The global increase in anthropogenic CO2 is leading to ocean warming and acidification, which is threatening corals. In Ischia, Italy, two species of Mediterranean scleractinian corals–the symbiotic Cladocora caespitosa and the asymbiotic Astroides calycularis–were collected from ambient pH sites (average pHT = 8.05) and adjacent CO2 vent sites (average pHT = 7.8) to evaluate their response to ocean acidification. Coral colonies from both sites were reared in a laboratory setting for six months at present day pH (pHT ~ 8.08) or low pH (pHT ~7.72). Previous work showed that these corals were tolerant of low pH and maintained positive calcification rates throughout the experiment. We hypothesized that these corals cope with low pH by increasing their heterotrophic capacity (i.e., feeding and/or proportion of heterotrophically derived compounds incorporated in their tissues), irrespective of site of origin, which was quantified indirectly by measuring δ13C, δ15N, and sterols. To further characterize coral health, we quantified energy reserves by measuring biomass, total lipids, and lipid classes. Additional analysis for C. caespitosa included carbohydrates (an energy reserve) and chlorophyll a (an indicator of photosynthetic capacity). Isotopic evidence shows that ambient-sourced Mediterranean corals, of both species, decreased heterotrophy in response to six months of low pH. Despite maintaining energy reserves, lower net photosynthesis (C. caespitosa) and a trend of declining calcification (A. calycularis) suggest a long-term cost to low heterotrophy under ocean acidification conditions. Conversely, vent-sourced corals maintained moderate (C. caespitosa) or high (A. calycularis) heterotrophic capacity and increased photosynthesis rates (C. caespitosa) in response to six months at low pH, allowing them to sustain themselves physiologically. Provided there is sufficient zooplankton and/or organic matter to meet their heterotrophic needs, vent-sourced corals are more likely to persist this century and potentially be a source for new corals in the Mediterranean.
Continue reading ‘Elevated heterotrophic capacity as a strategy for Mediterranean corals to cope with low pH at CO2 vents’Posts Tagged 'Mediterranean'
Elevated heterotrophic capacity as a strategy for Mediterranean corals to cope with low pH at CO2 vents
Published 2 August 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, corals, laboratory, Mediterranean, photosynthesis, physiology
Toward an ecologically realistic experimental system to investigate the multigenerational effects of ocean warming and acidification on benthic invertebrates
Published 19 July 2024 Science ClosedTags: biological response, BRcommunity, chemistry, Mediterranean, mesocosms, methods, mollusks, North Atlantic
Human activities over the past 150 yr have led to significant carbon dioxide (CO2) emissions, causing global warming and ocean acidification. Surface ocean temperature has risen by 0.93°C since 1850, with projections of an additional +1.42°C to 3.47°C by 2080–2099. Ocean acidification, driven by CO2 absorption, has already lowered seawater pH by 0.1 units, affecting calcifying organisms, including shelled mollusks. Long-term multigenerational studies on mollusk responses to both ocean acidification and warming, under realistic environmental conditions, are scarce. To address this knowledge gap, two mobile experimental units that can be deployed at the vicinity of shellfish farming areas were developed within the framework of the CocoriCO2 project. The experimental systems were designed to manipulate temperature and pH as offsets from ambient conditions. The experimental units have shown their effectiveness in terms of controlling and maintaining pH and temperature to assess the multigenerational effects of ocean warming and acidification on benthic invertebrates. Finally, the developed experimental systems can be modified easily to provide an educated assessment of the impact of other relevant environmental changes such as deoxygenation and changes in salinity.
Continue reading ‘Toward an ecologically realistic experimental system to investigate the multigenerational effects of ocean warming and acidification on benthic invertebrates’Long-term effects of ocean acidification and its interaction with warming on calcifying organisms and their associated microbiome: bryozoans as emerging sentinels of global change?
Published 4 July 2024 Science ClosedTags: biological response, BRcommunity, bryozoa, chemistry, laboratory, Mediterranean, molecular biology, morphology, physiology
Global ocean warming and acidification are two of the major threats to many marine calcifying habitat-forming species, potentially affecting entire ecosystems. Consequently, the need for a better understanding and predicting the response of marine calcifiers has never been more pressing. Paradoxically, the individual and combined long-term effects of these stressors on bryozoans have remained largely unexplored, despite their great abundance and diversity globally. Here, we first evaluate the changes in skeletal structure and mineralogy, and the associated microbiome composition on the populations of Pentapora ottomuelleriana (encrusting) and Myriapora truncata (erect) bryozoan species living inside and outside a volcanic CO2 vent in Ischia Island. We then examine the effects of a long-term exposure to elevated pCO2 and its combined effects of ocean warming on the proportion of cover of populations of the encrusting species through time after summer. Both bryozoan species show indicators of acclimatization by adjusting skeletal properties and having stable microbial communities under acidification conditions. However, we document novel patterns about microbiome shifts in response to future ocean acidification in bryozoans for the first time. Microbial genera known to have essential functions to the host such as biosynthesis of defense compounds or thermal protection were depleted at the acidified site, which suggest early warnings of potential deterioration of bryozoan health under near future ocean conditions. The proportion of cover of the encrusting species also decreased from 2016 to 2020 in both studied sites, with faster declines at the acidified ones. Our model suggests that the increasing seawater temperature drove a decline in the bryozoan cover although the combined effects with acidification accelerated its mortality rates in the CO2 vent. More multidisciplinary research combining both environmental stressors on a wider range of calcifying species is needed to better understand the adaptive capacity of the holobiont to a changing environment.
Continue reading ‘Long-term effects of ocean acidification and its interaction with warming on calcifying organisms and their associated microbiome: bryozoans as emerging sentinels of global change?’Preliminary investigation on the potential involvement of an ABC-like gene in Halomicronema metazoicum (Cyanobacteria) tolerance to low seawater pH in an ocean acidification scenario
Published 21 June 2024 Science ClosedTags: biological response, chemistry, laboratory, Mediterranean, molecular biology, physiology
Highlights
- The involvement of ABC transporters in bacterial acid stress resistance was tested.
- The Cyanobacterium H. metazoicum demonstrated tolerance towards low pH environments.
- The ABC slr2019-like gene is differentially expressed under low pH conditions.
- A new RNA extraction method for H. metazoicum mattes was developed.
Abstract
Decreasing ocean surface pH, called ocean acidification (OA), is among the major risks for marine ecosystems due to human-driven atmospheric pCO2 increase. Understanding the molecular mechanisms of adaptation enabling marine species to tolerate a lowered seawater pH could support predictions of consequences of future OA scenarios for marine life. This study examined whether the ATP-binding cassette (ABC)-like gene slr2019 confers tolerance to the marine cyanobacterium Halomicronema metazoicum to low seawater pH conditions (7.7, 7.2, 6.5) in short- and long-term exposures (7 and 30 d). Photosynthetic pigment content indicated that the species can tolerate all three lowered-pH conditions. At day 7, slr2019 was up-regulated at pH 7.7 while no changes were observed at lower pH. After 30-d exposure, a significant decrease in slr2019 transcript levels was observed in all low-pH treatments. These first results indicate an effect of low pH on the examined transporter expression in H. metazoicum.
