The existence of shallow hydrothermal vents in Mabini, Batangas, Philippines, has been recognized to contribute to CO2-rich submarine groundwater discharges. However, little is known about the existing coral community structure in the area which provides valuable ecosystem goods and ecological services. We characterized the reef community in this unique microenvironment falls within the predicted future reef condition with low pH and aragonite saturation using coral recruitment tiles, examined coral life-history strategies and size frequency distribution, and measured calcification of transplanted fragments from the genus Goniopora sp., Pectinia sp., and Porites sp. The availability of larval supply has proven that corals can still settle (45–73 recruits m−2) due to the presence of hard substrate and settlement cues such as the crustose coralline algae. The existing coral colonies were mostly dominated by stress-tolerant groups and sizes ranging from 5 to 20 cm. Deployed coral fragments showed growth via extension, and calcification was negatively affected by local conditions, such as Porites sp. fragments. Higher nutrient input may have promoted coral growth, but combined with low carbonate chemistry, it likely made the corals more susceptible to physical damage, as seen on the fragments. This study highlights the importance of naturally occurring extreme environments to determine climate-resilient corals that can adapt to changing conditions and recover from disturbances over time.
Continue reading ‘Characterization of coral communities in the shallow hydrothermal vents of Mabini, Batangas, Philippines’Posts Tagged 'vents'
Characterization of coral communities in the shallow hydrothermal vents of Mabini, Batangas, Philippines
Published 31 December 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, community composition, corals, field, growth, North Pacific, reproduction, vents
Genomic signals of adaptation to a natural CO2 gradient over a striking microgeographic scale
Published 14 November 2024 Science ClosedTags: adaptation, biological response, calcification, echinoderms, growth, laboratory, molecular biology, North Atlantic, otherprocess, physiology, vents
Highlights
- Arbacia lixula populations near CO2 vents show tolerance to acidification despite their vulnerable calcified structure.
- A. lixula population reveal genetic divergence and substructure in response to small-scale pH variation.
- Acidification potentially affects specific genes linked to growth, development, and calcification.
- lixula exhibits adaptability and plasticity to acidification, suggesting its potential resilience to cope with OA.
Abstract
Our study explores genomic signs of adaptation in A. lixula to different water pH conditions. To achieve this, we analysed the genomics variation of A. lixula individuals living across a natural pH gradient in Canary Islands, Spain. We use a 2b-RADseq protocol with 74 samples from sites with varying pH levels (from 7.3 to 7.9 during low tide) and included a control site. We identified 14,883 SNPs, with 432 identified as candidate SNPs under selection to pH variations through redundancy analysis. While all SNPs indicated genomic homogeneity, the 432 candidate SNPs under selection displayed genomic differences among sites and along the pH gradient. Out of these 432 loci, 17 were annotated using published A. lixula transcriptomes, involved in biological functions such as growth. Therefore, our findings suggest local adaptation in A. lixula populations to acidification in CO2 vents, even over short distances of 75 m, underscoring their potential resistance to future Ocean Acidification.
Continue reading ‘Genomic signals of adaptation to a natural CO2 gradient over a striking microgeographic scale’Chapter Four – reprint: The importance of natural acidified systems in the study of ocean acidification: what have we learned?
Published 25 September 2024 Science ClosedTags: field, review, vents
Human activity is generating an excess of atmospheric CO2, resulting in what we know as ocean acidification, which produces changes in marine ecosystems. Until recently, most of the research in this area had been done under small-scale, laboratory conditions, using few variables, few species and few life cycle stages. These limitations raise questions about the reproducibility of the environment and about the importance of indirect effects and synergies in the final results of these experiments. One way to address these experimental problems is by conducting studies in situ, in natural areas where expected future pH conditions already occur, such as CO2 vent systems. In the present work, we compile and discuss the latest research carried out in these natural laboratories, with the objective to summarize their advantages and disadvantages for research to improve these investigations so they can better help us understand how the oceans of the future will change.
Continue reading ‘Chapter Four – reprint: The importance of natural acidified systems in the study of ocean acidification: what have we learned?’Can niche plasticity mediate species persistence under ocean acidification?
Published 27 August 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, field, fish, performance, vents
Global change stressors can modify ecological niches of species, thereby altering ecological interactions within communities and food webs. Yet, some species might take advantage of a fast-changing environment, allowing species with high niche plasticity to thrive under climate change.
We used natural CO2 vents to test the effects of ocean acidification on niche modifications of a temperate rocky reef fish assemblage. We quantified three ecological niche traits (overlap, shift and breadth) across three key niche dimensions (trophic, habitat and behavioural).
Only one species increased its niche width along multiple niche dimensions (trophic and behavioural), shifted its niche in the remaining (habitat) was the only species to experience a highly increased density (i.e. doubling) at vents. The other three species that showed slightly increased or declining densities at vents only displayed a niche width increase in one (habitat niche) out of seven niche metrics considered. This niche modification was likely in response to habitat simplification (transition to a system dominated by turf algae) under ocean acidification.
We further showed that, at the vents, the less abundant fishes had a negligible competitive impact on the most abundant and common species. This species appeared to expand its niche space, overlapping with other species, which likely led to lower abundances of the latter under elevated CO2.
We conclude that niche plasticity across multiple dimensions could be a potential adaptation in fishes to benefit from a changing environment in a high-CO2 world.
Continue reading ‘Can niche plasticity mediate species persistence under ocean acidification?’Large CO2 seeps and hydrates field in the Indian Ocean (Mayotte Island)
Published 26 August 2024 Science ClosedTags: chemistry, vents
About 80% of Earth volcanic activity occurs underwater, releasing deep carbon to submarine environments and impacting Earth’s climate over geological timescales. The CO2 emitted during submarine eruptions and/or hydrothermal degassing creates local ocean acidification, affecting the seawater carbonate equilibrium and oceanic ecosystems at large regional scales. Here, we report for the first time the existence of a major CO2 hydrates field at the seafloor offshore Mayotte Island (Indian Ocean) associated with liquid CO2 venting, following the submarine eruption that occurred in 2018. Using detailed acoustic surveys and in situ Raman spectroscopy, we reveal multiple hydrate mounds and seep zones distributed over an area of 0.06 km². We show that the gas seeps are mainly composed of CO2, with minor contributions of CH4 and H2, with noble gas ratios and stable and radio-carbon isotopes clearly demonstrating their magmatic origin. Estimates of the CO2 emitted over the entire area represent about 0.5% of the global magmatic carbon flux. Our discovery also suggests that CO2 hydrates may potentially be stable at the seafloor at the right pressure-temperature conditions, bringing new prospects into CO2 sequestration and decarbonization pathways in the ocean, in particular regarding kinetics of hydrates dissolution and environmental impacts.
Continue reading ‘Large CO2 seeps and hydrates field in the Indian Ocean (Mayotte Island)’Mortality of mesozooplankton in an acidified ocean: investigating the impact of shallow hydrothermal vents across multiple monsoonal periods
Published 19 June 2024 Science ClosedTags: biological response, chemistry, laboratory, mortality, North Pacific, vents, zooplankton
Highlights
- Hydrothermal vents exert different mortalities on different mesozooplankton taxa.
- Low pH significantly increases mesozooplankton mortality.
- Lethal mesozooplankton effects decrease with increasing distance from hydrothermal vents.
- Mesozooplankton mortalities differ with monsoonal periods.
Abstract
The shallow hydrothermal vents (HVs) of Kueishan Island are considered as a template for studying the extremes of sulfide-polluted and acidified water. The present study examined the biological and spatiotemporal aspects of mesozooplankton mortality in waters around this extreme HV environment. Zooplankton sample collection was carried out in three monsoonal periods and the results revealed that there was a significant decrease in the mortality of total mesozooplankton with increasing distance from the HVs. The overall mortality of mesozooplankton showed a significant negative correlation with sea surface temperature and pH. Particularly, mortality of copepods showed a significant negative correlation with pH, whereas it was significantly positive correlated with sea surface temperature in the southwest monsoon prevailing period. Overall, the results may imply a situation that zooplankton will encounter in the more acidified environment of a future ocean.
