Tag Archives: ocean acidification

Ocean acidification is a myth

“The phrase “ocean acidification” was literally invented out of thin air in 2003 by Ken Colder to enable liberal arts majors to sound sciencey when scaring the bejesus out of the scientifically illiterate masses. The geochemical process has been well-understood for about 100 years… But didn’t get a crisis-monger nickname until 2003.” click here

The Great Barrier Reef adapts to ecosystem changes

“The Great Barrier Reef spans 2,000 kilometers and five degrees Celsius from 27 to 32°C and we’re still finding reefs we didn’t even know about. The pH swings on a daily basis, and fish do better when it does. One coral has adapted to ocean “acidification” in 6 months. Other fish remarkably adapted from salt to freshwater in just fifty years. As Peter Ridd says: Of all the ecosystems in the world, the reef is one that’s best at adapting to climate change.click here

Impact of CO2 on ocean chemistry

“The pH value higher than 7 allows seawater to dissolve and react huge amounts of CO2 , carbon dioxide, thus affecting the amount of this gas in the atmosphere by absorbing excess of it. To calculate this excess in respect to what would be the true equilibrium value in the air, all of the chemical reactions involved have to be simultaneously computed, accounting for their equilibrium constants, which in turn depend on temperature.” click here

Rising CO2 is coincident with less, not more ocean acidification

“A modest long-term (1800s-present) declining trend in ocean pH values predominantly occurred prior to 1930, or before anthropogenic CO2 emissions began rising precipitously. Since 1930, seawater pH trends have risen slightly, meaning sharply rising CO2 has been coincident with less, not more, ocean “acidification”.” click here

Great Barrier Reef corals can withstand pH variations

McCulloch M.T. et al. (2018) Boron Isotopic Systematics in Scleractinian Corals and the Role of pH Up-regulation. In: Marschall H., Foster G. (eds) Boron Isotopes. Advances in Isotope Geochemistry. Springer, Cham  https://doi.org/10.1007/978-3-319-64666-4_6

The boron isotopic composition (δ11B) of scleractinian corals has been used to track changes in seawater pH and more recently as a probe into the processes controlling bio-calcification. For corals that precipitate aragonite skeletons, up-regulation of pH appears to be a general characteristic, typically being ~0.3 to ~0.6 pH units higher than ambient seawater. The relationship between the pH of the corals calcifying-fluid (pHcf) and seawater pHT (total scale) is shown to be dependent on both physiological as well environmental factors. In laboratory experiments conducted on symbiont-bearing (zooxanthellate) corals under conditions of constant temperature and seawater pH, changes in the δ11B derived calcifying fluid pHcf is typically 1/3 to 1/2 of that of ambient seawater. Similar linear relationships are found for cold water corals that live in relatively stable, cold, deep-water environments but at significantly elevated levels of pHcf(~0.5–1 pH units above seawater), a likely response to the lower pH of their deep-sea environments. In contrast, zooxanthellae-bearing corals living in shallow-water reef environments that experience significant natural variations in temperature, light, nutrients and seawater pH, show different types of responses. For example, over seasonal time-scales Poritescorals from the Great Barrier Reef (GBR) have a large range in pHcf of ~8.3 to ~8.5, significantly greater (~×2 to ~×3) than that of reef-water (pHT ~8.01 to ~8.08), and an order of magnitude greater than that expected from ‘static’ laboratory experiments. Strong physiological controls, but of a different character, are found in corals grown in a Free Ocean Carbon Enrichment Experiment (FOCE) conducted in situ within the Heron Island lagoon (GBR). These corals exhibit near constant pHcf values regardless of external changes in temperature and seawater pH. This pattern of strong physiologically controlled ‘pHhomeostasis’, with elevated but constant pHcf has been found despite large natural seasonal variations in the pH (±0.15 pH units) of the lagoon waters, as well as the even larger super-imposed decreases in seawater pH (~0.25 pH units) designed to simulate year 2100 conditions. In natural reef environments we thus find that the processes influencing the up-regulation of pHcf in symbiont-bearing corals are subject to strong physiological controls, behaviour that is not well simulated in the current generation of aquaria-based experiments with fixed seawater pH and temperature. Conversely, cold-water corals that lack symbionts and inhabit the relatively stable deep-sea environments hold the best prospects for providing reliable reconstructions of seawater pH. Clearly, further studies utilising the δ11B-pHcfproxy combined with other DIC/carbonate-ion proxies (e.g. B/Ca), but conducted under realistic ‘natural’ conditions, are required to elucidate the processes controlling coral bio-calcification and to better understand the vulnerability of scleractinian corals to anthropogenic driven warming and ocean acidification.

No direct effects of ocean acidification observed in Arctic specie

Peter Thor, Fanny Vermandele, Marie-Helene Carignan, Sarah Jacque, Piero Calosi.  No maternal or direct effects of ocean acidification on egg hatching in the Arctic copepod Calanus glacialis PLOS ONE 13(2): e0192496. https://doi.org/10.1371/journal.pone.0192496

Widespread ocean acidification (OA) is transforming the chemistry of the global ocean and the Arctic is recognised as the region where this transformation will occur at the fastest rate. Moreover, many Arctic species are considered less capable of tolerating OA due to their lower capacity for acid-base regulation. This inability may put severe restraints on many fundamental functions, such as growth and reproductive investments, which ultimately may result in reduced fitness. However, maternal effects may alleviate severe effects on the offspring rendering them more tolerant to OA. In a highly replicated experiment we studied maternal and direct effects of OA predicted for the Arctic shelf seas on egg hatching time and success in the keystone copepod species Calanus glacialis. We incubated females at present day conditions (pHT 8.0) and year 2100 extreme conditions (pHT 7.5) during oogenesis and subsequently reciprocally transplanted laid eggs between these two conditions. Statistical tests showed no effects of maternal or direct exposure to OA at this level. We hypothesise that Cglacialis may be physiologically adapted to egg production at low pH since oogenesis can also take place at conditions of potentially low haemolymph pH of the mother during hibernation in the deep.

Evidence lacking for ocean acidification by carbon dioxide

Paul McElhany. CO2 sensitivity experiments are not sufficient to show an effect of ocean acidification. ICES Journal of Marine Science, Volume 74, Issue 4, 1 May 2017, Pages 926–928,https://doi.org/10.1093/icesjms/fsw085

“The ocean acidification (OA) literature is replete with laboratory studies that report species sensitivity to seawater carbonate chemistry in experimental treatments as an “effect of OA”. I argue that this is unintentionally misleading, since these studies do not actually demonstrate an effect of OA but rather show sensitivity to CO2. Documenting an effect of OA involves showing a change in a species (e.g. population abundance or distribution) as a consequence of anthropogenic changes in marine carbonate chemistry. To date, there have been no unambiguous demonstrations of a population level effect of anthropogenic OA, as that term is defined by the IPCC.”