AbstrakKepiting bakau (Scylla serrata) merupakan salah satu spesies kunci dalam ekosistem mangrove yang memegang peranan yang sangat penting. Hutan mangrove yang ada di Kelurahan Belawan Sicanang sudah banyak mengalami konversi lahan seperti tambak dan pemukiman. Kondisi ini menyebabkan terjadinya penurunan kualitas habitat dan penurunan populasi untuk sumberdaya kepiting bakau akibat terjadinya kerusakan daerah asuhan dan mencari makan biota ini. Penelitian ini bertujuan untuk mengetahui kondisi ekologi mangrove, untuk mengetahui kelimpahan kepiting bakau (Scylla serrata), untuk mengetahui pertumbuhan kepiting bakau (Scylla serrata) di Hutan Mangrove Kelurahan Belawan Sicanang Kecamatan Medan Belawan Provinsi Sumatera Utara. Penelitian berlangsung pada Mei  Juni 2016. Metode yang digunakan dalam penentuan lokasi adalah purposive sampling dan dibagi menjadi 3 stasiun berdasarkan aktivitas yang berbeda. Struktur populasi kepiting bakau (Scylla serrata) ditinjau dari kelimpahan kepiting bakau (Scylla serrata), hubungan lebar karapas dengan bobot tubuh, pola pertumbuhan, dan faktor kondisi. Kualitas habitat kepiting bakau (Scylla serrata) dilihat dari kualitas air, tekstur substrat, Corganik, dan pasang surut. Hasil menunjukkan bahwa kelimpahan kepiting bakau (Scylla serrata) 16300 -17000 ind/ha, dengan pola pertumbuhan allometrik negatif (b<3), faktor kondisi berkisar antara 0  1 yang tergolong ke dalam pipih atau tidak gemuk. Kualitas air dan substrat yang dikaji termasuk ke dalam kualitas air yang menunjang kehidupan kepiting bakau (Scylla serrata), tekstur substrat yaitu lempung berpasir dan lempung liat berpasir, serta C-organik < 1% tergolong sangat rendah, dimana tipe pasang surutnya adalah mixed prevailing semidiurnal. Kata kunci: kepiting bakau; struktur populasi; kualitas air dan tanah AbstractMangrove crab (Scylla serrata) is one of the keystone species in the mangrove ecosystem, which had a very important role. Mangrove forests existed in Village Belawan Sicanang have been many experienced land conversion as embankment and settlements. These conditions led to degradation in habitat quality and population decline for mangrove crab due to the occurrence of the damage to the nursery ground and the feeding ground. The research aimed to determine abundance mangrove crabs and to determine the growth of mangrove crab. The research took place in May  June 2016. The method used in the determination of the location is purposive sampling and divided into 3 stations based on different activities. The mangrove crab population structure in terms of the abundance of mangrove crab, carapace width relation with body weight, growth pattern, and factor condition. The quality habitat mangrove crab viewed the water quality, the substrate texture, C-organic, and tides. The results showed that the growth pattern was negative allometric (b < 3), factor condition ranges between 0  1 which classified into flat or not fat. The water quality and substrate were assessed included in the water quality that supported life mangrove...

