Development of periphytic diatoms on artificial substrates in the eastern Adriatic Sea

Substrates newly introduced in the marine environment are quickly colonised by fouling organisms, regardless of their origin or structure. Periphytic diatoms are among the pioneers of the fouling process and are well equipped for adhesion on various substrates in a short amount of time. Each substrate forms a distinctive micro- habitat with its specific physical and chemical characteristics. Final settlement of diatoms on a certain substrate is greatly influenced by substrate characteristics and preference of diatom community and diatom species. Distinction between substrates can be made by analysing specific abundance and composition of diatoms on different substrates. In this study 11 different artificial substrates were exposed to marine environment for a month (March 7th - April 6th 2012) at the location Puntamika near Zadar, Croatia. Abundance and taxonomic composition of periphytic diatoms was determined on each of the substrate and on the two shoots of marine seagrass Posidonia oceanica L. The aim was to compare diatom community structure on newly colonised surfaces. This research showed periphytic diatoms as pioneering organisms on all of the examined surfaces and differences were noted in quantitative and qualitative composition of diatoms among different substrates. Taxonomic analysis of diatom communities revealed 41 diatom taxa, with genera like Amphora, Cylindrotheca, Nitzschia, Cocconeis and Navicula recognized as dominant in peryphitic communities of the examined substrates. Given that all examined artificial substrates were solid materials, the differences in the abundance and species composition of diatoms found between the materials point to physical and chemical characteristics of substrates as a major influence on final settlement of diatoms. Anthropogenic materials too often end up in marine environment. Investigating the interaction of marine organisms with those materials as substrates, we can gain valuable insight in colonisation processes in general and it could possibly be the first step towards alleviating this initially negative impact on marine environments.