The significance of seagrass ecosystems.

Seagrass ecosystems provide habitats for a wide variety of marine organisms, both plant and animal; these include meiofauna and flora, benthic flora and fauna, epiphytic organisms, plankton and fish, not to mention microbial and parasitic organisms. The relatively high rate of primary production of seagrasses drives detritus-based food chains, which help to support many of these organisms. Seagrasses are also directly consumed by birds, dugongs and turtles.

As humans have encroached on the marine environment, there have been some dramatic effects on coastal ecosystems. The climactic role of many seagrass communities means that any disturbance is likely to have a significant effect on the associated ecosystem. Many recent examples exist of extensive damage done to marine and estuarine habitats through the inadvertent destruction of the seagrass population. The loss of a number of important seagrass habitats has resulted in extensive studies of some seagrass communities and an increasing awareness of the role these plants play in our coastal marine environment. In an effort to recover from some of the damage done to seagrass communities a number of attempts to transplant and artificially restore seagrasses have been attempted. While results to date have shown mixed success, work continues at many research centres around the world.

Seagrasses in south-Western Australia

As well as directly producing organic matter, seagrasses act as a substrate for many epiphytic organisms. Local species of the genus Amphibolis have been shown to harbour over 100 different epiphytic species (Ducker et al., 1977). The added productivity of the epiphytic population is very important, since they provide a food source for many grazers. Coralline algal epiphytes are believed to contribute significantly to sand formation in shallow coastal waters, adding to the sediment banks of Shark Bay for example.

On a physical level, dense seagrass meadows are believed to be responsible for extensive sediment bank build-up through a reduction in water flow. In Shark Bay mud banks of up to 10 m in depth have been attributed to seagrasses, both from the contribution by epiphytes and their physical influence on sedimentation. Because seagrasses form a dense rhizome/root system, they also act to stabilize the sediment, reducing potential sediment erosion in shallow waters.