Reef shallows at Green Island with quadrat.
Our first activity of the day was to survey the reef at Green Island. Green Island is a low-lying sand cay that has extensive seagrass beds and coral reef around it. We had anchored in the lee of the Island last night, and used the inflatable for the short trip to the actual site. Coral cover was estimated to be low at 8m (around 10%) and much higher (20-25%) at the 3m site. The majority of the substratum was hard with a cover of filamentous turf algae. This site had a steep slope bottoming out to a sandy substratum at approximately 11m. Though coral cover was not high there were patches of high cover in several places with large colonies of branching and tabular Acropora as well as Lobophyllia. There was some low level bleaching of Acropora tips and Stylophora colonies. We recorded some breakage of branching Acropora as well as some colonies knocked over. Green Island lies further north than Fitzroy Island and so was less under the influence of Cyclone Larry but this breakage could still be evidence of its path.
Michaelmas reef: steep reef wall and newly qualified divers in background with
scientist in foreground
Michaelmas Reef was the next stop and is the first of the three mid-shelf reefs to be surveyed on this Northern sector, the others being Hastings and Mackay reefs. As expected underwater visibility was better here than at the inshore reefs at 6-7 m. This was a good-looking reef with medium to high hard coral cover - 30% at depth and 70% for shallow sites. Soft coral cover was 30% at 8m and 5% at 4m. There were numerous large colonies of Pocillopora and branching as well as tabular Acropora, particularly at 4 m. The characteristic fluoro colour of low level bleaching was evident on some colonies but, generally, the reef was in good condition. The deep site was on a steep wall (see photo), the shallow site was at the top of the wall where the reef flattened out. We were accompanied by the newly trained divers for this survey (see photo).
Coral garden at Hastings reef. Note the large soft coral colony in foreground.
As we couldnŐt do two reefs yesterday we had to fit in three today so we made for our second mid-shelf site; Hastings reef. As with Michaelmas reef, the visibility was up to 7 m. Coral cover was moderate at depth with approximately 35% for both hard and soft corals. The shallow site had higher hard coral cover (up to 50%) frequently with large individual colonies (> 1m diameter). There was a high diversity of hard corals with hemispherical Favids as well as Symphyllia and Lobophyllia dispersed amongst the dominant tabular and branching Acroporas. The soft coral community was notable for the very large Lobophyton colonies present. There was some low to moderate bleaching of a few coral colonies. It was noted that, while both Michaelmas and Hastings reefs had much higher coverage of hardy corals on the open and exposed reef crest, there was an increased diversity of corals on the more sheltered, deeper slope habitats.