Chicxulub impact acidified the oceans

[Halichoeres]

Chemical analysis of small calcifying organisms points to an abrupt drop in ocean pH (acidification) after the bolide impact. That means organisms that form calcium carbonate skeletons would be unable to build them faster than they dissolve. They estimate that the change in pH was about 0.25 units, which is probably less than the change in pH that is expected under current carbon dioxide emission projections. This is bad news for corals, mollusks, and many crustaceans, among others.

Paper (appears to be open access): https://www.pnas.org/content/early/2019/10/15/1905989116

And a write-up on CNN: https://edition.cnn.com/2019/10/22/europe/ocean-acidification-asteroid-intl-hnk-scn/index.html

[ZoPteryx]

Lots of cool implications for this study.  Hopefully someone will examine calcifying microfossils from the controversial Tanis site, would certainly bolster or reject timing estimates for that locale.