Continue reading ‘Mortality of mesozooplankton in an acidified ocean: investigating the impact of shallow hydrothermal vents across multiple monsoonal periods’Living under natural conditions of ocean acidification entails energy expenditure and oxidative stress in a mussel species
Published 13 May 2024 Science ClosedTags: biological response, chemistry, laboratory, Mediterranean, mollusks, morphology, performance, physiology, vents
Highlights
- First investigation of Mytilus galloprovincialis from the CO2 vents of Castello Aragonese
- Strong corrosion of valves in organisms living at lower pH
- Content of amino acids, nucleotides, lipids and organic osmolytes reduced at lower pH
- No significant effects on most biochemical parameters in relation to pH variation
- Energy expenditure underpinning survival under acidified conditions
Abstract
We investigated the health conditions of the Mediterranean mussel Mytilus galloprovincialis recruited in the CO2 vents system of Castello Aragonese at Ischia Island (Mediterranean Sea). Individuals of M. galloprovincialis were sampled in three sites along the pH gradient (8.10, 7.7 and up to <7.4). Untargeted metabolomics and biochemical endpoints related to energetic metabolism, oxidative stress/damage, neurotoxicity and immune defense were analyzed. Corrosion of the valves occurred at low pH. A separation of the metabolome was observed along the pH gradient. Metabolites belonging to amino acids, nucleosides, lipids and organic osmolytes were significantly reduced in the organisms from the most acidified sites. The content of reactive oxygen species and the activity of glutathione peroxidase were reduced in organisms from the acidified sites compared to ambient pH, and no oxidative damage was induced. Overall results suggested the presence of an energy cost underpinning long-term survival in acidified conditions for this species.
Continue reading ‘Living under natural conditions of ocean acidification entails energy expenditure and oxidative stress in a mussel species’Functional diversity and metabolic response in benthic communities along an ocean acidification gradient
Published 1 May 2024 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, community composition, crustaceans, echinoderms, field, Mediterranean, mollusks, otherprocess, vents
Highlights
- Ocean acidification (OA) affect the distribution of traits within a community leading to the selection of specific functional traits.
- Along with the selection of traits, OA led to differences in oxygen consumption between benthic communities following acidification gradient.
- Altered acidified condition have a negative effect on the stability of the community resulting from changes in functional evennes of benthic communities.
Abstract
Altered ocean chemistry caused by ocean acidification (OA) is expected to have negative repercussions at different levels of the ecological hierarchy, starting from the individual and scaling up to the community and ultimately to the ecosystem level. Understanding the effects of OA on benthic organisms is of primary importance given their relevant ecological role in maintaining marine ecosystem functioning. The use of functional traits represents an effective technique to investigate how species adapt to altered environmental conditions and can be used to predict changes in the resilience of communities faced with stresses associated with climate change. Artificial supports were deployed for 1-y along a natural pH gradient in the shallow hydrothermal systems of the Bottaro crater near Panarea (Aeolian Archipelago, southern Tyrrhenian Sea), to explore changes in functional traits and metabolic rates of benthic communities and the repercussions in terms of functional diversity. Changes in community composition due to OA were accompanied by modifications in functional diversity. Altered conditions led to higher oxygen consumption in the acidified site and the selection of species with the functional traits needed to withstand OA. Calcification rate and reproduction were found to be the traits most affected by pH variations. A reduction in a community’s functional evenness could potentially reduce its resilience to further environmental or anthropogenic stressors. These findings highlight the ability of the ecosystem to respond to climate change and provide insights into the modifications that can be expected given the predicted future pCO2 scenarios. Understanding the impact of climate change on functional diversity and thus on community functioning and stability is crucial if we are to predict changes in ecosystem vulnerability, especially in a context where OA occurs in combination with other environmental changes and anthropogenic stressors.
Continue reading ‘Functional diversity and metabolic response in benthic communities along an ocean acidification gradient’Meiobenthos and ocean acidification: effects on meiobenthic communities inhabiting Mediterranean cold shallow CO2-vents
Published 5 April 2024 Science ClosedTags: biological response, BRcommunity, chemistry, community composition, field, Mediterranean, nematodes, otherprocess, sediment, vents
Highlights
- Ocean acidification modify the composition of marine communities.
- Meiobenthos around Castello Aragonese is influenced by CO2 emissions.
- Nematofauna inhabiting CO2 vents is adapted to pH variability.
- Acidification influences nematode diversity and functional diversity.
- Sediment type and O2 are major factors affecting the nematofauna.
Abstract
Ocean acidification is causing major changes in marine ecosystems, with varying levels of impact, depending both on the habitat and the studied organisms. Here, we investigated for the first time the meiobenthos and nematode fauna inhabiting the sediments around Castello Aragonese (Ischia, Italy), characterized by variable pH values due to coastal volcanic CO2 venting. In this scenario, nematode functional diversity changed according to different pH levels and grain size: maturity index was higher at most acidic stations and trophic composition spanned from the dominance of predators in the acidic stations, to the high abundance of non-selective deposit feeders and epistrate feeders in the ambient-pH stations. Overall, the present study revealed a relatively high tolerance of meiobenthos and nematodes to lower pH conditions. However, an in-depth analysis of nematode fauna showed differences in their assemblages at different pH levels with few nematode genera rather adapted to the extreme environmental conditions at the acidic stations.
