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The main ecosystems encountered in the coastal areas include mangroves,
coral reefs, coastal lagoons, estuaries and deltas; and seagrasses. These systems are the result of the active physical forces (i.e. crust or iso-static movement, winds, currents and tides, run-offs, erosion and sediment erosion. Playing an important role in these forces are the living communities of plants and associated animals in mangroves which trap sediments and absorb winds and tide energy. The coastal zone where the mangrove ecosystem (ME) is found, is the site of complex and intense interactions between land, sea and the atmosphere. Ecosystems in the coastal areas are among the most productive of the natural ecosystem.Mangroves grow in coastal areas that are sheltered from the direct action of waves and currents. Usually they are absent in areas with strong tidal action because such conditions prevent stable accumulation of mud and sand. In the Philippines, the mangrove areas are distributed along a considerable length in the shorelines, estuaries, banks and deltas as well as fringes and barrier beaches.
Philippine mangrove areas are classified into 5 zones, to wit:
1.) Coastal Area
a.) Along seacoast and occurring on exposed reefs;
b.) Towards the sandy or rocky shorelines;
c.) Along the coastal limits; and
d.) Near the shorelines.
2.) Outer inland areas
3.) Central Areas
4.) Upper inland areas
5.) Back of Mangrove Swamp Areas.
Occurrences of mangroves are controlled by several factors, viz.:
1. Salinity
2. Soil Drainage
3. Different Rooting Systems
4. Growth Patterns of Seedlings
5. Tidal Fluctuations
6. Coastal Morphology
Aside from the factors mentioned above, temperature is a factor which influences plant growth. This is because high temperature causes high salinity in shallow waters that is favorable to mangrove species.
Tidal flooding is considered as a factor influencing plant growth in mangrove ecosystems. The frequency of tidal flooding or inundation time regulates the productivity of mangrove species. Some authors came up with mangrove groupings based on inundation time. Moreover, tidal waves, tsunamis and storm surges can cause severe damage to the plants.
A distinct character of the mangrove ecosystem is its diversity of the vegetation itself. The substrate is usually a firm to soft mud wherein travelers may sink, so that walking during field observations is difficult, if not impossible. This is one of the characteristics of mangrove ecosystems, which prevents researchers to fully investigate the inner parts of the area for ground data analysis. If it is GIS (Geographic Information System) data analysis, the researcher has to come up with ground data to supplement certain analyses.
The substratum of ME can be richly organic and a strong smell of the
hydrogen sulfide (H2S) can disturb the student researcher. The presence of this substance indicates the completely anaerobic nature of the waterlogged soils in the ME. Canopy heights of the mangrove trees depends on the climate, topography and the extent of human disturbance. Unlike, desert vegetation, there are very few spiny plants. Dead snags of stems and roots of trees can be quite sharp that can harm the inexperienced researchers when walking in the muddy substrates during low tides or during sampling of macrofauna. Crabs (Uca spp.) and mudskippers (Periophthalmidae) are common.The ME is a fragile ecosystem, being a transition between marine and terrestrial environments. It is affected by many environmental factors, viz.:
salinity, tidal fluctuations, and geomorphological processes of the coastal areas. Alterations on any of its parts can cause profound and lasting consequences on the other parts. But, on the other hand, no serious disturbance is made on the ecosystem, the mangroves can easily regenerate and remain as one of the most productive natural systems.