Presentation: “Climate change and ocean acidification”, INDEMER international conference, Monaco (video)

Presentation on climate change and how it relates to ocean acidification given by Dr Lydia Kapsenberg, post-doctoral researcher, National Science Foundation (USA) & Centre National de la Recherche Scientifique (France), in the framework of the international conference “Knowledge of the ocean at the service of sustainable development”, 27-28 April 2017, Monaco, co-organized by INDEMER and the Oceanographic Institute – Prince Albert the 1st Foundation.

INDEMER, via Youtube, 17 July 2017. Video.

Carbon and nitrogen allocation strategy in Posidonia oceanica is altered by seawater acidification

Rising atmospheric CO2 causes ocean acidification that represents one of the major ecological threats for marine biota. We tested the hypothesis that long-term exposure to increased CO2 level and acidification in a natural CO2 vent system alters carbon (C) and nitrogen (N) metabolism in Posidonia oceanica L. (Delile), affecting its resilience, or capability to restore the physiological homeostasis, and the nutritional quality of organic matter available for grazers. Seawater acidification decreased the C to N ratio in P. oceanica tissues and increased grazing rate, shoot density, leaf proteins and asparagine accumulation in rhizomes, while the maximum photochemical efficiency of photosystem II was unaffected. The 13C-dilution in both structural and non-structural C metabolites in the acidified site indicated quali-quantitative changes of C source and/or increased isotopic fractionation during C uptake and carboxylation associated with the higher CO2 level. The decreased C:N ratio in the acidified site suggests an increased N availability, leading to a greater storage of 15N-enriched compounds in rhizomes. The amount of the more dynamic C storage form, sucrose, decreased in rhizomes of the acidified site in response to the enhanced energy demand due to higher shoot recruitment and N compound synthesis, without affecting starch reserves. The ability to modulate the balance between stable and dynamic C reserves could represent a key ecophysiological mechanism for P. oceanica resilience under environmental perturbation. Finally, alteration in C and N dynamics promoted a positive contribution of this seagrass to the local food web.

Continue reading ‘Carbon and nitrogen allocation strategy in Posidonia oceanica is altered by seawater acidification’

Effect of ocean acidification on growth, calcification, and gene expression in the pearl oyster, Pinctada fucata

In this study, shell growth, shell microstructure, and expression levels of shell matrix protein genes (aspein, n16, and nacrein) that play a key role in the CaCO3 crystal polymorphism (calcite and aragonite) of the shell were investigated in the pearl oyster Pinctada fucata at pH 8.10, 7.70, and 7.40. We found that the shell length and total weight index did not vary significantly between oysters reared at pH 8.10 and 7.70, but was significantly lower at pH 7.40. Calcium content and shell hardness were not significantly different between pH 8.10 and 7.70, but were significantly different at pH 7.40. At pH 7.40, the shell exhibited a poorly organized nacreous microstructure, and showed an apparent loss of structural integrity in the nacreous layer. The prismatic layer appeared morphologically dissimilar from the samples at pH 8.10 and 7.70. The internal layer was corroded and had dissolved. At pH 7.40, the expression levels of nacrein, aspein, and n16 decreased on day 1, and remained low between days 2 and 42. The expression levels of these genes were significantly lower at pH 7.40 than at pH 8.10 and 7.70 during days 2–42. These results suggest that ocean acidification will have a limited impact on shell growth, calcification, and associated gene expression levels at a pH of 7.70, which is projected to be reached by the end of the century. The negative effects were found on calcification and gene expression occurred at the lowest experimental pH (7.40).

Continue reading ‘Effect of ocean acidification on growth, calcification, and gene expression in the pearl oyster, Pinctada fucata’

Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification

The rise in anthropogenic CO2 and the associated ocean acidification (OA) will change trace metal solubility and speciation, potentially altering Southern Ocean (SO) phytoplankton productivity and species composition. As iron (Fe) sources are important determinants of Fe bioavailability, we assessed the effect of Fe-laden dust versus inorganic Fe (FeCl3) enrichment under ambient and high pCO2 levels (390 and 900 μatm) in a naturally Fe-limited SO phytoplankton community. Despite similar Fe chemical speciation and net particulate organic carbon (POC) production rates, CO2-dependent species shifts were controlled by Fe sources. Final phytoplankton communities of both control and dust treatments were dominated by the same species, with an OA-dependent shift from the diatom Pseudo nitzschia prolongatoides towards the prymnesiophyte Phaeocystis antarctica. Addition of FeCl3 resulted in high abundances of Nitzschia lecointei and Chaetoceros neogracilis under ambient and high pCO2, respectively. These findings reveal that both the characterization of the phytoplankton community at the species level and the use of natural Fe sources are essential for a realistic projection of the biological carbon pump in the Fe-limited pelagic SO under OA. As dust deposition represents a more realistic scenario for the Fe-limited pelagic SO under OA, unaffected net POC production and dominance of P. antarctica can potentially weaken the export of carbon and silica in the future.

