Posts Tagged 'Mediterranean'

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Impact of ocean acidification on skeletal structures in gilthead sea bream (Sparus aurata): in vitro and in vivo studies

Published 15 July 2025 Science Closed
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Highlights

  • Ocean acidification affects bone mineralization.
  • Ocean acidification modifies otolith size.
  • Low extracellular pH increases the viability and mineralization of osteoblasts.
  • Changes in cell culture pH modify the gene expression of osteoblasts.

Abstract

Ocean acidification is considered a significant risk to aquaculture, as it may adversely affect the growth and development of aquatic organisms. The effect of ocean acidification has been shown to impair the growth and survival of fish and to increase otoliths calcification in certain species; however, its effects on bone mineralization remain not well studied. The objective of the present study was to examine the effects of seawater acidification on the skeletal mineralization of gilthead sea bream juveniles, and to assess the direct impact of distinct pH levels on bone-derived cells development. After 68 days of exposure to low pH, fish exhibited a significantly reduced specific growth rate and elevated plasma pH levels, which influenced electrolyte concentrations such as potassium. Moreover, fish exposed to low pH showed increased otoliths size but no differences in shape. In bone, a higher vertebral length/height ratio was also observed, accompanied by significantly reduced opacity and increased expression of the osteoblast and osteoclast markers, alkaline phosphatase (alp) and matrix metalloproteinase 9 (mmp9), respectively, suggesting an elevated rate of bone turnover although reduced mineralization. In vitro, osteoblasts exposed to a low extracellular pH for 30 days exhibited increased viability and mineralization compared to cells maintained at a plasma pH or an alkaline pH. Additionally, the pH level significantly influenced the expression of several extracellular matrix components and osteoblast markers supporting those observations. Overall, these findings underscore the threat that ocean acidification poses to aquaculture, particularly through its impact on skeletal mineralization in gilthead sea bream, and highlight the importance of identifying approaches to farming resilient fish.

Continue reading ‘Impact of ocean acidification on skeletal structures in gilthead sea bream (Sparus aurata): in vitro and in vivo studies’

Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings 

Published 8 July 2025 Science Closed
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Ocean acidification (OA) and marine heatwaves (MHWs) are key drivers of marine ecosystem changes that can interact and influence marine organisms. Seagrasses, including the long-lived Posidonia oceanica endemic to the Mediterranean Sea, are widely distributed along coastal habitats, forming highly valuable underwater meadows. The germination and survival of the early life stages of P. oceanica are strongly affected by environmental changes. To assess the impact of warming and acidification on its future, we conducted a multifactorial experiment where P. oceanica seedlings were grown under OA conditions for six months and then exposed to a seawater warming event. Seedlings’ performance was investigated by analyzing photo-physiology, antioxidant capacity, energetic metabolism and transcriptomic profiles. The Weighted Gene Correlation Network Analysis (WGCNA) was used to integrate phenotypic plant traits with transcriptomic results to identify central genes involved in plant responses to OA and temperature exposure. Results demonstrated that prolonged OA exposure enhances P. oceanica seedling resilience to MHW. Specifically, seedlings regulated their antioxidant systems and transcriptomic machinery to better cope with thermal stress. Under current CO2 concentrations, elevated temperatures induced stress in P. oceanica seedlings, impacting photosynthesis and respiration. However, OA could mitigate the impact of warming in the future, enhancing P. oceanica‘s resilience to global stressors.

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Phenotypic plasticity in Mediterranean gorgonians Eunicella singularis and Paramuricea clavata at high temperature and low pH

Published 2 July 2025 Science Closed
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Highlights

  • The oxygen consumption of the gorgonian corals increased at high temperatures.
  • Energy reserves were not affected by high temperature, low pH or their interaction.
  • The global DNA methylation in Eunicella singularis was not affected by high temperature, low pH, or their combination.
  • Global DNA methylation in Paramuricea clavata decreased under high temperature and low pH.
  • High temperature alone caused more DEGs in E. singularis than low pH or combined treatment.

