Acidified marine systems represent “natural laboratories”, which provide opportunities to investigate the impacts of ocean acidification on different living components, including microbes. Here, we compared the benthic microbial response in four naturally acidified sites within the Southern Tyrrhenian Sea characterized by different acidification sources (i.e., CO2 emissions at Ischia, mixed gases at Panarea and Basiluzzo and acidified freshwater from karst rocks at Presidiana) and pH values. We investigated prokaryotic abundance, activity and biodiversity, viral abundance and prokaryotic infections, along with the biochemical composition of the sediment organic matter. We found that, despite differences in local environmental dynamics, viral life strategies change in acidified conditions from mainly lytic to temperate lifestyles (e.g., chronic infection), also resulting in a lowered impact on prokaryotic communities, which shift towards (chemo)autotrophic assemblages, with lower organic matter consumption. Taken together, these results suggest that ocean acidification exerts a deep control on microbial benthic assemblages, with important feedbacks on ecosystem functioning.
Continue reading ‘Ocean acidification induces changes in virus–host relationships in Mediterranean benthic ecosystems’Posts Tagged 'vents'
Ocean acidification induces changes in virus–host relationships in Mediterranean benthic ecosystems
Published 8 April 2021 Science ClosedTags: abundance, biological response, community composition, field, molecular biology, mortality, otherprocess, physiology, prokaryotes, sediment, vents, virus
Feedback mechanisms stabilise degraded turf algal systems at a CO2 seep site
Published 17 February 2021 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, community composition, corals, field, North Pacific, otherprocess, reproduction, vents
Human activities are rapidly changing the structure and function of coastal marine ecosystems. Large-scale replacement of kelp forests and coral reefs with turf algal mats is resulting in homogenous habitats that have less ecological and human value. Ocean acidification has strong potential to substantially favour turf algae growth, which led us to examine the mechanisms that stabilise turf algal states. Here we show that ocean acidification promotes turf algae over corals and macroalgae, mediating new habitat conditions that create stabilising feedback loops (altered physicochemical environment and microbial community, and an inhibition of recruitment) capable of locking turf systems in place. Such feedbacks help explain why degraded coastal habitats persist after being initially pushed past the tipping point by global and local anthropogenic stressors. An understanding of the mechanisms that stabilise degraded coastal habitats can be incorporated into adaptive management to better protect the contribution of coastal systems to human wellbeing.
Continue reading ‘Feedback mechanisms stabilise degraded turf algal systems at a CO2 seep site’Ocean acidification may slow the pace of tropicalization of temperate fish communities
Published 9 February 2021 Science ClosedTags: abundance, algae, biological response, BRcommunity, community composition, echinoderms, field, fish, otherprocess, South Pacific, vents
Poleward range extensions by warm-adapted sea urchins are switching temperate marine ecosystems from kelp-dominated to barren-dominated systems that favour the establishment of range-extending tropical fishes. Yet, such tropicalization may be buffered by ocean acidification, which reduces urchin grazing performance and the urchin barrens that tropical range-extending fishes prefer. Using ecosystems experiencing natural warming and acidification, we show that ocean acidification could buffer warming-facilitated tropicalization by reducing urchin populations (by 87%) and inhibiting the formation of barrens. This buffering effect of CO2 enrichment was observed at natural CO2 vents that are associated with a shift from a barren-dominated to a turf-dominated state, which we found is less favourable to tropical fishes. Together, these observations suggest that ocean acidification may buffer the tropicalization effect of ocean warming against urchin barren formation via multiple processes (fewer urchins and barrens) and consequently slow the increasing rate of tropicalization of temperate fish communities.
