No abstract

Kappaphycus alvarezii is the most widely grown seaweed known by the commercial name "cottoni." Several types or strains of K. alvarezii are grown in Indonesia, and each has a different appearance.

Seagrass is an aquatic biota that is ecologically and economically beneficial. This study aims to determine the community structure of seagrass in Harapan Island, Seribu Islands, Indonesia. The research was conducted using purposive sampling method, that divided into two sites which is considered to represent the ecology’s condition of Harapan Island. The site 1 was located adjacent to the mangroves area, while the site 2 was placed near a reclamation development and ship anchoring. Every site had three subsites as replications, each was 50 meters apart. Water parameters temperature, salinity, turbidity, pH, dissolved oxygen (DO), depth, and organic compound of each site were measured. The results showed that coverage of seagrass in site 2 is higher than site 1 that categorized as frequent-common coverage. The site 2 had the density of 220 individuals seagrass per square meter that dominated by Cymodocea rotundata. The highest diversity index was found in the site 1 at 1.15, with the lowest dominance index being 0.39. The distribution pattern in site 1 is clustered and uniform, while site 2 is uniform. The Importance Value Index in site 1 was 114,8 by Halodule uninervis, while site 2 was 125,5 by C. rotundata. It is thought that the low diversity of seagrass at the site 2 due to it was near a reclamation development and ship anchoring that disturb the abundance and community structure of seagrass in Harapan Island. Habitat destruction and anthropogenic impact of seagrass need to be minimized to support environmental coastal and fisheries sustainability.

Seagrass is one of the important ecosystems in coastal areas. This study aims to determine the biomass and carbon stock in the seagrass ecosystems of the Pamegaran Island, Seribu Islands National Park, Jakarta. Data collection was conducted on December 2021 to January 2022 is done by using SeagrassWatch method and carbon data sampling results were analyzed by Kurmies method / SNI 13-4720-1998 method. Cymodocea rotundata has the highest biomass value, while Halodule uninervis has the lowest biomass value. The seagrass biomass value at the bottom of the substrate was higher than the top of the substrate in all the species found was because the rhizome contained carbohydrates and nutrients produced in the photosynthesis process and stored at the bottom of the substrate. The total value of seagrass carbon stock in the entire area is 1,932,151.36 ± 265,280.90 g C or 1.932 ± 2.652 t C with an area of 3.63 ha of seagrass beds. Thalassia hemprichii has the highest carbon stock value, while Halodule uninervis species has the lowest biomass value. The carbon stock value of the bottom of the substrate was higher than that of the top of the substrate in all species found.   Lamun adalah salah satu ekosistem penting yang ada di daerah pesisir. Penelitian ini bertujuan untuk mengetahui biomassa dan stok karbon pada ekosistem padang lamun di Pulau Pamegaran, Taman Nasional Kepulauan Seribu, Jakarta. Pengambilan data dilakukan pada bulan Desember 2021 hingga Januari 2022 menggunakan metode SeagrassWatch dan analisis data karbon menggunakan metode Kurmies / metode SNI 13-4720-1998. Cymodocea rotundata memiliki nilai biomassa yang tertinggi, sedangkan Halodule uninervis memiliki nilai biomassa terendah. Nilai biomassa lamun bagian bawah substrat lebih tinggi dari bagian atas substrat pada semua spesies yang ditemukan hal ini karena rhizome mengandung karbohidrat serta zat hara yang dihasilkan pada proses fotosintesis dan tersimpan pada bagian bawah substrat. Nilai total stok karbon lamun pada keseluruhan luas wilayah sebesar 1.932.151,36 ± 265.280,90 g C atau 1,932 ± 2,652 t C dengan luas wilayah padang lamun sebesar 3,63 Ha. Thalassia hemprichii memiliki nilai stok karbon tertinggi, sedangkan Halodule uninervis memiliki nilai biomassa terendah. Nilai stok karbon bagian bawah substrat lebih tinggi dari bagian atas substrat pada semua spesies yang ditemukan.

The food habit is one of the important information used in the fisheries resource management. This study aimed to determine food preferences, index of preponderance, and trophic level of shortfin scad (D. macrosoma) captured from the southern waters of Gunungkidul Yogyakarta, Indonesia. A total of 325 fish samples were collected from March to September 2018. Each fish sample was measured in total length, body weight, determined its sex, and then dissected. The digestive tract was measured in total length then the gut contents were preserved in 5% formaldehyde to observe the type of food composition. The results showed that shortfin scad was carnivorous fish (relative gut length = 0.47) with the diet composing of fish (84.15%), phytoplankton (8.91%), zooplankton (4.47%), and snipping shrimp (3.19%). The molecular identification showed that the main fish species eaten by shortfin scad was Cololabis saira (Scomberesocoidae).AbstrakKebiasaan pakan ikan merupakan salah satu informasi penting yang digunakan dalam manajemen sumberdaya perikanan. Penelitian ini bertujuan untuk mengetahui preferensi pakan, indeks bagian terbesar dan tingkat trofik ikan layang deles (D. macrosoma) yang ditangkap dari Perairan Gunungkidul. Total 325 sampel ikan layang deles dikumpulkan selama bulan Maret sampai dengan September 2018. Setiap sampel ikan diukur panjang total, berat tubuh, ditentukan jenis kelaminnya kemudian dilakukan pembedahan. Saluran pencernaan diukur panjangnya, kemudian isi lambung ikan diawetkan dalam formalin 5% untuk diamati komposisi jenis makanannya. Analisis data meliputi panjang usus relatif, frekuensi kejadian, indeks bagian terbesar, dan tingkat trofik ikan layang deles. Hasil penelitian menunjukkan bahwa ikan layang deles bersifat karnivora (panjang usus relatif = 0,47) dengan komposisi jenis makanan utama adalah ikan (84,15%). Makanan pelengkap layang deles adalah fitoplankton (8,91%), sedangkan zooplankton (4,47%) dan potongan udang (3,19%) merupakan makanan tambahan. Berdasarkan identifikasi molekuler, spesies ikan yang menjadi makanan utama ikan layang deles adalah Cololabis saira (Scomberesocoidae).