Glass microscope slides placed in square polyvinyl chloride frames (112 per grid), exposing the top surface to the seawater, were deployed at Davies Reef, on the Great Barrier Reef at two depths - 4 m (shallow) and 10 m (deep) - within each of 2 sites. To allow biofilm development, slides were maintained at site 1 for 2, 4, and 8 weeks, and at site 2 for 8 weeks prior to the November 2000 mass coral spawning. Slides were used in larval metamorphosis assays, with a minimum of 20 replicate biofilm slides randomly selected for each treatment. To determine biofilm community composition, an additional 30 slides were randomly selected for DNA extraction, 30 slides for fluorescence in situ hybridization (FISH), and 10 slides for scanning electron microscopy (SEM).Coral larvae used in the metamorphosis assays were raised from gametes collected from live colonies of the reef-building coral Acropora microphthalma, from a depth of 6 to 8 m on a fringing reef of Pelorus Island, Great Barrier Reef. Slides were sorted according to whether or not they induced larval metamorphosis, and replicate slides were processed for SEM, FISH, and denaturing gradient gel electrophoresis (DGGE). Sequences of oligonucleotide probes used for FISH. DGGE: the 16S rRNA genes were amplified by PCR with bacterial and eukaryotic primers.Estimates were made of the relative densities of specific probe-targeted bacteria and archaea (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria, Firmicutes, Cytophaga-Flavobacterium, Bacteroidetes, Planctomycetales, Archaea). The importance of three factors (depth, time, and CCA presence) in inducing larval metamorphosis was investigated in an unbalanced repeated-measures analysis of variance (type IV SS; SPSS version 11).Quantitative estimates of biofilm community composition were made using group-specific FISH probes. All densities are expressed as a percentage of total bacterial numbers obtained using dual hybridization reactions with the bacterium-specific probe EUB338. A principal-component analysis (PCA) was used to summarize biofilm community composition using FISH data in which depth of biofilm formation and exposure time of slides were the variables. Cluster analysis was used to identify replicates that generated similar DGGE profiles.

To examine the community structure of developing coral reef biofilms and their ability to induce the metamorphosis of coral larvae.To examine the role microorganisms not associated with calcareous coralline algae in coral metamorphosis.