Continue reading ‘Meiobenthos and ocean acidification: effects on meiobenthic communities inhabiting Mediterranean cold shallow CO2-vents’Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents
Published 22 March 2024 Science ClosedTags: adaptation, biogeochemistry, biological response, laboratory, Mediterranean, molecular biology, nitrogen fixation, otherprocess, phanerogams, physiology, prokaryotes, protists, vents
Seagrass meadows form highly productive and diverse ecosystems in coastal areas worldwide, where they are increasingly exposed to ocean acidification (OA). Efficient nitrogen (N) cycling and uptake are essential to maintain plant productivity, but the effects of OA on N transformations in these systems are poorly understood. Here we show that complete N cycling occurs on leaves of the Mediterranean seagrass Posidonia oceanica at a volcanic CO2 vent near Ischia Island (Italy), with OA affecting both N gain and loss while the epiphytic microbial community structure remains largely unaffected. Daily leaf-associated N2 fixation contributes to 35% of the plant’s N demand under ambient pH, while it contributes to 45% under OA. Nitrification potential is only detected under OA, and N-loss via N2 production increases, although the balance remains decisively in favor of enhanced N gain. Our work highlights the role of the N-cycling microbiome in seagrass adaptation to OA, with key N transformations accelerating towards increased N gain.
Continue reading ‘Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents’Marine benthic communities of the future: use of acidified natural systems
Published 5 March 2024 Science ClosedTags: adaptation, biological response, BRcommunity, chemistry, community composition, echinoderms, field, molecular biology, morphology, North Atlantic, otherprocess, vents
Ocean acidification (OA) is one of the most significant threats to marine organisms and is linked to climate change. It occurs when anthropogenic CO2 is absorbed by the oceans, resulting in a decrease in seawater pH and the dissolution of calcium carbonate. Projections indicate that OA will exacerbate in the future, highlighting the need to understand its impact on marine ecosystems. Much of our knowledge about the effects of OA comes from laboratory experiments, as predicting responses in natural conditions is challenging. Therefore, studies focusing on species living in naturally acidified systems, such as shallow CO2 seeps or vents, are becoming increasingly popular to obtain more realistic predictions.
This doctoral thesis, consisting of 5 chapters, explores the effects of ocean acidification on benthic communities in the subtropical Atlantic Ocean, using the naturally acidified CO2 vent system off the southern coast of La Palma Island in the Canary Islands, Spain, as a natural laboratory. Chapter 1 serves as an introduction to this thesis, explaining what naturally acidified systems are and discussing the research conducted in various locations worldwide where they have been discovered. Specifically, it focuses on studies that have utilized CO2 vents, which originate from volcanic activity. This chapter provides an overview of the importance, advantages, and disadvantages of using these acidified systems as natural laboratories to study OA in situ. It highlights that although there is no perfect analogue for future oceans, these systems help us to better understand the direct and indirect impacts of OA on different marine communities.
Among all the CO2 vents in the world, one of the few naturally acidified shallow systems in the Atlantic Ocean, and the only one with subtropical communities is located off the southern coast of Fuencaliente municipality in La Palma Island, Canary Islands. Chapter 2 of the thesis characterizes the chemical properties of this natural CO2 system in La Palma. It provides information about its volcanic and hydrological origins, as well as the different emission points along the Punta de Fuencaliente. Furthermore, it describes the carbon dynamics of the system, including variations in total inorganic carbon (CT) from 2120.10 to 10784.84 μmol kg-1, alkalinity (AT) from 2415.20 to 10817.12 μmol kg-1, pH from 7.12 to 8.07, aragonite saturation state (Ω) from 0.71 to 4.15, and calcite Ω from 1.09 to 6.49 units. A high CO2 emission flux ranging from 2.8 to 28 kg of CO2 d-1 has also been detected, making this zone an important natural carbon source. Due to its origins, this acidified system presents disadvantages as a natural laboratory for studying OA, such as natural fluctuations caused by tides or additional input of alkaline substances. Nevertheless, it creates a natural gradient of CO2 or pH along the coast with chemical characteristics very similar to those predicted for future scenarios, making it an exceptional location for studying the long-term and multi-level effects of acidification on marine ecosystems.