Abstract

The Mediterranean gorgonian octocorals are threatened by acidification, warming and marine heat waves. Phenotypic plasticity is critical for slow-growing gorgonians, as adaptation through natural selection might not be fast enough to cope with rapid environmental changes. DNA methylation (DNAm) is a type of (trans)generational phenotypic plasticity mechanism that may help slow-growing corals better withstand the effects of environmental changes by adjusting gene expression. This study aimed to assess the physiological responses and epigenetic modifications associated with phenotypic plasticity in the Mediterranean gorgonians Eunicella singularis and Paramuricea clavata exposed to warming (+4 °C), acidification (−0.35 pHT units) and their combination over two weeks. In addition, RNA-Seq-based differential gene expression analysis was performed for E. singularis.

High temperature, low pH and their combination did not cause tissue death or necrosis in the corals. Polyp activity in E. singularis increased at high temperatures. Warming increased oxygen consumption in both species. Energy reserves (protein, lipid, carbohydrate contents) were not affected by temperature, pH or their interaction in either species. The global DNA methylation (gDNAm) rate was ten times higher in P. clavata than in E. singularis. There was no effect of temperature, pH or their interaction on gDNAm in E. singularis. gDNAm in P. clavata decreased at high temperatures and low pH. Differential gene expression analysis indicated that high temperature induced the most extensive transcriptional changes in E. singularis, while low pH alone had the least impact. The combined stress of high temperature and low pH also led to notable up- and downregulation of gene expression. Heat stress in E. singularis caused widespread downregulation of transcription factors (TFs), particularly those in the zf-C2H2, AP-2, and HMG families. Conversely, the IRF, RFX, P53, and NRF1 families were upregulated, highlighting the complex transcriptional response to thermal stress. Overall, these physiological, transcriptomic and epigenetic alterations have the potential to negatively impact the fitness of these emblematic species and their associated ecosystems.

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Primary characterization of pCO2 in the three bays of Algiers coast

Published 17 June 2025 Science Closed
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The carbonate system in Mediterranean coastal zones remains inadequately quantified, exhibiting substantial discrepancies in research on CO2 partial pressure (pCO2), particularly in the insufficiently studied Algero-Provencal sub-basin. This study addresses a critical knowledge gap by providing the first characterization of carbonate chemistry parameters along the Algerian coast, a region previously lacking published data. The findings contribute to enhancing the accuracy of regional and global ocean biogeochemical models, particularly for the southern Mediterranean.The Algiers coastline comprises three bays: Bou-Ismail Bay (BB) to the west, Algiers Bay (BA) at the center, and Zemmouri Bay (BZ) to the east. A detailed dataset was assembled from direct and indirect measurements of carbonate system parameters in the surface waters of the three bays collected during spring and summer campaigns from 2011 to 2017. The carbonate system exhibited significant heterogeneity.During the June 2014 campaign, pCO2levels exhibited considerable variation among the three bays. BA exhibited the lowest pCO2 at 284.6 µatm, whereas BB and BZ recorded markedly elevated values of approximately 516 µatm. The extensive spatial range of approximately 250 µatm was predominantly influenced by biological processes, with BA exhibiting greater photosynthetic activity and dissolved oxygen (DO) levels compared to BB and BZ. Sampling campaigns were conducted in BA and BB from 2011 to 2017. pCO2 and DO levels in BA and BB demonstrated considerable temporal variability. In BA, pCO2 fluctuated between a minimum of 227 µatm during a phytoplankton bloom in July 2013 (with DO supersaturation at 180 %) and a maximum of 466 µatm in April 2011, attributed to rainfall and respiratory processes(with DO undersaturation at 76 %). In BB, spring campaigns (March 2015 and 2017) exhibited DO saturation levels (102–112 %) and lower pCO2 values (392 µatm), while summer campaigns demonstrated pCO2 supersaturation (up to 541 µatm) and DO undersaturation (70 %) attributable to thermal and respiratory processes.