Continue reading ‘Ocean acidification may slow the pace of tropicalization of temperate fish communities’Unexpected high abundance of aragonite-forming Nanipora (Octocorallia: Helioporacea) at an acidified volcanic reef in southern Japan
Published 3 February 2021 Science ClosedTags: biological response, BRcommunity, corals, field, North Pacific, vents
Nanipora Miyazaki & Reimer, 2015 is a recently discovered genus of aragonite-skeleton producing octocorals closely related to the blue coral genus Heliopora de Blainville, 1830. Since its discovery, Nanipora has been reported from coral reefs in Okinawa, Japan, and Thailand, and from seagrass beds in the northern South China Sea. However, it remains little known and studied. Here, we report on the unexpected discovery of an abundance of Nanipora colonies in shallow waters less than 2-m deep around a CO2 vent from the uninhabited volcanic island of Iwotorishima, Okinawa, in southern Japan. Nanipora colonies were found covering both coral rubble and hard substrates, alongside a few soft coral and zoantharian species. Polyps were pale white in color with none brown or darker in coloration as in some recent reports. As the original description of N. kamurai from Zamami Island in Okinawa describes the species as azooxanthellate, as the current Iwotorishima specimens also appear to be, and recently reported specimens from Thailand, Dongsha Atoll, and Yaeyama are zooxanthellate, it may be that there are more than one Nanipora species; the type species N. kamurai that is also likely at Iwotorishima, and a zooxanthellate species that constitutes the other records. Although Nanipora is not well studied, its presence at this volcanic CO2 seep suggests it has the ability to survive under unique and extreme environmental conditions, rendering it as a potentially important subject of study in the face of increasing ocean acidification.
Continue reading ‘Unexpected high abundance of aragonite-forming Nanipora (Octocorallia: Helioporacea) at an acidified volcanic reef in southern Japan’Boosted fish abundance associated with Posidonia oceanica meadows in temperate shallow CO2 vents
Published 1 February 2021 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, field, fish, mollusks, otherprocess, phanerogams, vents
Highlights
- Ocean acidification (OA) may induce shifts in the structure and function of coastal marine ecosystems
- CO2 vents were used to assess the effects of OA on fish assemblages associated with Posidonia oceanica
- Posidonia structure and associated fish assemblages were compared at vents and off-vents using underwater visual census
- Posidonia density increases and fish show boosted abundance but not reduced diversity at vents
- Mediterranean Posidonia fish assemblages may cope with OA under near-future acidification level
Abstract
Ocean acidification (OA) may induce major shifts in the structure and function of coastal marine ecosystems. Studies in volcanic CO2 vents, where seawater is naturally acidified, have reported an overall simplification of fish assemblages structure, while some primary producers are likely to increase their biomass under elevated concentration of CO2. Here we used temperate shallow CO2 vents located around the coast of Ischia island (Italy) to assess the effects of OA on necto-benthic fish assemblages associated with the foundation seagrass species Posidonia oceanica in the Mediterranean Sea. We compared P. oceanica meadow structure, its epiphytic community and the associated fish assemblage structure and diversity at vents with low pH sites and reference sites with ambient pH using underwater visual census strip transects, in two seasons (fall 2018 and summer 2019). Data were analysed using both univariate and multivariate statistical techniques. Results showed greater P. oceanica habitat complexity (i.e. shoot density) and lower abundance of epiphytic calcareous species (e.g. coralline algae) at the vents than reference sites. Total abundance of adult and juvenile fish was higher at vents than reference sites, while no differences were found for species richness and composition. Overall, the herbivore Sarpa salpa stands out among the species contributing the most to dissimilarity between vents and reference sites, showing higher abundances under OA conditions. This pattern could be explained by the combined effect of a positive response to the higher structural meadows complexity and the greater seagrasses palatability / nutritional value occurring at the vents, which may help herbivores to withstand the higher energetic cost to live under high pCO2 / low pH conditions. Our results indicate that necto-benthic fish assemblages associated with the Mediterranean P. oceanica ecosystem may cope with OA under the CO2 emission scenarios forecasted for the end of this century.
Continue reading ‘Boosted fish abundance associated with Posidonia oceanica meadows in temperate shallow CO2 vents’Forecasting impacts of ocean acidification on marine communities: utilising volcanic CO2 vents as natural laboratories
Published 28 January 2021 Science ClosedTags: biological response, prokaryotes, vents
Oceans have absorbed approximately 30% of anthropogenic CO2 emissions, causing a phenomenon known as ‘ocean acidification’. With surface ocean pH changing at a rapid pace, continued uptake of CO2 is expected to decrease ocean pH by 0.3 pH units as early as 2081, accompanied by a decrease in the saturation of calcium carbonate minerals needed to produce skeletons and shells (RCP 8.5 scenario, IPCC 2019).
Continue reading ‘Forecasting impacts of ocean acidification on marine communities: utilising volcanic CO2 vents as natural laboratories’Genomic adaptation of Pseudomonas strains to acidity and antibiotics in hydrothermal vents at Kolumbo submarine volcano, Greece
Published 26 January 2021 Science ClosedTags: adaptation, biological response, field, Mediterranean, molecular biology, physiology, prokaryotes, vents
Although the rise of antibiotic and multidrug resistant bacteria is one of the biggest current threats to human health, our understanding of the mechanisms involved in antibiotic resistance selection remains scarce. We performed whole genome sequencing of 21 Pseudomonas strains, previously isolated from an active submarine volcano of Greece, the Kolumbo volcano. Our goal was to identify the genetic basis of the enhanced co-tolerance to antibiotics and acidity of these Pseudomonas strains. Pangenome analysis identified 10,908 Gene Clusters (GCs). It revealed that the numbers of phage-related GCs and sigma factors, which both provide the mechanisms of adaptation to environmental stressors, were much higher in the high tolerant Pseudomonas strains compared to the rest ones. All identified GCs of these strains were associated with antimicrobial and multidrug resistance. The present study provides strong evidence that the CO2-rich seawater of the volcano associated with low pH might be a reservoir of microorganisms carrying multidrug efflux-mediated systems and pumps. We, therefore, suggest further studies of other extreme environments (or ecosystems) and their associated physicochemical parameters (or factors) in the rise of antibiotic resistance.
Continue reading ‘Genomic adaptation of Pseudomonas strains to acidity and antibiotics in hydrothermal vents at Kolumbo submarine volcano, Greece’Ocean acidification boosts reproduction in fish via indirect effects
Published 25 January 2021 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, community composition, crustaceans, field, fish, molecular biology, mollusks, morphology, otherprocess, performance, physiology, reproduction, South Pacific, vents
Ocean acidification affects species populations and biodiversity through direct negative effects on physiology and behaviour. The indirect effects of elevated CO2 are less well known and can sometimes be counterintuitive. Reproduction lies at the crux of species population replenishment, but we do not know how ocean acidification affects reproduction in the wild. Here, we use natural CO2 vents at a temperate rocky reef and show that even though ocean acidification acts as a direct stressor, it can indirectly increase energy budgets of fish to stimulate reproduction at no cost to physiological homeostasis. Female fish maintained energy levels by compensation: They reduced activity (foraging and aggression) to increase reproduction. In male fish, increased reproductive investment was linked to increased energy intake as mediated by intensified foraging on more abundant prey. Greater biomass of prey at the vents was linked to greater biomass of algae, as mediated by a fertilisation effect of elevated CO2 on primary production. Additionally, the abundance and aggression of paternal carers were elevated at the CO2 vents, which may further boost reproductive success. These positive indirect effects of elevated CO2 were only observed for the species of fish that was generalistic and competitively dominant, but not for 3 species of subordinate and more specialised fishes. Hence, species that capitalise on future resource enrichment can accelerate their reproduction and increase their populations, thereby altering species communities in a future ocean.
Continue reading ‘Ocean acidification boosts reproduction in fish via indirect effects’Greater mitochondrial energy production provides resistance to ocean acidification in “winning” hermatypic corals
Published 20 January 2021 Science ClosedTags: adaptation, biological response, BRcommunity, chemistry, corals, field, North Pacific, otherprocess, physiology, protists, South Pacific, vents
Coral communities around the world are projected to be negatively affected by ocean acidification. Not all coral species will respond in the same manner to rising CO2 levels. Evidence from naturally acidified areas such as CO2 seeps have shown that although a few species are resistant to elevated CO2, most lack sufficient resistance resulting in their decline. This has led to the simple grouping of coral species into “winners” and “losers,” but the physiological traits supporting this ecological assessment are yet to be fully understood. Here using CO2 seeps, in two biogeographically distinct regions, we investigated whether physiological traits related to energy production [mitochondrial electron transport systems (ETSAs) activities] and biomass (protein contents) differed between winning and losing species in order to identify possible physiological traits of resistance to ocean acidification and whether they can be acquired during short-term transplantations. We show that winning species had a lower biomass (protein contents per coral surface area) resulting in a higher potential for energy production (biomass specific ETSA: ETSA per protein contents) compared to losing species. We hypothesize that winning species inherently allocate more energy toward inorganic growth (calcification) compared to somatic (tissue) growth. In contrast, we found that losing species that show a higher biomass under reference pCO2 experienced a loss in biomass and variable response in area-specific ETSA that did not translate in an increase in biomass-specific ETSA following either short-term (4–5 months) or even life-long acclimation to elevated pCO2 conditions. Our results suggest that resistance to ocean acidification in corals may not be acquired within a single generation or through the selection of physiologically resistant individuals. This reinforces current evidence suggesting that ocean acidification will reshape coral communities around the world, selecting species that have an inherent resistance to elevated pCO2.