Chapter 3 explores rocky benthic communities along the natural pH gradient generated by the CO2 vent system in front of Punta de Fuencaliente. The objective of this chapter was to understand the direct and indirect effects of OA on the diversity and species composition of these subtropical marine communities. The study utilized a high-resolution molecular technique called DNA metabarcoding, which sequences fragments of the mitochondrial gene Cytochrome C Oxidase subunit I (COI) to detect the actual species diversity in each area. In this chapter, metabarcoding analysis reveals, for the first time, high levels of taxonomic diversity in a naturally acidified area. These high levels of diversity are attributed to the detection of small and cryptic species that are undetectable by traditional techniques and are tolerant to natural acidification. The results of this chapter unveil that future subtropical communities could maintain high taxonomic diversity values under an acidification scenario, although they will tend toward miniaturization due to the dominance of small algae and invertebrate species. This will have significant consequences for benthic subtropical communities, leading to important changes in ecosystem functions.
It is not the first time that an increase in species diversity related to environmental variations has been detected. In 1978, Connell first proposed the “Intermediate Disturbance Hypothesis” (IDH), which suggests that ecosystems are more diverse when disturbances occur at intermediate scales.
Chapter 4 investigates whether the IDH can be applied to a naturally acidified system at different biological organization levels (from organisms to communities) using molecular data. In La Palma’s acidified system, a fluctuating pH gradient caused by tides can act as a physical disturbance to marine ecosystems. This chapter utilizes sequenced fragments of the mitochondrial COI gene from two species of sea urchins (Arbacia lixula and Paracentrotus lividus) and metabarcoding analyses of benthic communities from the previous chapter. High levels of genetic and taxonomic diversity were detected at both biological organization levels under intermediate pH fluctuation, respectively. Therefore, the results of this chapter support the validity of the IDH in marine ecosystems affected by natural pH fluctuations and at different biological organization levels. Among the species living under natural acidification in the CO2 vents of La Palma, the sea urchin Arbacia lixula stands out. This is because sea urchins, like other calcareous organisms, should be susceptible to acidification due to their calcareous skeletons, however, this species has been found to live apparently unaffected in both Mediterranean and Atlantic CO2 vents.
The final chapter 5 explores the adaptation potential of A. lixula populations along the natural pH gradient of La Palma Island. Using the 2bRADseq molecular technique, a total of 14,883 SNPs (Single Nucleotide Polymorphisms) were detected in 74 individuals, of which 432 loci were correlated with the pH gradient of La Palma and are considered potential SNPs under selection. Analysis of these SNPs demonstrates that despite the short distance between the studied A. lixula populations, significant differences exist in the genomic structure of the populations correlated with the pH gradient. Additionally, these sequences are aligned and compared with available A. lixula transcriptomes, revealing 17 annotated genes involved in biological functions related to growth, development, membrane functions, and calcification. This chapter suggests that A. lixula can adapt to acidification and, therefore, able to withstand future changes anticipated for the oceans.
This thesis is the first to be developed at the Marine Observatory of Climate Change in Punta de Fuencaliente (OMaCC), where the naturally acidified system of La Palma is located. It emphasizes the importance of these natural laboratories in overcoming the experimental limitations of laboratory studies and contributes to understand how subtropical benthic ecosystems may change in the future. Moreover, it has uncovered evidence of local adaptation to ocean acidification in populations living in these natural laboratories. This thesis highlights the importance of these special environments and observatories for future research on the effects of OA.
Continue reading ‘Marine benthic communities of the future: use of acidified natural systems’Characterization of an undocumented CO2 hydrothermal vent system in the Mediterranean Sea: implications for ocean acidification forecasting
Published 5 March 2024 Science ClosedTags: chemistry, field, Mediterranean, methods, vents
A previously undocumented shallow water hydrothermal field from Sicily (Southern Tyrrhenian Sea, Italy) is here described, based on a multidisciplinary investigation. The field, covering an area of nearly 8000 m2 and a depth from the surface to -5 m, was explored in June 2021 to characterise the main physico-chemical features of the water column, describe the bottom topography and features, and identify the main megabenthic and nektonic species. Twenty sites were investigated to characterise the carbonate system. Values of pH ranged between 7.84 and 8.04, ΩCa between 3.68 and 5.24 and ΩAr from 2.41 to 3.44. Geochemical analyses of hydrothermal gases revealed a dominance of CO2 (98.1%) together with small amounts of oxygen and reactive gases. Helium isotope ratios (R/Ra = 2.51) and δ13CCO2 suggest an inorganic origin of hydrothermal degassing of CO2 and the ascent of heat and deep-seated magmatic fluids to the surface. Visual census of fishes and megabenthos (mainly sessile organisms) allowed the identification of 64 species, four of which are protected by the SPA/BIO Protocol and two by the International Union for Conservation of Nature. The macroalgae Halopteris scoparia and Jania rubens and the sponge Sarcotragus sp. were the dominant taxa in the area, while among fishes Coris julis and Chromis chromis were the most abundant species. This preliminary investigation of San Giorgio vent field suggests that the site could be of interest and suitable for future experimental studies of ocean acidification.
