Search results for " carbonate"
showing 10 items of 381 documents
Physiological advantages of dwarfing in surviving extinctions in high-CO2 oceans
2015
Excessive CO2 in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future, mirroring effects in many past mass extinctions. Fossil records demonstrate that organisms surviving such events were often smaller than those before, a phenomenon called the Lilliput effect. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partial…
Seawater carbonate chemistry and kelp densities and coral coverages at three study locations and photosynthesis and calcification of corals measured …
2021
Ocean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed “tropicalization”. A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral-dominated systems…
Seagrass ecosystem response to long-term high CO2 in a Mediterranean volcanic vent
2014
We examined the long-term effect of naturally acidified water on a Cymodocea nodosa meadow growing at a shallow volcanic CO2 vent in Vulcano Island (Italy). Seagrass and adjacent unvegetated habitats growing at a low pH station (pH = 7.65 ± 0.02) were compared with corresponding habitats at a control station (pH = 8.01 ± 0.01). Density and biomass showed a clear decreasing trend at the low pH station and the below- to above-ground biomass ratio was more than 10 times lower compared to the control. C content and delta 13C of leaves and epiphytes were significantly lower at the low pH station. Photosynthetic activity of C. nodosa was stimulated by low pH as seen by the significant increase in…
Seawater carbonate chemistry and coralline algal diversity
2021
Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and …
On the reactivity of 3-bromo-2-nitrobenzo[ b ]thiophene with nucleophiles: elucidation of the base-catalysed mechanism with rearrangement
2001
Abstract The reactivity of 3-bromo-2-nitrobenzo[b]thiophene (1) with several (anionic and neutral) nucleophiles has been examined. Only with neutral, weak nucleophiles (as anilines) 1 gives, in the presence of non-nucleophilic bases (triethylamine or potassium carbonate), together with the ‘expected’ 3-amino-2-nitrobenzo[b]thiophenes (3) also the ‘unexpected’ 2-amino-3-nitrobenzo[b]thiophenes (4). The composition of the final isomeric mixture depends on the base added (nature and quantity) and on the solvent used. The results demonstrate the relevance of base-catalysis and support a reaction pathway involving the formation of an anionic intermediate (B) which undergoes addition of a second …
Di-n-butyltin oxide as a chemical carbon dioxide capturer
2010
Abstract Several synthetic routes to the decakis(di-n-butyltin(IV)) oxocluster, (n-Bu2SnO)6[(n-Bu2SnOCH3)2(CO3)]2 (1), a diorganotin compound previously shown to belong to the class of organotins able to store carbon dioxide, as well as its reactivity toward dimethyl carbonate (DMC), are described. The synthetic route from n-Bu2SnO and DMC was applied for the preparation of the ethoxy analogue of 1, oxocluster 2, using diethyl carbonate. The structural relationship connecting cluster 1, with its precursor PRE-1 isolated from recycling experiments and n-Bu2SnO is discussed. For this purpose, the reactivity of PRE-1 with trifluoromethanesulfonic acid was investigated in order to trace structu…
High-pressure NMR spectroscopy: An in situ tool to study tin-catalyzed synthesis of organic carbonates from carbon dioxide and alcohols. Part 2 [1]
2015
Dialkoxide diorganotin(IV) complexes are known to readily react with carbon dioxide under pressure and they are considered as suitable catalyst precursor models for the direct synthesis of organic carbonates. To gain a better understanding of CO2 insertion processes with Sn-OR bonds, the reactivity of n-Bu2Sn(OCH(CH3)(2))(2) (2) was investigated using high-pressure NMR (HP-NMR) spectroscopy. In deuterated solvents (isopropanol-d(8) and toluene-d(8)) under 50 bar of CO2 pressure at 80 degrees C, Sn-119{H-1} NMR experiments revealed the exclusive formation of an unprecedented tetraorganodistannoxane species, characterized as the bis[diisopropycarbonatotetrabutyldistannoxane] complex, {[n-Bu2S…
Strong stabilization of amorphous calcium carbonate emulsion by ovalbumin: gaining insight into the mechanism of 'polymer-induced liquid precursor' p…
2011
8 pages; International audience; The impact of the ovo proteins ovalbumin and lysozyme-present in the first stage of egg shell formation-on the homogeneous formation of the liquid amorphous calcium carbonate (LACC) precursor, was studied by a combination of complementing methods: in situ WAXS, SANS, XANES, TEM, and immunogold labeling. Lysozyme (pI = 9.3) destabilizes the LACC emulsion whereas the glycoprotein ovalbumin (pI = 4.7) extends the lifespan of the emulsified state remarkably. In the light of the presented data: (a) Ovalbumin is shown to behave commensurable to the 'polymer-induced liquid precursor' (PILP) process proposed by Gower et al. Ovalbumin can be assumed to take a key rol…
Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs
2015
International audience; Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermo-physiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endo-therms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but B6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to mod…