Continue reading ‘Preliminary investigation on the potential involvement of an ABC-like gene in Halomicronema metazoicum (Cyanobacteria) tolerance to low seawater pH in an ocean acidification scenario’Molecular bases and evolutionary constraints of cellular acid tolerance in cyanobacteria and invertebrates subjected to ocean acidification and other sources of stress (METASTRESS)
Published 14 June 2024 Science ClosedTags: biological response, chemistry, laboratory, Mediterranean, molecular biology, physiology, prokaryotes
The ongoing decreasing surface pH that seas and oceans are facing is termed ocean acidification (OA). The primary reason for this phenomenon is the emission of carbon dioxide (CO2) into the atmosphere from human activities, like the burning of fossil fuels, which has drastically increased since the industrial revolution, reaching higher levels during these decades. This environmental risk is considered among the most hazardous threats to marine ecosystems associated with global change and severely affects marine life worldwide. Responses of marine species to acidified seawaters have been deeply studied and adverse effects at different levels, from single species up to whole communities, have been pointed out. Although OA is clearly posing a threat to marine life, some species have demonstrated the ability to tolerate and thrive in such conditions. Information on the mechanisms driving the tolerance of adapted species to decrease seawater pH is limited, and new knowledge may be obtained from species inhabiting sites with naturally low pH, such as the volcanic CO2 system off the Castello Aragonese on the Ischia Island (Italy). Understanding the molecular mechanisms of adaptation enabling marine species to tolerate a lowered seawater pH could support predictions of the consequences of future OA scenarios for marine life. Growing evidence of the involvement of ABC transport proteins in resistance towards acid stress in bacteria and tumor cell lines has been demonstrated. Researchers have suggested that the tolerance to this kind of stress is due to the transport of substances that contribute to the maintenance of internal cell homeostasis carried out by the ABC proteins. Here, we aimed at elucidating the involvement of ABC transport proteins in tolerance to low-pH/high-pCO2 environments, by investigating their gene regulation, in species of marine microorganisms and metazoans considered tolerant to acidified environments. Halomicronema metazoicum is a marine filamentous cyanobacterium able to cope with hostile conditions and discovered in association with Posidonia oceanica leaves also in areas characterized by low pH. Mattes of this cyanobacterium were exposed in short- and long-term exposure experiments (7 and 30 d) to low seawater pH conditions (7.7, 7.2, 6.5), and the regulation of the ABC-like gene slr2019 was assessed. At day 7, slr2019 was up-regulated at pH 7.7 while no changes were observed at lower pH, compared to the controls (pH 8.2). However, after 30 d of exposure, a significant decrease in slr2019 transcript level was observed in all treatments. Furthermore, unchanged photosynthetic pigment content indicated that the species can tolerate all three lowered pH conditions. Platynereis dumerilii is a marine annelid extensively used as a model in genetics, single‐cell genomics, and ecotoxicology. It and its sibling, P. cfr massiliensis, were abundant in naturally acidified areas, such as the CO2 vents off Castello Aragonese. They are adapted to low-pH conditions, making them excellent models for studying acclimation and adaptation mechanisms to OA. Since its genome is completely sequenced, an attempt to identify ABC transport proteins in P. dumerilii has been made with the aim to investigate whether these proteins contribute to adaptation/tolerance to low-pH/high-pCO2 seawater conditions in the two sibling species P. dumerilii/cfr massiliensis before and after 30 d of in-situ transplant experiment. A total of 81 ABCs were found in P. dumerilii, belonging to seven distinct subfamilies (A–G) based on phylogenetic analysis. Furthermore, the distribution within the tissues of a subset of 40 ABC transport proteins from the subfamilies B, C and G was determined. Most of the analyzed ABCs were expressed in the annelid midgut but also found in the other organs and tissues: neurons, body epidermis and ectodermal cells, and somatic and visceral muscle. Based on these findings, we evaluated the expression profile of 7 genes belonging to the ABCB (ABCB_1, ABCB_2, ABCB_3), ABCC (ABCC_1, ABCC_2, ABCC_3) and ABCG (ABCG) subfamilies following a 30-d in-situ reciprocal transplant of specimens inhabiting normal-pH marine site (8.18 ± 0.005) and those living in naturally low-pH areas off Castello Aragonese (7.33 ± 0.312). Hypotheses on the involvement of each studied ABC gene in adaptation to low-pH were made based on the basal expression gene level of organisms inhabiting different pH environments and verified through the ABC transcription results of the in-situ transplant experiment. Three out of the 7 genes were confirmed to be involved in low-pH resistance. ABCB_1 and ABCG are up-regulated in worms living in low-pH sites compared to those from normal-pH areas while ABCB_3 were lower expressed. The results of transplant experiments supported these findings. ABCB_1 and ABCG gene expression increased in samples transplanted from normal-pH areas to acidified sites while decreased in the reverse transplant. On the contrary, ABCB_3 gene was down-regulated in organisms transferred from normal- to low-pH zones and was up-regulated in specimens subjected to the reverse transplantation. Taken together, our results demonstrate the capacity of the studied species to deal with low-pH environments and confirm previous findings on the involvement of ABC transporters in acid stress adaptation in marine organisms. These proteins were found to play a role in maintaining cellular homeostasis, buffering the internal cell pH and preventing cell death to guarantee the proper functioning of cellular activities. So, based on our findings, these functions may prevent negative effects following exposure to acidified conditions. This work will constitute a basis for further research on the physiological functions of ABCs behind the tolerance to low-pH/high-pCO2 environments to better understand how marine species can cope with OA and to provide vital information on the impact of climate change on marine biodiversity.
