English abstract
Marine biofouling is the undesirable accumulation of microorganisms (microfouling) and macro-organisms (macrofouling) on any surfaces immersed in the marine environment. The most common strategy to prevent biofouling includes the use of biocidal and non-biocidal fouling release (FR) antifouling (AF) coatings in the marine environment. Although AF coatings prevent macrofouling, limited information is available on AF efficiency in preventing microfouling in Oman waters. The current study investigated the development of microbial communities on various commercial AF coatings in two marinas in Muscat, Oman. As a preliminary investigation, the current method of estimating bacterial abundances was evaluated counting all fields of view using epifluorescence microscopy. Experiments were conducted to study the short-term (2 weeks) variations in the abundance of fouling bacteria on biocidal and non-biocidal FR antifouling coatings using epifluorescence microscopy in Marina Shangri La and Marina Bandar Rowdha, Muscat. Experiments investigating long-term microfouling were conducted after one year of immersion in both marinas in Muscat. The abundance and composition of fouling bacterial communities was estimated using epifluorescence microscopy and 454 pyrosequencing technology respectively. The abundance and composition of fouling diatom communities was estimated using both light and scanning electron microscopy (SEM) techniques. Counting bacterial cells from a minimum of 20 randomly selected fields of view using epifluorescence microscopy provided a reliable arithmetic mean to estimate the total abundance of bacteria in a sample. In case of short-term experiments, bacterial abundances on biocidal and non-biocidal fouling release coatings varied significantly on a temporal and spatial scale. In case of long-term experiments, the type of biocidal antifouling coatings, biocide composition and experimental location significantly influenced the abundance and composition of fouling bacterial and diatom communities. The bacteria belonging to the genera Maritimimonas and Acaryochloris were identified on cuprous oxide based antifouling coatings for the first time. Adnate, erect, motile and plocon diatom growth forms were dominated on the biocidal antifouling coatings. Hence, the findings of the current research show that the density and diversity of fouling microbial communities developed on antifouling coatings change on a temporal and spatial scale depending on the nature of the antifouling coatings.
