Ever since scientists honed in on the Cretaceous-ending asteroid that hit the Earth 66 million years ago, the details have gotten worse and worse. Aside from wiping out non-avian dinosaurs, punching a 110-mile-wide crater into the Gulf of Mexico, and possibly triggering massive volcanic eruptions on the other side of the planet, the asteroid that wiped out non-avian dinosaurs is also thought to have caused the extinction of many marine animals as well. The exact mechanics of how those creatures were killed haven’t been as thoroughly explored, although a recent study has put together a model that explains how an asteroid may affected so much sea life. It had an accomplice.
While shock waves, tsunamis, walls of flame, etc. would have all been more immediately devastating to terrestrial organisms, ocean life should have been insulated from those problems, at least to a certain degree. The initial blast of heat (and burning plant-life) shouldn’t have killed sea creatures like plesiosaurs and ammonites directly, as the water would have absorbed and distributed some of that thermal activity. The problem for these survivors much of the molten debris had to come down somewhere, and it might kick off a new chain of events that would bring havoc to the seas.
Only good for the algae
To see how the asteroid’s vaporized rock field would react in the air, scientists looked at data and models from spaceship re-entry. This lead to the conclusion that massive amounts of nitrogen oxide would have been created, which is further backed up by geological evidence. The extra nitrogen oxide could have then created acid rain. The acid rain could then lead to an algal bloom thanks to the increased amounts of nitrates in the ocean. The bloom would have basically been spread across the already soot-covered globe, choking off the underwater ecosystem’s supply of oxygen and nutrients.
Source: Dino-Killing Asteroid Impact Triggered Lethal Algal Bloom by Laura Geggel, Live Science