## ABSTRACT

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 The Importance of Water Clarity in GBR Waters . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Loss of Catchment Vegetation — More Mud in Estuarine Waters . . . . . . . . . . . . . 79 Mud Accumulation and New Mangroves in Downstream Parts of Estuaries and Nearshore Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 The Cost of Ignoring the Role of Mangroves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 A Consequence of Catchment and Mangrove Degradation — The Loss of Seagrass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Conclusion — A Holistic Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Along the tropical northeastern coast of Queensland is one of the outstanding biotic ecosystems in the world, the Great Barrier Reef (GBR), attested to be the only biotic structure in the world visible from space. This complex series of reef communities is based on tiny coral polyps and deep accumulations of their carbonate skeletons over eons. The resulting barrier to ocean waves has created a vast and relatively sheltered coastal lagoon in which other complex biotic tropical ecosystems have flourished in association with coral reefs. Two types of ecosystems dominate these sheltered waters, namely, the mostly sub-tidal seagrass meadows in the extensive coastal lagoon, and mangrove and salt marsh growing along the upper intertidal zone and within all estuaries. These ecosystems are highly dependent not only on each other, but also on prevailing environmental conditions in a dynamic equilibrium.