Continue reading ‘Greater mitochondrial energy production provides resistance to ocean acidification in “winning” hermatypic corals’Dichotomy between regulation of coral bacterial communities and calcification physiology under ocean acidification conditions
Published 14 January 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, corals, field, molecular biology, North Pacific, physiology, prokaryotes, vents
Ocean acidification (OA) threatens the growth and function of coral reef ecosystems. A key component to coral health is the microbiome, but little is known about the impact of OA on coral microbiomes. A submarine CO2 vent at Maug Island in the Northern Marianas Islands provides a natural pH gradient to investigate coral responses to long-term OA conditions. Three coral species (Pocillopora eydouxi, Porites lobata, and Porites rus) were sampled from three sites where mean seawater pH is 8.04, 7.98, and 7.94. We characterized coral bacterial communities (using 16S rRNA gene sequencing) and determined pH of the extracellular calcifying fluid (ECF) (using skeletal boron isotopes) across the seawater pH gradient. Bacterial communities of both Porites species stabilized (decreases in community dispersion) with decreased seawater pH, coupled with large increases in the abundance of Endozoicomonas, an endosymbiont. P. lobata experienced a significant decrease in ECF pH near the vent, whereas P. rus experienced a trending decrease in ECF pH near the vent. By contrast, Pocillopora exhibited bacterial community destabilization (increases in community dispersion), with significant decreases in Endozoicomonas abundance, while its ECF pH remained unchanged across the pH gradient. Our study shows that OA has multiple consequences on Endozoicomonas abundance and suggests that Endozoicomonas abundance may be an indicator of coral response to OA. We reveal an interesting dichotomy between two facets of coral physiology (regulation of bacterial communities and regulation of calcification), highlighting the importance of multidisciplinary approaches to understanding coral health and function in a changing ocean.
Continue reading ‘Dichotomy between regulation of coral bacterial communities and calcification physiology under ocean acidification conditions’Ocean acidification locks algal communities in a species‐poor early successional stage
Published 12 January 2021 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, community composition, field, North Pacific, otherprocess, vents
Long‐term exposure to CO2‐enriched waters can considerably alter marine biological community development, often resulting in simplified systems dominated by turf algae that possess reduced biodiversity and low ecological complexity. Current understanding of the underlying processes by which ocean acidification alters biological community development and stability remains limited, making the management of such shifts problematic. Here, we deployed recruitment tiles in reference (pHT 8.137 ± 0.056 SD) and CO2‐enriched conditions (pHT 7.788 ± 0.105 SD) at a volcanic CO2 seep in Japan to assess the underlying processes and patterns of algal community development. We assessed (i) algal community succession in two different seasons (Cooler months: January–July, and warmer months: July–January), (ii) the effects of initial community composition on subsequent community succession (by reciprocally transplanting preestablished communities for a further 6 months), and (iii) the community production of resulting communities, to assess how their functioning was altered (following 12 months recruitment). Settlement tiles became dominated by turf algae under CO2‐enrichment and had lower biomass, diversity and complexity, a pattern consistent across seasons. This locked the community in a species‐poor early successional stage. In terms of community functioning, the elevated pCO2 community had greater net community production, but this did not result in increased algal community cover, biomass, biodiversity or structural complexity. Taken together, this shows that both new and established communities become simplified by rising CO2 levels. Our transplant of preestablished communities from enriched CO2 to reference conditions demonstrated their high resilience, since they became indistinguishable from communities maintained entirely in reference conditions. This shows that meaningful reductions in pCO2 can enable the recovery of algal communities. By understanding the ecological processes responsible for driving shifts in community composition, we can better assess how communities are likely to be altered by ocean acidification.
