Analysis of physicochemical properties of natural biofilm matrices formed in a sub-tropical region (Lake Biwa, Japan) and a tropical region (Karangkates reservoir, Indonesia)

Aquatic ecosystems consist of various biotic and abiotic components. One of the biotic components that plays essential roles in the aquatic ecosystem are microbes. Most microbes live by forming a biofilm. The matrix of the biofilm provides a microhabitat that supports microbial life. Hence, the physicochemical properties of the biofilm matrix are essential to support the microbial activities in the aquatic ecosystems. The comprehension of the physicochemical characteristics of natural aquatic biofilms is critically urgent in order to fully understand the ecology of microbial biofilms providing specific habitats for microorganisms and to utilize the biofilms for the benefit of humans. The physicochemical properties of the biofilm are affected by the environmental factors that can differ by region. This study analyzed the physicochemical properties (electrical charge properties, functional groups, nutrient ions, dissolved organic substances) of the natural biofilm matrices by comparing the biofilms formed in lotic ecosystems. The biofilms were sampled from a sub-tropical region (Lake Biwa, Kyoto – Shiga, Japan) and a tropical region (Karangkates Reservoir, East Java, Indonesia). The following were observed as the results of this study: the similar kinds of functional groups, such as carboxyl and amino groups that exist in polymers of both biofilm matrices; the ionization of the functional groups resulting in the positively and negatively charged sites in the biofilm matrices; the fact that the biofilm matrices present similar kinds of nutrient ions and dissolved organic nutrients; inside the biofilm, the matrices are nutrient-rich microhabitats available for microbes in the aquatic ecosystems. According to the results of this study, the biofilm matrices analyzed (tropical and sub-tropical regions) share similar physicochemical properties.