A new technique for evaluating short-term rates of coastal bioerosion and bioprotection

A multi-scale and multi-method approach has been developed to evaluate the nature and effects of short-term biological colonisation. This method has been used at Falasarna, on the western coast of Crete, to investigate bioprotection and bioerosion on a microtidal rocky coast. Eighteen blocks of limestone (5×5×2 cm) were exposed for 7 months (September 1998 to April 1999) at mean sea level at two exposed sites and one sheltered site. Biological colonization and its impacts were assessed by optical microscopy (OM), scanning electron microscopy (SEM) and multiphoton laser scanning microscopy (MPLSM). Exposed sites became colonized more quickly than the sheltered site and once a cover of foliose and filamentous algae had become established, bioerosion (by cyanobacteria), biological etching and chemical weathering were reduced. Consequently, there appears to be an inverse relationship between macroalgal abundance and bioerosion of experimental substrata after 7 months of colonisation. Thus, some level of bioprotection appears to be provided by macro algae under exposed site conditions and would probably become increasingly apparent in longer-term research trials.