KONTRIBUSI KOMUNITAS FITOPLANKTON DAN MIKROBA HALOFILIK TERHADAP KUALITAS GARAM TRADISIONAL

Abstract

RINGKASAN RINI SUSILOWATI. Kontribusi Komunitas Fitoplankton dan Mikroba Halofilik Terhadap Kualitas Garam Tradisional. Dibimbing oleh DIETRIECH G. BENGEN, MAJARIANA KRISANTI, HEDI INDRA JANUAR dan IMAN RUSMANA. Garam adalah komoditas penting yang memiliki peranan vital dalam berbagai aspek kehidupan. Produksi garam di Indonesia sebagian besar tergantungan pada kondisi alam sering menimbulkan permasalahan dalam produksi garam tradisional, termasuk kualitas garam yang tidak konsisten dan produksi yang fluktuatif setiap tahunnya. Situasi ini berdampak pada pemenuhan kebutuhan garam nasional, terutama untuk keperluan industri, yang tidak tercukupi oleh produksi dalam negeri. Upaya peningkatan kualitas garam dapat dilakukan melalui peningkatan manajemen tambak garam, termasuk pemanfaatan komunitas biologi dalam lingkungan tambak untuk menghasilkan garam yang berkualitas tinggi. Penelitian ini bertujuan mengkaji interaksi antara parameter lingkungan dan struktur komunitas biologi dalam tambak garam yang memegang peranan penting dalam meningkatkan kualitas lingkungan tambak, serta mengetahui peranan komunitas biologi terhadap kualitas garam. Proses pengambilan sampel dilakukan pada waktu musim kemarau di tiga lokasi yaitu Kabupaten Brebes, Tuban, dan Sampang. Parameter kualitas air dianalisis sesuai dengan prosedur standar nasional Indonesia (SNI) yang meliputi analisis parameter nutrien dan fisik seperti suhu, salinitas, bahan organik total, serta karbon organik. Struktur komunitas plankton diidentifikasi morfologinya secara visual, keanekaragaman mikroba halofilik dieksplorasi menggunakan pendekatan metagenomik berbasis gen 16S rRNA. Analisis kristal garam meliputi evaluasi parameter kemurnian, jenis impuritas, serta analisis terhadap permukaan dan ukuran kristal garam. Konsentrasi nutrien Brebes paling tinggi dibandingkan dengan dua lokasi lainnya, yaitu fosfat (5,38–5,66 mg/L); nitrat (0,17–0,74 mg/L); nitrit (0,07–0,1 mg/L); oksigen terlarut (DO) sebesar 9,29–11,82 mg/L; karbon organik total (KOT) sebesar 0,01–0,03 mg/L; dan bahan organik total (BOT) sebesar 0,03–0,07 mg/L. Kelimpahan fitoplankton dan zooplankton tertinggi tercatat di Brebes yaitu (127.721±11.227 sel/L) dan (3.339±391 individu/L). Kelompok fitoplakton Bacillariophyceae mendominasi di tiga lokasi. Kelompok zooplankton Litostomatea mendominasi di Brebes dan Sampang, sedangkan kelompok Oligotrichea mendominasi di Tuban. Kelimpahan relatif pada tingkatan filum tertinggi dari salinitas rendah sampai tinggi berturut-turut pada komunitas bakteri ditemukan pada lokasi Sampang salinitas rendah yaitu 96,44%; Brebes salinitas sedang dan tinggi masing-masing sebesar 90,29%; 23,74%, komunitas arkea ditemukan pada lokasi Sampang salinitas rendah sebesar 1,38%; Brebes salinitas sedang dan tinggi berturut-turut sebesar 8,31% dan 75,43%. Komunitas bakteri didominasi filum Proteobacteria (14,64–71,39%) dan komunitas arkea didominasi filum Euryarchaeota (1,05–72,92%). Garam Brebes secara visual memiliki penampakan kuning muda dengan nilai derajat putih terendah (55,90), hasil pengukuran diameter kristal paling kecil yaitu 252,50 µm dan kemurnian garam paling rendah yaitu 81,41%. Analisis SEM menunjukkan garam Brebes memiliki permukaan yang kasar. Sedangkan garamv Tuban memiliki kemurnian NaCl sebesar 88,29% dan ukuran kristal 292,33 µm; kualitas garam Tuban lebih bagus dibandingkan Brebes namun masih dibawah garam Sampang. Tambak Sampang menghasilkan garam berkualitas tinggi dibandingkan dua lokasi lainnya. Warna garam putih dengan nilai derajat putih garam 82,70. Kemurnian garam 90,72%, permukaan garam Sampang tampak halus, hasil pengukuran diameter kristal 337,25 µm. Kualitas garam dipengaruhi oleh karakteristik lingkungan dan komunitas biologis. Lokasi Brebes menghasilkan kualitas garam paling rendah yang dicirikan dengan tingkat nutrien dan konsentrasi DO tinggi yang memicu kelimpahan fitoplankton dan mikroba halofilik. Jenis fitoplankton yang melimpah adalah jenis Nitzschia sp., Pleurosigma sp., Rhizosolenia sp., Trichodesmium sp., Peridinium sp. sedangkan komunitas arkea yang melimpah sebanyak 57,9% di petak kristalisasi (B.20) dengan kelimpahan >1% jenis Halorubrum sp., Haloarcula sp., Halonotius sp., Haloplanus sp., Halohasta sp., Salinigranum sp., Halobaculum sp., Halomicroarcula sp. Halorientalis sp., Komunitas bakteri yang mendominasi di petak salinitas rendah (20,19%) dan sedang (25,24%) dengan kelimpahan >1% adalah Methylophaga sp., Pseudoalteromonas sp., Synechococcus sp., Puniceicoccus sp., Spiribacter sp., Litoricola sp. Keberadaan komunitas arkea yang memiliki kelimpahan tinggi di Brebes tidak berpengaruh terhadap peningkatan kemurnian garam. Hal ini disebabkan karena gen yang meregulasi protein Br sebagai agen biokatalisator penyerap panas tidak berfungsi optimal pada konsentrasi DO yang tinggi. Sebaliknya Sampang menghasilkan kualitas garam paling tinggi diantara dua lokasi lainnya. Lokasi Sampang dicirikan dengan karakteristik lingkungan konsentrasi nutrien dan DO rendah yang mengakibatkan pertumbuhan fitoplankton rendah dan kelimpahan bakteri halofilik melimpah. Pada salinitas tinggi komunitas bakteri di Sampang mencapai kelimpahan tertinggi sebesar 43, 67% dengan dominansi kelimpahan >1% yaitu Methylophaga sp., Pseudoalteromonas sp., Synechococcus sp., Puniceicoccus sp., Spiribacter sp., Alteromonas sp., Salinivibrio sp., Halomonas sp. Melimpahnya komunitas bakteri di lokasi Sampang memungkinkan senyawa organik komplek terdegradasi karena aktivitas bakteri. Hal ini memungkinkan terbentuknya kristal garam yang lebih murni dan terbebas dari bahan organik. Penelitian ini menemukan bahwa pada tambak garam yang menghasilkan kualitas garam rendah dapat dicirikan dengan karakteristik lingkungan sebagai berikut bahan organik dan konsentrasi DO tinggi yang memicu kelimpahan fitoplankton seperti Nitzschia sp., Pleurosigma sp., Rhizosolenia sp., Trichodesmium sp., Peridinium sp dan komunitas arkea tinggi seperti jenis Halorubrum sp., Haloarcula sp., Halonotius sp., Haloplanus sp., Halohasta sp., Salinigranum sp., Halobaculum sp., Halomicroarcula sp. Halorientalis sp. Sebaliknya pada lingkungan dengan konsentrasi organik rendah dan DO rendah yang memicu kelimpahan fitoplankton dan kelimpahan bakteri tinggi seperti Methylophaga sp., Pseudoalteromonas sp., Synechococcus sp., Puniceicoccus sp., Spiribacter sp., Alteromonas sp., Salinivibrio sp., Halomonas sp pada petak kristalisasi dapat menghasilkan kualitas garam yang tinggi. Kata kunci: kristal garam, mikroba halofilik, plankton, tambak garam,

SUMMARY RINI SUSILOWATI. The Contribution of Phytoplankton and Halophilic Microbial Communities to the Quality of Traditional Salt. Supervised by DIETRIECH G. BENGEN, MAJARIANA KRISANTI, HEDI INDRA JANUAR, and IMAN RUSMANA. Salt is an important commodity that plays a vital role in various aspects of life. Salt production in Indonesia largely depends on natural conditions, often causing issues in traditional salt production, including inconsistent quality and fluctuating annual production. This situation impacts the fulfillment of national salt needs, especially for industrial purposes, which are not met by domestic production. Efforts to improve salt quality can be made through better management of salt ponds, including the use of biological communities in the pond environment to produce high-quality salt. This study aimed to examine the interaction between environmental parameters and the structure of biological communities in salt ponds, which play an important role in improving the quality of the pond environment, and to understand the role of biological communities in salt quality. Sampling was conducted during the dry season at three locations: Brebes, Tuban, and Sampang. Water quality parameters were analyzed according to Indonesian National Standard (SNI) procedures, including the analysis of nutrient and physical parameters such as temperature, salinity, total organic matter, and organic carbon. The structure of plankton communities was identified morphologically through visual inspection, while the diversity of halophilic microbes was explored using a metagenomic approach based on the 16S rRNA gene. Salt crystal analysis included the evaluation of purity parameters, types of impurities, and analysis of the surface and size of salt crystals. In this study, Brebes was found to have the highest nutrient concentrations compared to the other two locations, with