Judul: Macrozoobenthos Community Structure in Seagrass Ecosystem in Tidung Island, Seribu Islands
Abstrak: Pulau Tidung terbagi menjadi dua gugusan pulau, yaitu Pulau Tidung Besar dipengaruhi aktivitas antropogenik, dan Pulau Tidung Kecil tidak dipengaruhi aktivitas antropogenik. Salah satu ekosistem di Pulau Tidung yang keberadaannya kurang diperhatikan ialah ekosistem lamun. Penelitian ini bertujuan menganalisis struktur komunitas makrozoobenthos pada ekosistem lamun di kedua pulau. Stasiun pengambilan contoh terdiri dari dua stasiun, yakni di Utara Tidung Besar dan di Utara Tidung Kecil dengan menggunakan metode garis transek. Analisis yang dilakukan meliputi kepadatan makrozoobenthos, indeks ekologi, dan keterkaitan makrozoobenthos dengan parameter pendukung. Makrozoobenthos yang ditemukan di Pulau Tidung terdiri dari 34 ordo, 57 famili, 76 genus didominasi oleh kelas Gastropoda. Rata-rata kepadatan makrozoobenthos pada masing-masing stasiun sebanyak 24 ind/m2 dan 20 ind/m2. Indeks ekologi menunjukkan bahwa makrozoobenthos berada dalam kondisi yang baik. Hasil PCA menunjukkan bahwa kepadatan makrozoobenthos memiliki hubungan yang kuat dengan suhu., Tidung Island has two islands, namely Tidung Besar Island which is affected by anthropogenic activities, and Tidung Kecil Island which is less affected by anthropogenic activities. One of the ecosystems in Tidung Island whose existence is less considered is seagrass ecosystem. This study aims to analyze the structure community of macrozoobenthos in seagrass ecosystems on both island. The sampling stations consisted of two stations, North of Tidung Besar and North of Tidung Kecil using the line transect method. The analysis included macrozoobenthos density, ecological index, and macrozoobenthos association with supporting parameters. Macrozoobenthos found in Tidung Island consisted of 34 orders, 57 families, 76 genus dominated by Gastropoda class. The average density of macrozoobenthos at each station was 24 ind/m2 and 20 ind/m2. Ecological index shows that macrozoobenthos are in good condition. PCA results showed that macrozoobenthos density had a strong relationship with temperature.
Keyword: water quality, seagrass, anthropogenic, gastropoda, gastropoda, macrozoobenthos

Judul: Relationship between Seagrass Community Structure and Habitat Quality in Tidung Island, Seribu Islands
Abstrak: Ekosistem padang lamun merupakan ekosistem penting pesisir. Namun demikian, luas padang lamun di dunia terus menurun setiap tahunnya sekitar 7% per tahun. Salah satu wilayah yang memiliki ekosistem padang lamun adalah Pulau Tidung, Kepulauan Seribu. Penelitian ini bertujuan menganalisis keterkaitan struktur komunitas padang lamun dengan kualitas habitat di Pulau Tidung. Penelitian dilakukan pada bulan November 2023 dengan metode line transect untuk pengamatan lamun. Selain itu, juga dilakukan pengukuran kualitas air dan substrat (fraksi dan C-organik substrat). Analisis data yang digunakan antara lain penutupan jenis lamun, kerapatan jenis, frekuensi jenis, indeks nilai penting, indeks ekologi, serta Spearman rank correlation. Hasil penelitian ini menunjukkan kesehatan padang lamun di Pulau Tidung tergolong kategori miskin hingga kurang kaya/kurang sehat. Jenis lamun yang ditemukan sebanyak enam spesies. Thalassia hemprichii adalah jenis lamun dengan peran terbesar dalam komunitas padang lamun di Pulau Tidung. Kerapatan lamun berkaitan dengan suhu dan liat kasar secara kuat positif. Kandungan C-organik substrat memiliki kaitan yang kuat terhadap penutupan dan kerapatan lamun di Pulau Tidung., Seagrass ecosystems are important coastal ecosystems. However, the area of seagrass beds in the world continues to decline annually by about 7% per year. One of the areas that has seagrass ecosystem is Tidung Island, Seribu Islands. This study aims to analyze the relationship between seagrass community structure and habitat quality in Tidung Island. The research was conducted in November 2023 using line transect method for seagrass observation. Water quality and substrate (substrate fraction and C-organic) were also conducted. Data analysis used included seagrass species closure, species density, species frequency, importance index, ecological index, and Spearman rank correlation. The results of this study show that the health of seagrass beds on Tidung Island is classified as poor to less rich/unhealthy. Six species of seagrass were found with Thalassia hemprichii is a type of seagrass that has the largest role in the seagrass community in Tidung Island. Seagrass density was strongly positively related to temperature and coarse clay. Substrate C-organic content has a strong relationship with seagrass cover and density in Tidung Island.
Keyword: habitat, lamun, Pulau Tidung, struktur komunitas

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.
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