New type of reef identified in the Kimberley

The remote Kimberley coast is characterised by its extreme tidal ranges, warm turbid waters and frequent cyclonic events, and is also home to a newly recognised form of coral reef, one which grows higher than any other reef type in the world.

Curtin University researcher Dr Mick O’Leary has been leading a Western Australian Marine Science Institution (WAMSI) project team that’s been characterising the surface morphology and internal architecture of Kimberley coral reefs using mutlibeam sonar and seismic profiling technologies, as well as collecting reef cores to establish growth histories and ecological change on thousand year time scales.

The findings, published in the journal Coral Reefs, provide new insights into the ability of Kimberley corals to survive, endure, and thrive, in what is generally considered to be environmentally challenging conditions for coral growth.

The seismic profiling revealed that the living coral veneer does not represent simple coral communities growing on rock foundations but are in fact the surface expression of massive and complex reef structures comparable to what we might see at Ningaloo or the Abrolhos or even the Great Barrier Reef.

Percussion coring on Bathurst-Irvine Island, core length up to six metres were recovered using this method. (Mick O’Leary)

The research team drove 6.5 metre lengths of aluminium tubing into the reef structure to recover a record of reef growth. Radiocarbon dating of corals collected from reef cores revealed that coral growth commenced in the Kimberley almost immediately after the continental shelf was flooded by rising sea levels that followed the end of the last ice age some 12 to 15 thousand years ago, with the oldest dated inshore corals returning ages of more than 9000 years.

The most unusual feature of Kimberley reefs is the elevation of their reef flats. Typically coral reefs will grow vertically until they reach sea level, then having used up all the available vertical space, they switch growth directions and begin to grow laterally into deeper water. The upper vertical limit of reef growth is the mean low water tide level, as corals can only tolerate exposure to the atmosphere for brief periods, which usually occurs around spring low tides.

However, the team’s multibeam sonar surveys have precisely measured the elevation of the reef flats and revealed that Kimberley reefs have grown vertically through the mean low water level limit up to the mean tide level.

“This basically means the corals on the reef flat spend half their life exposed above the level of the tide,” Dr O’Leary said. “The sight of water cascading off the edges of a Kimberley coral reef as the tide falls is something that you can experience nowhere else on Earth.”

Somehow Kimberley corals have managed to adapt over many thousands of years to these extreme tidal ranges, high levels of turbidity, really warm water temperatures and exposure, and are thriving in the Kimberley despite these conditions.

So as we see the beginnings of yet another major bleaching event on the Great Barrier Reef, we might look to these more robust Kimberley coral reefs and ask what is unique about these corals? How long did it take to adapt to the unique Kimberley marine environments and are there lessons here that can be applied to the more sensitive coral reef regions of the world?

Water cascading off the reef at Tallon Island (Tubagus Solihuddin)

Related Links:

• Solihuddin T, O’Leary M, Blakeway D, Parnum I, Kordi M, Collins L (March 2016) Holocene reef evolution in a macrotidal setting: Buccaneer Archipelago, Kimberley Bioregion, Northwest Australia Coral Reefs DOI 10.1007/s00338-016-1424-1
• Ryan J. Lowe, Arturo S. Leon, Graham Symonds, James L. Falter, and Renee Gruber The intertidal hydraulics of tide-dominated reef platforms Journal of Geophysical Research: Oceans Volume 120, Issue 7 July 2015 Pages 4845–4868 DOI: 10.1002/2015JC010701
• http://www.wamsi.org.au/research-site/geomorphology

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

By Natalie Jones, ABC

Dolphins in Western Australia’s Kimberley are heavily reliant on their specific habitats and “quite vulnerable” to human activity, researchers have said.

The researchers published the findings of a four-year study which provides the first estimates of the abundance of three shallow, inshore species of dolphin — the Australian snubfin, the Australian humpback and the Indo-Pacific bottlenose dolphin.

The Murdoch University team travelled to five remote locations in the Kimberley to collect data, counting dolphins and mapping the sightings.

They focused mostly on the West Kimberley, visiting Roebuck Bay, Beagle Bay, Cygnet Bay and Cone Bay, but also took in the Inner Cambridge Gulf in the region’s east.

“The motivation for this research was that these animals, from what we know elsewhere in Australia, tend to occur in quite small populations that really depend on the near-shore environment,” lead researcher Alexander Brown said.

ABC TV News story by reporter Natalie Jones

“So that makes them quite vulnerable to human activity that occurs in these habitats.

“Particularly in the Kimberley region, we really had no idea of how many of these species were out there and what key areas there might be.”

The researchers found there was a high degree of population variance between the sites.

“We could go just 100 kilometres up the coast and we’d see quite a change in the dominance of a species over another,” Mr Brown said.

He found that snubfin dolphins were most abundant at Roebuck Bay, and bottlenose dolphins were most abundant at Beagle Bay on the west side of the Dampier Peninsula.
Boosting dolphin conservation

Mr Brown said the team thought each species favoured some habitats over others, and said there may also be some competition between species.

“Without this abundance of data it makes it very difficult to assess the conservation status of the species, to determine if they should qualify as threatened species or otherwise, and it’s very difficult to determine appropriate conservation and management measures,” he said.

