Summary
- 10 reefs were surveyed in the Whitsundays sector.
- Sector-wide hard coral cover was moderate (10- 30%) and had increased since 2019.
- Hard coral cover had increased on five reefs and had declined on five reefs.
- No outbreaks of crown-of-thorns starfish (COTS) were recorded.
- Low levels of hard coral bleaching were observed.
Hard Coral Cover 0-10% 10-30% 30-50% 50-75% 75-100%
Figure 1: Map showing location of reefs in the Whitsundays sector. Click the points for more information.
Table 1: Overview of results obtained from manta tow surveys of reefs in the Whitsundays sector
| Whitsundays Sector | Summary | Trend since last survey |
|---|---|---|
| Average Coral Cover (%) | 27.6 | Increased |
| COTS status: | No Outbreaks | Stable |
| Coral bleaching: | Low | Stable |
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 were completed on 10 reefs were surveyed in the Whitsundays sector of the Great Barrier Reef (GBR) (Fig 1).
Preliminary results of the manta tow surveys are presented in Tables 1 and 2. The overall median hard coral cover for the sector was moderate (10-30%) (Table 1) (Fig 2) and had increased since previous surveys in 2019 (Fig 2).
Hard coral cover was very high (50 to 75%) on two reefs, high (30-50%) on three reefs, moderate (10-30%) on three reefs and low (10-30%) on two reefs. (Table 2). Since the previous surveys hard coral cover had increased on five reefs and declined on five reefs (Table 2).
Sector-wide numbers of COTS remained stable since previous surveys (Table 1, Fig 2). One COTS was observed at Reef 19138S.
Low levels of coral bleaching were recorded at eight reefs, restricted to scattered individual colonies.
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 Long-Term Monitoring Program can be found on the AIMS website.
Table 2: Summary of manta tow surveys of reefs in the Whitsundays sector. Arrows indicate the trend in live coral cover and A. solaris since last survey; ▲ = increase, ▼ = decrease, " " = no change. Outbreak Status: NO no outbreak, PO potential outbreak >0.1 COTS per tow, IO incipient outbreak >.22 COTS per tow, RE recovering, AO = Active Outbreak>1 COTS per tow.
| Reef | Shelf Position | Tows | Previous survey year | Total A. solaris per reef | A. solaris per tow | A. Solaris Outbreak Status | Live Hard Coral Cover % | Soft Coral Cover % | Survey Year |
|---|---|---|---|---|---|---|---|---|---|
| BORDER ISLAND REEF (NO 1) | Inner | 53 | 2017 | 0 | 0 | NO | 9.8 ▼ | 22.2 ▼ | 2021 |
| HAYMAN ISLAND REEF | Inner | 26 | 2017 | 0 | 0 | NO | 11.1 ▼ | 18.8 ▼ | 2021 |
| LANGFORD-BIRD REEF | Inner | 29 | 2017 | 0 | 0 | NO | 8.8 ▼ | 15.1 ▼ | 2021 |
| 19131S | Mid | 47 | 2019 | 0 | 0 | NO | 17.1 ▲ | 3 ▲ | 2021 |
| 19138S | Mid | 28 | 2019 | 1 | 0.04 ▲ | NO | 20.3 ▲ | 2.9 ▲ | 2021 |
| 20104S | Mid | 23 | 2017 | 0 | 0 | NO | 30.1 ▼ | 3 ▲ | 2021 |
| HARDY REEF | Mid | 123 | 2017 | 0 | 0 | NO | 34.8 ▼ | 4.8 ▼ | 2021 |
| HYDE REEF | Outer | 48 | 2017 | 0 | 0 | NO | 52.1 ▲ | 10.6 ▲ | 2021 |
| REBE REEF | Outer | 35 | 2019 | 0 | 0 | NO | 60.1 ▲ | 8.1 ▲ | 2021 |
| SLATE REEF | Outer | 39 | 2019 | 0 | 0 | NO | 44.9 ▲ | 7.3 ▲ | 2021 |
Figure 2: - Sector-wide changes in coral cover and the numbers of A. solaris for survey reefs in the Whitsundays sector of the GBR. Orange trend line = Hard coral. Purple bars = Crown-of-thorns (COTS)
Image 1. A turtle rests on the southern reef flank at Border Island.
Image 2. A coral trout swims above the reef slope where high hard coral cover and complexity were observed on the southern reef flank at Hyde Reef.
Image 3. Baitfish school along the slope of the reef front at reef 20104S.
Image 4. Hard coral recruitment on the reef crest of the northern flank at Hayman Island.
