The tropics weren't always the most diverse marine environments, study finds

Today, tropical waters typically host a wider range of marine animals than polar waters. This decline in marine biodiversity from the equator toward the North and South poles is known as the latitudinal diversity gradient.

Today, tropical waters typically host a wider range of marine animals than polar waters. This decline in marine biodiversity from the equator toward the North and South poles is known as the latitudinal diversity gradient.