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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.

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Diel variability affects the inorganic marine carbon system in the sea-surface microlayer of a Mediterranean coastal area (Šibenik, Croatia)

Published 2 June 2025 Science Closed
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The ocean plays a crucial role in the global carbon cycle by absorbing and storing substantial amounts of atmospheric carbon dioxide (CO2). It is estimated that the ocean has sequestered approximately 26% of CO2 emissions over the last decade, resulting in significant changes in the marine carbon system and impacting the marine environment. The sea-surface microlayer (SML) plays a crucial role in these processes, facilitating the transfer of materials and energy between the ocean and the atmosphere. However, most studies on the carbon cycle in the SML have primarily addressed daily variability and overlooked nocturnal processes, which may lead to inaccurate global carbon estimates. We analysed temperature, salinity, pHT25, and pCO2 using data collected over three complete diel cycles during an oceanographic campaign along the Croatian coast near Šibenik in the Middle Adriatic. Our analysis revealed statistically significant differences (p < 0.05) between daytime and nighttime measurements of temperature, salinity, and pHT25. These differences may be related to the occurrence of buoyancy fluxes, which are typically more pronounced during the day and could enhance CO2 fluxes, as observed with values of 1.98 ± 2.52 mmol cm⁻² h⁻¹ during the day, while at night, they dropped to 0.01 ± 0.02 mmol cm⁻² h⁻¹. These findings emphasise the importance of considering complete diurnal cycles to accurately capture the variability in thermohaline features and carbon exchange processes, thereby improving our understanding of the role of the ocean in climate change.

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Positive interactions in a warmer and more acidic ocean: crustose coralline algae holobionts enhance gorgonian larval settlement under climate change

Published 21 May 2025 Science Closed
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Background: The increasing frequency of marine heatwaves is leading to mass mortality of gorgonians in the Mediterranean Sea, threatening some populations with local extinction. A better understanding of the dynamics of gorgonians’ early life stages under climate change is urgent to ensure their conservation. Crustose coralline algae (CCAs) and their associated bacteria are known to induce the larval settlement of several coral species through the production of chemical cues. The larvae of the white gorgonian Eunicella singularis have been observed to preferentially settle and metamorphose on CCAs. Here, we investigated this positive interaction, and explored how it might be altered by climate change. Specifically, we tested the capacity of two Mediterranean CCA holobionts, Macroblastum dendrospermum and Lithophyllum stictiforme, to foster E. singularis larval settlement after exposure to SSP5-8.5 projected conditions for 2100 (warming and acidification), combined or not with a simulated marine heatwave event.

Results: Our results showed a threefold increase of larval settlement in presence of the CCAs previously exposed to acidification and warming treatments. After these treatments, both CCAs hosted a consistently high abundance of bacteria belonging to the Pirellulaceae family, and exhibited a higher abundance of monosaccharides in their exudates. We hypothesize that the enhanced larval settlement was driven by the bacterial breakdown and utilization of CCA polysaccharides, in combination with their release through the CCA cell walls. This release may have been enhanced by a decalcification process induced by climate change conditions. Furthermore, we showed that CCAs act as sources of bacterial taxa that can establish and persist in adult E. singularis holobiont, independently of climate change effects.

Conclusions: Our results highlight that CCA-larvae interaction is critical for E. singularis recruitment success, especially under future climatic conditions, and influences the development of its microbiome. This research underscores the importance of studying positive interspecific interactions across biological levels (from microorganisms to macroorganisms) under climate change scenarios, and provides valuable insights that inform the conservation and restoration of the Mediterranean white gorgonian.

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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.

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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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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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Long-term impacts of ocean acidification on the Mediterranean mussel Mytilus galloprovincialis

Published 10 April 2025 Science Closed
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This study aims to elucidate the long-term physiological impacts of ocean acidification on a key seafood species. The Mediterranean mussel Mytilus galloprovincialis, was subjected to three pH conditions over a period of six months: two pH values within the present range of natural variability (pHT: 8.10 and 7.80) and a lower pH condition (pHT: 7.50) relevant in the context of near-future ocean acidification. A comprehensive assessment was conducted at the conclusion of the fourth and sixth months and encompassed a suite of physiological endpoints, including mortality, oxygen consumption, clearance rate, total haemocyte count (THC), nutritional content analysis, and polonium-210 (210Po) depuration rates. The findings revealed a marked decrease in survival rates at pH 7.50 compared with those at pH 8.10 and 7.80 after six months of exposure. This was associated with a significant increase in THC and a decrease in lipid content. No significant pH effects were observed for other endpoints (namely clearance rate, condition index, oxygen consumption rate, protein and carbohydrate contents, and 210Po). While the lack of response to low pH at some of these physiological endpoints may be a consequence of a lack of statistical power, our data clearly demonstrate the effects of low pH on the survival, THC, and lipid content of M. galloprovincialis. Such effects on a species’ overall fitness have the potential to negatively impact this key seafood species, associated ecosystems, and the socioeconomic dynamics of communities depending on this resource.

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Effect of ocean acidification on the oxygen consumption of the sea urchins Paracentrotus lividus (Lamarck, 1816) and Arbacia lixula (Linnaeus, 1758) living in CO2 natural gradients

Published 7 February 2025 Science Closed
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Ocean acidification (OA) stands out as one of the main threats to marine ecosystems. OA leads to a reduction in the availability of carbonate ions, which are essential for marine calcifiers such as echinoderms. We aim to understand the physiological responses of two sea urchin species, Paracentrotus lividus and Arbacia lixula to low pH conditions and determine whether their responses result from phenotypic plasticity or local adaptation. The study is divided into two parts: plasticity response over time, measuring respiration rates of individuals from the Mediterranean Sea exposed to low pH over seven days, and adaptation and plasticity under changing pH, analyzing individuals inhabiting a pH gradient in a natural CO2 vent system located in La Palma Island, Spain. Over the seven days of low pH exposure, distinct patterns in respiration rates were revealed, with both species demonstrating potential for acclimatization. Notably, P. lividus and A. lixula displayed unsynchronized acidosis/alkalosis cycles, suggesting different physiological mechanisms. Additionally, environmental history seemed to influence adaptive capacity, as specimens from fluctuating pH environments exhibited respiration rates similar to those from stable environments with heightened phenotypic plasticity. Overall, our results suggest that both species possess the capacity for metabolic plasticity, which may enhance their resilience to future OA scenarios but likely involve energetic costs. Moreover, CO2 vent systems may serve as OA refugia, facilitating long-term survival. Understanding the plastic responses versus adaptations is crucial for predicting the effects of OA on species distribution and abundance of marine organisms in response to ongoing climate change.

Continue reading ‘Effect of ocean acidification on the oxygen consumption of the sea urchins Paracentrotus lividus (Lamarck, 1816) and Arbacia lixula (Linnaeus, 1758) living in CO2 natural gradients’

Extreme abiotics drive sediment biocomplexity along pH gradients in a shallow submarine volcanic vent

Published 3 January 2025 Science Closed
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Highlights

  • Shallow CO2 vents generate pH gradients that influence sediment biogeochemistry
  • Sedimentary organic matter (SOM) and prokaryotic community were analysed along a pH gradient
  • Environmental gradients drive distribution and abundance of benthic prokaryotic communities and origin of SOM
  • Vent-derived sources contributed largely to SOM up to 350 m from the vent
  • CO2-driven benthic community shifts affect spatial dynamics of SOM origin and composition with expected rebounds on biota

