags: , , , , , ,

Ocean acidification, a direct consequence of anthropogenic carbon dioxide emissions, is among the major challenges for marine organisms. While an increased body of evidence is documenting the negative effects of ocean acidification, most of these studies are still based on short-term exposure. Long-term experiments, studying multiple traits simultaneously, and accounting for short-term local pH variability in the species’ habitat are needed. This study investigated the impact of a 310-day exposure to low pH on the banded-dye murex, Hexaplex trunculus (Linnaeus, 1758), a predatory Mediterranean gastropod. Temperature strongly influences the behavior and activity of the banded-dye murex, so we allowed it to vary naturally in this experiment. Our results showed that the net calcification rate was negatively affected by low pH throughout the duration of the experiment. While the banded-dye murexes were able to maintain their total body weight at the beginning of the experiment, it decreased under chronic exposure to low pH. Soft tissue body weight remained unaffected for more than 200days, followed by a pronounced decrease when exposed to lower pH. No sex-specific differences in response to low pH were observed, but females generally exhibited higher rates of calcification and growth during the winter period, likely due to energy allocation strategies associated with the reproductive cycle. These results suggest that while the banded-dye murex can temporarily reallocate energy to maintain essential physiological functions under low pH, this capacity diminishes over time, revealing physiological limits to long-term stress tolerance. This finding highlights the importance of incorporating long-term, multi-trait experiments in ocean acidification research to better predict species vulnerability, ecosystem-level impacts, and the resilience of coastal marine communities under future climate change scenarios.

Continue reading ‘When time reveals the cost: effects of long-term exposure to low pH on a predatory gastropod’

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

Published 13 August 2025 Press releases Closed
Tags: , ,

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
Tags: , , , , , , , , , , , , , , ,

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
Tags: , , , , , ,

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’

Climate change in the “vulnerable” Eastern Mediterranean and adjacent areas: a literature review of ecological impacts and threats

Published 29 July 2025 Science Closed
Tags: , ,

The Mediterranean Sea (MS) represents a complex system that acts as a convergence zone for various biogeographical influences stemming from both temperate and tropical oceanic bodies. Its intricate topography has promoted speciation and adaptation, leading to the development of distinctive and varied marine sites. The MS has a greater total alkalinity than the open ocean, which allows it to absorb a larger amount of human-induced CO2 per unit of surface area, suggesting an increased threat of acidification. The Eastern Mediterranean (EM) region has been identified as a critical climate change (CC) hotspot; by the end of the 21st century, it is anticipated that heatwaves in the EM will occur more than seven times as often and last more than three times as long. Here, we provide an extensive literature review on the CC-induced impacts and threats on biota throughout EM and adjacent areas, supporting potential mitigation actions.

The key elements contributing to the impacts and threats posed by CC in the region are: ocean warming (OW), ocean acidification (OA), and the synergistic effects of OW and OA. Additional factors encompass the combination of: i) OW and marine heatwaves (MHWs), ii) OW and non-indigenous species (NIS), iii) OW and desertification, and iv) OW and water circulation. However, the primary factor causing biodiversity decline, not just in the EM region but throughout the entire MS, seems to be the introduction of NIS, which is further worsened by OW. The primary route through the Suez Canal (SC) and its continuous expansions have sparked worry about the rising propagule pressure. There is a growing consensus that if these environmental risks are not comprehended and mitigated, a significant portion of the Mediterranean ecosystem may face severe threats to its integrity.

Ultimately, the initiative of dumping brine waste into the SC, acting as a high salinity barrier that would reduce the transfer of new species carried by the currents, is likely a practical and attractive first step towards mitigation. We suggest that this action should be embraced not only by other countries but also by international environmental organizations and agencies, through a variety of strategies, including financial support. This initiative, along with other measures aimed at alleviating the impacts of invasions on biodiversity, ecosystem services, and health, is an essential next step in the process of mitigation.

Continue reading ‘Climate change in the “vulnerable” Eastern Mediterranean and adjacent areas: a literature review of ecological impacts and threats’

Metabolic responses of the European flat oyster (Ostrea edulis) to combined ocean acidification and hypoxia

Published 18 July 2025 Science Closed
Tags: , , , , , , , ,

Ocean acidification and the accompanying hypoxia, which have become increasingly important environmental stress factors, can have varying effects on marine organisms, such as impaired physiological metabolism and immune function. Here, I studied the effects of high pCO2 and low dissolved oxygen (DO) in European flat oyster Ostrea edulis. Changes in physiological and immunological parameters were investigated in oysters during 18 days of exposure at two different pH ​​(7.90 and 7.30) and DO levels (7.5 and 2 mg L-1). Low pH and low DO reduced haemocye count and viability, both individually and in combination. Low pH and combined exposure decreased feeding and respiration, which exacerbated by duration. Low pH and low dissolved oxygen increased ammonia excretion rate, which exacerbated by time. I suggest that the low pH and low DO lead metabolic depression, impaired immune function, and alteration in energy allocation in oysters, which further collectively negatively affect fitness of the oyster.

Continue reading ‘Metabolic responses of the European flat oyster (Ostrea edulis) to combined ocean acidification and hypoxia’

Climate change risks on key open marine and coastal mediterranean ecosystems

Published 18 July 2025 Science Closed
Tags: , ,

Mediterranean open marine and coastal ecosystems face multiple risks that impact their unique biodiversity, with climate change representing a major ongoing threat. While these ecosystems are also under pressure from non-climatic anthropogenic drivers (e.g., overfishing, pollution), this study primarily focuses on risks related to climate change. To assess these risks and evaluate their confidence levels, we adopt the scenario-based approach of the Intergovernmental Panel on Climate Change (IPCC), relying on a review of literature projecting changes in Mediterranean Sea ecosystems. The main drivers of environmental change are sea level rise, ocean warming and acidification. Similar to global conditions, all Mediterranean ecosystems face high risks under all climate scenarios, with coastal ecosystems being more strongly impacted than open marine ecosystems. For these coastal ecosystems, risk levels are expected to become very high already once global warming exceeds 0.8 °C with respect to the 1976–2005 period. A few Mediterranean ecosystems (e.g., coralligenous and rocky coasts) are relatively more resilient compared to others, probably because of their long evolutionary history and the presence of a variety of climatic and hydrological conditions. However, high-emission scenarios in specific sub-basins, in addition to acidification impacts, could reduce this resilience, decreasing both habitat extent and ecosystem function dramatically. Overall, due to the higher observed and projected rates of climate change in the Mediterranean, compared to global trends, for variables such as seawater temperature and pH, marine ecosystems (particularly coastal) are projected to be under higher risks compared to the global ocean.

Continue reading ‘Climate change risks on key open marine and coastal mediterranean ecosystems’

Subscribe

Search

  • Reset

OA-ICC Highlights

Resources