Continue reading ‘Characterization of an undocumented CO2 hydrothermal vent system in the Mediterranean Sea: implications for ocean acidification forecasting’Turf algae drives coral bioerosion under high CO2
Published 20 February 2024 Science ClosedTags: abundance, algae, biogeochemistry, biological response, BRcommunity, calcification, chemistry, communityMF, corals, dissolution, field, laboratory, morphology, multiple factors, North Pacific, otherprocess, photosynthesis, respiration, temperature, vents
Turf algal prevalence will increase in coral ecosystems under ocean acidification yet their contribution towards the ongoing and projected degradation of reefs is often overlooked. Turf algal settlement was induced on exposed coral skeleton adjacent to live coral tissue to investigate coral-turf algal interactions through a combination of laboratory and field transplantation (shallow volcanic CO2 seep) experiments across two temperature regimes. Here, we show that turf algae are competitively favored over corals under high pCO2 conditions. Turf algae-associated biological activity locally acidified the microenvironment overlying the exposed coral skeleton, leading to its bioerosion. Increases in coral-turf algal interactions could shift coral ecosystems towards net dissolution and should be integrated into global accretion models when considering future carbonate budgets under climate change.
Continue reading ‘Turf algae drives coral bioerosion under high CO2’Divergent morphological and microbiome strategies of two neighbor sponges to cope with low pH in Mediterranean CO2 vents
Published 14 February 2024 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, Mediterranean, molecular biology, morphology, otherprocess, porifera, prokaryotes, vents
Highlights
- Sponges are seen as winner taxa of future OA, yet not all species respond equally.
- Neighbor sponges had different morphology and microbiome patterns in CO2 vents.
- Vent S. cunctatrix displayed morphology changes and incipient microbial dysbiosis.
- C. reniformis microbiomes were normobiotic, diverse and functionally flexible.
- Symbioses supplying C–N–S cycles, vitamins and probiotics uphold resilience to OA.
Abstract
Ocean Acidification (OA) profoundly impacts marine biochemistry, resulting in a net loss of biodiversity. Porifera are often forecasted as winner taxa, yet the strategies to cope with OA can vary and may generate diverse fitness status. In this study, microbial shifts based on the V3–V4 16S rRNA gene marker were compared across neighboring Chondrosia reniformis sponges with high microbial abundance (HMA), and Spirastrella cunctatrix with low microbial abundance (LMA) microbiomes. Sponge holobionts co-occurred in a CO2 vent system with low pH (pHT ~ 7.65), and a control site with Ambient pH (pHT ~ 8.05) off Ischia Island, representing natural analogues to study future OA, and species’ responses in the face of global environmental change. Microbial diversity and composition varied in both species across sites, yet at different levels. Increased numbers of core taxa were detected in S. cunctatrix, and a more diverse and flexible core microbiome was reported in C. reniformis under OA. Vent S. cunctatrix showed morphological impairment, along with signs of putative stress-induced dysbiosis, manifested by: 1) increases in alpha diversity, 2) shifts from sponge related microbes towards seawater microbes, and 3) high dysbiosis scores. Chondrosia reniformis in lieu, showed no morphological variation, low dysbiosis scores, and experienced a reduction in alpha diversity and less number of core taxa in vent specimens. Therefore, C. reniformis is hypothesized to maintain an state of normobiosis and acclimatize to OA, thanks to a more diverse, and likely metabolically versatile microbiome. A consortium of differentially abundant microbes was identified associated to either vent or control sponges, and chiefly related to carbon, nitrogen and sulfur-metabolisms for nutrient cycling and vitamin production, as well as probiotic symbionts in C. reniformis. Diversified symbiont associates supporting functional convergence could be the key behind resilience towards OA, yet specific acclimatization traits should be further investigated.
Continue reading ‘Divergent morphological and microbiome strategies of two neighbor sponges to cope with low pH in Mediterranean CO2 vents’Skeletal Mg content in common echinoderm species from Deception and Livingston Islands (South Shetland Islands, Antarctica) in the context of global change
Published 17 January 2024 Science ClosedTags: Antarctic, biological response, chemistry, echinoderms, field, physiology, vents
Highlights
- This is the first assessment of the Mg content in echinoderms from Deception and Livingston Islands.