Continue reading ‘Molecular bases and evolutionary constraints of cellular acid tolerance in cyanobacteria and invertebrates subjected to ocean acidification and other sources of stress (METASTRESS)’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’Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers and limits poleward range shifts
Published 21 March 2024 Science ClosedTags: biological response, BRcommunity, echinoderms, laboratory, Mediterranean, mortality, performance, physiology, reproduction
Ongoing climate change has caused rapidly increasing temperatures and an unprecedented decline in seawater pH, known as ocean acidification. Increasing temperatures are redistributing species toward higher and cooler latitudes that are most affected by ocean acidification. While the persistence of intertidal species in cold environments is related to their capacity to resist sub-zero air temperatures, studies have never considered the interacting impacts of ocean acidification and freeze stress on species survival and distribution. Here, a full-factorial experiment was used to study whether ocean acidification increases mortality in subtidal Mytilus trossulus and subtidal M. galloprovincialis, and intertidal M. trossulus following sub-zero air temperature exposure. We examined physiological processes behind variation in freeze tolerance using 1H NMR metabolomics, analyses of fatty acids, and amino acid composition. We show that low pH conditions (pH = 7.5) significantly decrease freeze tolerance in both intertidal and subtidal populations of Mytilus spp. Under current day pH conditions (pH = 7.9), intertidal M. trossulus was more freeze tolerant than subtidal M. trossulus and subtidal M. galloprovincialis. Conversely, under low pH conditions, subtidal M. trossulus was more freeze tolerant than the other mussel categories. Differences in the concentration of various metabolites (cryoprotectants) or in the composition of amino acids and fatty acids could not explain the decrease in survival. These results suggest that ocean acidification can offset the poleward range expansions facilitated by warming and that reduced freeze tolerance could result in a range contraction if temperatures become lethal at the equatorward edge.
Continue reading ‘Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers and limits poleward range shifts’Physiological impacts of CO2-Induced acidification and UVR on invasive alga Caulerpa racemosa
Published 11 March 2024 Science ClosedTags: algae, biological response, laboratory, light, Mediterranean, multiple factors, photosynthesis, physiology
Anthropogenically increasing atmospheric CO2 causes changes in the carbon chemistry of seawater. With these changes, the HCO3− and CO2 concentration of seawater increases, while the pH decreases. CO2-induced ocean acidification by interacting with ultraviolet radiation (UVR) affects the metabolic pathways of seaweeds such as photosynthesis, growth, and nutrient uptake in a species-specific manner. This study was designed to determine the future ecological success of Caulerpa racemosa, an invasive species in the Mediterranean. In laboratory culture, C. racemosa was exposed to CO2-induced low pH (pH: 7.7) with or without UVR (UVA: 1.2 W m−2; UVB: 0.55 W m−2) and its physiological responses were investigated. Maximum quantum yield of photosystem-II (Fv/Fm) and light utilization efficiency (α) of C. racemosa was negatively affected by low pH and UVR. However, low pH increased the rETRmax (maximum relative electron transfer rate) of C. racemosa. This increased rETRmax indicated that the photosynthesis of C. racemosa was not photosynthetically saturated at the ambient inorganic carbon pool. This could be an advantage in competing with other species in the predicted future ocean acidification. The combined effect of low pH and UVR affected the rETRmax of C. racemosa in different ways along with the incubation time. The synergistic effect observed in the first two weeks turned into an antagonistic effect in the last two weeks. The data obtained from this study suggest that incubation time is the most effective factor in the response of C. racemosa to CO2-induced low pH and moderate-level UVR. In addition, our results support the hypothesis that C. racemosa may be one of the species that will benefit from CO2-induced ocean acidification.
