Judul: Diversity and Association of Gastropods in the Seagrass Ecosystem on Tidung Kecil Island, Seribu Islands.
Abstrak: Gastropoda berperan dalam proses dekomposisi dan kestabilan ekosistem. Penelitian ini bertujuan menganalisis keanekaragaman dan asosiasi gastropoda pada ekosistem lamun Pulau Tidung Kecil, Kepulauan Seribu. Pengamatan menggunakan metode Seagrass Watch di empat stasiun ekosistem lamun. Tiap stasiun diukur parameter lingkungan perairan dan sedimen. Gastropoda yang ditemukan terdiri dari 53 spesies yang tergolong dalam 13 famili dengan kepadatan tertinggi di seluruh stasiun dimiliki oleh famili Cerithiidae yaitu 1503 ind/m2. Spesies dengan nilai kepadatan tertinggi adalah Cerithium punctatum di Stasiun 3 sebesar 303 ind/m2. Spesies lamun yang ditemukan yaitu Thalassia hemprichii, Enhalus acoroides, Cymodocea rotundata, dan Halophila ovalis. Kualitas perairan di ekosistem lamun masih berada dalam baku mutu gastropoda dengan substrat didominasi pasir. Analisis korespondensi (CA) menunjukkan terdapat tiga kelompok utama asosiasi gastropoda dengan vegetasi lamun. Komposisi gastropoda pada lamun jenis T. hemprichii dan lamun campuran memiliki nilai tertinggi. Analisis korelasi Pearson menunjukkan kerapatan lamun dengan kepadatan gastropoda memiliki hubungan sangat kuat dan searah., Gastropods significantly contribute to ecosystem stability and decompositions. This study examines the diversity and association of gastropods in seagrass ecosystem of Tidung Kecil Island, Seribu Islands. Observations were conducted at four stations using the Seagrass Watch method, measuring aquatic and sedimentary parameters. Gastropods found consisted of 53 species from 13 families with the highest density throughout the stations is Cerithiidae of 1503 ind/m2. The species with the highest density value is Cerithium punctatum at Station 3 of 303 ind/m2. Seagrass species found were Thalassia hemprichii, Enhalus acoroides, Cymodocea rotundata, and Halophila ovalis. The water quality in the seagrass ecosystem aligns with the gastropod life standards with sand-dominated substrate. The results of correspondence analysis (CA) revealed three main groups of gastropod associations with seagrass vegetation. The composition of gastropods in T. hemprichii seagrass and mixed seagrass has the highest value. Pearson correlation showed that seagrass density and gastropod density have a very strong and proportional relationship.
Keyword: association, diversity, gastropods, seagrass

Judul: Community Structure of Bivalve and Its Relationship with the Seagrass Ecosystem on Tidung Kecil Island, Seribu Islands.
Abstrak: Pulau Tidung Kecil merupakan pulau yang memiliki padang lamun yang dapat menunjang keberlangsungan hidup organisme laut salah satunya bivalvia. Penelitian bertujuan menganalisis struktur komunitas bivalvia dan keterkaitannya dengan ekosistem lamun di Pulau Tidung Kecil, Kepulauan Seribu. Penelitian dilakukan pada empat stasiun dengan tiap stasiun diukur kualitas lingkungan perairan dan sedimen. Pengambilan data lamun dan bivalvia menggunakan transek garis dengan panjang 50 m dan transek kuadrat ukuran 0,5 x 0,5 m². Hasil penelitian ditemukan empat spesies lamun dengan kerapatan tertinggi yaitu Thalassia hemprichii. Bivalvia yang ditemukan terdiri dari tujuh famili dan 15 spesies, dengan kepadatan spesies tertinggi yaitu Tellina timorensis sebesar 6,67 ind/m2. Kualitas lingkungan perairan Pulau Tidung Kecil tergolong baik dengan substrat dominan pasir. Analisis Koresponden menunjukkan terdapat tiga kelompok keterkaitan bivalvia dan lamun. Famili Tellinidae dan Cardiidae dengan lamun Thalassia hemprichii, Famili Lucinidae, Arcidae dan Veneridae dengan lamun Halophila ovalis dan Enhalus acoroides dan famili Mactridae dan Donacidae dengan lamun Cymodocea rotundata., Tidung Kecil Island is an island that has seagrass beds can support the survival of marine organisms, including bivalves. The study aims to analyze the bivalve community structure and its relationship with the seagrass ecosystem on Tidung Kecil Island, Seribu Islands. The study was conducted at four stations with measures quality of the aquatic and sedimentary. The collection of seagrass data used line transect 50 m and quadrat transect 0,5 x 0,5 m2. The results of the study found four seagrass species with the highest density is Thalassia hemprichii. Bivalves were found consisting of seven families and 15 species, with the highest density is Tellina timorensis at 6,67 ind/m2. The quality of Tidung Kecil Island aquatic environment is good with a dominant sandy substrate. Correspondence analysis showed that there are three groups related of bivalve and seagrass on Tidung Kecil Island. The families Tellinidae and Cardiidae with seagrass Thalassia hemprichii, families Lucinidae, Arcidae and Veneridae with seagrasses Halophila ovalis and Enhalus acoroides and famili Mactridae and Donacidae with seagrass Cymodocea rotundata.
Keyword: bivalve, correspondence analisys, seagrass, Tidung Kecil Island

Judul: Construction of Strongly Optimal Binary Linear Code with Minimum Distance 9 and 11
Abstrak: A binary linear code of length n over q F is a subspace of n q F . A code has three parameters that attached to it, namely length, dimension, and minimum distance. A code with length n, dimension k and minimum distance d is often called [n, k, d ]-code. Usually, when two parameters are given, then we want to find a code that has the best value for the last parameter. Based on Gilbert- Varshamov bound, if a [n, k, d ]-code exists and can not be expanded, we call it a strongly optimal code. In this paper, we construct strongly optimal code with minimum distance 9 and 11. In constructing the code, we created a theorem and algorithm based on Gilbert-Varshamov bound before we implement the algorithm to MAPLE programming language. Because of computational limitations, the program can only construct up to k = 10 for d = 9 and k = 12 for d = 11.
Keyword: