The nutrient ion concentrations in the interstitial waters of biofilms (BFs) formed on reed and stone surfaces were investigated in the northern and southern basins of Lake Biwa over several years. The following were observed for both types of BF: 1) Concentrations of ammonium, nitrate, nitrite, and phosphate ions were much (hundreds to thousands of times) higher in the BFs than in the surrounding lake water; 2) the concentration of ions, especially nitrate ions, in the BFs changed seasonally, being higher from winter to spring and lower from summer to autumn, synchronizing with the changes in the lake water; 3) dissolved-form N:P ratios were higher in the lake water than BFs; and 4) the bacterial flora of the BFs differed from that of the lake water, with smaller seasonal variations. The present study reveals for the first time that the inside of BFs in a natural environment is rich in nutrient ions and shows similar seasonal changes as the lake water. The BFs in an aquatic environment provide a microenvironment capable of sustaining a specific bacterial flora different from that in the surrounding lake water.Key words: biofilm, nutrient ions, bacterial flora, Lake Biwa Microbial biofilms (BFs) are ubiquitous in aquatic environments and perform important environmental functions, including nutrient recycling (2, 5, 27) and purification of pollutants (8,14,15). Natural BFs are generally composed of a variety of microbes and their secretory products, such as extracellular polymeric substances (EPS). The EPS-containing matrix confers on the constituent microbes certain advantages over their free-living counterparts (16,17). An important advantage is the ability to trap and retain dissolved nutrients through an entrapment mechanism that has been proposed (4, 7, 11) and proven (9) to depend on ion exchange processes.However, few studies have been conducted on the nutrient conditions inside BFs formed in natural environments over a long period of observation. Therefore, the present study was designed to compare over several years the concentrations of various nutrient ions in the interstitial waters of BFs and the surrounding lake water. An additional aim was to examine the relationship between the nutrient conditions and bacterial flora inside the BFs. Moreover, the BFs formed on reed and stone surfaces were compared, to clarify the influences of the substratum surfaces.Here, we report for the first time that the nutrient conditions in a BF and in the surrounding water are significantly different with respect to concentrations of ions, particularly nitrate ions, while exhibiting similar seasonal variations. The relationships among the nutrient conditions, bacterial flora constitution, and the physicochemical properties of the BFs are discussed. Materials and Methods Study area and samplingLake Biwa is located in the central part of the Japanese Archipelago (Lat. 35°15' N, Long. 136°05' E). The lake has a surface area of 670 km 2 and a total storage volume of 2.75×10 10 m 3 , consisting of two basins that differ in wa...

The characteristics of biofilm polymers formed on stone surfaces in Lake Biwa and ion adsorption and desorption to and from these biofilms were investigated. The results indicated that both positively and negatively charged sites exist in the biofilm polymer. A physicochemical interaction between these sites and ions in the surrounding water seems to promote the adsorption of ions to the biofilm through an attractive electrostatic interaction and an ion-exchange mechanism. The results also indicated that, in comparison with ion-exchange resins, ions were more loosely bound to and desorbed more easily from the biofilm polymer. This suggests that microbes in the biofilm can readily use these ions as nutrient ions. Our present findings indicate that the biofilm may play an important role in supplying nutrient ions to microbes in the biofilm and in the development of a nutrient-rich environment within the biofilm through both ion adsorption and desorption. This study shows for the first time that the inside of a biofilm can be a sustainable environment for microbes.

The process by which a biofilm forms on the surface of the aquatic macrophyte Phragmites australis was investigated over a period of about two months (from mid-May to late-July, 2008) in Lake Biwa. The biofilm formed relatively quickly, its wet weight per unit area after seven day being that of a mature biofilm. This speed can be attributed to the many active bacteria in the early stage of its formation and the extracellular polymeric substances (EPS) they produce. The EPS carried electric charges that attracted nutrient ions from surrounding lake water, which, by electrostatic interaction, reached a high concentration as early as day 7 of the formation process. This significantly affected the biofilm community, which differed greatly from that of the lake water even at the beginning of biofilm formation. Brown amorphous compounds (a complex of organic and inorganic substances), covered the biofilm in the second half of its formation process producing a different community structure from that initially. This study revealed a fast and dynamic process of biofilm formation on the reed surface of reed.

Garam merupakan komoditas penting yang banyak digunakan secara luas dari kepentingan konsumsi sampai dengan industri. Salah satu faktor utama yang menentukan keberhasilan produksi garam ini adalah kesesuaian lokasi produksi garam. Hanya saja, belum ada metode yang dapat digunakan sebagai acuan dalam penentuan tingkat kesesuaian lokasi produksi garam. Penelitian ini bertujuan untuk menyusun Indeks Kesesuaian Garam (IKG) untuk menganalsis kesesuaian lokasi produksi garam. Dalam penelitian ini, IKG digunakan untuk menganalisis lokasi produksi garam di Kabupaten Tuban dan Kabupaten Probolinggo, Jawa Timur. IKG disusun berdasarkan sembilan parameter kesesuaian yang terdiri dari curah hujan, permeabilitas tanah, jenis tanah, lama penyinaran, kelembapan udara, kecepatan angin, suhu udara, tingkat penguapan dan tingkat kejenuhan air bahan baku. Hasil penelitian ini menunjukkan bahwa nilai IKG lokasi produksi garam di Kabupaten Tuban (Desa Leranwetan) adalah sebesar 86,84 % yang mengindikasikan kalau lokasi ini sudah sangat sesuai untuk produksi garam. Nilai IKG lokasi produksi garam di Kabupaten Probolinggo (Desa Kalibuntu) adalah sebesar 81,57% yang mengindikasikan lokasi ini cukup sesuai sebagai lokasi produksi garam. Studi ini melaporkan untuk pertama kali metode yang dapat digunakan untuk menganalisis tingkat kesesuaian lokasi untuk produksi garam.

Abstract. Kurniawan A, Hariati AM, Kurniawan A, Wiadnya DGR. 2021. First genetic record and the phylogenetic relationship of Osteochilus spilurus (Cyprinidae: Labeoninae) originating from Bangka and Belitung Islands, Indonesia. Biodiversitas 22: 794-802. Osteochilus spilurus is a freshwater fish from Southeast Asia. Species identification for this fish in Indonesia is still solely limited to morphological characteristics. Therefore it is highly important to validate using short DNA sequences that have been proven to be fast, effective, and accurate. Fish specimens were collected from Lenggang river in Belitung island, and Lebak river in Bangka island, Indonesia. Mitochondrial cytochrome b gene (cyt b, 408 bp) was amplified and sequenced. We collected fish specimens from Lenggang River in Belitung Island and Lebak River in Bangka Island, Indonesia. The results suggested that individuals from both islands are clustered together with a strong bootstrap value (100%) in a monophyletic clade. The specimens deposited at NCBI as the first Indonesian genetic records. They have a sister lineage to individuals from Sabah, Malaysia, although supported by a low bootstrap value. While geographical connection during the Pleistocene period allowed wide distribution of the species, differences in the evolutionary processes of historical biogeography and environmental changes are the predicted cause of the low genetic similarity. These findings can be used as a sequence reference and basic information for conservation of this species.

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