Environmental Monitoring of Coral Reefs in Calatagan, Batangas, Phillippines Using multi-Temporal Satellite Images

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Environmental Monitoring of Coral Reefs in Calatagan, Batangas, Phillippines Using multi-Temporal Satellite Images

Photo-interpretation on the Landsat TM Color Composite Images
Four sets of Landsat TM false color images (BGR = 1,2,3; scale 1:50,000) acquired different periods (1989, 1993, 1995 and 1996) were used to classify the bottom materials in the Calatagan coral reef area. The geometry was corrected to the UTM coordinates system. The photo-interpretation was based on the tonal difference and distribution patterns on the image. These features were verified in the field (Fig. 2). Figure 3 shows the 12 categories resulting from the classification of bottom materials in the coral reef area. Table 1 gives a brief description of each category.

Figure 2: The location map of the Sea Truth Survey Points in the Calatagan Coral Reef Area.

Figure 3: Photo-interpretation Map of the Calatagan Coral Reef Area using Landsat TM False Color Composite Image.
Table 1. The 12 Categories of Bottom Materials in the Calatagan Coral Reef Area based on photo-interpretation and field survey. (Use Fig. 3, i.e., the 1993 Landsat TM image BGR = 1,2,3 for the descriptions).

Category	Description
Dense seagrass(bottom materials unknown)	It shows as a dark gray color on the image. It is distributed in front of reef-flats about 100 m from the coast to 250m towards the sea.
Sparse seagrass(muddy bottom)	It shows as dark gray t gray, and it distributed near the mangrove areas along the coast, it is sometimes located at the front of the fishponds.
Sparse seagrass(sandy bottom)	It shows as dark gray to gray, and is distributed near the sparse seagrass (muddy bottom) but farther out towards the sea.
Algae	It shows as gray on the image and is distributed locally in front of reef-flats. Considering its distribution pattern, algae were interpretated to be correlated to the reef crest.
Coral	It shows as gray color, and it distributed outside the front of reef-flats in the Luzon Sea, especially the outside the front of reef-flats to the west of Calatagen.
Beach sand	It shows as white color, and is distributed near the coast of the Calatagan peninsula.
Muddy bottom(no seagrass)	It shows as gray color. It is distributed near the coasts of Pagaspas Bay and Balayan
Sandy bottom(no seagrass)	It shows as whitish blue to gray tones. It is observed in the reef-flats. This is essentially coralline sand, Dead corals are frequently observed.
Reef slope(living coral, sandy bottom)	It shows as light blue color. It sometimes occurs outside the living coral area.
Reef slope(muddy bottom)	It shows as light blue color. It is distributed in the coastal zone of the Pagaspas Bay and Balayan Bay.
Mangrove(muddy bottom)	It shows as black to dark green color. It is distributed along the coast of Pagaspas Bay and Balayan Bay. It was also observed near the mouth of Bigaa River.
Fish pond(muddy bottom)	It shows as black color on the image. It is distributed on shore near the coast of the peninsula.

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