The paper once again demonstrates alarmist claims about ocean 'acidification' are overblown.
In-life pteropod shell dissolution as an indicator of past ocean carbonate saturation
- School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth PL4 8AA, UK
- In-life dissolution of fossil pteropod shells was examined using the LDX scale.
- Average shell diameter was used as an indicator of calcification rate.
- LDX shows significant correlation to CO2 and surface water carbonate concentration.
- Smaller, more corroded shells were found during interglacial periods.
- Larger, pristine shells were found during glacial periods.
Recent concern over the effects of ocean acidification upon calcifying organisms has highlighted the aragonitic shelled thecosomatous pteropods as being at a high risk. Both in-situ and laboratory studies have shown that an increased dissolved CO2 concentration, leading to decreased water pH and low carbonate concentration, causes reduced calcification rates and enhanced dissolution in the shells of living pteropods. In fossil records unaffected by post-depositional dissolution, this in-life shell dissolution can be detected. Here we present the first evidence of variations of in-life pteropod shell dissolution due to variations in surface water carbonate concentration during the Late Pleistocene by analysing the surface layer of pteropod shells in marine sediment cores from the Caribbean Sea and Indian Ocean. In-life shell dissolution was determined by applying the Limacina Dissolution Index (LDX) to the sub-tropical pteropod Limacina inflata. Average shell size information shows that high in-life dissolution is accompanied by smaller shell sizes inL. inflata, which may indicate a reduction in calcification rate. Comparison of the LDX profile to Late Pleistocene Vostok atmospheric CO2 concentrations, shows that in-life pteropod dissolution is closely associated to variations in past ocean carbonate saturation. This study confirms the findings of laboratory studies, showing enhanced shell dissolution and reduced calcification in living pteropods when surface ocean carbonate concentrations were lower. Results also demonstrate that oceanic pH levels that were less acidic and changing less rapidly than those predicted for the 21st Century, negatively affected pteropods during the Late Pleistocene.
I think you are misreading this paper. First there is the last sentence of the abstract:ReplyDelete
"Results also demonstrate that oceanic pH levels that were less acidic and changing less rapidly than those predicted for the 21st Century, negatively affected pteropods during the Late Pleistocene."
Translation = Even when things were not as bad as they are today it still screwed up pteropods pretty badly.
Second, since the horizontal axis of the graph is in 'kyr' not in 'yr' it is not possible to draw the conclusions you do about pH changes. In fact the rate of current ocean pH change may be unprecedented in Earth's history, with only the Permian extinction coming close (but we will never know for sure since we cannot measure changes over a 200 year period from that long ago.)
Problem is that pH levels "predicted for the 21st Century" are highly exaggerated and the multiple reasons why are outlined in many of the links in the sentence "The paper once again demonstrates alarmist claims about ocean 'acidification' are overblown." aboveDelete
Pteropods evolved around 500 million years ago when CO2 levels were ~13 times higher than today.
It's not even clear that ocean pH in modern times has changed at all outside of natural variability. Please review the links
and at CO2 Science
ferd berple says:ReplyDelete
November 14, 2013 at 8:00 am
The enormous deposits of marine limestone worldwide are evidence of the physical process by which the oceans turn CO2 into rock, and thereby neutralize the ability of CO2 to acidify the oceans. limestone is fossilized CO2.
climate science observes that acid dissolves limestone, so they propose that adding CO2 to the oceans will dissolve limestone. Nothing could be further from the truth. Limestone contains CO2. Adding CO2 to the oceans must increase the precipitation of limestone, until such time as the oceans run out of calcium salts. Over billions of years, with CO2 levels much higher than present, that has never happened.