- Echinoderms showed interclass as well as inter- and intraspecific differences in their Mg content.
- The sea stars displayed the highest Mg content levels, followed by the brittle stars and sea urchins.
- The Mg content of echinoderms inhabiting Deception Island may be influenced by local environmental conditions.
Abstract
Echinoderms with high levels of magnesium (Mg) in their skeletons may be especially sensitive to ocean acidification, as the solubility of calcite increases with its Mg content. However, other structural characteristics and environmental/biological factors may affect skeletal solubility. To better understand which factors can influence skeletal mineralogy, we analyzed the Mg content of Antarctic echinoderms from Deception Island, an active volcano with reduced pH and relatively warm water temperatures, and Livingston Island. We found significant interclass and inter- and intraspecific differences in the Mg content, with asteroids exhibiting the highest levels, followed by ophiuroids and echinoids. Specimens exposed to hydrothermal fluids showed lower Mg levels, which may indicate local environmental effects. These patterns suggest that environmental factors such as seawater Mg2+/Ca2+ ratio and temperature may influence the Mg content of some echinoderms and affect their susceptibility to future environmental changes.
Continue reading ‘Skeletal Mg content in common echinoderm species from Deception and Livingston Islands (South Shetland Islands, Antarctica) in the context of global change’Functional changes across marine habitats due to ocean acidification
Published 15 January 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, chemistry, community composition, communitymodeling, field, growth, Mediterranean, modeling, otherprocess, performance, photosynthesis, reproduction, vents
Global environmental change drives diversity loss and shifts in community structure. A key challenge is to better understand the impacts on ecosystem function and to connect species and trait diversity of assemblages with ecosystem properties that are in turn linked to ecosystem functioning. Here we quantify shifts in species composition and trait diversity associated with ocean acidification (OA) by using field measurements at marine CO2 vent systems spanning four reef habitats across different depths in a temperate coastal ecosystem. We find that both species and trait diversity decreased, and that ecosystem properties (understood as the interplay between species, traits, and ecosystem function) shifted with acidification. Furthermore, shifts in trait categories such as autotrophs, filter feeders, herbivores, and habitat-forming species were habitat-specific, indicating that OA may produce divergent responses across habitats and depths. Combined, these findings reveal the importance of connecting species and trait diversity of marine benthic habitats with key ecosystem properties to anticipate the impacts of global environmental change. Our results also generate new insights on the predicted general and habitat-specific ecological consequences of OA.
Continue reading ‘Functional changes across marine habitats due to ocean acidification’Microbial associates of an endemic Mediterranean seagrass enhance the access of the host and the surrounding seawater to inorganic nitrogen under ocean acidification
Published 21 November 2023 Science ClosedTags: biogeochemistry, biological response, BRcommunity, field, Mediterranean, molecular biology, nitrogen fixation, otherprocess, phanerogams, physiology, primary production, prokaryotes, vents
Seagrasses are important primary producers in oceans worldwide. They live in shallow coastal waters that are experiencing carbon dioxide enrichment and ocean acidification. Posidonia oceanica, an endemic seagrass species that dominates the Mediterranean Sea, achieves high abundances in seawater with relatively low concentrations of dissolved inorganic nitrogen. Here we tested whether microbial metabolisms associated with P. oceanica and surrounding seawater enhance seagrass access to nitrogen. Using stable isotope enrichments of intact seagrass with amino acids, we showed that ammonification by free-living and seagrass-associated microbes produce ammonium that is likely used by seagrass and surrounding particulate organic matter. Metagenomic analysis of the epiphytic biofilm on the blades and rhizomes support the ubiquity of microbial ammonification genes in this system. Further, we leveraged the presence of natural carbon dioxide vents and show that the presence of P. oceanica enhanced the uptake of nitrogen by water column particulate organic matter, increasing carbon fixation by a factor of 8.6–17.4 with the greatest effect at CO2 vent sites. However, microbial ammonification was reduced at lower pH, suggesting that future ocean climate change will compromise this microbial process. Thus, the seagrass holobiont enhances water column productivity, even in the context of ocean acidification.
