Report on surveys of the Townsville sector of the Great Barrier Reef


Summary

  • Some reefs in this sector remain to be surveyed in this reporting year.

Figure 1: Map showing location of reefs in the Townsville sector. Click on figure to go to AIMS Spatial Maps for information on individual reefs.

Table 1: Overview of the results obtained from manta tow surveys of reefs in the Townsville sector.

Townsville Sector Summary Trend since last survey
Median Coral Cover Moderate (10-30%) Stable
COTS status: 1 Active Outbreaks, 0 Incipient Outbreaks Increased
Coral bleaching: Low Decreased

As part of the Long Term Monitoring Program (LTMP), surveys of coral cover and the abundance of the coral feeding crown-of-thorns starfish (COTS), Acanthaster cf. solaris* on three reefs in the Townsville sector of the Great Barrier Reef (GBR) were completed using the manta tow technique. Preliminary results of the manta tow surveys are presented in Tables 1 and 2. These show that median sector-wide live coral cover had remained stable at moderate levels (10 to 30%), although more reefs still remain to be surveyed (Table 1).Cover of live hard coral had increased at two reefs, Helix and Roxburgh, since previous surveys (Table 2). There was a decrease in hard coral cover at Rib Reef that was largely the result of Active Outbreak levels of COTS in recent years, although there was likely also some mortality due to recent coral bleaching events, especially in 2017.

Scuba surveys on fixed transects recorded low levels of coral bleaching on Helix and Kelso Reef, which was limited to scattered individual colonies. There were numerous dead Acropora colonies, in growth position but well covered with algae. In the absence of COTS, these corals had presumably been killed by coral bleaching over the previous two summers. There were cases of white syndrome coral disease on all reefs except Rib Reef and incidences were generally within the historical range. Occurrence of three other coral diseases (black-band, brown-band and skeletal eroding band) were low. The corallivorous snail, Drupella spp. was observed at most reefs; numbers were generally within the range of past values.

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 Townsville sector. Arrows indicate the trend in live coral cover and A. cf. solaris since last survey;   = increase,   = decrease, “ ” = no change.

Reef Shelf Position Tows Previous survey year A. solaris A. solaris per tow Median Live Coral Cover Median Soft Coral Cover Reef Status
HELIX Mid 16 2016 0 0 30-40%  0-5% NO
RIB Mid 33 2017 195  5.91 5-10%  0-5% AO
ROXBURGH Mid 21 2016 0 0 20-30%  0-5% NO

Dates: 17th - 28nd February 2018
Vessel: RV Flying Fish V
Survey leader: Mike Emslie

Details of the manta tow method and results can be found here.

Click here for further details of the monitoring program design, sampling methods and a full explanation of the A. solaris outbreak terminology.

For enquiries, please contact monitoring@aims.gov.au

Figure 2: Sector-wide changes in coral cover and the numbers of A. cf. solaris on survey reefs in the Townsville sector of the GBR.

Image 1: High numbers of A. cf. solaris have ravaged large sections of Rib Reef in the Townsville sector. 

Image 2: Recent impacts from coral bleaching and A. cf. solaris outbreaks have reduced coral cover to low levels on Rib Reef, although there are still some remnant patches of live coral remaining.

Image 3: Moderate levels of live hard coral were seen on Roxburgh Reef.