Survey report 4 Jan

Dates: 4^th January to 23^rd January 2012

Vessel: MV Capricorn Star

Survey leader: Mike Emslie

Manta tow surveys were completed on eight reefs in the Swain sector and five in the Pompey sector of the Great Barrier Reef (GBR). Detailed surveys for benthic organisms, visual census of fishes and surveys for agents of coral mortality (scuba search) were made on all these reefs and a further three reefs in the Pompey sector. Preliminary results of the manta tow and scuba search surveys are presented in this report.

Though early signs of recovery (i.e. numerous small coral recruits) were observed on many reefs, median reef-wide live coral cover remained at similar levels to those recorded during previous surveys in 2010. At that time hard coral cover was low because Severe Tropical Cyclone Hamish had passed through both these sectors in March 2009.

Combined results from manta tow surveys and scuba surveys suggest the Pompey sector is currently a centre for crown-of-thorns starfish (COTS) activity on the GBR. Manta tow and scuba surveys detected a COTS outbreak on Reef 21-064 in the Pompey sector.

This is the second active outbreak recently recorded from this sector: another COTS outbreak on Reef 21-060 was recorded in November 2011. Small numbers of COTS, well below outbreak densities, were also recorded during manta tow surveys on Reef 25-353 in the Pompey sector and Jenkins Reef in the Swain sector. Manta tow survey results are summarised in Tables 1 and 3.

Combined results from manta tow surveys and scuba surveys suggest the Pompey sector is currently a centre for crown-of-thorns starfish (COTS) activity on the GBR. Manta tow and scuba surveys detected a COTS outbreak on Reef 21-064 in the Pompey sector. This is the second active outbreak recently recorded from this sector: another COTS outbreak on Reef 21-060 was recorded in November 2011.

Small numbers of COTS, well below outbreak densities, were also recorded during manta tow surveys on Reef 25-353 in the Pompey sector and Jenkins Reef in the Swain sector. Manta tow survey results are summarised in Tables 1 and 3.

Substantial numbers of COTS were also recorded during scuba search surveys: outbreak densities were found on Reef 21-064 and Reef 21-062 in the Pompey sector. Low numbers of COTS were also recorded at Reef 20-348 and Reef 20-353. No COTS were recorded during scuba surveys on any reef in the Swain sector. Incidence of coral disease, counts of Drupella spp. and coral bleaching were generally below those seen in previously on all the reefs. The SCUBA search results are summarised in Tables 2 and 4.

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]. For a full explanation of the COTS outbreak terminology used in this report refer to the following web-page: Crown-of-thorns on the Great Barrier Reef.

Swain Sector

Perimeters of eight reefs were surveyed using manta tow (Table 1). Three sites on each of these reefs were also surveyed in detail using scuba (Table 2).One COTS was recorded at Jenkins Reef in the Swains during manta tow surveys, but none were recorded during the intensive scuba search surveys on any reefs in this sector. This, combined with results of recent previous surveys, provides further evidence that the COTS outbreaks that occurred during the early part of last decade have run their course.

In general coral cover has declined on reefs in this region due to Cyclone Hamish that passed through the area in March 2009. Coral cover was moderate (10-30%) to low (0-10%) on all reefs surveyed. Reefs 21-139, 21-187, 21-550 and Chinaman Reef showed no change in coral cover from previous surveys. Small Lagoon Reef, Jenkins Reef, Wade Reef and Reef 22-084 all showed small increase in reef-wide live coral cover since they were last surveyed. These results suggest that reefs in this sector are still in the early stages of recovery from the effects of cyclone Hamish. Localized bleaching of hard corals was recorded during manta tow surveys on the front of Reef 21-187, but it was restricted to just a few scattered colonies.

Scuba searches on the intensive survey sites recorded white syndrome disease on the majority reefs in this sector. However, the number of infected colonies had either decreased since the most recent surveys in 2010, or was lower than historical records. The two exceptions were Wade Reef and Small Lagoon Reef where white-syndrome has become more common in recent years. Signs of black band disease and brown band disease remained negligible on the majority of reefs, with the possible exception of Wade Reef that has shown a small increase in brown band disease in recent years, though this figure still appears low. Similarly, instances of skeletal eroding band disease were at or below levels seen in previous surveys. Numbers of Drupella spp. were also generally lower than in previous surveys.

Table 1.Summary of manta tow survey results for the Swain sector.

Table 2.Summary of SCUBA search survey results for the Swain sector.

M=mid, O=outer, WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band Disease.

For more information on coral disease refer to the AIMS web site at:

AIMS Research – Coral Disease.

Pompey Sector

Perimeters of five reefs in the Pompey sector were surveyed using manta tow (Table 3). Marked sites on each of these and three other reefs were also surveyed in detail using scuba (Table 4). Eleven COTS were recorded at Reef 21-064 during manta tow surveys and twenty-three were recorded during the detailed SCUBA search surveys. Based on the large number of COTS observed in scuba surveys, this reef has been reclassified as an Active Outbreak. COTS numbers have been increasing on this reef since it was first surveyed in 2006; it was classified as an Incipient Outbreak in 2010. Small numbers of COTS were recorded at Reef 20-353 during manta tow surveys.

Median reef-wide live coral cover varied considerably among the survey reefs reflecting their exposure to Severe Tropical Cyclone Hamish that passed through this sector in March 2009. In general coral cover on reefs had changed little since they were last surveyed in 2010. No bleaching of hard corals was recorded during manta tow surveys of reefs in this sector in 2012.

Scuba searches on the intensive survey sites in the Pompey sector revealed a surprising amount of COTS activity. Outbreak densities of COTS were recorded on two reefs (21-062 and 21-064) and sub-outbreak levels of COTS were seen on two others (20-348 and 20-353). A survey of two reefs in this sector earlier this survey year recorded one outbreak at Reef 21-060 (manta tow), plus low numbers of COTS were seen in scuba surveys of both reefs (Pompey#1 and Reef 21-060). This all suggests that the Pompey sector is currently a centre for COTS activity on the Great Barrier Reef.

Scuba searches found levels of coral disease that were generally lower than in previous years. The exception was Reef 20-348 that had relatively high counts of skeletal eroding band disease, though these were not considered exceptional. Similarly, counts of Drupella spp. at all reefs were lower than when they were last surveyed in 2010.

Table 3.Summary of manta tow survey results for the Pompey sector.

Table 4.Summary of SCUBA search survey results for the Pompey sector.

M=mid, WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band Disease.

References

English, S., Wilkinson, C. and Baker, V. (1997) Survey Manual for Tropical Marine Resources (2ndEdition). Australian Institute of Marine Science. Townsville.

 

This project is partially supported by the Marine and Tropical Sciences Research Facility

For further information contact

Dr. Hugh Sweatman , AIMS

Telephone: +61 7 4753 4470

Fax: +61 7 4753 4288

Email: h.sweatman@aims.gov.au