Continue reading ‘Ocean acidification locks algal communities in a species‐poor early successional stage’Life-long coral skeletal acclimatization at CO2 vents in Papua New Guinea reveals species- and environment-specific effects
Published 6 January 2021 Science ClosedTags: adaptation, biological response, calcification, corals, field, morphology, otherprocess, South Pacific, vents
The responses of corals and other marine calcifying organisms to ocean acidification (OA) are variable and span from no effect to severe responses. Here we investigated the effect of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals living at two CO2 vents in Papua New Guinea, namely in Dobu and Upa Upasina. The skeletal porosity of Galaxea fascicularis, Acropora millepora, and Pocillopora damicornis was higher (from 17% to 38%, depending on the species) at the seep site compared to the control only at Upa Upasina. Massive Porites showed no differences at any of the locations. Pocillopora damicornis also showed a ~ 7% decrease of micro-density and an increase of the volume fraction of the larger pores, a decrease of the intraskeletal organic matrix content with an increase of the intraskeletal water content, and no variation in the organic matrix related strain and crystallite size. The fact that the skeletal parameters varied only at one of the two seep sites suggests that other local environmental conditions interact with OA to modify the coral skeletal parameters. This might also contribute to explain the great deal of responses to OA reported for corals and other marine calcifying organisms.
Continue reading ‘Life-long coral skeletal acclimatization at CO2 vents in Papua New Guinea reveals species- and environment-specific effects’Leaf proteome modulation and cytological features of seagrass Cymodocea nodosa in response to long-term high CO2 exposure in volcanic vents
Published 29 December 2020 Science ClosedTags: adaptation, biological response, field, Mediterranean, otherprocess, phanerogams, physiology, vents
Seagrass Cymodocea nodosa was sampled off the Vulcano island, in the vicinity of a submarine volcanic vent. Leaf samples were collected from plants growing in a naturally acidified site, influenced by the long-term exposure to high CO2 emissions, and compared with others collected in a nearby meadow living at normal pCO2 conditions. The differential accumulated proteins in leaves growing in the two contrasting pCO2 environments was investigated. Acidified leaf tissues had less total protein content and the semi-quantitative proteomic comparison revealed a strong general depletion of proteins belonging to the carbon metabolism and protein metabolism. A very large accumulation of proteins related to the cell respiration and to light harvesting process was found in acidified leaves in comparison with those growing in the normal pCO2 site. The metabolic pathways linked to cytoskeleton turnover also seemed affected by the acidified condition, since a strong reduction in the concentration of cytoskeleton structural proteins was found in comparison with the normal pCO2 leaves. Results coming from the comparative proteomics were validated by the histological and cytological measurements, suggesting that the long lasting exposure and acclimation of C. nodosa to the vents involved phenotypic adjustments that can offer physiological and structural tools to survive the suboptimal conditions at the vents vicinity.
