ltm200901-02

Dates: 12thJanuary - 2ndFebruary 2009

Vessel: RV Cape Ferguson

Survey leaders:

Mike Emslie

Cairns sector reefs

Summary

As part of the ongoing Long Term Monitoring Program (LTMP) surveys and the Marine and Tropical Science Research Facility (MTSRF) "COTS early warning surveys" (Project 1.1.2), four reefs in the Cairns sector of the Great Barrier Reef were surveyed using manta tows by the AIMS Long Term Monitoring Team. Intensive SCUBA surveys for benthic organisms, reef fishes and agents of coral mortality (SCUBA searches) were also completed on five reefs in the Cairns sector. Preliminary results of the manta tow surveys and SCUBA searches are presented in this report.

No crown-of-thorns starfish (COTS) were seen on any of the survey reefs. Hard coral cover was moderate (10-30%) on all of the reefs. Coral cover remained stable from previous year's manta tow surveys. Very low levels of coral bleaching, restricted to small numbers of scattered coral colonies, were recorded at two of the survey reefs, Agincourt and St. Crispin. In SCUBA search surveys on these reefs, the number of transects where bleached corals were recorded was low, being 2 and 1 transects respectively, though once again bleaching was restricted to small numbers of scattered colonies on each transect.

SCUBA searches found relatively low occurrence of "white syndrome" (a disease-like necrosis found particularly on tabulate Acropora spp.) and "skeletal eroding band" coral disease on all reefs. Numbers of Drupella spp. (coral feeding snails) were variable with no consistent patterns among reefs and numbers were generally lower than in recent years, except at Low Isles where the highest number ever were recorded and Mackay Reef, where moderate numbers were found compared to previous surveys.

A summary of the results is presented in Tables 1 and 2. A full list of survey reefs appears in the

Long-term Monitoring Status Report Number 8.Details of the monitoring program design, the sampling methods and a full explanation of the COTS outbreak terminology used in this report can be found on the AIMS reef monitoring website.

Cairns Sector reefs

Four reefs were surveyed using manta tows (Table 1) and five core reefs were surveyed intensively using SCUBA (Table 2). No COTS were recorded on any of the survey reefs. Median reef-wide live coral cover was moderate (10-20%) on all four reefs, Agincourt, St. Crispin, Opal and Mackay Reefs. There has been little change in coral cover on these reefs is recent years. No coral bleaching was recorded during manta tow surveys on all reefs.

Image 3:Photograph of a large massivePoritessp. colony that has provided a healthy meal for a school parrotfish. While tending to prefer algae in their diet these bottom feeders will sometimes eat coral. All the little white spots on the colony show where a school of these powerful grazers has come along and peppered the colony with fish bites. Photo:AIMS LTMT	Image 2: Despite coral cover remaining moderate on the reefs in recent years there were signs that barring any major disturbance coral cover could increase in the future. In this photo from Opal(2) Reef small tabulate tabulateAcroporaspp. hard corals are likely to grow rapidly in coming years. Photo:AIMS LTMT

Table 1. Summary of manta tow survey results for four reefs in the Cairns sector.

SCUBA searches on the intensive survey sites (Table 2) showed that the incidence of the coral disease, "white syndrome" (a disease-like necrosis found particularly on tabulate Acropora spp.) was generally lower than the long term average and levels when these reefs were last surveyed (2007). Levels of another coral disease, "skeletal eroding band" (SEB), were generally higher than averages at reefs in each shelf position in the last surveys.

Numbers of Drupella spp. (coral feeding snails) were much higher at Low Isles and Mackay Reef than the previous survey (2007) and the long term average. Numbers of Drupella spp. on the three outer reefs were lower than the long term average but similar to those recorded when last surveyed in 2007.

Small numbers of bleached hard coral colonies were recorded on a few transects of two reefs surveyed using SCUBA, but these colonies made up only a small percentage (<1%) of the total hard coral cover.

Table 2. Summary of results of SCUBA searches at five reefs in the Cairns sector.

WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band Disease. Figures are the number of starfish (COTS), infected coral colonies (WS, BBD, BrB, SEB) or snails ( Drupella ) recorded at each reef.

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

Dr. Hugh Sweatman , AIMS

Telephone: +61 7 4753 4470

Fax: +61 7 4753 4288

Email: h.sweatman@aims.gov.au