Rehabilitation of Abandoned Shrimp Ponds through Mangrove Planting at Nakhon Si Thammarat, Southern Thailand: Investigation of a Food Chain System at a Newly Developed Mangrove Ecosystem

The complete food chain system of mangrove plantations on shrimp ponds sites were studied using the stable nitrogen (15N) and carbon isotopes (13C) to complete food chain (web) system studies of mangrove plantations. The analyzed data clearly indicates that heavy nitrogen (15N) was gradually accumulated during each stage of the food chain system and finally in large fishes. On the other hand, heavy carbon (13C) increased only slightly during each stage of the food chain system. The δ15N values for carnivores were much higher than those of herbivores and omnivores. Carnivores consume nitrogen accumulated fishes and animals as their feed sources. Finally these carnivores gradually accumulate nitrogen in protein forms in their bodies from their metabolic activities. Herbivores eat only plants, whereas omnivores consume both plants and animals (including fishes). Usually, the δ15N values of herbivores and omnivores are low. This promising data truly represents the food chain system occurring in a natural marine ecosystem. The above analyzed data suggests that carnivorous fishes are at least 4 to 5 steps from the mangrove leaves. Mangrove forests can contribute to the reduction of greenhouse gases acting as a carbon sink and a rich biodiversity ecosystem