Vessel: RV Cape Ferguson
Survey leader: Ian Miller
Summary
- Most reefs in this sector remain to be surveyed in 2020. The hard coral cover trend in Figure 2 is based on the two reefs completed to date, and will be updated once all reefs in this sector have been surveyed
Hard Coral Cover 0-10% 10-30% 30-50% 50-75% 75-100%
Figure 1: Map showing location of reefs in the Swain sector.
Table 1: Overview of results obtained from manta tow surveys of reefs in the Swain sector
| Swains Sector | Summary | Trend since last survey |
|---|---|---|
| Average Coral Cover (%) | 31.45 | Increased |
| COTS status: | No Outbreaks | Decreased |
| Coral bleaching: | None | Stable |
As part of the Long Term Monitoring Program (LTMP), manta tow surveys of coral cover and the abundance of the coral feeding crown-of-thorns starfish (COTS), Acanthaster cf. solaris* were completed on two reefs, Reef 21-245 and Reef 21-278, in the Swain sector of the Great Barrier Reef. The preliminary results of the manta tow surveys are presented in Table 1. Median reef-wide live coral cover (coral cover) had increased at Reef 21-245 and remained stable at Reef 21-278. Low numbers of COTS (below outbreak levels) were recorded from Reef 21-245.
Scuba surveys of fixed transects were conducted at both reefs and recorded no COTS or coral bleaching. For both reefs cases of disease and numbers of the corallivorous snail, Drupella spp. were within the range of past values recorded from reefs within this region.
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 Swain 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 | Live Hard Coral Cover % | Soft Coral Cover % | Survey Year | Reef Status |
|---|---|---|---|---|---|---|---|---|---|
| 21245S | Mid | 57 | 2016 | 2 | 0.04 | 28.17 | 2.45 | 2020 | NO |
| 21278S | Mid | 27 | 2016 | 0 | 0 | 32.16 | 2.87 | 2020 | NO |
Figure 2: - Sector-wide changes in coral cover and the numbers of A. solaris for survey reefs in the Swain sector of the GBR. Orange trend line = Hard coral. Purple bars = Crown-of-thorns (COTS)
Image 1. Coral cover on Reef 21-245 was very good in places showing a remarkable recovery since Severe Cyclone Hamish in March 2009 and despite the presence of crown-of-thorns starfish on the reef.
Image 2. Submassive hard corals growing on the crest of Reef 21-245 were a refreshing sight as these corals are particularly susceptible to the depredations resulting from coral bleaching.
Image 3. Panoramic view of the front reef slope on Reef 21-278 showing many small coral colonies suggesting plenty of room for improvement as it continues to recover from the effects of Severe Cyclone Hamish in March 2009.
Image 4. A grey reef shark patrol's the sandy back reef area that supported only patchy coral cover on Reef 21-278.
