Mangrove ecosystems provide a large role in the presence of macrozoobenthos which will have an impact on the availability of food sources for fish. Research carried out in the mangrove ecosystem of Lubuk Damar, Aceh Tamiang, Aceh showed the results of and percentage of the presence of macrozoobenthos in the study site was Sipuncula with values ranging from 65.31% - 95.69%, Annelids (3.32-23.02), Mollusca 0.37-3.18, Arthropods (0.13- 6.26%), Nemertea (0.12-1.87%), Brachiopoda (0.26-0.99%), Echinodermata (0.06-0.72%), Cnidaria (0.02-0.46), 0.07% Platyhelminthes and 0.02% nematodes. Macrozoobenthos abundance in the range of 595 ind/m2 - 4,335 ind/m2. The research substrate included with texture percentage are sandy loam and loam classes. The ratio of carbon and nitrogen isotope in food sources in the mangrove ecosystem was the highest -26.96 ‰ (δ13C), 5.14 ‰ (δ15N), the lowest was -29.08 ‰ (δ13C), 0.00 ‰ (δ15N). The average isotope ratio in macrozoobenthos has the highest value of -14.75 ‰ (δ13C), 8.29 ‰ (δ15N) and lowest of -25.00 ‰ (δ13C), 5.59 ‰ (δ15N). The test results of the analysis of carbon and nitrogen isotopes on several phyllum found at the study site showed that such as D. cuprea and Sipunculus sp.8 were directly related to different mangrove leaves as food sources. While the transverse A., Anthozoa D. myctiroides, Gastrana sp., O. woodmasoni, Lingula sp. Pugillina sp., S. serrata does not describe the similarity of the results of assimilation with food sources. In this ecosystem food web, there is a disconnected net at the trophic levels of 2.07 and 2.11, so there is an imbalance in transfers with the rhik level above and below. The trophic level at the research location ranges from 2.03-2.81.
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