Continue reading ‘Microbial associates of an endemic Mediterranean seagrass enhance the access of the host and the surrounding seawater to inorganic nitrogen under ocean acidification’Deciphering the evolvement of microbial communities from hydrothermal vent sediments in a global change perspective
Published 8 November 2023 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, Mediterranean, mesocosms, otherprocess, physiology, prokaryotes, respiration, sediment, vents
Microbial communities first respond to changes of external environmental conditions. Observing the microbial responses to environmental changes in terms of taxonomic and functional biodiversity is therefore of great interest, particularly in extreme environments, where the already extreme conditions can become even harsher. In this study, sediment samples from three different shallow hydrothermal vents in Levante Bay (Vulcano Island, Aeolian Islands, Italy) were used to set up microcosm experiments with the aim to explore the microbial dynamics under changing conditions of pH and redox potential over a 90-days period. The leading hypothesis was to establish under microcosm conditions whether the starting microbial communities of the sediments evolved differently depending on their origin. To profile the dynamics of microbial populations over time, biodiversity, enzymatic profile, total cell abundance estimations, total/respiring cell ratio were estimated by using different approaches. An evident change in the microbial community structure was observed, mainly in the microcosm containing the sediment from the most acidified site, which was characterized by a highly diversified microbial community (in prevalence composed of Thermotoga, Desulfobacterota, Planctomycetota, Synergistota and Deferribacterota). An increase in microbial resistant forms (e.g., spore-forming species) with anaerobic metabolism was detected in all experimental conditions. Differential physiological responses characterized the sedimentary microbial communities. Proteolytic activity appeared to be stimulated under microcosm conditions, whereas the alkaline phosphatase activity was significantly depressed at low pH values, like those that were measured at the station showing intermediate pH-conditions. The results confirmed a differential response of microbial communities depending on the starting environmental conditions.
Continue reading ‘Deciphering the evolvement of microbial communities from hydrothermal vent sediments in a global change perspective’Ocean warming and acidification detrimentally affect coral tissue regeneration at a Mediterranean CO2 vent
Published 19 October 2023 Science ClosedTags: biological response, corals, field, Mediterranean, physiology, vents
Highlights
- This is the first transplant experiment investigating coral tissue regeneration with decreasing pH and increasing temperature
- Increasing temperature and decreasing pH could detrimentally impact coral tissue regeneration following injury
- Zooxanthellate corals might be particularly impacted by ocean warming and acidification in terms of lesion recovery
Abstract
Among the main phenomena that are causing significant changes in ocean waters are warming and acidification, largely due to anthropogenic activities. Growing evidence suggests that climate change is having more substantial and rapid effects on marine communities than on terrestrial ones, triggering several physiological responses in these organisms, including in corals. Here we investigated, for first time in the field, the combined effect of increasing seawater acidification and warming on tissue regeneration rate of three Mediterranean scleractinian coral species characterized by different trophic strategies and growth modes. Balanophyllia europaea (solitary, zooxanthellate), Leptopsammia pruvoti (solitary, non-zooxanthellate) and Astroides calycularis (colonial, non-zooxanthellate) specimens were transplanted, during a cold, intermediate, and warm period, along a natural pH gradient generated by an underwater volcanic crater at Panarea Island (Mediterranean Sea, Italy), characterized by continuous and localized CO2 emissions at ambient temperature. Our results show a decrease in regenerative capacity, especially in the zooxanthellate species, with increasing seawater temperature and acidification, with demonstrated species-specific differences. This finding suggests that increasing seawater temperature and acidification could have a compounding effect on coral regeneration following injury, potentially hindering the capacity of corals to recover following physical disturbance under predicted climate change.
Continue reading ‘Ocean warming and acidification detrimentally affect coral tissue regeneration at a Mediterranean CO2 vent’Microbial communities inhabiting shallow hydrothermal vents as sentinels of acidification processes
Published 4 September 2023 Science ClosedTags: abundance, archaea, biological response, BRcommunity, community composition, field, Mediterranean, molecular biology, otherprocess, prokaryotes, sediment, vents
Introduction: Shallow hydrothermal vents are considered natural laboratories to study the effects of acidification on biota, due to the consistent CO2 emissions with a consequent decrease in the local pH.
Methods: Here the microbial communities of water and sediment samples from Levante Bay (Vulcano Island) with different pH and redox conditions were explored by Next Generation Sequencing techniques. The taxonomic structure was elucidated and compared with previous studies from the same area in the last decades.
Results and discussion: The results revealed substantial shifts in the taxonomic structure of both bacterial and archaeal communities, with special relevance in the sediment samples, where the effects of external parameters probably act for a long time. The study demonstrates that microbial communities could be used as indicators of acidification processes, by shaping the entire biogeochemical balance of the ecosystem in response to stress factors. The study contributes to understanding how much these communities can tell us about future changes in marine ecosystems.
Continue reading ‘Microbial communities inhabiting shallow hydrothermal vents as sentinels of acidification processes’
