Judul: Contribution of Mangrove Ecosystems to Primary Productivity of Coastal Waters in the Beejay Bakau Resort, Probolinggo
Abstrak: Probolinggo City is a coastal area with a mangrove area of about 90 hectares, located close to the Coastal Fishery Port (PPP) Mangunharjo Village, Probolinggo City. The mangrove ecosystem in this area was previously a waste disposal area with degraded mangrove conditions, then managed and rehabilitated into a tourist attraction under the name Beejay Bakau Resort (BJBR). Rehabilitation of the mangrove ecosystem can maintain the balance of the ecosystem by maintaining the supply of nutrients around it. The recovered mangrove ecosystem will produce more litter, which becomes a source of nutrients for the ecosystem. The nutrient content and abundance of plankton is one indicator for water productivity. This research was conducted in December 2020 in the BJBR mangrove ecosystem, Probolinggo. Determination of research stations using the purposive sampling method. Data collection of mangrove vegetation and environmental characteristics was carried out using the quadratic transect method. Water samples were taken at high and low tide and then analyzed for nutrients and plankton. Variations in environmental characteristics between research stations and the abundance of plankton between stations and environmental conditions were analyzed using Principal Component Analysis (PCA). Furthermore, multiple linear regression analysis was performed to determine the relationship between chlorophyll-a and dissolved nutrients. The results showed that the mangrove ecosystem of BJBR, Probolinggo has three mangrove species, namely Avicennia marina, Rhizophora stylosa, and Rhizophora mucronata. Mangrove density in this ecosystem varies, with dense density for the tree category, moderate for the sapling category, and medium-rare for the seedling category. The concentration of available P ranged from 37.00-69.32 mg/kg, the concentration of C-organic ranged from 1.30-2.61% and the concentration of N-total ranged from 2.57-4.80%. The estimation results using multiple linear regression showed that nitrate and orthophosphate significantly affected the chlorophyll-a concentration of 68.6% (F= 37.22, P=0.007). Phytoplankton found in the waters of the BJBR ecosystem consisted of three classes of phytoplankton, namely Bacillariophyceae, Cyanophyceae, and Dinophyceae, with the highest abundance were the class Bacillariophyceae. The zooplankton found consisted of the Protozoa, Crustaceae, Urochordata, Pelecypoda, Gastropods, Nematodes, Polychaeta, and Coelenterata groups, with the highest abundance in the Crustaceae class. The results of this study are expected to be used for management policies of BJBR's mangrove ecosystem based on fishery resources.
Keyword: BeeJay Bakau Resort, mangrove, klorofil-a, Probolinggo, produktivitas primer, plankton

Judul: Biologi Populasi Kerang (Telescopium telescopium dan Cerithidea obtusa) dan Keterkaitannya dengan Karakteristik Habitat Mangrove di Kawasan Beejay Bakau Resort, Probolinggo
Abstrak: Ekosistem mangrove BeeJay Bakau Resort (BJBR) adalah ekosistem mangrove rehabilitasi seluas 89 ha yang dimanfaatkan masyarakat sekitar untuk mencari berbagai macam sumberdaya, salah satunya adalah gastropoda. Gastropoda merupakan biota yang dapat ditemukan secara luas baik di darat, air, dan sebagian di ekosistem mangrove. Dua spesies yang banyak ditemukan adalah Telescopium telescopium dan Cerithidea Obtusa. Biota ini memiliki potensi untuk dikembangkan menjadi bioindikator, secara ekonomi, dapat pula dimanfaatkan untuk dijual dan dikonsumsi. T. telescopium memiliki kandungan protein sebesar 12,16% dan lemak 0,38%. C. obtusa memiliki kandungan gizi protein 13,8% dan lemak 2,8%. Pemanfaatan yang berlebihan dapat menyebabkan menurunnya kelimpahan dari gastropoda. Berdasarkan potensi tersebut, dua spesies yang dapat ditemukan di pesisir Probolinggo Jawa Timur menarik untuk ditelaah lebih lanjut mengenai interaksinya dengan ekosistem mangrove untuk dapat dikelola secara berkelanjutan. Penelitian ini dilakukan pada Bulan Desember 2020 di ekosistem mangrove BJBR, Probolinggo. Penentuan stasiun dilakukan dengna menggunakan purposive sampling berdasasrkan karakteristik ekosistem mangrove. Pengumpulan data gastropoda dilakukan dengan menggunakan transek kuadran gastropoda (1x1m). Karakteristik lingkungan di semua stasiun dianalisis menggunakan PCA (Principal Component Analysis) sedangkan sebaran gastropoda berdasarkan struktur ekosistem mangrove dianalisis menggunakan CA (Correspondence Analysis). Hasil penelitian menunjukkan bahwa kelimpahan gastropoda T. telescopium sebesar 144 ind dan C. obtusa sebanyak 29 ind. T. telescopium memiliki kepadatan yang lebih tinggi dibandingkan C. obtusa dengan pola persebaran mengelompok hampir di seluruh stasiun. Secara umum, kedua jenis gastropoda memiliki pola pertumbuhan allometrik negatif dengan kondisi yang baik untuk dimanfaatkan karena memiliki bentuk yang montok. Kehidupan gastropoda dipengaruhi oleh karakteristik ekosistem mangrove. C. obtusa berkuran kecil dan besar berasosiasi dengan mangrove dengan kerapatan jarang A. marina (<10). T. telescopium berkuran kecil berasosiasi dengan mangrove R. mucronata (<10). T. telescopium berukuran sedang dapat ditemukan di mangrove R. stylosa (≥ 15) kerapatan tinggi. Sedangkan T. telescopium besar dapat ditemukan di mangrove A. marina dan R. mucronata dengan kerapatan sedang hingga tinggi (≥ 15 dan ≥ 10 - <15).
Keyword: Beejay Bakau Resort, gastropoda, abundance, mangrove

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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