Biofilms have been shown to influence the larval settlement of a number of marine invertebrate species although the exact mechanism of these interactions remains unclear. This study used terminal restriction fragment length polymorphism (tRFLP) analysis of PCR amplified 16S rRNA genes to examine the species composition of the bacterial component of marine biofilms as potential cues for larval settlement.
Natural biofilms from top and underside of intertidal rocks were examined. Biofilms present on the top surfaces of rocks from the upper shore were grouped together and separate from biofilms from the lower shore by principal component analysis (PCA) of terminal restriction fragments (tRFs ). Biofilms from the under surface of rocks however showed no obvious pattern in relation to intertidal origin. Biofilms from similar heights on two different rocky shores were grouped more closely by PCA than biofilms from different heights on the same shore. The species composition of biofilms also varied seasonally. Taken together the results indicate that the species composition of bacterial
films has the potential to influence larval settlement in the intertidal.
Flow has also been shown to influence larval settlement of several marine
invertebrate species. The influence of flow on biofilm development and larval
settlement was investigated in the field and laboratory using biofilms formed on plastic tubes of various diameters. In the laboratory, the bacterial portion of biofilms developed at a range of flows had different species compositions and elicited differential settlement in the barnacle Semibalanus balanoides, but there was no correlation between the bacterial tRFs and flow rates. In the field, although the biofilms were occasionally grouped by tube size, tube section or tube half according to PCA, no obvious pattern between the biofilm composition and the settlement of either barnacles or Pomatoceros were observed, indicating the possibility of a hierarchy of cues influencing larval settlement in the field.