Three months after the intensive installation of large amount of tiles at one of our study sites (Navakavu Reef), we have finally removed them all and are excited with the results! Removal was luckily far simpler than installation, and every single tile survived the three months including Cyclone Ula which passed over Fiji. The tiles had been installed inside and outside of the tabu area (closed to fishing) at two depths (1-2m and 5-6m). To account for high variability in recruitment, we installed fifteen replicate tiles at each depth within each site.
After photographing the tiles immediately after collection, we measured the length of the turf community that had grown on the tiles. The photographs and turf length allow us to explore which characteristics of turf communities affect coral recruitment. As recent research has highlighted that turf algae dominance should be considered as an alternative regime (be it transitory or permanent), it is critical to understand its impact on key coral reef processes such as recruitment. We have already noted differences in turf communities as a result of management, so this adds another dimension to our evaluation of the effect of local management on coral reef functioning.
Once the photographs and measurements were complete, the tiles were bleached and left to dry in the sun (which is finally shining nearly every day in Suva). This was followed by the recruit analysis, which is a very time intensive process… First, on the underside, the sides and the top of each tile, each recruit (which were often smaller than 1mm) was circled and total number was recorded. Then, using a microscope incorporating a digital camera (thanks to the University of the South Pacific for providing this), each individual recruit was photographed to allow identification to family level. Other informative parameters can also be measured for this including size of recruits, development stage, and neighbouring organisms such as crustose coralline algae. With a total of over 900 recruits, this requires quite a lot of patience…
Our initial analysis shows that coral recruitment is indeed significantly higher inside locally managed tabu areas, irrespective of the depth of our tiles; recruitment inside the tabu was over twice as high on the underside of the tiles, where recruits preferentially settle. One further analysis we will do is to analyse the effect of providing a microstructure to recruits. As mentioned in an earlier blog, we drilled 196 holes (1mm deep) into the top and bottom of fifteen tiles which were placed alongside ‘normal’ tiles at one site. This should provide more shelter for the recruits, which we hypothesised may provide a more realistic representation of bare reef substrate. Not much is known about coral recruitment in Fiji, so these results are useful for the region and our local collaborators at Wildlife Conservation Society and the University of the South Pacific are also looking forward to the results. A huge thank you from the team to Stephanie Helber for taking time out of her PhD at such a critical stage to come out and help us finish our diving!!!