noun
red tide
A harmful algal bloom that discolors seawater, often causing marine life die-offs. Common in news and environmental contexts.
今年の夏、沿岸で赤潮が発生した。
This summer, a red tide occurred along the coast.
赤潮の影響で多くの魚が死んだ。
Many fish died due to the red tide.
Compound of 赤 (あか, 'red') and 潮 (しお, 'tide'), referring to the reddish discoloration of seawater caused by algal blooms.