Seagrasses are marine flowering plants found in shallow coastal waters globally. Unlike seaweeds, they possess true roots, stems, leaves, and produce flowers and seeds, similar to terrestrial plants. These plants form extensive underwater meadows, recognized as highly productive ecosystems. Seagrass meadows are foundational marine environments, supporting diverse marine life.
Major Seagrass Grazers
Many marine animals directly consume seagrass, making them significant grazers. Marine mammals like manatees and dugongs, often called “sea cows,” primarily feed on seagrass. Their grazing helps maintain seagrass bed health.
Marine reptiles, such as green sea turtles, also consume seagrass. While juveniles have varied diets, adult green sea turtles are primarily herbivorous, consuming seagrass and macroalgae. Their distinct green-tinted fat results from this plant-based diet.
Certain fish species, including parrotfish and surgeonfish, graze on seagrass blades. Their grazing helps control seagrass growth and influences habitat structure.
Invertebrates also graze on seagrass. Sea urchins consume seagrass using their mouthparts to scrape off blades or epiphytes. Some conch species, like the queen conch, feed on seagrass blades. Smaller invertebrates, such as amphipods and polychaete worms, have been observed feeding on seagrass pollen.
Seagrass as a Critical Habitat
Beyond direct consumption, seagrass meadows serve as habitats, supporting marine life. They function as nursery grounds, providing shelter for juvenile fish, crustaceans, and other marine organisms. These sheltered environments offer protection from predators and ample food, supporting a significant portion of the world’s fisheries.
The dense network of seagrass blades provides physical shelter for marine species, protecting smaller organisms from strong currents and predators. Many fish, crabs, and shrimp find safety within these beds during early life stages.
Seagrass also contributes indirectly to the marine food web. As blades die and decompose, they form detritus, a food source for many invertebrates and smaller organisms. Epiphytes—algae, bacteria, and tiny invertebrates on seagrass leaves—are grazed by snails, crustaceans, and small fish, adding to the ecosystem’s food dynamics.
Protecting Seagrass Ecosystems
Despite their ecological significance, seagrass ecosystems face numerous threats, largely due to human activities. Coastal development, pollution from nutrient runoff, sedimentation, and toxins degrade seagrass habitats. Physical damage from boat propellers and dredging further contributes to their decline.
Climate change poses a risk, with warming ocean temperatures, sea level rise, and increased storm intensity impacting seagrass survival. These pressures have led to widespread loss of seagrass meadows globally.
The loss of seagrass has consequences for marine animals that depend on these habitats. It can lead to declines in fish populations, disrupt marine food webs, and reduce biodiversity. Protecting these ecosystems involves reducing pollution, promoting responsible boating practices, and supporting restoration efforts.