Kimberley reefs based on ancient history

WAMSI’s Kimberley Marine Research Program has provided the first definitive evidence that the region’s fringing coral reefs are long lived features growing over a two-billion-year-old land surface recording changes through post-glacial time and dispelling the theory that the reefs are thin veneers over bedrock.

The findings, published in the Australian Journal of Maritime and Ocean Affairs, make significant inroads into understanding the poorly known coral reefs of the Kimberley in an area that is considered an internationally significant ‘biodiversity hotspot’.

Co-author of the paper, Curtin University’s Mick O’Leary, said the project is working to determine just how unique the Kimberley reef system is.

“We hope to establish whether Kimberley reef morphology conforms to established geomorphic models, like the Great Barrier Reef,” Dr O’Leary said. “It may be that the reefs have developed their own distinctive morphologies driven by extreme environmental conditions, like the massive 11 metre tides that are unique to the Kimberley.”

 The research team used a combination of remote sensing, sub-bottom profiling and associated sedimentological work to produce a regional geodatabase of coral reefs and to determine the internal architecture and growth history of the coral reefs over the last 12,000 years.

More than 860 nearshore reefs were mapped from Cape Londonderry to Cape Leveque with a total of 30 reefs studied in detail and their substrates documented across the Kimberley Bioregion.

The prevalence of rhodolith dominated substrates on high intertidal reefs (both planar and fringing reefs) contrasts with the more coral dominated fringing reefs, with inner to mid-shelf planar reefs having some shared attributes with these contrasting categories.

Satellite images used to map intra-reef geomorphology and associated substrates for the targeted reefs of this study:  (a) Bathurst and Irvine Islands; (b) Cape Londonderry; (c) Montgomery Reef; (d) Maret Island; (e) Adele Reef; (f) Long Reef; (g) Molema Island; and (h) Tallon Island.

 

Over 294 km of sub-bottom profiling records were aquired from a representative suite of reefs to determine reef growth history.

Two seismic horizons were identified in the inshore reefs (Sunday Islands, Molema Island, Montgomery Reef and the Buccaneer Archipelago, where seismic calibration was available), marking the boundaries between Holocene reef (Marine Isotope Stage 1, MIS 1, last 12 ky) commonly 10 – 15 m thick, and MIS 5 (Last Interglacial, 120 ky; LIG) and Proterozoic rock foundation over which Quaternary reef growth occurred. In the offshore reefs of the Adele Complex, two additional deeper acoustic reflectors were identified (possibly MIS 7 and MIS 9 or 11)

SBP images of the NW channel bank complex associated with North Turtle Reef

 

The transition of reef building organisms was investigated by shallow coring (up to 6 m) providing the first subsurface sedimentary samples for the key types of reef found in the southern Kimberley.

The core study sheds considerable light on the growth history of the reefs and has shown that the inshore reefs are muddy in character, similar to the Cockatoo island fringing reef.

Adele Reef, offshore, is distinctly sandier in character. Radiocarbon dating showed that, like Cockatoo Island, reef growth initiated soon after the inner shelf was flooded (~10,000 years ago).

Early reef buildups are likely to be muddy with branching, plate, and massive corals. This is replaced on many reefs (particularly exemplified by Montgomery and Turtle Reefs) by coralline red algae (rhodoliths), small robust corals and coral rubble as reefs become intertidal at their surface.

Multibeam surveys of reef flats discovered a new reef morphotype, the “High Intertidal Reef” which are uniquely characterised by having reef flats that have a surface elevation that sits above the level mid-tide level. Typically reef flats sit at the level of mean low water spring tide.

Getting ready for coring with help from Bardi Jawi Rangers and Erin McGinty from KMRS.

 

The project’s findings have been integrated into a GIS based database called ‘ReefKIM’ which incorporates a wide range of datasets, including remote sensing images, bathymetric charts, site photos and many geological and biological datasets into one inclusive geodatabase.

The main purpose of ReefKIM is to compile various types and sources of reef and marine environment-related information, fostering data fusion and maximising the accessibility of important information to better understand the Kimberley reefs.

It is intended to provide researchers with an overview of essential information on the Kimberley reefs. It also constitutes a significant decision-support tool, providing managers and stakeholders with practical information for the implementation of their plans and will also help shape the direction of future management policies of the Kimberley region.

