海洋 かいよう 酸素 さんそ事変 じへんでしょう
kaiyōmusansojihendeshō

Noun
Desu Copula

Expresses probability in a polite manner ("probably…") of 海洋無酸素事変

1. Probably an oceanic anoxic event.

Polite
Presumptive
Conjecture