Continue reading ‘Physiological impacts of CO2-Induced acidification and UVR on invasive alga Caulerpa racemosa’Morphometric changes in Watznaueria barnesiae across the mid Cretaceous: Paleoecological implications
Published 5 March 2024 Science ClosedTags: biological response, field, Mediterranean, morphology, paleo, phytoplankton, sediment
Highligthts
- W. barnesiae evidenced moderate size variations in the mid Cretaceous (western Tethys).
- Size variations in W. barnesiae differed from those of B. constans.
- During OAE1a and OAE1b both species showed size reduction and ellipticity increase.
- The effects of fertility were opposite on the two species size variations.
Abstract
This study reveals moderate yet important variations in Watznaueria barnesiae coccolith and central unit size throughout the Aptian–late Cenomanian (27 my) time interval in western Tethys. A new statistical approach was applied to determine whether non-random size trends apply to these metrics and to identify possible links between their variation and fertility or temperature. During OAE 1a, W. barnesiae coccoliths were the smallest and the most elliptical, with reduced central unit size. A further minor size decrease occurs during OAE 1b but not during OAE 1d. From the middle Albian to the middle Cenomanian, larger and less elliptical coccoliths are observed, with unchanged central unit dimensions. These results, together with concomitantly larger size changes in Biscutum constans confirm that W. barnesiae is a tolerant taxon. High-frequency, high-amplitude paleoenvironmental changes during the Aptian–early Albian indicate that temperature and fertility – either individually or in combination – had no direct impact on the mean coccolith size and potentially other factors affected coccolith size. Instead, lower nutrients with lower temperatures probably played a role in promoting larger W. barnesiae but smaller B. constans coccoliths during the middle Albian–Cenomanian. The size and ellipticity changes during OAE 1a and 1b were the strongest, likely resulting from ocean acidification and trace metal inputs, in addition to (or independently of) fertility and temperature variations.
Continue reading ‘Morphometric changes in Watznaueria barnesiae across the mid Cretaceous: Paleoecological implications’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’Two new coastal time-series of seawater carbonate system variables in the NW Mediterranean Sea: rates and mechanisms controlling pH changes
Published 23 February 2024 Science ClosedTags: chemistry, field, Mediterranean
In this work, we present, for the first time, the seawater carbonate system measurements of two coastal time-series in the NW Mediterranean Sea, L’Estartit Oceanographic Station (EOS; 42.05°N 3.2542°E) and the Blanes Bay Microbial Observatory (BBMO; 41.665°N 2.805°E). At these two time-series, measurements of total alkalinity (TA), pH, and associated variables, such as dissolved inorganic nutrients, temperature, and salinity, have been performed monthly since 2010 in surface seawater. Seasonality and seasonal amplitude are analogous in both time-series, with seasonality in pHT in situ(pH at in situ seawater conditions on the total hydrogen ion scale) primarily determined by seasonality in sea surface temperature. The evaluated pHT in situtrends at BBMO (-0.0021 ± 0.0003 yr-1) and EOS (-0.0028 ± 0.0005 yr-1) agree with those reported for coastal and open ocean surface waters in the Mediterranean Sea and open ocean surface waters of the global ocean, therefore indicating that these time-series are representative of global ocean acidification signals despite being coastal. The decreases in pHT in situcan be attributed to increases in total dissolved inorganic carbon (DIC; 1.5 ± 0.4 µmol kg-1 yr-1 at BBMO and 1.6 ± 0.6 µmolESkg-1 yr-1 at EOS) and sea surface temperature (0.08 ± 0.02 °C yr-1 at BBMO and 0.08 ± 0.04 °C yr-1 at EOS). The increases in carbon dioxide fugacity (fCO2; 2.4 ± 0.3 µmol kg-1 yr-1 at BBMO and 2.9 ± 0.6 µmol kg-1 yr-1 at EOS) follow the atmospheric CO2 forcing, thus indicating the observed DIC increase is related to anthropogenic CO2 uptake. The increasing trends in TA (1.2 ± 0.3 µmol kg-1 yr-1 at BBMO and 1.0 ± 0.5 µmol kg-1 yr-1 at EOS) buffered the acidification rates, counteracting 60% and 72% of the pHT in situdecrease caused by increasing DIC at EOS and BBMO, respectively. Once accounted for the neutralizing effect of TA increase, the rapid sea surface warming plays a larger role in the observed pH decreases (43% at EOS and 62% at BBMO) than the DIC increase (36% at EOS and 33% at BBMO).
