Missions CARIOCA – Papouasie-Nouvelle-Guinée – Acclimatation des coraux à l’acidification des océans (in French)

Une équipe internationale pilotée par l’IRD embarque à bord de l’Alis pour étudier en Papouasie-Nouvelle-Guinée des espèces de coraux capables de se développer dans des sites naturellement plus acides. Objectif : en savoir plus sur leur capacité d’acclimatation et d’adaptation aux conditions prévues d’ici la fin du siècle dans le cadre du changement climatique.
En péril… Plus de la moitié des récifs coralliens dans le monde sont menacés de disparition par le changement climatique. Outre l’élévation de la température,  l’augmentation dans l’atmosphère du dioxyde de carbone CO2, engendre une plus grande absorption de ce gaz par l’océan. Environ 800 kg de CO2 sont ainsi dissous dans les mers et océans de la planète par seconde. Sans ce puits de carbone, l’effet de serre sur la Terre serait encore plus important. Mais l’augmentation de ce phénomène provoque une acidification de l’océan et perturbe la biologie des organismes marins. Pour les coraux bâtisseurs de récifs, ceci se traduit par une plus grande difficulté à construire leur squelette calcaire et par une  augmentation de sa dissolution. Or les récifs coralliens hébergent un tiers de la biodiversité marine et fournissent des biens et des services écosystémiques à plus de 500 millions de personnes dans le monde.

Continue reading ‘Missions CARIOCA – Papouasie-Nouvelle-Guinée – Acclimatation des coraux à l’acidification des océans (in French)’

A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum

Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures pCO2 and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO2 for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO2 exposure, photosynthesis increased with CO2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO2, such as temperature, irradiance and nutrients.

Continue reading ‘A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum’

Ocean Acidification “State of the Science” Workshop, 30 November – 1 December 2016, Anchorage, Alaska

Date and time: November 30, 2016 9:00 AM – December 1, 2016 6:00 PM (AKST)

Location: Anchorage Downtown Marriott

Registration: This workshop is free and open to the public. Please register by November 7.

The Alaska Ocean Acidification Network is hosting a TWO-day workshop in Anchorage, inviting a broad audience across the state interested in ocean acidification issues.

There will be opportunities for remote participation at satellite viewing sites and via personal computer.

Workshop goals include educating the broader Alaska community on the processes and consequences of OA, creating connections between researchers and stakeholders, and developing new ideas and partnerships to enhance monitoring and community engagement. A report on the state of the science in Alaska will be produced after the workshop, as well as a set of recommendations to help guide the Alaska OA Network.

Continue reading ‘Ocean Acidification “State of the Science” Workshop, 30 November – 1 December 2016, Anchorage, Alaska’

Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean) (update)

The Rhône River is the largest source of terrestrial organic and inorganic carbon for the Mediterranean Sea. A large fraction of this terrestrial carbon is either buried or mineralized in the sediments close to the river mouth. This mineralization follows aerobic and anaerobic pathways, with a range of impacts on calcium carbonate precipitation and dissolution in the sediment near the sediment–water interface. This study focuses on the production of dissolved inorganic carbon (DIC) and total alkalinity (TA) by early diagenesis, consequential pH variations and the effect on calcium carbonate precipitation or dissolution. The sediment porewater chemistry was investigated along a transect from the Rhône River outlet to the continental shelf. TA and concentrations of DIC, SO42− and Ca2+ were analyzed on bottom waters and extracted sediment porewaters, whereas pH and oxygen concentrations were measured in situ using microelectrodes. The average oxygen penetration depth into the sediment was 1.7 ± 0.4 mm close to the river mouth and 8.2 ± 2.6  mm in the continental shelf sediments, indicating intense respiration rates. Diffusive oxygen fluxes through the sediment–water interface ranged between 3 and 13 mmol O2 m−2 d−1. In the first 30 cm of the sediment, TA and DIC porewater concentrations increased with depth up to 48 mmol L−1 near the river outlet and up to 7 mmol L−1 on the shelf as a result of aerobic and anaerobic mineralization processes. Due to aerobic processes, at all stations pH decreased by 0.6 pH units in the oxic layer of the sediment accompanied by a decrease of the saturation state regarding calcium carbonate. In the anoxic layer of the sediments, sulfate reduction was the dominant mineralization process and was associated with an increase of porewater saturation state regarding calcium carbonate. Ultimately anoxic mineralization of organic matter caused calcium carbonate precipitation demonstrated by a large decrease in Ca2+ concentration with depth in the sediment. Carbonate precipitation decreased in the offshore direction, together with the carbon turnover and sulfate consumption in the sediments. The large production of porewater alkalinity characterizes these sediments as an alkalinity source to the water column, which may increase the CO2 buffering capacity of these coastal waters. Estuarine sediments should therefore receive more attention in future estimations of global carbon fluxes.

Continue reading ‘Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean) (update)’

Benthic foraminiferal shell weight: Deglacial species-specific responses from the Santa Barbara Basin

Here we present a record of size-normalized shell weight for four species of benthic foraminifera through a period of rapid environmental change during the most recent deglaciation (Santa Barbara Basin, CA). A strong Oxygen Minimum Zone (OMZ), the product of high surface productivity and poor ventilation, characterizes the eastern Pacific; this subsurface zone is mechanistically coupled with high concentrations of dissolved inorganic carbon. The OMZ migrated vertically during warming of the last deglaciation, leading to rapid shifts in the oxygenation and inorganic carbon system of the benthos. The size-normalized weight (SNW) of benthic foraminifers Uvigerina peregrina, Bolivina interjuncta, and Bolivina tumida reflects only the broad trends of the vertical migration of the OMZ, and inorganic carbon system, overshadowed by clear species-specific trends. The relative importance of OMZ migrations versus other environmental variables and optimal growth conditions differs across species of benthic foraminifera. In U. peregrina, SNW primarily peaks with foraminiferal density and increased abundance of that species, while B. interjuncta and B. tumida increase in SNW with a shrinking of the OMZ (and carbon maximum) in the late Holocene. Bolivina argentea shows no long-term trends in SNW potentially due to its ability to migrate through the sediment. Our results suggest that, while inorganic carbon and dissolved oxygen may play a role in determining shell weight across species of benthic foraminifera, neither parameter alone is responsible for changes in benthic foraminiferal shell weight in the fossil record.

Continue reading ‘Benthic foraminiferal shell weight: Deglacial species-specific responses from the Santa Barbara Basin’

Sea food industry faces threat from ocean acidification, rising temperatures: Study

Researchers observed that ocean acidification could threaten lobsters and also affect the behavior and size of the larva.

Rise in the water temperatures of Gulf of Maine within a century can be threatening for lobsters and the sea food industry, according to the latest research conducted by the University of Maine Darling Marine Center and Bigelow Laboratory for Ocean Sciences. The study got published in the ICES Journal of Marine Science on September 21, 2016.

This study focuses on the impact of ocean acidification and rise of temperature on the larvae of the American lobster.

Ocean acidification is an outcome of climate change, which leads to the entry of more carbon dioxide in our environment while turning the oceans more acidic.

This study revealed that the survival of young lobsters was not affected by ocean acidification, but the lobster larvae reared by the researchers in water with 3 degree higher temperature, which will be similar to that of the temperature in the Gulf of Maine by the year 2100, were found to struggle.

Continue reading ‘Sea food industry faces threat from ocean acidification, rising temperatures: Study’

Biogeographic variability in the physiological response of the cold-water coral Lophelia pertusa to ocean acidification

While ocean acidification is a global issue, the severity of ecosystem effects is likely to vary considerably at regional scales. The lack of understanding of how biogeographically separated populations will respond to acidification hampers our ability to predict the future of vital ecosystems. Cold-water corals are important drivers of biodiversity in ocean basins across the world and are considered one of the most vulnerable ecosystems to ocean acidification. We tested the short-term physiological response of the cold-water coral Lophelia pertusa to three pH treatments (pH = 7.9, 7.75 and 7.6) for Gulf of Mexico (USA) and Tisler Reef (Norway) populations, and found that reductions in seawater pH elicited contrasting responses. Gulf of Mexico corals exhibited reductions in net calcification, respiration and prey capture rates with decreasing pH. In contrast, Tisler Reef corals showed only slight reductions in net calcification rates under decreased pH conditions while significantly elevating respiration and capture rates. These differences are likely the result of environmental differences (depth, pH, food supply) between the two regions, invoking the potential for local adaptation or acclimatization to alter their response to global change. However, it is also possible that variations in the methodology used in the experiments contributed to the observed differences. Regardless, these results provide insights into the resilience of L. pertusa to ocean acidification as well as the potential influence of regional differences on the viability of species in future oceans.

Continue reading ‘Biogeographic variability in the physiological response of the cold-water coral Lophelia pertusa to ocean acidification’

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Ocean acidification in the IPCC AR5 WG II

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