Abundance of macroalgal organic matter in biofilms: Evidence from n-alkane biomarkers

Abstract

Biofilm development on titanium panels immersed in the surface waters of Dona Paula Bay, Goa, India was investigated using molecular biomarkers such as n-alkanes and other chemical and biological parameters. Biofilm biomass measured as organic carbon (OC), organic nitrogen (ON), chlorophyll a, diatoms and bacterial numbers on the titanium panels generally increased over the period of immersion. Total lipids and n-alkane concentration also showed similar trends. n-alkanes from C sub(12) to C sub(30) were detected in the biofilm samples, which showed a bimodal distribution. The first mode consisted of n-alkanes greater than C sub(23) with a strong even over odd predominance. In the second mode, the n-alkanes less than C sub(23) were more abundant with odd carbon number maxima at C sub(15), C sub(17) and C sub(19) and a strong odd over even carbon number predominance (Carbon Preference Index greater than 2). The predominance of these odd-chain n-alkanes strongly indicates that the organic matter derived from macroalgal sources was the major contributor to the biofilm organic matter developed on the titanium panels over the 15 d period of study. The data suggest that molecular characterization is a useful tool in understanding the sources of biofilm organic matter. The observed abundance of macroalgal organic matter during the 15 d period of biofilm development may play an important role in subsequent fouling by micro- and macrofouling organisms.