- Hard coral cover remained stable at low values (0-10%).
- Crown-of-thorns starfish were detected on one reef, where the coral cover was low.
- No coral bleaching was recorded.
Hard Coral Cover 0-10% 10-30% 30-50% 50-75% 75-100%
Figure 1: Map showing location of reefs in the Innisfail sector.
Table 1: Overview of results obtained from manta tow surveys of reefs in the Innisfail sector
| Innisfail Sector | Summary | Trend since last survey |
|---|---|---|
| Median Coral Cover | Low (0-10%) | Stable |
| COTS status: | No Outbreaks | Decreased |
| Coral bleaching: | None | Decreased |
As part of the Long-term Monitoring Program (LTMP), manta tow surveys of hard coral cover and the abundance of the coral feeding crown-of-thorns starfish (COTS), Acanthaster cf. solaris* was completed on three reefs in the Innisfail sector of the Great Barrier Reef (GBR). Preliminary results of the manta tow surveys are presented in Tables 1 and 2. The overall reef-wide median coral cover was stable at low levels (0-10%). Median coral cover declined on two reefs and remained stable on the other reef. No Active outbreaks of COTS were recorded, although COTS were detected on Feather reef, which had the same COTS/tow value in the previous survey.
No coral bleaching was detected on manta tow surveys. White syndrome disease was detected on the front and southern flanks of two reefs.
Details of the manta tow method can be found in the Standard Operational Procedure No. 9 [AIMS Research - Crown-of-thorns Starfish and Coral Surveys - Standard Operational Procedure 9]. Further details of the monitoring program design, sampling methods and a full explanation of the A. solaris outbreak terminology can be found on the AIMS website.
*Note: genetic studies show that there are at least four species of COTS. These are the North and South Indian Ocean species (A. planci and A. mauritiensis), a Red Sea species (not yet named) and a Pacific species. The range of the Pacific includes the Great Barrier Reef and it has been provisionally named Acanthaster solaris (Haszprunar et. al. 2017).
Table 2: Summary of manta tow surveys of reefs in the Innisfail sector. Arrows indicate the trend in live coral cover and A. solaris since last survey; ▲ = increase, ▼ = decrease, " " = no change. Outbreak Status: NO no outbreak, IO incipient outbreak >.22 COTS per tow, RE recovering, AO = Active Outbreak>1 COTS per tow.
| Reef | Shelf Position | Tows | Previous survey year | A. solaris | A. solaris per tow | Median Live Coral Cover | Median Soft Coral Cover | Reef Status |
|---|---|---|---|---|---|---|---|---|
| BEAVER | Mid | 30 | 2015 | 0 | 0 | 5-10% ▼ | 0-5% | NO |
| ELLISON | Mid | 69 | 2015 | 0 | 0 | 0-5% ▼ | 0-5% | NO |
| FEATHER | Mid | 46 | 2018 | 5 | 0.11 | 0-5% | 0-5% | NO |
Figure 2: - Sector-wide changes in coral cover and the numbers of A. solaris for survey reefs in the Innisfail sector of the GBR. Orange trend line = Hard coral. Purple bars = Crown-of-thorns (COTS)
Image 1. Surgeonfish patrol the reef slope characterised by the patchy cover of hard and soft corals at Beaver Reef.
Image 2. A view down the slope at Feather Reef, where dead and live branching corals are interspersed over the reef framework.
Image 3. View looking down the slope at Ellison Reef, showing how a once vibrant reef has been set back to one covered in algae.
