海洋 かいよう 酸素 さんそ事変 じへんだったら
kaiyōmusansojihendattara

Noun
Da Copula

The "-tara" conditional form ("if/when…") of 海洋無酸素事変

1. If/when the marine oxygen depletion incident…; If the marine oxygen depletion incident happened…

Tara Conditional