Continue reading ‘Leaf proteome modulation and cytological features of seagrass Cymodocea nodosa in response to long-term high CO2 exposure in volcanic vents’Volcanic CO2 seep geochemistry and use in understanding ocean acidification
Published 15 December 2020 Science ClosedTags: abundance, algae, annelids, biogeochemistry, BRcommunity, bryozoa, chemistry, cnidaria, community composition, corals, crustaceans, echinoderms, field, fish, Mediterranean, mollusks, otherprocess, phanerogams, phytoplankton, polychaetes, protists, review, vents
Ocean acidification is one of the most dramatic effects of the massive atmospheric release of anthropogenic carbon dioxide (CO2) that has occurred since the Industrial Revolution, although its effects on marine ecosystems are not well understood. Submarine volcanic hydrothermal fields have geochemical conditions that provide opportunities to characterise the effects of elevated levels of seawater CO2 on marine life in the field. Here, we review the geochemical aspects of shallow marine CO2-rich seeps worldwide, focusing on both gas composition and water chemistry. We then describe the geochemical effects of volcanic CO2 seepage on the overlying seawater column. We also present new geochemical data and the first synthesis of marine biological community changes from one of the best-studied marine CO2 seep sites in the world (off Vulcano Island, Sicily). In areas of intense bubbling, extremely high levels of pCO2 (> 10,000 μatm) result in low seawater pH (< 6) and undersaturation of aragonite and calcite in an area devoid of calcified organisms such as shelled molluscs and hard corals. Around 100–400 m away from the Vulcano seeps the geochemistry of the seawater becomes analogous to future ocean acidification conditions with dissolved carbon dioxide levels falling from 900 to 420 μatm as seawater pH rises from 7.6 to 8.0. Calcified species such as coralline algae and sea urchins fare increasingly well as sessile communities shift from domination by a few resilient species (such as uncalcified algae and polychaetes) to a diverse and complex community (including abundant calcified algae and sea urchins) as the seawater returns to ambient levels of CO2. Laboratory advances in our understanding of species sensitivity to high CO2 and low pH seawater, reveal how marine organisms react to simulated ocean acidification conditions (e.g., using energetic trade-offs for calcification, reproduction, growth and survival). Research at volcanic marine seeps, such as those off Vulcano, highlight consistent ecosystem responses to rising levels of seawater CO2, with the simplification of food webs, losses in functional diversity and reduced provisioning of goods and services for humans.
Continue reading ‘Volcanic CO2 seep geochemistry and use in understanding ocean acidification’Seawater acidification affects beta-diversity of benthic communities at a shallow hydrothermal vent in a Mediterranean marine protected area (underwater archaeological park of Baia, Naples, Italy)
Published 10 December 2020 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, community composition, crustaceans, field, Mediterranean, nematodes, otherprocess, vents
One of the most important pieces of climate change evidence is ocean acidification. Acidification effects on marine organisms are widely studied, while very little is known regarding its effects on assemblages’ β-diversity. In this framework, shallow hydrothermal vents within a Marine Protected Area (MPA) represent natural ecosystems acting as laboratory set-ups where the continuous carbon dioxide emissions affect assemblages with consequences that can be reasonably comparable to the effects of global water acidification. The aim of the present study is to test the impact of seawater acidification on the β-diversity of soft-bottom assemblages in a shallow vent field located in the Underwater Archeological Park of Baia MPA (Gulf of Naples, Mediterranean Sea). We investigated macro- and meiofauna communities of the ‘Secca delle fumose’ vent system in sites characterized by sulfurous (G) and carbon dioxide emissions (H) that are compared with control/inactive sites (CN and CS). Statistical analyses were performed on the most represented macrobenthic (Mollusca, Polychaeta, and Crustacea), and meiobenthic (Nematoda) taxa. Results show that the lowest synecological values are detected at H and, to a lesser extent, at G. Multivariate analyses show significant differences between hydrothermal vents (G, H) and control/inactive sites; the highest small-scale heterogeneities (measure of β-diversity) are detected at sites H and G and are mainly affected by pH, TOC (Total Organic Carbon), and cations concentrations. Such findings are probably related to acidification effects, since MPA excludes anthropic impacts. In particular, acidification markedly affects β-diversity and an increase in heterogeneity among sample replicates coupled to a decrease in number of taxa is an indicator of redundancy loss and, thus, of resilience capacity. The survival is assured to either tolerant species or those opportunistic taxa that can find good environmental conditions among gravels of sand.
Continue reading ‘Seawater acidification affects beta-diversity of benthic communities at a shallow hydrothermal vent in a Mediterranean marine protected area (underwater archaeological park of Baia, Naples, Italy)’Ocean acidification increases phytobenthic carbon fixation and export in a warm-temperate system
Published 3 December 2020 Science ClosedTags: abundance, algae, biological response, BRcommunity, community composition, field, North Pacific, otherprocess, photosynthesis, phytoplankton, vents
Highlights
- Diatoms dominated settlement surfaces at elevated CO2 in a warm-temperate zone.
- Photosynthesis of recruited algal communities increased in high CO2 conditions.
- Increased photosynthesis at high CO2 did not increase algal biomass.
