Karakteristik Pengikatan dan Stabilitas Hamparan Pecahan Karang (Rubble Beds) di Taman Nasional Laut Bunaken, Sulawesi Utara

Abstract

Perairan Taman Nasional Bunaken (TNB) yang termasuk ke dalam kawasan konservasi, terkenal dengan keanekaragaman hayati lautnya yang tinggi, khususnya pada ekosistem terumbu karang. Namun demikian, tekanan alami dan antropogenik yang terjadi secara berkala pada ekosistem terumbu karang di TNB, mengakibatkan transformasi ekosistem terumbu karang yang sehat menjadi rusak, seperti hamparan pecahan karang (rubble). Lebih dari 40 tahun, kondisi hamparan rubble di wilayah perairan TNB tidak mengalami kestabilan dan berubah menjadi ekosistem terumbu alami. Penelitian ini bertujuan menganalisis karakteristik fisik, komposisi biota pengikat, serta stabilitas hamparan rubble di perairan TNB. Penelitian ini dilaksanakan di perairan TNB, yaitu Pulau Manado Tua, Pulau Bunaken, dan Pulau Siladen pada bulan Maret hingga Desember 2023. Pengamatan dilakukan dengan penyelaman SCUBA, dengan mengamati 90 sampel rubble pada setiap stasiun. Pengamatan karakteristik fisik rubble dilakukan untuk setiap sampel dan kemiringan serta kedalaman substrat dilakukan di setiap transek kuadrat. Pengambilan sampel menggunakan metode purposive sample dengan alat bantu belt transect. Analisis data mencakup komposisi relatif kategori bentik dan morfologi rubble, probabilitas pengikatan dan stabilitas rubble dengan generalized linear mixed-effect model (GLMM), serta komposisi biota pengikat dengan PERMANOVA. Hasil penelitian menunjukkan bahwa luas, kemiringan, dan ketebalan hamparan rubble, panjang rubble, serta jumlah rekrutmen karang bervariasi signifikan antarstasiun. Model probabilitas pengikatan dan stabilitas rubble dari 360 sampel yang diambil ditinjau berdasarkan kemiringan lereng, ketebalan hamparan dan panjang rubble, serta morfologi rubble. Sebanyak 18% dari sampel rubble mengalami pengikatan, dengan probabilitas pengikatan rubble tertinggi dimiliki oleh morfologi rubble other (25%), tingkat probabilitas pengikatan rubble yang semakin tinggi seiring dengan bertambahnya kedalaman dan panjang rubble, namun menurun seiring dengan bertambahnya kemiringan lereng. Sementara hanya 7% dari seluruh sampel rubble mengalami stabilitas, dengan probabilitas pengikatan meningkat signifikan seiring dengan bertambahnya panjang rubble. Tidak ada perbedaan komposisi biota pengikat antarastasiun, dengan CCA sebagai biota pengikat paling umum yang ditemukan (46%), diikuti dengan spons (17%) dan karang keras (14%). Hamparan rubble terluas terdapat pada wilayah landai (Siladen Selatan), sementara terkecil pada wilayah curam (Manado Tua). Probabilitas pengikatan meningkat seiring dengan bertambahnya panjang dan ketebalan hamparan rubble, namun menurun seiring dengan curamnya lereng. Probabilitas stabilitas hanya meningkat secara signifikan seiring dengan bertambahnya panjang rubble. Ditemukan tujuh jenis biota pengikat dan satu pengikatan abiotik pada sampel rubble yang ada di lokasi studi.

The waters of Bunaken National Park (TNB), which are included in the conservation area, are well known for their high marine biodiversity, in particular the coral reef ecosystem. However, natural and anthropogenic pressures that occur periodically on coral reef ecosystems in TNB, resulted in the transformation of healthy coral reef ecosystems into damaged ones, such as a rubble beds. For more than 40 years, the condition of the rubble beds in TNB waters has not experienced stability and turned into a natural reef ecosystem. This research aims to analyze the physical characteristics, composition of binding organism, and stability of rubble beds in TNB waters. This research was carried out in TNB waters, namely Manado Tua Island, Bunaken Island and Siladen Island from March to December 2023. Observations were carried out using SCUBA diving, by observing 90 rubble samples at each station. Observations of the physical characteristics of rubble were carried out for each sample and the slope and depth of the substrate were carried out at each quadrat transect. Sampling was taken using a purposive sample method with a belt transect tool. Data analysis includes the relative composition of benthic categories and rubble morphology, binding probability and rubble stability using generalized linear mixed-effect models (GLMM), as well as binding biota composition using PERMANOVA. The results showed that the area, slope and thickness of the rubble bed, the length of the rubble and the amount of coral recruitment varied significantly between stations. Models of the probability of binding and stability of rubble from 360 samples taken were reviewed based on slope slope, bed thickness and rubble length, as well as rubble morphology. As many as 18% of the rubble samples undergone binding, with the highest probability of rubble binding belonging to other rubble morphology (25%), the level of rubble binding probability which was higher as the depth and length of the rubble increased, but decreased as the slope angle increased. Meanwhile only 7% of all rubble samples undergone stability, with the binding probability increasing significantly as the rubble length increased. There were no differences in the composition of binding biota between stations, with CCA as the most common binding biota found (46%), followed by sponges (17%) and hard corals (14%). The widest length of rubble is found in the steeper area (Siladen Selatan), while the smallest is in the gentle slope area (Manado Tua). The probability of binding increases with increasing length and thickness of the rubble bed, but decreases with steeper slopes. The probability of stability only increases significantly as the rubble length increases. Seven types of binding biota and one abiotic binding type were found in the rubble samples at the study location.