an ecosystem (system of an ecological community and its environment)

a coral reef

important, significant

importance, consequence, significance

extraordinary, unusual

emergency

very; extremely / exceedingly; tremendously

ecology, mode of life of living creatures / way of life, the way people live

system, family / style

a sea, an ocean / a lake / (figuratively) an object covering over a large area, as in 血の海 (chi no umi, “pool of blood”) or 火の海 (hi no umi, “sea of fire”)