Crowdsourcing new information into ReefKIM (also known as the ‘citizen science’ approach) is a promising method for filling knowledge gaps and enhancing understanding of complex reef ecosystems.

 

 

Methodological scheme of data acquisition, processing, integration and storage for the Kimberley reef geodatabase (ReefKIM) (source: Kordi et al., 2016).

 

“Satellite image analysis has revealed that fringing reefs in the Kimberley bioregion grow very well and differ geomorphologically from middle-shelf planar reefs both inshore and offshore,” Dr O’Leary said.

 “The acoustic mid-shelf reef (Adele complex) profiles marked boundaries between Holocene reef (last 12,000 years) and MIS 5 (last 125,000 years) and an ancient Neoproterozoic rock (1,000 to 541 million years ago).

“Correlating the seismic data with the reef chronology determined in Cockatoo and Adele Island, it has been possible to highlight the evolution of multiple stages of reef building, stacked by repeated high sea levels (Adele, 3 stages, at least; Sundays Group, Buccaneer Archipelago and Montgomery Reef, 2 stages; some patch reefs, 1 stage).

“What we’ve found is that the foundation over which reef growth occurred is the two-billion-year-old land surface seen in many Kimberley islands composed of Neoproterozoic rocks. That confirms that Kimberley reefs are not thin growths over bedrock,” Dr O’Leary said.

The findings provides a better understanding of the Kimberley reefs and demonstrate their capacity to succeed in challenging environments while generating complex habitats to support diverse species.

Research Articles:

Collins, L.B., O’Leary, M.J., Stevens, A. M., Bufarale, G., Kordi, M., Solihuddin, T, 2015. Geomorphic Patterns, internal architecture and Reef Growth in a macrotidal, high turbidity setting of coral reefs from the Kimberley Bioregion. Australian Journal of Maritime & Ocean Affairs, Volume 7, Issue 1, pp 12-22. (open access from Nov 2017)

Moataz N. Kordia, Lindsay B. Collins, Michael O’Leary, Alexandra Stevensa (November 2015) ReefKIM: An integrated geodatabase for sustainable management of the Kimberley Reefs, North West Australia Ocean & Coastal Management doi:10.1016/j.ocecoaman.2015.11.004

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.

Kimberley Marine Research Program

CSIRO, with the Western Australian Marine Science Institution (WAMSI), has partnered with four Kimberley Aboriginal organisations to build and deliver a course in aerial survey methodology to Aboriginal Rangers, with a focus on dugongs. The three-day course was hosted by Wunambal Gaambera Aboriginal Corporation’s Uunguu Rangers at their Garmbemirri camp in the north Kimberley.

Representatives from the Balanggarra, Uunguu, Dambimangari and Bardi Jawi ranger groups came together with researchers from CSIRO, training staff from Kimberley TAFE and two specialist consultants to learn best-practice survey techniques for monitoring dugong and other wildlife populations.

Rangers learnt via theory and practice how to conduct aerial surveys, with each participant taking off in a Gippsland G8 Airvan to practice surveying dugongs, dolphins and turtles from the air.

Dugong aerial survey training camp

“We need to know more about where balguja (dugong) live, feed and travel so we can look after them,” Uunguu Head Ranger Neil Waina said. “Learning these survey methods with other Traditional Owner groups will help us keep these animals healthy in our Country and keep our saltwater culture strong.”

Course accreditation on two of the modules (aerial navigation & safety around aircraft) was sought and co-funded by the Aboriginal research partners. The newly trained Rangers then worked closely with CSIRO researchers during September and October to undertake an aerial survey of their sea country and to contribute to critical baseline population surveys of dugongs and other marine wildlife species identified as target species in their Healthy Country Plans such as sea turtles, dolphins and whales.

Rangers conducting aerial surveys

The training course and aerial survey are components of the WAMSI Kimberley Marine Science Program’s Dugong Management project being run through the Coastal Program of the CSIRO Oceans & Atmosphere Flagship.

The dugong project aims to integrate Indigenous knowledge, including that related to seagrass feeding grounds and seasonal effects on distribution and abundance, with existing and new data to better understand dugongs in the Kimberley.