- Significantly more of the carbon fixed at high CO2 was exported offshore.
Abstract
The response of photosynthetic organisms to rising CO2 levels is a key topic in ocean acidification research. Most of the work in this field has focused on physiological responses in laboratory conditions which lack ecological realism. Studies using seeps as natural analogues for ocean acidification have demonstrated shifts in algal community composition, but the effect of CO2 on carbon fixation and export remains unclear. Here, we deployed artificial substrata in a warm-temperate region of Japan to collect algal communities using a CO2 seep off Shikine Island. Diatoms became dominant on settlement substrata in areas with elevated CO2 levels, whereas macroalgae dominated at present-day levels of CO2 (reference site). This was supported by pigment composition; fucoxanthin content, characteristic of diatoms, was higher at the high CO2 site, while more Chlorophyll b, which is characteristic of Chlorophyta, was found in the reference site. Algal communities that recruited in water with high levels of CO2 had elevated rates of photosynthesis. Algal biomass was similar on all settlement panels, regardless of CO2 concentration. Much of the carbon that was fixed by algae in the high CO2 conditions was exported, likely due to detachment from the substratum. Diatoms that dominated under high CO2 conditions are more easily transported away as they have no holdfast, whereas newly settled macroalgae became firmly attached at present-day levels of CO2. These results show that ocean acidification may fundamentally alter coastal carbon cycling, increasing photosynthesis and carbon export from coastal ecosystems in warm-temperate biogeographic regions due to a shift in community composition from perennial to ephemeral algae.
Evidences on alterations in skeleton composition and mineralization in a site-attached fish under naturally acidified conditions in a shallow CO2 vent
Published 2 November 2020 Science ClosedTags: biological response, field, fish, Mediterranean, morphology, vents
Highlights
- CO2 vents provide natural laboratories to study the effects of multiple pressures (i.e., ocean acidification and metal contamination).
- The demersal and highly territorial fish species Gobius bucchichi did not show skeletal malformations in the vent site.
- Higher Ca/P in fish skeleton at the vent than at control pH sites suggests that skeleton maturation may be sped up in acidified oceans.
Abstract
Background
Ocean acidification may affect fish mineralized structures (i.e. otoliths and skeleton).
Methods
Here, we compared the elemental composition of muscle and skeleton and the mineral features of skeleton in the site-attached fish Gobius bucchichi naturally exposed to high pCO2 / low pH conditions in a shallow CO2 vent with fish of the same species exposed to normal pH.
Results
Overall, no skeleton malformations were found in both pH conditions, but among-site differences were found in the elemental composition. Interestingly, higher Ca/P values, inducing a moderate skeleton maturation, were found in fish exposed to acidified conditions than in controls.
Conclusion
Our findings suggest that ocean acidification may play a significant role in physiological processes related to mineralization, fostering skeleton pre-aging.
Continue reading ‘Evidences on alterations in skeleton composition and mineralization in a site-attached fish under naturally acidified conditions in a shallow CO2 vent’Ocean acidification impacts on zooplankton
Published 22 October 2020 Science ClosedTags: biological response, methods, review, vents, zooplankton
Rising atmospheric CO2 alters the ocean biochemistry in the process known as ocean acidification (OA). It influences biodiversity at different levels, including zooplankton, which is a key component of aquatic communities and plays a pivotal role in the structure and functioning of marine planktonic food webs as a major link between pelagic primary producers and planktivorous. The effect of OA on the fitness of individual zooplanktonic species has been reported by many studies mostly developed under laboratory conditions. In this context, this chapter reviews the OA effects on zooplankton and describes the potential of natural shallow-water CO2 vents as in situ laboratories. The impact on zooplankton assemblages is shown from a study in the North Atlantic (Azores islands) and the suitability of this area for future studies on marine organisms and ecosystems. Sites with naturally elevated CO2 conditions are described, including which variables and limitations must be considered. Results shown are highly relevant to improve our predictions of the responses of zooplankton to climate change stressors including OA. Future studies including long-term multigenerational exposure to multiple stressors (e.g. increased pCO2 and food shortage) are a priority to understand the adaptation capacity of common species and how the zooplankton communities will shift.
