Image 1. Reefs in the Townsville sector are in the early stages of recovery from extensive crown-of-thorns outbreaks that caused major coral mortality over the last decade. This picture taken on the front of Centipede Reef shows a benthic community dominated by algae. This scene was often repeated on other reefs in the sector. Photo: AIMS LTMP.

Dates: 22ndMarch - 1stApril and 6thApril - 16thApril 2010
Vessel: MV Kalinda
Survey leader: Ian Miller

 

SummaryManta tow surveys and intensive SCUBA surveys for benthic organisms, reef fishes and agents of coral mortality (SCUBA searches) were completed on three reefs in the Innisfail sector of the Great Barrier Reef. Ten reefs in the Townsville sector were surveyed using both manta tow and intensive SCUBA. Two additional reefs in the Townsville sector were surveyed using intensive SCUBA surveys alone. Preliminary results of the manta tow surveys and SCUBA searches are presented in this report.No crown-of-thorns starfish (COTS) were recorded in the Innisfail sectors. Hard coral cover on reefs in the Innisfail sector was low to moderate with two reefs (Taylor and Peart) showing signs of recovery in coral cover from prior COTS and cyclone damage since they were last surveyed two years before. Hard coral cover at Farquharson Reef in the Innisfail sector was very low as had been the case for at least five years.Two of the ten reefs surveyed by manta tow in the Townsville sector had very low (0-5%) reef-wide live hard coral cover; cover was low to moderate (5-30%) on the other eight reefs. Many of the Townsville survey reefs had large COTS outbreaks that caused major coral mortality during the previous 10 years. Recovery of hard coral communities in the Townsville sector has generally been limited except for Rib Reef where there are strong signs of recovery from a COTS outbreak that ended in 2003.SCUBA searches revealed that incidence of " white syndrome " (a disease-like necrosis found particularly on tabulate Acropora spp.) was higher on Peart Reef in the Innisfail sector than recorded in previous surveys. Also the numbers of Drupella spp. (coral feeding snails) were generally higher than recorded previously. A similar pattern was seen in the Townsville sector where levels of white syndrome and " skeletal eroding band " disease (SEB) were conspicuous on a few reefs (particularly Helix and Knife) and Drupella spp. activity had increased on several reefs.A summary of the results is presented in Tables 1 - 4. A full list of survey reefs appears in the Long-term Monitoring Status Report Number 8. Details of the monitoring program design and sampling methods are available on the AIMS reef monitoring website(see link below). A full explanation of the COTS outbreak terminology used in this report can be found at the same site.Innisfail SectorThree reefs were surveyed by manta tow and SCUBA search (Tables 1 and 2). No COTS were recorded. Median reef-wide live coral cover at Farquharson Reef remained very low (0-5%) and this reef appears to have recovered little from damage due to Cyclone Larry in 2006 and from COTS outbreaks prior to that. In contrast Taylor Reef and Peart Reef are showing good signs of recovery and reef-wide live coral cover had increased on both to moderate levels (10-30%) in 2010 from the low (1-10%) levels recorded in 2008.Incidences of coral disease were generally similar to those recorded in previous years, with the exception of Peart Reef where white syndrome had become more common. Occurrence of Drupella spp. increased on all reefs surveyed compared to previous surveys, though the observed densities would not be expected to affect living coral cover.

 

Table 1. Summary of results from manta tow surveys in the Innisfail sector.

Reef Shelf Position Tows COTS COTS per tow Median % Live Coral Cover Median % Dead Coral Cover Median % Soft Coral Cover Reef Status
PEART Mid 50 0 0 20 to 30 0 to 5 0 to 5 RE
FARQUHARSON B Mid 58 0 0 0 to 5 0 to 0 0 to 5 NO
TAYLOR Mid 47 0 0 10 to 20 0 to 5 0 to 5 RE
Overall GBR average for last survey - visit 16 All     0.08 10 to 20 0 to 5 0 to 5 -
Long-term average value Mid     0.24 0 to 5 0 to 5 0 to 5 -
Average last survey - visit 16 Mid     0 0 to 5 0 0 to 5 -

Table 2. Summary of results of SCUBA searches on the intensive survey sites on reefs in the Innisfail sector.

Reef Shelf Position COTS (<5cm) COTS (>5cm) COTS (>15cm) COTS (>25cm) WS BBD BrB SEB Drupella
PEART M 0 0 0 0 12 0 4 7 12
FARQUHARSON M 0 0 0 0 1 0 3 3 46
TAYLOR M 0 0 0 0 2 0 0 0 32
Overall GBR Average for last survey - visit 16 All 0 0.054 0.34 0.57 10 0.18 3.1 6.9 8.1
Long term average M 0 0 0 0 5.5 0.22 1.3 5.3 8.4

WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band DiseaseTownsville SectorTen of reefs were surveyed using manta tow (Table 1); these and two additional reefs were surveyed in detail using SCUBA (Table 2).