Abstract

Volcanic emissions in shallow vents influence the biogeochemistry of the sedimentary compartment, creating marked abiotic gradients. We assessed the spatial dynamics of the sediment compartment, as for the composition and origin of organic matter and associated prokaryotic community, in a volcanic shallow CO2 vent (Vulcano Island, Italy). Based on elemental (carbon, nitrogen content and their ratio) and isotopic composition (δ13C, δ15N and δ34S), the contribution of vent-derived organic matter (microbial mats) to sedimentary organic matter was high close to the vent, while the marine-derived end-members (seagrasses) contributed highly at increasing distance. Chemoautotrophic Campylobacterota and hyperthermophilic Achaea prevailed close to the vent, whilst phototrophic and chemoheterotrophic members dominated at increasing distance. Abiotic gradients generated by the volcanic CO2 vent drive relevant changes in the composition, origin and nutritional quality of sedimentary organic matter, and influence the structure and complexity of associated prokaryotic communities, with expected relevant impact on the entire food-web.

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Impacts of UV-filter pollution and low pH: sperm and adult biomarkers in the mussel Mytilus galloprovincialis in a multi-stressor context

Published 7 November 2024 Science Closed
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Highlights

  • Low pH emerged as a main driver of responses, amplifying UV-filters’ effects on both biological levels.
  • Sperm quality was relatively unaffected by UV-filters but significantly impacted by pH 7.7.
  • Exposure to low pH resulted in redox imbalance and reduced lipid peroxidation levels in sperm cells.
  • UV-filters, alone or combined with low pH, increased adults’ metabolic activity and energy storage.
  • Activation of antioxidant and biotransformation defense systems, with increased ACP activity across all treatments.

Abstract

In an era of unprecedented environmental changes, understanding the combined effects of multiple stressors on species’ performance is urgent. The increasing UV-filter incorporation in daily-life products raises concerns about their potential impact on marine-coastal environments upon release. As stressors rarely act alone, global change-induced factors, such as ocean acidification (OA), can amplify ecological hazards promoted by contaminants in coastal realms. This study investigated the combined impacts of UV-filters 4-methylbenzylidene camphor (4-MBC) and benzophenone-3 (BP-3), at ecologically relevant concentrations (1 and 10 µg/L), under two target pH levels (8.2 and 7.7, reflecting a ∆pH of 0 and -0.3 relative to the average pH at the sampling site), on the biochemical performance and male reproductive health of the mussel Mytilus galloprovincialis. Using sperm and adult assays alongside a multi-biomarker approach, the study revealed that pH was the primary driver of the decline in mussel physiological and biochemical performances, further intensifying UV-filters’ impacts. While sperm cells showed adaptive responses to low pH conditions alone, characterized by reduced lipid peroxidation (LPO) levels and superoxide anion overproduction, adult mussels experienced more pronounced effects, particularly under simultaneous exposure to low pH and UV-filters. Specifically, the adults exhibited distinct bioconcentration patterns under low pH, along with enhanced cellular metabolic activity and energy-demand compensatory processes, activation of biotransformation pathways, and regulation of antioxidant defenses. Given the ecological and socio-economic importance of M. galloprovincialis and its demonstrated vulnerability to these stressors, these findings highlight the need for further studies on potential transgenerational impacts and evolutionary implications for mussel populations.

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Ecophenotypic variation in a cosmopolitan reef-building coral suggests reduced deep-sea reef growth under ocean change

Published 7 November 2024 Science Closed
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Sensitivity of reef-building corals to environmental factors has far-reaching ecosystem implications, especially in the limited number of cold-water coral (CWC) species that form reefs in the deep sea. Understanding CWC responses to large-scale oceanographic variation in their natural habitat can elucidate their sensitivity to global anthropogenic stressors. Here, we use skeletal samples to analyse fine-scale phenotypic variation in the widespread reef-building CWC Desmophyllum pertusum (Lophelia pertusa) in relation to broad physicochemical gradients in different sites across the Atlantic Ocean and Mediterranean Sea. We find evidence, amidst local and regional differentiation, of species-wide growth responses to physicochemical factors, mainly affecting corallite length, width and their ratio (slenderness). Our results suggest that higher temperature and lower oxygen levels negatively affect skeletal linear extension and budding rate of polyps. As also hinted by the reduced corallite length and slenderness in less developed reefs, these widespread responses may lead to a general decline in CWC reef growth rates as a long-term consequence of ocean warming and deoxygenation. Given this relevance, such responses can be used to model reef growth in a changing ocean.

