Report on surveys of the Cairns and Innisfail, Townsville and Cape Upstart sectors of the Great Barrier Reef

Dates: 25^th April to 12^th May 2015

Vessel: RV Cape Ferguson

Survey leaders: Kate Osborne and Michelle Jonker

Manta tow surveys of Thetford Reef in the Cairns sector, five reefs in the Innisfail sector, eight reefs in the Townsville sector and four reefs in the Cape Upstart sector of the Great Barrier Reef (GBR) were made as part of the Long-term Monitoring Program (LTMP). Fieldwork for 2015 survey year is now complete. Detailed surveys of benthic organisms, visual census of fishes and surveys for agents of coral mortality (scuba search) were made on two reefs in the Cairns sector and six reefs in the Townsville sector. Preliminary results of the manta tow and scuba search surveys are presented in this report.

Coral communities in the Innisfail, Townsville and Cape Upstart sectors are recovering well from storm damage. Median reef-wide live coral cover (coral cover) had increased on all five Innisfail reefs, on three mid-shelf Townsville reefs and on two mid-shelf Cape Upstart reefs since they were last surveyed. These reefs are recovering from damage from Severe Tropical Cyclone Yasi in 2011. Coral cover on three outer-shelf Townsville reefs and one mid-shelf Cairns reef was the same as in the previous survey in 2013. However, coral cover had declined on one mid-shelf and one-outer shelf reef in the Cape Upstart sector. While the long gap (10 – 14 years) since the last survey makes reasons for the decline speculative, COTS outbreaks and/or storm damage from Severe Tropical Cyclone Yasi and Severe Tropical Cyclone Hamish in 2009 are likely to have played a role.

Crown-of-thorns-starfish (COTS) were observed on outer-shelf reefs of the Cairns, Innisfail and Townsville sectors and on mid-shelf reefs of the Cairns, Townsville and Cape Upstart sectors, but not at outbreak densities. Surveys from earlier in the 2015 field season showed Active and Incipient outbreaks of COTS were present in the Cooktown-Lizard sector and in the Cairns sector. Coral bleaching was observed at low levels on manta tows and during intensive scuba searches on all reefs in the Townsville sector. Bleaching was also observed on reef perimeters surveyed by manta tow in the Innisfail and Cape Upstart sectors, but generally affected less than 1% of total coral cover.

Coral diseases such as white syndrome, black band and skeletal eroding band disease were rare in intensive scuba searches in both the Cairns and Townsville sector. Small adult COTS were recorded on Opal Reef, Chicken Reef and Davies Reef. Bleaching was observed on most transects in the Townsville sector and also on the two reefs that were surveyed in the Cairns sector.

A complete summary of the results is presented in Tables 1 to 6. These summaries include web links to individual reefs for more detailed results. The monitoring program design and sampling methods can be found in the Standard Operational Procedure Numbers 3, 9 and 10. An explanation of the COTS outbreak terminology can be found in here. For more information on coral disease refer to the AIMS web site at: AIMS Long Term Monitoring - Coral Diseases on the Great Barrier Reef - Introduction

The perimeter of Thetford Reef was surveyed using manta tow (Table 1). Three sites on Thetford and Opal Reefs were surveyed in detail using scuba to look at agents of coral mortality (Table 2). Manta tow surveys recorded five COTS at Thetford Reef.

Table 1. Summary of manta tow surveys for reefs in the Cairns sector.

Two juvenile COTS were recorded during scuba search surveys at Opal Reef. Coral cover at Thetford Reef was moderate (10-30%) in 2015 and similar to the cover levels in recent surveys. Scuba searches on the intensive survey sites (Table 2) found that coral diseases and Drupella spp. were rare. The main impact of coral bleaching was observed on sensitive species, such as Seriatopora, Stylophora and Pocillopora. Some occasional bleaching was also observed on soft corals including some Sinularia and Sarcophyton colonies. At Opal Reef a green macroalgae, Caulerpa spp. was unusually abundant.