A dugong, photographed at Roebuck Bay (Kimberley). (Photo: Dave Holley www.roebuckbay.org.au)

The dugong is listed internationally as “vulnerable to extinction” and northern Australia is home to the largest remaining populations. They have very high conservation value and are also culturally important to coastal Aboriginal communities.

New distribution and abundance data will be collected using well established aerial survey methodology, and movements of Kimberley dugongs will be studied also using satellite tracking and acoustic tagging technologies in areas important to sea country plans and Indigenous Protected Areas. This new information will be used to work out how best to monitor and manage Kimberley dugongs into the future.

The team.

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 

Kimberley Marine Research Program

WAMSI oceanographic research has contributed to new findings documenting historic weather maps contained within WA’s coral reefs.

The research, led by The University of Western Australia (UWA), which involved researchers from Australian Institute of Marine Science (AIMS), Curtin University, CSIRO, and the University of California Santa Barbara, drilled into giant porite coral cores from Ningaloo Reef, the Abrolhos Islands and Rowley Shoals to find the marine climate data.

Each of the cores contains seasonal growth bands, similar to tree rings, and provides information about past climate conditions.

The study concentrated on the relationship between the climate conditions in the central-western Pacific and the southeast Indian Ocean referred to as the Maritime Continent, which includes Indonesia, Borneo, New Guinea, the Phillipine Islands, the Malay peninsula and the surrounding areas.

WAMSI researcher CSIRO’s Dr Ming Feng said analysis of the coral core growth bands enabled the team to successfully reconstruct ocean conditions of the West Australian shelf for 215 years and determine what conditions cause marine heat waves among WA’s unique coral reefs.

 “What we found is that when the Maritime Continent is warmer than the central Pacific, a pattern amplified during strong La Niña events in the tropical Pacific, it creates an ocean temperature gradient which reinforces warming in the far western Pacific and south-eastern Indian Ocean,” Dr  Feng said.

Dr Jens Zinke, Senior Research Fellow at UWA and lead author of the research paper published in the journal Nature Communications, said the long coral records allowed the scientists to look at the occurrence of marine heatwaves as far back as 1795.

Dr Zinke said the marine heat waves happened through a series of ocean-atmosphere interactions that resulted in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off Western Australia.

“A prominent example is the 2011 heat wave along WA’s reefs which led to coral bleaching and fish kills,” he said.

The international team found that the temperature gradient in the western Pacific was particularly strong after the late 1990s, which can be linked to the series of marine heatwaves off the WA coast in the recent decade. The coral cores also reveal that this temperature gradient was intensified in the early and late 1800s, yet against a much lower background ocean temperature off WA.

The authors concluded that strong warming over the past 215 years made it easier for natural climate events, such as La Niña and West Pacific temperature gradient events, to exceed the critical temperature threshold for marine heat waves and mass coral bleaching to occur off Western Australia.

Dr Feng, said it was likely that under a warming climate, future La Niña events coupled with a strong West Pacific temperature gradient would result in more extreme ocean warming and high sea-level events with potentially significant consequences for the maintenance of WA’s unique marine ecosystems.

This will likely reduce the future ability of the reefs of Western Australia to serve as a climatically stable area for coral under future ocean warming.

The research builds on previous work and contributes to more accurate thermal reconstructions necessary for better informed resource management.

Figure 1: Southeast Indian Ocean reefs and tropical Indo-Pacific SST variability. From the paper, Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient, by Jens Zinke, A. Hoell, J.M. Lough, M. Feng, A.J. Kuret, H. CLarke, V. Ricca, K. Rankenburg, & M.T. McCulloch, Nature Communications (DOI doi:10.1038/ncomms9562) (a) Locations of the three reef areas (1–3) sampled for long coral cores, (b) rotated empirical orthogonal function 2 (REOF2) covariance of ERSSTv3b15 anomalies, and (c) REOF2 time series, 1960–2013, which explains 21% of the variance. The WPG11 is defined as the standardized difference between average SST over the Niño4 domain14 (black box) and the Western Pacific (WP; blue box), while the Western Australian region is highlighted in grey with coral sampling locations indicated, 1, Houtman Abrolhos, 2, Ningaloo Reef and 3, Rowley Shoals. The black-dashed box marks the Indonesian warm pool region (IWP06 (ref. 26)).

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 

Kimberley Marine Research Program