phosphate levels ranging from 5.38–5.66 mg/L, nitrate from 0.17–0.74 mg/L, nitrite from 0.07–0.1 mg/L, dissolved oxygen (DO) levels from 9.29–11.82 mg/L, total organic carbon (TOC) from 0.01–0.03 mg/L, and total organic matter (TOM) from 0.03–0.07 mg/L. The highest abundance of phytoplankton and zooplankton was recorded in Brebes, with counts of 127,721±11,227 cells/L and 3,339±391 individuals/L, respectively. The Bacillariophyceae group of phytoplankton dominated across all three locations. The Litostomatea zooplankton group dominated in Brebes and Sampang, whereas the Oligotrichea group dominated in Tuban. The highest relative abundance at the phylum level from low to high salinity was found in the bacterial community in Sampang at low salinity (96.44%) and in Brebes at medium and high salinity (90.29% and 23.74%, respectively). The archaeal community was found in Sampang at low salinity (1.38%) and in Brebes at medium and high salinity (8.31% and 75.43%, respectively). The bacterial community was dominated by the phylum Proteobacteria (14.64–71.39%) and the archaeal community by the phylum Euryarchaeota (1.05–72.92%). Visually, Brebes salt appeared light yellow with the lowest whiteness degree (55.90), the smallest crystal diameter (252.50 µm), and the lowest salt purity (81.41%). SEM analysis revealed that Brebes salt had a rough surface. In contrast,vii Tuban salt had a NaCl purity of 88.29% and a crystal size of 292.33 µm, indicating better quality than Brebes salt but still lower than Sampang salt. Sampang produced the highest quality salt among the three locations, characterized by white salt with a whiteness degree of 82.70, a purity of 90.72%, a smooth surface, and a crystal diameter of 337.25 µm. Salt quality was influenced by environmental characteristics and biological communities. Brebes produced the lowest quality salt, characterized by high nutrient levels and DO concentrations that promoted the abundance of phytoplankton and halophilic microbes. Dominant phytoplankton species included Nitzschia sp., Pleurosigma sp., Rhizosolenia sp., Trichodesmium sp., and Peridinium sp. The archaeal community was abundant, with 57.9% in the crystallization pond (B.20), including Halorubrum sp., Haloarcula sp., Halonotius sp., Haloplanus sp., Halohasta sp., Salinigranum sp., Halobaculum sp., Halomicroarcula sp., and Halorientalis sp. Dominant bacterial species in low (20.19%) and medium (25.24%) salinity ponds included Methylophaga sp., Pseudoalteromonas sp., Synechococcus sp., Puniceicoccus sp., Spiribacter sp., and Litoricola sp. The high abundance of the archaeal community in Brebes did not enhance salt purity due to the suboptimal functioning of Br protein-regulating genes as biocatalysts under high DO concentrations. Conversely, Sampang produced the highest quality salt among the three locations, characterized by low nutrient and DO concentrations that resulted in low phytoplankton growth and a high abundance of halophilic bacteria. At high salinity, the bacterial community in Sampang reached the highest abundance (43.67%) with dominant species including Methylophaga sp., Pseudoalteromonas sp., Synechococcus sp., Puniceicoccus sp., Spiribacter sp., Alteromonas sp., Salinivibrio sp., and Halomonas sp. The abundance of bacteria in Sampang facilitated the degradation of complex organic compounds, leading to the formation of purer salt crystals free from organic matter. This study found that salt ponds producing low-quality salt are characterized by high levels of organic matter and DO, which promote the abundance of phytoplankton such as Nitzschia sp., Pleurosigma sp., Rhizosolenia sp., Trichodesmium sp., and Peridinium sp., as well as a high abundance of archaeal species like Halorubrum sp., Haloarcula sp., Halonotius sp., Haloplanus sp., Halohasta sp., Salinigranum sp., Halobaculum sp., Halomicroarcula sp., and Halorientalis sp. In contrast, environments with low organic and DO concentrations that promote high bacterial abundance, such as Methylophaga sp., Pseudoalteromonas sp., Synechococcus sp., Puniceicoccus sp., Spiribacter sp., Alteromonas sp., Salinivibrio sp., and Halomonas sp., in crystallization ponds, can produce high-quality salt. Keywords: salt crystals, halophilic microbes, plankton, salt ponds