Continue reading ‘Two new coastal time-series of seawater carbonate system variables in the NW Mediterranean Sea: rates and mechanisms controlling pH changes’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’Effects of acidification on the biogeochemistry of unvegetated and seagrass marine sediments
Published 14 February 2024 Science ClosedTags: chemistry, field, Mediterranean, sediment
Highlights
- A −0.3 pH units difference causes minor effects on unvegetated sediments organic matter
- Acidification slows down organic C degradation in unvegetated sediments
- Acidification stimulates organic C in seagrass sediments
- Acidification will affect benthic trophic webs under worsening ocean scenarios
Abstract
Many studies addressed ocean acidification (OA) effects on marine life, whereas its effects on sedimentary organic matter (OM) have received less attention. We investigated differences in OM features in sediments from unvegetated and seagrass (Posidonia oceanica) beds in a shallow hydrothermal area (Aeolian Archipelago, Mediterranean Sea), under natural (8.1–8.0) and acidified (7.8–7.9) conditions. We show that a pH difference of −0.3 units have minor effects on OM features in unvegetated sediments, but relevant consequences within acidified seagrass meadows, where OM quantity and nutritional quality are lower than those under natural pH conditions. Effects of acidified conditions on OM biogeochemistry vary between unvegetated and seagrass sediments, with lower C degradation rates and longer C turnover time in the former than in the latter. We conclude that OA, although with effects not consistent between unvegetated and vegetated sediments, can affect OM quantity, composition, and degradation, thus having possible far-reaching consequences for benthic trophic webs.
Continue reading ‘Effects of acidification on the biogeochemistry of unvegetated and seagrass marine sediments’A synthesis of ocean total alkalinity and dissolved inorganic carbon measurements from 1993 to 2022: the SNAPO-CO2-v1 dataset (update)
Published 31 January 2024 Science ClosedTags: Antarctic, chemistry, field, Indian, Mediterranean, North Atlantic, North Pacific, South Atlantic, South Pacific
Total alkalinity (AT) and dissolved inorganic carbon (CT) in the oceans are important properties with respect to understanding the ocean carbon cycle and its link to global change (ocean carbon sinks and sources, ocean acidification) and ultimately finding carbon-based solutions or mitigation procedures (marine carbon removal). We present a database of more than 44 400 AT and CT observations along with basic ancillary data (spatiotemporal location, depth, temperature and salinity) from various ocean regions obtained, mainly in the framework of French projects, since 1993. This includes both surface and water column data acquired in the open ocean, coastal zones and in the Mediterranean Sea and either from time series or dedicated one-off cruises. Most AT and CT data in this synthesis were measured from discrete samples using the same closed-cell potentiometric titration calibrated with Certified Reference Material, with an overall accuracy of ±4 µmol kg−1 for both AT and CT. The data are provided in two separate datasets – for the Global Ocean and the Mediterranean Sea (https://doi.org/10.17882/95414, Metzl et al., 2023), respectively – that offer a direct use for regional or global purposes, e.g., AT–salinity relationships, long-term CT estimates, and constraint and validation of diagnostic CT and AT reconstructed fields or ocean carbon and coupled climate–carbon models simulations as well as data derived from Biogeochemical-Argo (BGC-Argo) floats. When associated with other properties, these data can also be used to calculate pH, the fugacity of CO2 (fCO2) and other carbon system properties to derive ocean acidification rates or air–sea CO2 fluxes.