<strong>Limnological Status of Lake Siombak, Medan, North Sumatra.</strong> Lake Siombak is located in the coastal area of Medan city, making its waters influenced by the tides. The lake serves as a water catchment, flood control, fishing area, and tourist destination. Various activities in the lake have led to changes in the environmental quality of the lake. To maintain the sustainability of the lake, efforts are needed for proper management. Lake management should begin with a good understanding of the nature and characteristics of the waters. This study aimed to determine the limnological status of Lake Siombak through morphometric analysis, aspects of physics, chemistry, and biology, as well as trophic status of the waters. Morphometry included dimensions of water surface and subsurface. Physics parameters included temperature, Total Suspended Solid (TSS), water clarity, electrical conductivity (EC), and salinity. Chemical parameters included pH, dissolved oxygen (DO), Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), nitrates, and phosphates. Biological parameters included community structure of nekton and benthos. Measurement of lake morphometry was performed in April 2014 at high and low tides. Measurements of water quality and biological sample collection were conducted in May-July 2014 at high and low tides. The results showed that Lake Siombak has an area of 41.44 ha with a maximum depth of 5 m at high tide and 4 m at low tide. Based on the aspects of physics, chemistry, and biology of the waters, Lake Siombak was categorized as an open waters influenced by the tides and was saline with high level of oxygen. The lake water retention time (Rt) was 15.65 hours and discharged (Q) 3.7 x 107 m3/h of water at high tide and 3.0 x 107 m3/h at low tide. High phosphate concentration indicated these waters have already been polluted. However, the water quality of Lake Siombak was still suitable for fishing activities. Benthos and nekton communities were relatively unstable. Benthic community was dominated by Blue Mussel (Mytilus edulis) at high tide (57%) and Red-rimmed Melania (Melanoides tuberculata) at low tide (41.34%). Nekton community was dominated by Blue Panchax (Aplocheilus panchax) at high tide (74.07%) and low tide (64.79%). In general, Lake Siombak was classified as eutrophic. <br /><br />

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.

A research to study the microwave absorption  properties of manganase ferrite in the X-band range have been conducted by using high energy milling technique. The synthesis of manganase ferrite (Mn1+xFe2-xO4) was performed using solid state reaction method with the material composition (x)MnO : (2-x) Fe2O3 (x = 0.25; 0.50; 0.75 and 1.0) according to the molar ratio. This powder mixture was being milled for 10 hours then sintered at 1200 °C temperature for 3 hours. Material characterization was done by using FTIR spectroscopy (Fourier Transform Infra Red Spectroscopy) to observe the functional group, XRD (X-ray diffractometer) for phase identification, SEM (Scanning Electron Microscope) for surface morphology observation and VNA (Vector Network Analyzer) to determine the ability of materials to absorb microwaves. Analysis by FTIR showed two absorption peaks in the range of ~ 446 and ~ 557 cm-1 were associated with the octahedral and tetrahedral sites in structure of MnFe2O4. Phase identification by XRD showed that the increasing content of Mn (above x=0.25 composition) caused a single phase of MnFe2O4 turned into two phases (MnFe2O4 and Fe2O3), this results correspond to the SEM results which showed the morphological structure of those compositions are inhomogenous. The Absorption of microwaves was also decreased along with the increasing of Mn content. The maximum refflection loss was reached in the composition of Mn (x=0.0) which equal to ~ 82%, while for the composition of Mn (x=0.0) only reached ~ 55%.

AbstrakPantai Bali terletak di Batu Bara dengan luas sekitar 637,22 ha dengan luas kawasan pesisir sekitar 30,6% dari total area. Penelitian ini bertujuan untuk inventarisasi sarana dan prasarana pendukung di Pantai Bali dan membuat pola pengelolaan ekowisata mangrove di Pantai Bali. Penelitian ini dilakukan pada bulan Maret hingga April 2014. Metode penelitian yang digunakan adalah purposive sampling untuk wawancara. Konsep manajemen ekowisata Pantai Bali sepenuhnya bergantung kepada pemerintah daerah dan memberikan izin kepada publik sebagai pengelola. AbstractBali Beach is a located in Batu Bara with an area of approximately 637.22 ha which is a coastal area about 30.6% of the total area. This study aims to inventory of facilities and supporting infrastructurein Bali Beach and create patterns of mangrove ecotourism management at Bali Beach. This research was conducted in March to April 2014. Research method used was purposive sampling for interviews. The oncept of Bali Beach ecotourism management entirely to local governments and gives permission to public as the manager.