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Carbonate system and acidification of the Adriatic Sea

Published 17 October 2024 Science Closed
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Although the marginal seas represent only 7 % of the total area of the ocean, CO2 fluxes are important for the carbon budget, exposing them to the intense process of anthropogenic ocean acidification. The Adriatic Sea is currently a CO2 sink (−0.5 to −1 mol C m−2 y−1) with an annual flux comparable to the net sink rates in the NW Mediterranean. Based on a comparison of two winter cruises carried out in the 25-years interval between 1983 and 2008, an acidification rate of 0.003 pHT units y−1 was estimated in the northern Adriatic which is similar to the Mediterranean open waters (with recent estimations of −0.0028 ± 0.0003 pHT units y−1) and the surface coastal waters (−0.003 ± 0.001 and − 0.0044 ± 0.00006 pHT units y−1). The computed Revelle factor for the Adriatic Sea (approximately 10) indicates that the buffer capacity is rather high and that the waters do not appear to be particularly exposed to acidification. Total alkalinity (TA) in the Adriatic (2.6–2.7 mmol kg−1) is in the upper range of TA measured in the Mediterranean Sea. This is primarily due to the riverine inputs which transport carbonates dissolved from the Alpine dolomites and karstic watersheds. The Adriatic Sea is the second sub-basin (319 Gmol y−1), following the Aegean Sea (which receives the TA contribution from the Black Sea), that contribute to the riverine TA discharges into the Mediterranean Sea. About 60 % of the TA inflow into the Adriatic Sea is attributed to discharge from the Po River with a TA of ~3 mmol kg−1 and TA decreases with increasing salinity. The north Adriatic dense water spreading and cascading is an efficient mechanism for exporting TA and DIC at depth, from the northern Adriatic towards the bottom of the South Adriatic Pit and possibly to the eastern Mediterranean. Saturation states indicate that the waters of the Adriatic are supersaturated throughout the year with respect to aragonite (ΩAr). However, the saturation state is considerably lower in the bottom water layers, due to the prevalence of the bottom layer and benthic remineralisation in the stratification period. Effects on calcifying organisms and phytoplankton are expected in the future.

Continue reading ‘Carbonate system and acidification of the Adriatic Sea’

Low sensitivity of a heavily-calcified coccolithophore under increasing CO2: the case study of Helicosphaera carteri

Published 17 October 2024 Science Closed
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Studies on CO2 effects on coccolithophores, unicellular calcifying phytoplankton, show species-specific responses, although only less than 5 % of the ~280 living species have been tested so far. Helicosphaera carteri significantly contributes to carbon fluxes and CaCO3 storage due to its size and high calcite production. Despite its importance, few studies have examined H. carteri under experimental conditions, and only one has addressed the effects of rising CO2/decreasing pH. Being H. carteri a large-sized, obligated calcifier species, an important aspect to understand is how changes in seawater carbonate chemistry may affect its morphology. It has already been suggested for other coccolithophores species, that the presence of malformed coccoliths may represent a disadvantage for these organisms. Moreover, an alteration in coccolith morphology may affect their contribution to CaCO3 sedimentation and ballasting. As for H. carteri, it has also been suggested that due to its high PIC:POC ratio, the species could show a high-sensitivity to CO2 rise. In this study, we investigate for the first time whether high pCO2/low pH does affect the morphology of H. carteri coccoliths, by culturing this species under pre-industrial CO2 levels (~295 µatm) and ~600 µatm, i.e., the SSP 2-4.5 scenario for 2100 (IPCC, 2021). We also analyzed cellular PIC and POC quotas using morphometric data, roundness, and protoplast and coccosphere size to observe the pCO2 influence on the calcification and photosynthesis ratio.