Continue reading ‘A synthesis of ocean total alkalinity and dissolved inorganic carbon measurements from 1993 to 2022: the SNAPO-CO2-v1 dataset (update)’Early stage ecological communities on artificial algae showed no difference in diversity and abundance under ocean acidification
Published 24 January 2024 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, calcification, chemistry, community composition, crustaceans, echinoderms, field, Mediterranean, mesocosms, mitigation, mollusks, otherprocess, photosynthesis, protists, respiration
Marine habitat-forming species create structurally complex habitats that host macroinvertebrate communities characterized by remarkable abundance and species richness. These habitat-forming species also play a fundamental role in creating favourable environmental conditions that promote biodiversity. The deployment of artificial structures is becoming a common practice to help offset habitat loss although with mixed results. This study investigated the suitability of artificial flexible turfs mimicking the articulated coralline algae (mimics) as habitat providers and the effect of ocean acidification (OA) on early stage ecological communities associated to flexible mimics and with the mature community associated to Ellisolandia elongata natural turfs. The mimics proved to be a suitable habitat for early stage communities. During the OA mesocosms experiment, the two substrates have been treated and analysed separately due to the difference between the two communities. For early stage ecological communities associated with the mimics, the lack of a biologically active substrate does not exacerbate the effect of OA. In fact, no significant differences were found between treatments in crustaceans, molluscs and polychaetes diversity and abundance associated with the mimics. In mature communities associated with natural turfs, buffering capability of E. elongata is supporting different taxonomic groups, except for molluscs, greatly susceptible to OA.
Continue reading ‘Early stage ecological communities on artificial algae showed no difference in diversity and abundance under ocean acidification’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’Assessing seasonal and interannual changes in carbonate chemistry across two time-series sites in the North Western Mediterranean Sea
Published 8 December 2023 Science ClosedTags: chemistry, field, Mediterranean
Sustained time-series measurements are crucial to understand changes in oceanic carbonate chemistry. In the North Western Mediterranean Sea, the temporal evolution of the carbonate system is here investigated based on two 10-year time-series (between January 2010 and December 2019) of monthly carbonate parameters measurements at two sampling sites in the Ligurian Sea (ANTARES and DYFAMED). At seasonal timescale, the seawater partial pressure of CO2 (pCO2) within the mixed layer is mostly driven by temperature at both sites, and biological processes as stated by the observed relationships between total inorganic carbon (CT), nitrate and temperature. This study suggests also that mixing and water masses advection could play a role in modulating the CT content. At decadal timescale, significant changes in ocean chemistry are observed with increasing trends in CT (+3.2 ± 0.9 µmol.kg−1.a−1 – ANTARES; +1.6 ± 0.8 µmol.kg−1.a−1 – DYFAMED), associated with increasing pCO2 trends and decreasing trends in pH. The magnitude of the increasing trend in CT at DYFAMED is consistent with the increase in atmospheric pCO2 and the anthropogenic carbon transport of water originating from the Atlantic Ocean, while the higher trends observed at the ANTARES site could be related to the hydrological variability induced by the variability of the Northern Current.
Continue reading ‘Assessing seasonal and interannual changes in carbonate chemistry across two time-series sites in the North Western Mediterranean Sea’