The aims of the research was to examine the lenght weight relationships, growth pattern and condition factor of mudskipper (Family: Gobiidae) at the mangrove ecosystem. The research was conducted for two months from March to April 2016 at the mangrove ecosystem in the Sembilan Island village. The result showed that there are three species of mudskipper found in study area, namely Periophthalmus chrysospilos, Periophthalmus gracilis, and Boleophthalmus boddarti.  The growth pattern of mudskipper with a value b 3,  indicate a allometrik negative growth pattern and the condition factor was between 1-2.Penelitian ini bertujuan untuk menganalisis hubungan panjang bobot, pola pertumbuhan dan faktor kondisi ikan belodok (Famili: Gobiidae) pada ekosistem mangrove di di desa Pulau Sembilan Langkat. Penelitian dilaksanakan selama dua bulan yaitu Maret sampai April 2016. Penelitian ini menggunakan metode purposive random sampling. Hasil penelitian ditemukan 3 spesies ikan belodok di lokasi penelitian yaitu Periophthalmus chrysospilos, Periophthalmu sgracilis, dan Boleophthalmus boddarti. Pola pertumbuhan ikan belodok dengan nilai b 3, mengindikasikan pola pertumbuhan allometrik negatif. Faktor kondisi dari Ikan Belodok berkisar 1 – 2.

<strong>Morphometry and Pollution Load Capacity of Lake Pondok Lapan in Langkat Regency, North Sumatra.</strong> Morphometry is necessary to know the physical characteristics of a lake and how much the ability of the lake to receive pollutant loads. Determination of water quality status and pollution load capacity of lake water is very important to do with the utilization of lake by the community for cultivation activity of floating net cage (KJA). This study aimed to determine the characteristics of morphometry and bathymetry of the lake, determine the status of water quality and the capacity of lake pollution load. The study was conducted in January–March 2015. Mapping was done by making a path of 100 trajectories which was then processed with ArcView. The observation station for water quality consisted of 4 stations. The status of water quality was determined by the Pollution and Storage Index method based on PerMen LH. No. 115 of 2003. The capacity of lake pollution loud refers to PerMen LH. 28 of 2009. The results showed that Lake Pondok Lapan area reached 63,472.78 m2 (6.35 ha) with a maximum depth of 4.15 m. This lake is classified as a closed water, aerobic, with a residence time of 11–12 days. The depth of compensation is at a depth of 2.61–2.85 m. The water discharge coming out of the lake ranges 12,963.45–14,111.71 m³ per day. The status of water quality of Lake Pondok Lapan is categorized as uncontaminated with score 0 for the Storet method and 0.46–0.86 for Pollution Index method. Lake pollution load capacity is of 1.98 kg of phosphorus per year. <br /><br />

Nickel ferrite doped by neodymium in the form of (Ni(1-x)NdxFe2O4) with (x =  0.0 ; 0.2 and 0.4) have been synthesized using solid state reaction method with milling technique from NiO, Nd2O3 and Fe2O3 powder. The mixture of those compound materials was milled using High Energy Milling (HEM) machine for 10 hours and then sintered at 1000 °C for 5 h. X-ray diffraction patterns showed that a single phase of spinel ferrite has been formed in all of the compositions. The result of morphological observation using Scanning Electron Microscope (SEM) exhibited a homogeneous structure has been formed with particle size about 200 nm. The magnetic measurement using vibrating sample magnetometer (VSM) showed that the sample exhibited a ferromagnetic behavior, where the Ms value decrease (around of 58.4 to 39.40 emu/g) and value of Hc increased (around of 116-170 Oe) along with the addition of the Nd3+ ion (x values) content. While the ability of microwaves absorption measured by using Vector Network Analyzer (VNA) indicates that the maximum value of Reflection Loss (RL) obtained at the composition of x = 0.4 up to -29 dB at a frequency of 10.81 GHz. It means the Ni0,6Nd0,4Fe2O4 sample can absorb microwave up to ~ 96.5% at a frequency of 10.81 GHz.