Seagrass Meadows: The Overlooked Ecosystem Supporting Ocean Life

They lack the visual drama of coral reefs or the mysterious allure of the deep sea. But seagrass meadows — underwater meadows of true flowering plants rooted in the seafloor — are among the ocean's most ecologically critical habitats. Covering approximately 300,000 square kilometres of shallow coastal seafloor worldwide, they support extraordinary biological diversity, sequester carbon at rates comparable to tropical forests, stabilise sediments that would otherwise cloud coastal waters, and provide nursery habitat for the juvenile stages of many commercially important fish species. And they are disappearing at an alarming rate.

What Makes Seagrass Unique

Seagrasses are not seaweeds — they are true flowering plants, descended from terrestrial ancestors that colonised the marine environment approximately 100 million years ago. Unlike seaweeds, which are algae, seagrasses have roots, stems, leaves, and flowers. They photosynthesise using sunlight filtered through the water column, produce oxygen, and reproduce both vegetatively (by extending underground rhizomes) and sexually (by producing pollen and seeds dispersed by water currents). A single seagrass meadow may be a clone of a single individual that has been growing for thousands of years.

The Seagrass Food Web

Seagrass meadows support food webs of remarkable complexity. Sea turtles — particularly green turtles — are specialist grazers of seagrass, consuming large quantities and helping to maintain meadow health by preventing the accumulation of dead material. Dugongs (and their relative, the manatee) are obligate seagrass grazers, consuming up to 35 kilograms per day. The invertebrates that live within seagrass meadows — shrimps, crabs, urchins, clams, and hundreds of small polychaete worm species — are consumed by juvenile fish that use the meadow as a nursery, as well as by seabirds working the edges at low tide.