• Coral Monitoring: Start date 21st April 2015; Duration: 6.43 weeks
• Dredging: Start date 29th April 2015; Duration: 5.29 weeks
• Dredging Locations: Northern end of Tegako
• Coral bleaching is below trigger levels (50% bleaching C1-C5) and no action is required.

Results this week

The coral watch results for this week (1-5th June) are shown in the latest 3 bars on each of the two 2 graphs that follow. This week we are showing several different types of graphs to provide a bit more context, with the left graph below showing the average stress in sensitive corals, and the right graph showing the overall impact on all monitored corals.

Levels of bleaching at the impact sites, 1 North End and 2 Tegako Jetty were moderate this week and increased slightly. Bleaching remains high at Site 3 Catalina Patch ( a current Control), remaining at about the same level seen last week. Bleaching observed at 4 South End (Control) is now at normal background levels. Overall the level of bleaching is of low in terms of the overall coral population at all sites except 3 Catalina Patch.

FIG 1: Average levels of bleaching in corals that showed bleaching in that category. FIG 2: Average level of bleaching in each category (C1-C6) across all corals. If all corals behaved about the same these two graphs would be the same. The high levels seen in the first graph show that certain individual corals are showing high stress, while others (the majority) are not bleaching significantly (FIG 2).

Coral Species

In terms of coral species (FIG 3) bleaching has been greatest in Acropora florida at Site 3 Catalina, where all of the species have been showing significant bleaching. At the dredging sites (1 & 2), the coral with the most bleaching was A. nobilis.

Conclusions

The corals at the two dredging locations are bleached, but not to levels of concern and the trigger criteria have not be reached. Bleaching at Site 3 Catalina Patch, a current control, remains high (mostly for Acropora florida) but is not likely to be related to dredging. The high levels of bleaching at Site 3 is likely to be due to other factors (e.g. pollution adjacent to the main urban area). Recovery at Site 4 South End has continued and corals are now considered back to normal levels of bleaching.