Our results indicate that H. carteri morphology is only slightly affected by increasing CO2, in contrast to other heavily calcified species. Helicosphaera carteri protoplast and coccosphere shapes did not vary with changes in CO2, indicating unaltered general health. The low PIC:POC ratio found in this work for H. carteri compared to ratios previously measured in the same strain under different experimental conditions, and compared to other highly-calcified species, could explain the observed low sensitivity of H. carteri to CO2. Moreover, the observation of a stable ratio between calcification and photosynthesis in H. carteri under increasing CO2 might suggest a constant contribution to the rain ratio under climate change. However, further studies comparing experimental and field data from past ocean acidification events will be required to confirm the conclusions drawn here.

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Impact of warming and acidification of the Mediterranean Sea on statolith formation of the scyphozoan jellyfish Rhizostoma pulmo Macri (1778)

Published 16 October 2024 Science Closed
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Highlights

  • R. pulmo ephyrae statoliths size is affected by ocean warming and acidification.
  • Bigger statoliths are produced due to warming, but smaller under acidification.
  • Number of statoliths in R. pulmo ephyrae do not depend on temperature nor acidity.
  • R. pulmo statoliths composition is not altered due to temperature or acidification.
  • Survivability of jellyfishes could be affected by ocean warming and acidification.

Abstract

Ocean warming and acidification negatively affect organisms and biogeochemical cycles. To date, emphasis has been placed on the study of the impact on the structures of calcifying species; however, there is limited knowledge about the influence of the increase of these two variables on the solid structures of non-calcifying species as jellyfish. Here, we study the effects that the increase of temperature and acidity would cause on the statoliths of newly released ephyrae of the Mediterranean jellyfish Rhizostoma pulmo. Six combinations of temperature and PCO2 (18, 24 and 30ºC with a PCO2 of 500 and 1000 ppm each), according to the projections of the SSP5-8.5 (IPCC, 2021) scenario for the year 2100, were applied during 32 days to different groups of polyps randomly selected. Statoliths of the released ephyrae were counted and their size was measured. Our results show that, even though neither temperature nor PCO2 increase exerted a representative effect on the amount of statoliths synthesized in newly released ephyra from R. pulmo, it did exert an impact on the size of these structures: warming led to the formation of larger statoliths, while the rise in PCO2 induced the production of smaller structures. Under the simultaneous increase of both variables, acidification attenuated the effects of temperature, but still slightly larger statoliths were synthesized. The size differences observed in these structures could negatively impact the equilibrium system of this jellyfish species, potentially affecting its ability to survive.

Continue reading ‘Impact of warming and acidification of the Mediterranean Sea on statolith formation of the scyphozoan jellyfish Rhizostoma pulmo Macri (1778)’

Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change

Published 19 September 2024 Science Closed
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Climate change has presented a serious problem in recent times, which is why a new approach is being sought in terms of aquacultural food quality. In this study, the influence of temperature increase (by 2 °C) and pH decrease (by 0.2) was investigated on the queen scallop, Aequipecten opercularis (Linnaeus, 1758). Furthermore, the effect of a food-enriched diet with the probiotic culture Lactiplantibacillus plantarum I was assessed in climate-changed conditions. Scallops’ morphometric parameters were measured before the experimental setup and after one month of being kept in controlled conditions. Morphometric parameters included the elongation index, compactness index, convexity index, density index, condition index, meat yield, gonadosomatic index, adductor muscle index, and hepatosomatic index. Climate-changed conditions had no effect on the scallop condition index, meat yield, or hepatosomatic index. Nevertheless, the addition of probiotics to their diet had a positive effect on the queen scallops cultivated under conditions of climate change, influencing positive allometry and the increase of the gonadosomatic indices. On the other hand, the same conditions negatively affected the adductor muscle index of the scallops. To conclude, in the context of climate change conditions, queen scallops could be a good organism of choice that can be very well adapted to the changed environmental conditions, especially with the addition of the lactic acid bacteria culture Lpb. plantarum I.

Continue reading ‘Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change’

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