Mangrove menghasilkan serasah yang akan mengalami proses dekomposisi yang kemudian dimanfaatkan sebagai sumber hara bagi tanaman dan juga merupakan sumber makanan bagi ikan serta invertebrata yang penting. Tujuan dari penelitian ini adalah untuk mengukur dekomposisi serasah daun R. apiculata dan mengetahui kandungan unsur hara karbon (C), nitrogen (N) dan fosfor (P) pada serasah daun Rhizophora apiculata yang dilepas selama proses dekomposisi. Penelitian dilakukan pada bulan Februari hingga Mei 2017 di Desa Bagan Asahan Kecamatan Tanjungbalai Kabupaten Asahan Provinsi Sumatera Utara. Penentuan stasiun penelitian menggunakan metode purposive sampling pada tiga stasiun dengan penentuan stasiun berdasarkan pengamatan ketersediaan jenis mangrove R. apiculata. Hasil penelitian menunjukkan laju dekomposisi serasah daun R. apiculata pada hari ke-90 yaitu pada stasiun I bernilai 13,04 stasiun II bernilai 11,42 dan stasiun III bernilai 10,24. Kandungan unsur hara karbon selama proses dekomposisi 90 hari yaitu stasiun I sebesar 16,24 %, stasiun II sebesar 15,29% dan stasiun III sebesar 15,42 %. Unsur hara nitrogen yang terdekomposisi pada hari ke 90 yaitu stasiun I sebesar 2,69%, stasiun II sebesar 2,57 % dan stasiun III sebesar 2,75%. Kandungan unsur hara fosfor selama proses dekomposisi 90 hari yaitu stasiun I 0,02 %, stasiun II 0,02 % dan stasiun III 0,01 %.Mangroves produced litter that will undergo decomposition process which used as a source of nutrients for plants and also source of food for fish and important invertebrates. The purpose of this research is to measure the decomposition of Rhizophora apiculata leaf litter and to know the content of carbon (C), nitrogen (N) and phosphorus (P) nutrient in leaf litter of R. apiculata released during the decomposition process. The research was conducted from February to May 2017 in Bagan Asahan Village, Tanjungbalai District, Asahan Regency, North Sumatera Province. The method of this research used purposive sampling and determined three stations sampling based on observation of availability R. apiculata mangrove species. The result showed that decomposition rate of R. apiculata leaf on the 90 day at station I was 13,04, station II was 11,42, and station III was 10,24. The content of carbon nutrients during the 90 day decomposition process in station I was 16.24%, station II was 15.29% and station III was 15.42%. Nitrogen nutrient elements decomposed on the 90 day were station I was 2.69%, station II was 2.57% and station III was 2.75%. Phosphorus nutrient content during 90 day decomposition process was 0,02% for station I, 0,02% for station II and 0,01% for station III.

No abstract

Apriadi T, Pratama G, Putra RD, Jumsurizal, Jaya YV, Firdaus M, Arpas HD, Suryanti A. 2018. Comparative study on the fish diversity from natural and bauxite post-mining in wetland system of Bintan Island, Indonesia. Biodiversitas 19: 967-973. In this study, the fish populations between two different wetland systems in Bintan Island, Indonesia, i.e., bauxite post-mining (Kijang) and natural wetland (Toapaya) were compared and to propose a newly index namely Environomic of Fishes Index (EFI) to their respective ecosystems. The purposive random sampling at six stations, each of three stations representing bauxite mining (Kijang) and three stations representing a natural wetland (Toapaya) were used in this research. The numbers of fish species and the abundance were enumerated. The new index derived from the value of diversity index (Shannon), similarity index (Evenness), dominance index (Simpson's), conservation status, and economic value were also evaluated. The natural wetland has higher fish diversity than bauxite post-mining. The total species found were twenty-four. The same seven species were found in both areas. Twelve species were obtained from bauxite post-mining, and nineteen species were obtained from natural wetland. Puntius tetrazona and Rasbora heteromorpha were the common species in area study. The diversity and dominance index was at low category, Evenness index was at high category in all stations, except in tidal swamp station at bauxite post-mining. The EFI in natural wetland was higher than bauxite post-mining. The three community index value, economic value, and conservation status of natural wetland were higher than bauxite post-mining.

Abstract. Coral reefs are one of the most highly productive marine ecosystems, with the largest transfer of energy attributed to the trophic interaction between herbivores and algae. Rapid demographic growth, leading to transmigration to small islands such as Natuna Island where located on outer Island Indonesia.The aim of the present study is to test for significant associations between herbivore fish species traits and Habitat complexity was derived from coral reef cover. Method to record each observed herbivore fish species with UVC (Underwater Visual Census) using SCUBA diving equipment along modification line transects. A total of 39 different fish species belonging to 3 families" herbivore fish were identified. Total biomass of herbivorous fish correlated with Dead Coral Algae (DCA). Biplot of the first two axes for the nonmetric multidimensional a scaling (NMDS) analysis for family and grazer showed the dominance of herbivore fish grazer.