Abstract Biofouling is undesirable accumulation and growth of organisms on submerged surfaces. Biofouling has a huge industrial importance by increasing drag and resistance, and changing properties of the substratum. Replacement parts of fishing traps with natural fibers that easily degrade in the marine environment due to biofouling has been proposed as a processing strategy to prevent ghost fishing. In this study, the formation of microfouling communities and their impact on breaking strength of natural fibers (palm and coconut) were investigated at two sites; Marina Bandar Rawdha (BR) and Marina Shangri La (SH) in the Sultanate of Oman and at two different depths (1 m and 5 m) for 12 weeks. The breaking strength of both fibers at both marinas and depths decreased with development of biofouling. The breaking strength of palm fibers decreased quicker than the strength of coconut fibers. The number of bacteria significantly increased on all fibers during the period of investigation and bacteria were growing quicker on coconut in comparison to palm fibers. Chlorophyll a concentration in biofilms developed on coconut fibers declined, while no changes in chlorophyll a concentrations were detected in biofilms from palm fibers. Three categories of cyanobacteria were identified namely thin filamentous cyanobacteria, thick filamentous cyanobacteria and spirulina- like filaments in biofilms developed on natural fibers. A total of 16 different genera of benthic diatoms were identified in biofilms developed on natural fibers. The time and the location of sampling affected the diversity of diatoms. Species number increased with time. Some diatom species were unique for each sampling location and depth. Dinoflagellate and Foraminifera species were mainly observed in marina Bandar Rawdha. In conclusion, our experiments showed that different microbial communities have developed on the studied fibers and could affect differently the breaking strengths of coconut and palm fibers