Posts Tagged 'vents'

Changes in the metabolic potential of the sponge microbiome under ocean acidification

Anthropogenic CO2 emissions are causing ocean acidification, which can affect the physiology of marine organisms. Here we assess the possible effects of ocean acidification on the metabolic potential of sponge symbionts, inferred by metagenomic analyses of the microbiomes of two sponge species sampled at a shallow volcanic CO2 seep and a nearby control reef. When comparing microbial functions between the seep and control sites, the microbiome of the sponge Stylissa flabelliformis (which is more abundant at the control site) exhibits at the seep reduced potential for uptake of exogenous carbohydrates and amino acids, and for degradation of host-derived creatine, creatinine and taurine. The microbiome of Coelocarteria singaporensis (which is more abundant at the seep) exhibits reduced potential for carbohydrate import at the seep, but greater capacity for archaeal carbon fixation via the 3-hydroxypropionate/4-hydroxybutyrate pathway, as well as archaeal and bacterial urea production and ammonia assimilation from arginine and creatine catabolism. Together these metabolic features might contribute to enhanced tolerance of the sponge symbionts, and possibly their host, to ocean acidification.

Continue reading ‘Changes in the metabolic potential of the sponge microbiome under ocean acidification’

Effects of long-term exposure to reduced pH conditions on the shell and survival of an intertidal gastropod

Highlights

• Prolonged exposures to high pCO2 can severely affect Phorcus sauciatus shell.

• No effects of high pCO2 were found on size-frequency or population density of P. sauciatus.

• Shells from reduced pH sites exhibited a higher shell aspect ratio and greater percentages of shell dissolution and break.

• Shells from high pCO2 areas exhibited changes in mechanical strength.

• Similar desiccation tolerance was found among contrasting environment populations.

Abstract

Volcanic CO2 vents are useful environments for investigating the biological responses of marine organisms to changing ocean conditions (Ocean acidification, OA). Marine shelled molluscs are highly sensitive to changes in seawater carbonate chemistry. In this study, we investigated the effects of reduced pH on the intertidal gastropod, Phorcus sauciatus, in a volcanic CO2 vent off La Palma Island (Canary Islands, North East Atlantic Ocean), a location with a natural pH gradient ranging from 7.0 to 8.2 over the tidal cycles. Density and size-frequency distribution, shell morphology, shell integrity, fracture resistance, and desiccation tolerance were evaluated between populations from control and CO2 vent sites. We found no effects of reduced pH on population parameters or desiccation tolerance across the pH gradient, but significant differences in shell morphology, shell integrity, and fracture resistance were detected. Individuals from the CO2 vent site exhibited a higher shell aspect ratio, greater percentages of shell dissolution and break, and compromised shell strength than those from the control site. Our results highlight that long-term exposure to high pCO2 can negatively affect the shell features of P. sauciatus but may not have a significant effect on population performance. Moreover, we suggest that loss of shell properties could lead to changes in predator-prey interactions.

Continue reading ‘Effects of long-term exposure to reduced pH conditions on the shell and survival of an intertidal gastropod’

Geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the Kermadec intraoceanic arc

During the R/V Sonne cruise SO253 in 2016/2017, hydrothermal vent sites along the Kermadec intraoceanic arc were sampled for hydrothermal fluids at four active volcanoes: Macauley, Haungaroa, Brothers and Rumble III, respectively. Water depths ranged between 290 m and 1700 m. A new vent field was discovered at Haungaroa. The samples were taken from diffuse-flow sites as well as from white and black smokers – rich in metals and gases – with discharge temperatures as high as 311 °C. Their fluid composition is very variable but basically divides into two types: one that indicates distinct magmatic input and another that shows evidence for intense water-rock interaction under hot, acidic conditions.

Fluid samples from Macauley, the shallowest sampling site (~300 m), had Fe concentrations as high as 1.7 mM, Al concentrations up to 122 μM and H2S up to 10 mM at a pH of only 1.2. At Brothers, the deepest sampling site (down to 1600 m), we identified two different fluid types: 1) A magmatically-influenced type at the Upper and Lower Cone with highest temperatures of 115 °C, up to 95.6 mM Mg (the highest Mg concentration measured in fluids from intraoceanic arc systems so far), elevated SO42− (76.9 mM), high H2S (5.0 mM), but Fe concentrations of only 15 μM and 2) A fluid with low Mg (5.4 mM), low H2S (1.1 mM), temperatures reaching 311 °C and high Fe contents (12.4 mM) at the Upper Caldera and NW Caldera Wall, typical of a black smoker fluid. Chloride concentrations in all fluids were similar, or highly enriched when compared to seawater (e.g. up to 787 mM, brine fluids), with also one low-chlorinity vapor-phase fluid sample recovered, indicating that phase separation is occurring at Brothers. Unusual highly elevated Mg concentrations in fluids from the Brothers Lower Cone (95.6 mM, compared to 53.2 mM in ambient seawater) combined with highly elevated concentrations of SO42− (76.9 mM, compared to 29.0 mM in ambient seawater) indicate dissolution of Mg- and SO42−-bearing minerals in the subsurface, such as caminite.

Our data show how highly diverse and variable island arc systems can be with respect to their fluid chemistry, both spatially and temporally. It adds to the still limited data set of arc systems compared to mid-ocean ridges and supplies an important contribution towards a better understanding of geochemical processes along arc volcanoes.

The higher range in fluid chemistry together with shallower water depth implies that the fluids from intraoceanic arcs may contribute a significant fraction of dissolved metals not only to the global oceanic biogeochemical cycle but also into the photic zone, the area of highest bioproductivity.

Continue reading ‘Geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the Kermadec intraoceanic arc’

Ocean acidification impact on ascidian Ciona robusta spermatozoa: new evidence for stress resilience

Highlights

• Impact of ocean acidification on sperm quality of the ascidian Ciona robusta was investigated.

• Two experimental approaches were set up to simulate the ocean conditions predicted for the end of this century.

• Alteration of sperm motility, morphology and physiology was detected in short-term exposure.

• A rapid recovery of physiological conditions was observed within one week.

• New evidence of resilience in ascidian C. robusta spermatozoa in response to ocean acidification.

Abstract

Rising atmospheric CO2 is causing a progressive decrease of seawater pH, termed ocean acidification. Predicting its impact on marine invertebrate reproduction is essential to anticipate the consequences of future climate change on species fitness and survival. Ocean acidification may affect reproductive success either in terms of gamete or progeny quality threating species survival. Despite an increasing number of studies focusing on the effects of ocean acidification on the early life history of marine organisms, very few have investigated the effects on invertebrate gamete quality. In this study, we set up two experimental approaches simulating the ocean conditions predicted for the end of this century, in situ transplant experiments at a naturally acidified volcanic vent area along the Ischia island coast and microcosm experiments, to evaluate the short-term effects of the predicted near-future levels of ocean acidification on sperm quality of the ascidian Ciona robusta after parental exposure. In the first days of exposure to acidified conditions, we detected alteration of sperm motility, morphology and physiology, followed by a rapid recovery of physiological conditions that provide a new evidence of resilience of ascidian spermatozoa in response to ocean acidification. Overall, the short-term tolerance to adverse conditions opens a new scenario on the marine species capacity to continue to reproduce and persist in changing oceans.

