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: Diversity and Association of Epifauna Gastropods in Mangrove and Seagrass of Tidung Kecil Island, Seribu Island
Abstrak: Pulau Tidung Kecil memiliki berbagai ekosistem pesisir, seperti ekosistem mangrove dan lamun. Kedua ekosistem tersebut menjadi tempat berlindung, mencari makan, dan memijah bagi gastropoda. Penelitian ini bertujuan menganalisis keanekaragaman dan asosiasi gastropoda epifauna pada mangrove dan lamun Pulau Tidung Kecil, Kepulauan Seribu. Pengamatan data mangrove, lamun, dan gastropoda dilakukan pada 4 (empat) stasiun dengan metode transek garis dan transek kuadrat, setiap stasiun dilakukan pengukuran kualitas perairan. Gastropoda epifauna yang ditemukan pada lokasi penelitian terdiri dari 25 spesies dan 11 famili yaitu famili Cerithiidae, Ellobiidae, Littorinidae, Muricidae, Nassariidae, Naticidae, Neritidae, Potamididae, Strombidae, Trochidae, dan Turbinidae dengan nilai keanekaragaman keseluruhan stasiun tergolong sedang. Spesies gastropoda epifauna yang mendominasi yaitu Terebralia palustris dari famili Potamididae. Spesies mangrove yang ditemukan pada lokasi penelitian yaitu Rhizophora stylosa, sedangkan spesies lamun yaitu Thalassia hemprichii, Enhalus acoroides, Cymodocea rotundata, dan Halophila ovalis. Kualitas perairan pesisir Pulau Tidung Kecil tergolong baik untuk mangrove, lamun, dan gastropoda dengan tipe substrat lempung berdebu. Hasil analisis CA menunjukkan bahwa famili gastropoda Cerithiidae, Ellobiidae, Muricidae, Naticidae, Neritidae, Strombidae, dan Turbinidae berasosiasi dengan lamun, sedangkan famili gastropoda Littorinidae dan Trochidae berasosiasi dengan mangrove., Tidung Kecil Island has various coastal ecosystems, such as mangrove and seagrass ecosystems. Both ecosystems provide shelter, foraging, and spawning for gastropods. This study aims to analyze the diversity and association of epifauna gastropods in the mangrove and seagrass of Tidung Kecil Island, Seribu Island. Observation of mangrove, seagrass, and gastropod data was carried out at 4 (four) stations using line transect and quadratic transect methods, each station measuring water quality. The epifauna gastropods found at the study site consisted of 25 species and 11 families, namely Cerithiidae, Ellobiidae, Littorinidae, Muricidae, Nassariidae, Naticidae, Neritidae, Potamididae, Strombidae, Trochidae, and Turbinidae with the overall diversity value of the stations classified as moderate. The dominant epifauna gastropod species was Terebralia palustris from family Potamididae. The mangrove species found at the research site was Rhizophora stylosa, while the seagrass species were Thalassia hemprichii, Enhalus acoroides, Cymodocea rotundata, and Halophila ovalis. The coastal water quality of Tidung Kecil Island was classified as good for mangroves, seagrasses, and gastropods with a silt loam type of substrate. The results of CA analysis showed that the gastropod families Cerithiidae, Ellobiidae, Muricidae, Naticidae, Neritidae, Strombidae, and Turbinidae were associated with seagrass, while the gastropod families Littorinidae and Trochidae were associated with mangrove.
Keyword: lamun, association, diversity, gastropod, mangrove, seagrass, asosiasi, gastropod, keanekaragaman

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: