Posts Tagged 'vents'

Evidences on alterations in skeleton composition and mineralization in a site-attached fish under naturally acidified conditions in a shallow CO2 vent

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

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

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

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’

Ervilia castanea (Mollusca, Bivalvia) populations adversely affected at CO2 seeps in the North Atlantic

Highlights

  • The bivalve Ervilia castanea was studied at volcanic CO2 seeps and reference sites.
  • Abundance, size and net-calcification were inversely related to CO2 levels.
  • Large individuals were scarce or absent at high CO2 sites.
  • Recruitment of this bivalve was highest at the CO2 seeps.
  • Abundance and size of E. castanea were positively correlated with Chl-a in sediment.

Abstract

Sites with naturally high CO2 conditions provide unique opportunities to forecast the vulnerability of coastal ecosystems to ocean acidification, by studying the biological responses and potential adaptations to this increased environmental variability. In this study, we investigated the bivalve Ervilia castanea in coastal sandy sediments at reference sites and at volcanic CO2 seeps off the Azores, where the pH of bottom waters ranged from average oceanic levels of 8.2, along gradients, down to 6.81, in carbonated seawater at the seeps. The bivalve population structure changed markedly at the seeps. Large individuals became less abundant as seawater CO2 levels rose and were completely absent from the most acidified sites. In contrast, small bivalves were most abundant at the CO2 seeps. We propose that larvae can settle and initially live in high abundances under elevated CO2 levels, but that high rates of post-settlement dispersal and/or mortality occur. Ervilia castanea were susceptible to elevated CO2 levels and these effects were consistently associated with lower food supplies. This raises concerns about the effects of ocean acidification on the brood stock of this species and other bivalve molluscs with similar life history traits.

Continue reading ‘Ervilia castanea (Mollusca, Bivalvia) populations adversely affected at CO2 seeps in the North Atlantic’

Ervilia castanea (Mollusca, Bivalvia) populations adversely affected at CO2 seeps in the North Atlantic

Highlights

  • The bivalve Ervilia castanea was studied at volcanic CO2 seeps and reference sites.
  • Abundance, size and net-calcification were inversely related to CO2 levels.
  • Large individuals were scarce or absent at high CO2 sites.
  • Recruitment of this bivalve was highest at the CO2 seeps.
  • Abundance and size of E. castanea were positively correlated with Chl-a in sediment.

 

Abstract

Sites with naturally high CO2 conditions provide unique opportunities to forecast the vulnerability of coastal ecosystems to ocean acidification, by studying the biological responses and potential adaptations to this increased environmental variability. In this study, we investigated the bivalve Ervilia castanea in coastal sandy sediments at reference sites and at volcanic CO2 seeps off the Azores, where the pH of bottom waters ranged from average oceanic levels of 8.2, along gradients, down to 6.81, in carbonated seawater at the seeps. The bivalve population structure changed markedly at the seeps. Large individuals became less abundant as seawater CO2 levels rose and were completely absent from the most acidified sites. In contrast, small bivalves were most abundant at the CO2 seeps. We propose that larvae can settle and initially live in high abundances under elevated CO2 levels, but that high rates of post-settlement dispersal and/or mortality occur. Ervilia castanea were susceptible to elevated CO2 levels and these effects were consistently associated to lower food supplies. This raises concerns about the effects of ocean acidification on the brood stock of this species and other bivalve molluscs of similar life history traits.

 

Continue reading ‘Ervilia castanea (Mollusca, Bivalvia) populations adversely affected at CO2 seeps in the North Atlantic’

Calcifiers can adjust shell building at the nanoscale to resist ocean acidification

Ocean acidification is considered detrimental to marine calcifiers based on laboratory studies showing that increased seawater acidity weakens their ability to build calcareous shells needed for growth and protection. In the natural environment, however, the effects of ocean acidification are subject to ecological and evolutionary processes that may allow calcifiers to buffer or reverse these short‐term negative effects through adaptive mechanisms. Using marine snails inhabiting a naturally CO2‐enriched environment over multiple generations, it is discovered herein that they build more durable shells (i.e., mechanically more resilient) by adjusting the building blocks of their shells (i.e., calcium carbonate crystals), such as atomic rearrangement to reduce nanotwin thickness and increased incorporation of organic matter. However, these adaptive adjustments to future levels of ocean acidification (year 2100) are eroded at extreme CO2 concentrations, leading to construction of more fragile shells. The discovery of adaptive mechanisms of shell building at the nanoscale provides a new perspective on why some calcifiers may thrive and others collapse in acidifying oceans, and highlights the inherent adaptability that some species possess in adjusting to human‐caused environmental change.

