SEAGRASS BEDS ARE UNDERWATER MEADOWS OF FLOWERING PLANTS THAT PLAY A CRITICAL ROLE IN SUPPORTING MARINE BIODIVERSITY AND MAINTAINING COASTAL ECOSYSTEM HEALTH.
Seagrass beds or seagrass meadows are a unique and vital marine ecosystem found in coastal areas around the world. They consist of flowering plants adapted to grow in shallow, nutrient-rich waters of coastal areas, including bays, estuaries, lagoons, and coral reefs.
Seagrasses belong to a group of plants known as angiosperms, which is unusual for an aquatic environment. They can withstand the constant movement of water and are remarkably efficient at absorbing sunlight for photosynthesis. They produce oxygen through this process and contribute significantly to the oxygen levels of the surrounding water, benefiting a wide array of marine organisms.
SEAGRASS BEDS PROVIDE SHELTER, NURSERY AREAS, AND FORAGING GROUNDS FOR A WIDE ARRAY OF MARINE ORGANISMS.
Seagrass leaves offer attachment surfaces for the eggs and larvae of various organisms, including sea squirts and molluscs and a safe environment for juvenile fish and invertebrates.
Some species, like manatees, dugongs and green sea turtles, directly graze on seagrass leaves, while others rely on seagrass indirectly for nutrients. Dead seagrass plants decompose, generating debris that serves as food for worms, sea cucumbers, crabs, and filter feeders such as anemones and ascidians. This decomposition process releases nutrients like nitrogen and phosphorus, which are absorbed by seagrasses and phytoplankton when dissolved in water.
Seagrass meadows support a complex network of interconnected organisms, facilitating the transfer of energy and nutrients throughout the ecosystem.
Dugongs (Dugong dugon) are the only marine mammals known to have a strictly herbivorous diet, consisting mainly of seagrass. To compensate for the low nutritional value of seagrass, dugongs have an elongated digestive tract that allows for prolonged digestion and absorption of nutrients.
Thornback cowfish (Lactoria fornasini) is equipped with a remarkable defence mechanism called "boxfish syndrome." When they feel threatened or stressed, they can release a toxin called ostracitoxin from their skin, which acts as a potent deterrent to predators. This toxin can be fatal to other fish in the vicinity, making the cowfish an intimidating presence in the underwater world.
SEAGRASS BEDS SERVE AS NATURAL CARBON RESERVOIRS, HELPING TO REDUCE GREENHOUSE GAS LEVELS IN THE ATMOSPHERE AND COMBAT THE EFFECTS OF CLIMATE CHANGE BY TRAPPING AND STORING CARBON DIOXIDE.
Seagrass meadows are remarkably proficient at absorbing carbon dioxide (CO2) from seawater. Their carbon capture and storage capabilities surpass those of tropical rainforests of similar size by up to 35 times. Despite occupying only 0.2% of the ocean floor, seagrasses are responsible for storing a substantial amount of carbon.
Estimates suggest that they store around 10% of the ocean's carbon, which makes them a substantial contributor to the global carbon cycle.
Seagrass meadows have the remarkable ability to filter pathogens, bacteria, and pollutants from seawater, enhancing water quality. Seagrass beds act as natural filters, enhancing water clarity by capturing sediments and absorbing excessive nutrients. They also excel at removing nitrogen, a key element responsible for harmful algae blooms that can adversely impact both human and animal health.
SEAGRASS BEDS PLAY A VITAL ROLE IN SUPPORTING COASTAL COMMUNITIES AND MARINE LIFE.
Seagrass meadows, spanning over 300,000 km² and present in more than 159 countries, offer indispensable ecological services, such as nurturing fish populations, acting as natural defences against storm surges, and providing essential nursery habitats for approximately 20% of the top 25 global fisheries.
However, about 7% of seagrass habitat is lost annually worldwide, with at least 22 out of 72 seagrass species experiencing declines. This ongoing decline traces back to the late 19th century, resulting in the loss of nearly 30% of known seagrass areas across the globe.
Unfortunately, seagrasses face numerous threats that have led to their degradation and loss worldwide.
The main threats include urban, industrial and agricultural runoff, coastal development activities, dredging, unregulated fishing practices and nautical activities, which have the potential to damage these delicate ecosystems.
Climate change exacerbates these challenges by affecting the health of seagrass beds through rising sea levels and alterations in water temperature and acidity.
Addressing these challenges is imperative for the preservation of seagrass ecosystems, as they provide invaluable ecological, economic, and societal benefits to coastal regions and the global marine environment.