Similarly Bi\u00f1a 1982 described how Landsat MSS products were used to high light

Similarly biña 1982 described how landsat mss

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of greater than 10% small islands. Similarly, Biña (1982) described how Landsat MSS products were used to high- light potential sites for marine reserve status. The selec- tion criteria included: (i) clusters of reefs that occurred within 300 km 2 , (ii) atolls and fringing reefs greater than 10 km in length, (iii) a diverse range of habitats both within and adjacent to reefs, and (iv) areas not situated near potential threats. In the Surin Marine National Park (Thailand) efforts are currently under way to manage snorkelling activity using large scale digital aerial photography (Thamrongnawa- sawat and Hopley 1995). Analysis of these photographs reveals the presence of living corals and areas of dead coral and sand. The authors suggest that such data will allow planners to lay interpretative snorkelling routes for tourists and estimate the reefs' carrying capacity for snorkelling activity based on the ratio of massive to branching coral (assuming that massive corals are less vulnerable to snorkelling-induced damage). Environmental sensitivity mapping has also been car- ried out for mangrove ecosystems. By using mangrove canopy cover as a surrogate measure of tree density, SPOT data were used to map mangrove density in Florida (Jensen et al . 1991). The authors suggest that such information will be important in identifying which mangrove areas are most susceptible to oil spill (assuming that oil dispersal is inversely proportional to tree density). 6. Mapping boundaries of management zones Maps of coastal habitats have been used to demarcate the boundaries of management zones (Kenchington and Claasen 1988, Danaher and Smith 1988). This may include the delineation of fisheries-exclusion zones, marine park areas and so on. 7. Bathymetric charting A great deal has been published on the application of remote sensing techniques for mapping bathymetry. Chapter 15 discusses the theory and methods behind bathymetric mapping but the fundamental principle is described here. Different wavelengths of light penetrate water to varying degrees: red light attenuates rapidly in water and does not penetrate deeper than 5 m or so, whereas blue light penetrates much further and, in clear water, the seabed will reflect enough light to be detected by a satellite sensor even when the depth of water approaches 30 m. The depth of penetration depends on the wavelength of light and the water turbidity. Suspended sediment parti- cles, phytoplankton and dissolved organic compounds will all affect the depth of penetration because they scatter and absorb light. Taking a Landsat MSS example from the Great Barrier Reef, it is known that green light (band 1, 0.50–0.60μm) will penetrate to a maximum depth of about 15 m, red light (band 2, 0.60–0.70 μm) to 5 m, near infra- red (band 3, 0.70–0.80 μm) to 0.5 m and infra-red (band 4, 0.80–1.1 μm) is fully absorbed (Jupp 1988). Appropriate image processing enables the analyst to derive a ‘depth of penetration’ image which is segmented into depth zones.

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