The Importance of Seagrass

Seagrass meadows are like underwater lawns. But more than just being nice-looking, they play important ecological and environmental roles. These carpets of green, lush leaves have a special relationship with many marine animals by providing food and shelter. The largest animals associated with seagrasses in the Caribbean are the endangered Green sea turtle and the Caribbean manatee.

The seagrasses act as a nursery for many species of reef and deep sea fish. The females come to the lagoon to lay the eggs. After hatching, the newly emerged fish live, feed and hide between the blades of grass from predators. They remain there until they are big and strong enough to leave the protected shallow lagoon and become part of life on the coral reefs.

By this we see how seagrasses help to make sure there is biodiversity or a wide range of life on the reefs. This is good for local communities that make a living from fishing and for people who enjoy seeing the beauty of the reefs by either snorkelling or SCUBA diving.

Seagrasses also provide environmental services to people by helping to clean water by absorbing harmful chemicals and nutrients. Seagrasses protect the coastlines by weakening wave energy. Seagrass stabilize sediments so they also make it easy for dust bits to settle at the bottom. And last but not least, much of the seaweed you see washed up on the beach is dead seagrass that brings good nutrients to the beach and help to form dunes.

Threats to seagrasses
The most important threats to seagrasses are damages from boat anchors, pollution and dredging. Anchoring destroys the seagrass beds by uprooting them. When roots are damaged, the plants die. There are all types of pollution that can affect seagrasses, some invisible and some visible. Chemicals, sometimes invisible, can kill the plants from inside out when the plants absorb the harmful substances. But also pollution like plastic bags can also kill seagrasses.

When a plastic bag covers a grass patch, sunlight cannot reach the grass and they die. Dredging is usually done to make the water deeper for the purpose of ship traffic. Dredging makes the water very cloudy with lots of bits of soil particles. This is called particle suspension. When these bits of soil eventually fall to the bottom, a process called sedimentation, the thick blanket of sediment covers and suffocates the grasses. Both particle suspension and heavy sedimentation prevent sunlight from reaching the grasses.

CONTINUE: Take the Seagrass Quiz (Downloadable in.pdf format)