One adult COTS was recorded at Little Kelso Reef during SCUBA search surveys. This indicates that there is minimal COTS activity at present, though there were active outbreaks on reefs in this sector as recently as 2006. Seven of ten manta tow reefs were designated as Recovering from previous recent COTS outbreaks. Two reefs (Knife and Fork) are classified as still Recovering from historic COTS outbreaks in 1987 and one reef (Roxburgh) has no history of COTS activity and is classified as No Outbreak. In general reefs in this sector are showing limited signs of recovery from past COTS activity.Five of the ten reefs surveyed by manta tow: Kelso, Little Kelso, Chicken, Centipede and Lynch's, had low median reef-wide live coral cover (<10%) with the latter two reefs having very low cover (<5%). Kelso and Little Kelso were showing minimal signs of increasing coral cover since COTS outbreaks ended on these reefs in 2003. Chicken and Centipede were yet to show signs of increasing coral cover since COTS outbreaks ended in 2005 and 2006 respectively. While no outbreaks have been recorded at Lynch's Reef, many neighbouring reefs had outbreaks in the early part of the decade. For this reason and because of it's the limited survey history, Lynch's Reef is also classified as Recovering. Lynch's Reef showed no signs of increasing coral cover since it was last surveyed in 2006. A pattern of little or no increases in coral cover was also seen on four of the five reefs that had moderate (10-30%) median reef-wide coral cover. Roxburgh, Knife and Fork Reefs were showing no signs of increasing coral cover possibly because they have had no recent history of outbreaks. Helix Reef was showing limited signs of increasing coral cover since a COTS outbreak that ended in 2006. In contrast Rib Reef showed strong recovery from a COTS outbreak that ended in 2003 when coral cover was very low (<5%).SCUBA searches on the intensive survey sites showed that the occurrence of coral diseases and numbers of Drupella spp. (coral feeding snails) were generally low and comparable to records from previous surveys. Possible exceptions were Helix and Knife Reefs, where the incidence of white syndrome and skeletal eroding band disease was higher than at other reefs in the sector and higher than the long term average for the region (though not unusually high overall). Similar densities of Drupella spp. were recorded from Fork Grub, Knife, Lynch's and Roxburgh Reefs.

Table 3. Summary of results of manta tow surveys in the Townsville sector

Reef Shelf Position Tows Cots COTS per tow Median % Live Coral Cover Median % Dead Coral Cover Median % Soft Coral Cover Reef Status
KELSO Mid 63 0 0 5 to 10 0 to 0 0 to 5 RE
LITTLE KELSO Mid 31 0 0 5 to 10 0 to 5 0 to 5 RE
RIB Mid 35 0 0 20 to 30 0 to 0 0 to 5 RE
ROXBURGH Mid 19 0 0 10 to 20 0 to 5 0 to 5 NO
HELIX Mid 15 0 0 20 to 30 0 to 5 0 to 5 RE
CENTIPEDE Mid 58 0 0 0 to 5 0 to 0 0 to 5 RE
LYNCH'S Mid 64 0 0 0 to 5 0 to 0 0 to 5 RE
KNIFE Outer 27 0 0 20 to 30 0 to 0 0 to 5 RE
FORK Outer 31 0 0 10 to 20 0 to 5 0 to 5 RE
CHICKEN Outer 39 0 0 5 to 10 0 to 0 0 to 5 RE
Overall GBR average for last survey - visit 16 All     0.08 10 to 20 0 to 5 0 to 5 -
Long-term average value Mid     1.68 10 to 20 0 to 5 0 to 5 -
Long-term average value Outer     1.07 10 to 20 0 to 5 0 to 5 -
Average last survey - visit 16 Mid 0 0 to 5 0 0 to 5 -
Average last survey - visit 16 Outer     0 20 to 30 0 0 to 5 -

Table 4. Summary of results of SCUBA searches on the intensive survey sites on reefs in the Townsville sector.

Reef Shelf COTS (<5cm) COTS (>5cm) COTS (>15cm) COTS (>25cm) WS BBD BrB SEB Drupella
KELSO M 0 0 0 0 0 0 0 0 1
LITTLE KELSO M 0 0 0 1 2 0 0 2 8
RIB M 0 0 0 0 3 0 4 0 20
ROXBURGH M 0 0 0 0 4 0 0 1 18
FORE AND AFT M 0 0 0 0 3 0 0 0 0
GRUB M 0 0 0 0 5 0 0 4 20
CENTIPEDE M 0 0 0 0 1 0 0 3 0
HELIX M 0 0 0 0 8 0 4 13 29
LYNCH'S M 0 0 0 0 3 0 0 8 22
KNIFE O 0 0 0 0 12 0 1 13 21
FORK O 0 0 0 0 1 0 3 7 46
CHICKEN O 0 0 0 0 1 0 0 8 15
Overall GBR Average for last survey - visit 16 All 0 0.054 0.34 0.57 10 0.18 3.1 6.9 8.1
Long term average M 0.015 0.52 5 1.2 3.2 0.019 0.47 2 16
Long term average O 0.1 0.68 1.8 0 2.9 0 0.38 5.3 23
Average for last survey - visit 16 M 0 0 0 0 3.3 0 0.44 3.8 6.3

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