Continue reading ‘Ocean acidification impact on ascidian Ciona robusta spermatozoa: new evidence for stress resilience’

Simulating and quantifying multiple natural subsea CO2 seeps at Panarea Island (Aeolian Islands, Italy) as a proxy for potential leakage from subseabed carbon storage sites

Carbon dioxide (CO2) capture and storage (CCS) has been discussed as a potentially significant mitigation option for the ongoing climate warming. Natural CO2 release sites serve as natural laboratories to study subsea CO2 leakage in order to identify suitable analytical methods and numerical models to develop best-practice procedures for the monitoring of subseabed storage sites. We present a new model of bubble (plume) dynamics, advection-dispersion of dissolved CO2, and carbonate chemistry. The focus is on a medium-sized CO2 release from 294 identified small point sources around Panarea Island (South-East Tyrrhenian Sea, Aeolian Islands, Italy) in water depths of about 40–50 m. This study evaluates how multiple CO2 seep sites generate a temporally variable plume of dissolved CO2. The model also allows the overall flow rate of CO2 to be estimated based on field measurements of pH. Simulations indicate a release of ∼6900 t y–1 of CO2 for the investigated area and highlight an important role of seeps located at >20 m water depth in the carbon budget of the Panarea offshore gas release system. This new transport-reaction model provides a framework for understanding potential future leaks from CO2 storage sites.

Continue reading ‘Simulating and quantifying multiple natural subsea CO2 seeps at Panarea Island (Aeolian Islands, Italy) as a proxy for potential leakage from subseabed carbon storage sites’

High pCO2 promotes coral primary production

While research on ocean acidification (OA) impacts on coral reefs has focused on calcification, relatively little is known about effects on coral photosynthesis and respiration, despite these being among the most plastic metabolic processes corals may use to acclimatize to adverse conditions. Here, we present data collected between 2016 and 2018 at three natural CO2 seeps in Papua New Guinea where we measured the metabolic flexibility (i.e. in hospite photosynthesis and dark respiration) of 12 coral species. Despite some species-specific variability, metabolic rates as measured by net oxygen flux tended to be higher at high pCO2 (ca 1200 µatm), with increases in photosynthesis exceeding those of respiration, suggesting greater productivity of Symbiodiniaceae photosynthesis in hospite, and indicating the potential for metabolic flexibility that may enable these species to thrive in environments with high pCO2. However, laboratory and field observations of coral mortality under high CO2 conditions associated with coral bleaching suggests that this metabolic subsidy does not result in coral higher resistance to extreme thermal stress. Therefore, the combined effects of OA and global warming may lead to a strong decrease in coral diversity despite the stimulating effect on coral productivity of OA alone.

Continue reading ‘High pCO2 promotes coral primary production’

Ocean acidification alters meiobenthic assemblage composition and organic matter degradation rates in seagrass sediments

Seagrass meadows are an important organic matter (OM) reservoir but, are currently being lost due to global and regional stressors. Yet, there is limited research investigating the cumulative impacts of anthropogenic stressors on the structure and functioning of seagrass benthic assemblages, key drivers of OM mineralization and burial. Here, using a 16‐month field experiment, we assessed how meiobenthic assemblages and extracellular enzymatic activities (as a proxy of OM degradation) in Posidonia oceanica sediments responded to ocean acidification (OA) and nutrient loadings, at CO2 vents. P. oceanica meadows were exposed to three nutrient levels (control, moderate, and high) at both ambient and low pH sites. OA altered meiobenthic assemblage structure, resulting in increased abundance of annelids and crustaceans, along with a decline in foraminifera. In addition, low pH enhanced OM degradation rates in seagrass sediments by enhancing extracellular enzymatic activities, potentially decreasing the sediment carbon storage capacity of seagrasses. Nutrient enrichment had no effect on the response variables analyzed, suggesting that, under nutrient concentration unlikely to cause N or P imitation, a moderate increase of dissolved nutrients in the water column had limited influence on meiobenthic assemblages. These findings show that OA can significantly alter meiobenthic assemblage structure and enhance OM degradation rates in seagrass sediments. As meiofauna are ubiquitous key actors in the functioning of benthic ecosystems, we postulated that OA, altering the structure of meiobenthic assemblages and OM degradation, could affect organic carbon sequestration over large spatial scales.

Continue reading ‘Ocean acidification alters meiobenthic assemblage composition and organic matter degradation rates in seagrass sediments’


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Ocean acidification in the IPCC AR5 WG II

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