Continue reading ‘Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification’

Ocean acidification narrows the acute thermal and salinity tolerance of the Sydney rock oyster Saccostrea glomerata

Coastal and estuarine environments are characterised by acute changes in temperature and salinity. Organisms living within these environments are adapted to withstand such changes, yet near-future ocean acidification (OA) may challenge their physiological capacity to respond. We tested the impact of CO2-induced OA on the acute thermal and salinity tolerance, energy metabolism and acid-base regulation capacity of the oyster Saccostrea glomerata. Adult S. glomerata were acclimated to three CO2 levels (ambient 380 μatm, moderate 856 μatm, high 1500 μatm) for 5 weeks (24 °C, salinity 34.6) before being exposed to a series of acute temperature (15–33 °C) and salinity (34.2–20) treatments. Oysters acclimated to elevated CO2 showed a significant metabolic depression and extracellular acidosis with acute exposure to elevated temperature and reduced salinity, especially at the highest CO2 of 1500 μatm. Our results suggest that the acute thermal and salinity tolerance of S. glomerata and thus its distribution will reduce as OA continues to worsen.

Continue reading ‘Ocean acidification narrows the acute thermal and salinity tolerance of the Sydney rock oyster Saccostrea glomerata’

Acidification des oceans: Une menace que le Sénégal se doit d’étudier, de comprendre, et d’anticiper (in French)

La surpêche dans les eaux du Sénégal a reçu beaucoup d’attention, mais des menaces tout aussi importantes pèsent également sur les ressources marines dont les effets pervers peuvent s’avérer irréversibles pour nos sociétés. L’acidification des océans et les autres problèmes liés au dioxyde de carbone (CO2) représentent en effet un risque pour la biodiversité marine, les écosystèmes et la société humaine que le Sénégal se doit de bien prendre en compte pour une gestion durable de ses eaux marines.

L’augmentation des concentrations du CO2 atmosphérique liée aux activités humaines telles que la combustion des énergies fossiles a conduit à l’acidification d’environ 30 % des eaux océaniques de surface par rapport à l’époque préindustrielle. Les modifications chimiques induites par l’augmentation du CO2 dissous dans l’eau réduisent la disponibilité des composés chimiques essentiels à la formation des coquilles et des squelettes calcaires des organismes marins, notamment ceux des mollusques, des crustacés et des coraux.  La réduction de l’oxygène dissous et le réchauffement des océans sont deux facteurs importants également liés au CO2.

Continue reading ‘Acidification des oceans: Une menace que le Sénégal se doit d’étudier, de comprendre, et d’anticiper (in French)’

All aboard the carbon cruise

University of Miami students and researchers are blogging during a month-long expedition in the Gulf of Mexico to study ocean acidification.

An interdisciplinary and international team of scientists and students set sail aboard the NOAA (National Oceanic and Atmospheric Administration) ship Ronald H. Brown on Tuesday, July 18 for a 36-day expedition in the Gulf of Mexico.

The researchers – including graduate student Joletta Silva and two recent alumni, Emma Pontes and Leah Chomiak, from the University of Miami Rosenstiel School of Marine and Atmospheric Science – represent institutions from the United States, Mexico and Cuba.

The expedition, entitled the Gulf of Mexico Ecosystems and Carbon Cruise (GOMECC), is the third of such research cruises led by NOAA AOML (Atlantic Oceanographic and Meteorological Laboratory) for its Ocean Acidification Program to better understand how ocean chemistry along U.S. coasts is changing in response to ocean acidification. This cruise is the first that will explore Mexican waters of the Gulf of Mexico, and is considered to be the most comprehensive ocean acidification cruise to date in the region.

Continue reading ‘All aboard the carbon cruise’


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Ocean acidification in the IPCC AR5 WG II

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