Continue reading ‘Ocean acidification impacts on zooplankton’
Effects of ocean acidification on acid-base physiology, skeleton properties, and metal contamination in two echinoderms from vent sites in Deception Island, Antarctica
Published 13 October 2020 Science ClosedTags: Antarctic, biological response, chemistry, echinoderms, field, morphology, otherprocess, physiology, vents
Highlights
- Acid-base characteristics of adult Antarctic echinoderms are similar to those of tropical and temperate echionderms
- Skeleton properties of both species were weaker than those of tropical and temperate echinoderms
- Reduced seawater pH and metals had no impact on the skeleton mechanical properties of the two investigated species
- Reduced pH was correlated to increased contamination by most metals but this relation was weak
Abstract
Antarctic surface waters are expected to be the first to experience severe ocean acidification (OA) with carbonate undersaturation and large decreases in pH forecasted before the end of this century. Due to the long stability in environmental conditions and the relatively low daily and seasonal variations to which they are exposed, Antarctic marine organisms, especially those with a supposedly poor machinery to eliminate CO2 and protons and with a heavily calcified skeleton like echinoderms, are hypothesized as highly vulnerable to these environmental shifts. The opportunities offered by the natural pH gradient generated by vent activities in Deception Island caldera, Western Antarctic Peninsula, were used to investigate for the first time the acid-base physiologies, the impact of OA on the skeleton and the impact of pH on metal accumulation in the Antarctic sea star Odontaster validus and sea urchin Sterechinus neumayeri. The two species were sampled in four stations within the caldera, two at pH (total scale) 8.0- 8.1 and two at reduced pH 7.8. Measured variables were pH, alkalinity, and dissolved inorganic carbon of the coelomic fluid; characteristic fracture force, stress and Young’s modulus using Weibull statistics and Cd, Cu, Fe, Pb and Zn concentrations in the integument, gonads and digestive system. Recorded acid-base characteristics of both studied species fit in the general picture deduced from temperate and tropical sea stars and sea urchins but conditions and possibly confounding factors, principally food availability and quality, in the studied stations prevented definitive conclusions. Reduced seawater pH 7.8 and metals had almost no impact on the skeleton mechanical properties of the two investigated species despite very high Cd concentrations in O. validus integument. Reduced pH was correlated to increased contamination by most metals but this relation was weak. Translocation and caging experiments taking into account food parameters are proposed to better understand future processes linked to ocean acidification and metal contamination in Antarctic echinoderms.
Continue reading ‘Effects of ocean acidification on acid-base physiology, skeleton properties, and metal contamination in two echinoderms from vent sites in Deception Island, Antarctica’Ocean acidification causes variable trait shifts in a coral species
Published 5 October 2020 Science ClosedTags: adaptation, biological response, calcification, chemistry, corals, field, growth, Mediterranean, molecular biology, morphology, otherprocess, vents
High pCO2 habitats and their populations provide an unparalleled opportunity to assess how species may survive under future ocean acidification conditions, and help to reveal the traits that confer tolerance. Here we utilize a unique CO2 vent system to study the effects of exposure to elevated pCO2 on trait‐shifts observed throughout natural populations of Astroides calycularis, an azooxanthellate scleractinian coral endemic to the Mediterranean. Unexpected shifts in skeletal and growth patterns were found. Colonies shifted to a skeletal phenotype characterized by encrusting morphology, smaller size, reduced coenosarc tissue, fewer polyps, and less porous and denser skeletons at low pH. Interestingly, while individual polyps calcified more and extended faster at low pH, whole colonies found at low pH site calcified and extended their skeleton at the same rate as did those at ambient pH sites. Transcriptomic data revealed strong genetic differentiation among local populations of this warm water species whose distribution range is currently expanding northward. We found excess differentiation in the CO2 vent population for genes central to calcification, including genes for calcium management (calmodulin, calcium‐binding proteins), pH regulation (V‐type proton ATPase), and inorganic carbon regulation (carbonic anhydrase). Combined, our results demonstrate how coral populations can persist in high pCO2 environments, making this system a powerful candidate for investigating acclimatization and local adaptation of organisms to global environmental change.
Continue reading ‘Ocean acidification causes variable trait shifts in a coral species’
