Seagrass Beds

Seagrass beds are major features of both temperate and tropical seas throughout the world, but they are best developed and most diverse in the lagoonal systems that are associated with coral reefs. From the results of scientific investigations in both tropical and temperate areas, it is known that seagrass beds serve a number of ecological functions. The trapping and stabilization of bottom sediments, and the consequent increase in water clarity is one of the important ecological functions. Clearer waters improve light penetration, and consequently increase photosynthesis and rates of organic matter production. Sediment trapping contributes to coastal accretion, while sediment stabilization helps prevent coastline erosion, especially under storm conditions. The removal of terrigenous (originating on land) sediment from lagoonal and estuarine water is a very important function of seagrasses, and may be essential in some areas to allow sediment-sensitive corals to exist on adjacent reefs.

Seagrasses invariably support more fish than bare areas. It is known that seagrass meadows may have a nursery function, or may be the permanent habitat of epibenthic fish species. In addition, they may provide food and shelter for migrating pelagic species as. Obviously, environmental changes that threaten the vitality and persistence of seagrass beds also endanger indirectly the ecological functions that seagrass meadows may have for fish.

Over the past decades, anthropogenic impacts on the coastal zone have increased worldwide. Industrialization, coastal engineering, urbanization and agricultural intensification often have led to changes in coastal water quality, with concomitant negative impacts on seagrass meadows. With deteriorating light conditions in the water column (an often occurring phenomenon in coastal waters nowadays) seagrasses are expected to release less oxygen in the rhizosphere (root system). This may aggravate hypoxic (low-oxygen) conditions in the sediment, which on its turn may have a negative impact on seagrass functioning.