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

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

Perimeters of five reefs were surveyed using manta tow (Table 3). Reefs in the Innisfail sector have suffered a number of large disturbances over the last decade (COTS outbreaks, Severe Tropical Cyclone Larry, Severe Tropical Cyclone Yasi). Manta tow surveys in 2015 found clear signs of recovery and all reefs all had moderate coral cover (10-30%). Four COTS were recorded during manta tows on two outer-shelf reefs, Wardle and Potter. Filamentous green algal mats were caught on some corals, particularly branching corals and were smothering some colonies. The algal mats were particularly evident on leeward side of the three reefs (Feather, Ellison and Potter Reefs).

Table 3. Summary of manta tow surveys for reefs in the Innisfail sector.

Townsville sector reefs have suffered from large disturbances (COTS outbreaks, Severe Tropical Cyclone Yasi and bleaching) in recent years. In 2015 manta tow surveys showed that coral cover was low (0-10%) on four reefs (all outer shelf reefs and one mid-shelf), moderate (10-30%) on two reefs and high (30-50%) on two mid-shelf reefs. The outer-shelf reefs were still recovering from storm damage from Severe Cyclone Yasi in 2011. Two mid-shelf reefs in particular, John Brewer Reef and Rib Reef, showed exceptional recovery of coral cover that was at the highest levels recorded since the beginning of surveys in 1986.

The intensive scuba search surveys showed adult COTS less than 15cm in diameter on survey sites on a four of five mid-shelf reefs and one outer-shelf reef (Table 4). White syndrome, black band and skeletal eroding band diseases were rarely recorded on the surveyed sites. However bleaching of less than 1% of coral colonies was recorded on most transects. Bleaching of both hard and soft corals was observed. The hard coral genera most affected were Seriatopora, Montipora, Stylophora, Pocillopora, Favia and Goniopora. Some partial mortality had occurred on many Seriatopora colonies that were bleached and a few Montipora and Goniopora colonies. Other genera of hard corals that also showed signs of bleaching included Porites, Acropora, Favites, Goniastrea, Montastrea, Fungia, Platygyra, Pachyseris, Leptoseris, Mycedium, Merulina, Symphyllia, Lobophyllia, Pavona, Echinopora, Cyphastrea, Hydnophora, Galaxea, Podobacia. The soft coral genera that showed signs of bleaching included Sinularia, Briareum and Sarcophyton.

Table 4. Summary of manta tow surveys for reefs in the Townsville sector.

Table 5. Summary of SCUBA search survey results for the Townsville sector.

I=inner, M=mid, O=outer, WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band Disease, Drup=Drupella spp.

Reefs in the Cape Upstart sector had not been surveyed for between eight and fourteen years. Cape Upstart reefs have had a history of COTS outbreaks but limited surveys in recent year’s makes changes in coral cover on these reefs difficult to interpret. Two reefs had declined to low levels (5-10%) of coral cover by 2015, whilst the other two reefs had increased to moderate levels (10-30%). The two reefs, Elizabeth and Jacqueline, with the lowest coral cover had not been surveyed for between ten and fourteen years and COTS were present on both reefs when last surveyed. The previous survey of Elizabeth Reef was in 2005 when COTS where at outbreak levels. The previous survey of Jacqueline Reef was in 2001, when COTS were also present in low numbers. Interestingly Jacqueline Reef is a Preservation reef within an extensive Marine National Park zone so the reasons for the low coral cover remain particularly enigmatic, though both of these reefs may have been damaged by storms in the recent past. The two reefs where coral cover had increased, Bowden and Charity, were surveyed more recently (2011 and 2007 respectively). Disturbances at Bowden Reef included a COTS outbreak that peaked in 2007 and storm damage in 2011, while Faith Reef hosted an Incipient COTS outbreak in 2004. Low level bleaching was observed on all four reefs.

Table 6. Summary of manta tow surveys for reefs in the Cape Upstart sector.