Severity of ocean acidification following the end-Cretaceous asteroid impact

Abstract

Most paleo-episodes of ocean acidification (OA) were either too slow or too small to be instructive in predicting near-future impacts. The end-Cretaceous event (66 Mya) is intriguing in this regard, both because of its rapid onset and also because many pelagic calcifying species (including 100% of ammonites and more than 90% of calcareous nannoplankton and foraminifera) went extinct at this time. Here we evaluate whether extinction-level OA could feasibly have been produced by the asteroid impact. Carbon cycle box models were used to estimate OA consequences of (i) vaporization of up to 60 × 10 15 mol of sulfur from gypsum rocks at the point of impact; (ii) generation of up to 5 × 10 15 mol of NO x by the impact pressure wave and other sources; (iii) release of up to 6,500 Pg C as CO 2 from vaporization of carbonate rocks, wildfires, and soil carbon decay; and (iv) ocean overturn bringing high-CO 2 water to the surface. We find that the acidification produced by most processes is too weak to explain calcifier extinctions. Sulfuric acid additions could have made the surface ocean extremely undersaturated (Ω calcite <0.5), but only if they reached the ocean very rapidly (over a few days) and if the quantity added was at the top end of literature estimates. We therefore conclude that severe ocean acidification might have been, but most likely was not, responsible for the great extinctions of planktonic calcifiers and ammonites at the end of the Cretaceous.ocean acidification | asteroid impact | K/Pg boundary | mass extinction

Biogeochemical significance of pelagic ecosystem function: an end-Cretaceous case study

“…To better discern the effects of each gas, scenarios for CO 2 and SO 2 release were also tested in isolation ( figure 3). As in [21], SO 2 release and rain-out were simulated by reducing alkalinity in the surface ocean box (see electronic supplementary material for more details). A wide range of possible timescales and modes of degassing were also tested (see electronic supplementary material, table S1).…”

“…In contrast, the impact of an approximately 10 km wide bolide at Chicxulub at the K-Pg boundary [18] led to instantaneous release of SO x , NO x and CO 2 ([19] and references within), and rapid and transient (probably less than 5 year) acidification of the surface ocean [20,21]. Besides the very different timescales of these environmental perturbations, a critical difference is that the Chicxulub impact coincides with a major mass extinction and Late Cretaceous Deccan volcanism does not [19].…”

Global bioevents and the Cretaceous/Paleogene boundary in Texas and Alabama: Stratigraphy, correlation and ocean acidification

“…and It has recently been suggested (Gibbs et al, 2016) that ocean warming and not acidification controlled coccolithophore responses during past greenhouse climates. While this may be the case, the features we describe here would not be caused by warm temperatures alone and the damage to the nannofossils requires quite significant dissolution (but see Tyrrell et al, 2015).…”

Chamber volume development, metabolic rates, and selective extinction in cephalopods

“…At the end of the Cretaceous, ammonoids went extinct while nautilids survived 4 . After the asteroid impact and the Deccan trap-eruptions 59 , acidification of sea water occurred, which presumably caused a dramatic decrease in the abundance of primary producers and planktic animals 8,60 , thereby drastically cutting the food supply of ammonoids. It is likely that metabolic rate determined the degree to which the respective species could survive…”