Continue reading ‘Calcifiers can adjust shell building at the nanoscale to resist ocean acidification’

Chemical characterization of Punta de Fuencaliente CO2 seeps system (La Palma Island, NE Atlantic Ocean): a new natural laboratory for ocean acidification studies

We present a new natural carbon dioxide (CO2) system located off the southern coast of La Palma Island (Canary Islands, Spain). Like others CO2 seeps, these seeps can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present an accurate chemical characterization of the seeps system carbon emissions, describing the carbon system dynamics, by measuring pH, AT and CT, as well as, Ω aragonite and calcite. Our explorations on the area have found several emission points with similar chemical features. Here, the CO2 emission flux varies between 2.8 kg CO2 d−1 to 28 kg CO2 d−1, becoming a significant source of carbon. CO2 seeps are of volcanic origin and the alteration of local ocean chemistry is due to acid brackish water discharges. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma island is an exceptional spot to perform studies aimed to understand the effect of different levels of OA on the functioning of marine ecosystems. These studies can then be used to comprehend how life has persisted through past Eras, with higher atmospheric CO2, or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.

Continue reading ‘Chemical characterization of Punta de Fuencaliente CO2 seeps system (La Palma Island, NE Atlantic Ocean): a new natural laboratory for ocean acidification studies’

Long-term effects of elevated CO2 on the population dynamics of the seagrass Cymodocea Nodosa: evidence from volcanic seeps

We used population reconstruction techniques to assess for the first time the population dynamics of a seagrass, Cymodocea nodosa, exposed to long-term elevated CO2 near three volcanic seeps and compare them with reference sites away from the seeps. Under high CO2, the density of shoots and of individuals (apical shoots), and the vertical and horizontal elongation and production rates, were higher. Nitrogen effects on rhizome elongation and production rates and on biomass, were stronger than CO2 as these were highest at the location where the availability of nitrogen was highest. At the seep where the availability of CO2 was highest and nitrogen lowest, density of shoots and individuals were highest, probably due to CO2 effects on shoot differentiation and induced reproductive output, respectively. In all three seeps there was higher short- and long-term recruitment and growth rates around zero, indicating that elevated CO2 increases the turnover of C. nodosa shoots.

Continue reading ‘Long-term effects of elevated CO2 on the population dynamics of the seagrass Cymodocea Nodosa: evidence from volcanic seeps’

Long-term response of Dictyota dichotoma var. intricata (C. Agardh) Greville (Phaeophyceae) to ocean acidification: Insights from high pCO2 vents

Highlights

•We observed a reduced abundance and individual size of Dictyota at 8.1 compared to pH 6.7

•The photochemical efficiency differs between the two populations of Dictyota, living at two different pH for decades

•Individuals at low pH (6.7) have lower photochemical efficiency, low energetic costs but a higher capability to face the oxidative stress

•The saved energy may be invested in growth and reproduction, ensuring the biological success under ocean acidification

•First physiological plasticity and, then the adaptive response may be at base of short- and long-term response of Dictyota

Abstract

The ocean acidification may severely affect macroalgal communities of the shallowest coastal habitats where they play relevant structural and functional roles. In this paper were investigated the physiological traits of two populations of Dictyota dichotoma var. intricata, living at two different pH for several generations to assess the reasons of the algae reduced abundance at current (8.1) compared to low pH (6.7). Besides, through transplant experiments, the two populations were analysed for the stress response and reversibility of physiological performance at different pH. The long-term acclimation to high pCO2/low pH favours an ecotype characterised by low energetic costs, higher photochemical efficiency and more resistance to the oxidative stress, compared to individuals living at current pH. These traits promoted the growth and reproduction of the community living at pH 6.7, favouring a lower macroalgal diversity, but a higher ecological success under ocean acidification. The similar behaviour observed between Dictyota living at pH 6.7 and transplanted thalli from pH 6.7 to 8.1, suggested a high tolerance to pH changes in the short-term. On the contrary, adaptive responses may have favoured molecular adjustments on the long-term, as showed by the significant differences between the wild populations at pH 8.1 and 6.7. The overall data indicate that both plasticity and adaptive mechanisms may be the reasons for the success of the brown seaweeds under future high pCO2/low pH. The plasticity due to photochemistry adjustments is likely involved in the early response to environmental changes. Conversely, modifications in the photosynthetic biochemical machinery suggest that more complex adaptive mechanisms occurred in the current population of Dictyota living at pH 6.7. Further studies on population genetics will reveal if any differentiation is taking place at the population level or a local adaptation has already occurred in Dictyota and other brown algae under chronic low pH.

Continue reading ‘Long-term response of Dictyota dichotoma var. intricata (C. Agardh) Greville (Phaeophyceae) to ocean acidification: Insights from high pCO2 vents’


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