Snubfin and humpback dolphins are unique to the waters off northern Australia and Southern New Guinea, but little is known about the species in the tropical north.

The research comes as the State and Federal Governments plan and gazette several marine parks across the Kimberley coast.

Mr Brown — a Murdoch University Cetacean Research Unit (MUCRU) PhD student who partnered with Lars Bejder, Kenneth Pollock and Simon Allen on the study — said his team’s work could help manage those areas.
Snubfin dolphins swimming off the Kimberley coast.

Snubfin dolphins (Jenny Smith, MUCRU)

He also warned the three species of dolphin would be particularly vulnerable to any new development.

“If any coastal development or potentially threatening activity is likely to take place, site-specific surveys need to be conducted in order to ascertain if the area’s of particular importance for any one or all three of these species,” he said.

“We also really recommend building upon these abundance estimates in the future by establishing more long-term monitoring programs, in order to determine if populations are stable, increasing or in decline.”

Existing threats to dolphins remain largely unknown, as the study surveyed just six per cent of the Kimberley’s coastline.

The MUCRU research was funded by the Federal Government’s Australian Marine Mammal Centre, WWF Australia and the Western Australian Marine Science Institution’s Kimberley Marine Research Program.

Related Links:
ABC http://ow.ly/YA91g 
http://mucru.org/new-publication-inshore-dolphins/
http://journal.frontiersin.org/article/10.3389/fmars.2016.00004/full

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

More than 40,000 aerial photographs of the Kimberley coast have been taken and scrutinised for signs of nesting turtles as part of the Western Australian Marine Science Institution (WAMSI) turtle research project.

Information about adult females and turtle hatchling numbers and species gleaned from tracks seen in the images of more than 2500 islands and 1300 mainland beaches is now being verified through a process of ‘ground truthing’.

The aerial and ground surveys are part of the distribution and abundance facet of the WAMSI Kimberley Research Program’s sea turtle project that aims to identify when and where turtles nest, develop climate change models to predict how turtles might be impacted and work out relationships between different turtle nesting groups.

Aerial view of the winter-nesting flatback turtle rookery at Cape Domett, north of Kununurra, showing turtle tracks and a lurking crocodile. (DPaW)

Department of Parks and Wildlife senior research scientist Dr Tony Tucker said more than 90 per cent of the Kimberley coastline’s available turtle nesting habitat was accessible only by foot, boat or helicopter posing significant challenges for field surveys.

“The aerial images taken during the summer and winter surveys in 2014 have helped identify hotspots of relative density for follow-up by ground survey,” he said.

The ground truthing phase of the project, started during 2015, will continue this year, as will work on the other facets of the project.

Dr Tucker said, during the ground surveys, tissue samples had been collected from more than 700 turtles, including a rare WA sample from an olive ridley turtle, and by the end of the year the number of samples could be close to 1000.

“The genetic analysis will help us work out the relationships between groups of nesting turtles and define breeding units for the four predominant nesting species,” he said.

“We need to know what are the breeding groups for summer and winter-nesting flatback, green, loggerhead and hawksbill turtles to protect and conserve these species through effective strategic management of habitats.”

Dr Tucker said the sea turtle project team was working with 10 different Traditional Owner groups who had assisted in the ground surveys and were helping to establish how traditional and scientific knowledge complemented each other.

Partners in the WAMSI Kimberley sea turtle project include Parks and Wildlife, The University of Western Australia, CSIRO, Griffith University and Pendoley Environmental. The project will provide a knowledge base for future monitoring and information to help understand if populations are increasing or decreasing.

It will also develop effective and efficient monitoring methods that can be conducted over the long term and build capacity amongst Indigenous ranger groups to enable ongoing monitoring. Together this assists in management across the entire Kimberley, including the four new and proposed marine parks.

Ground view of turtle tracks at Cape Domett. (DPaW)

WAMSI’s $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 and co-investment by the WAMSI partners.

Kimberley Marine Research Program

A team of CSIRO and UWA researchers has just returned from a 10-day field trip to Bardi Jawi country, where they took the last of their seagrass, seaweed and microalgae measurements for a WAMSI project that will determine the current state of the area’s primary food source for rabbitfish and green sea turtles.

The team worked with the Bardi Jawi Rangers on Tallon Island (Jalarn) and Sunday Island (Iwany) off the Dampier Peninsular in the Kimberley. They measured the growth of seagrass and macroalgae on the reef platforms, and microalgae in the sand that forms the beaches. These are all primary producers that sustain food webs, and the area’s seagrass is a key food source for fish and turtles that are important for the Bardi Jawi.

Preparing for seagrass tethering study (Mat Vanderklift)

Some seagrass was punched with holes to measure growth — researchers measure how far the holes have moved after a week to see how much the grass has grown. Other seagrass was collected, pegged out, measured and returned to the seagrass meadow for a 24 hour period before being measured again to determine how much had been eaten.

CSIRO’s Mat Vanderklift, who is also working on green sea turtle tagging as part of another WAMSI project, said the findings were providing the first comprehensive picture of productivity and seasonality of seaweed, seagrasses and microalgae in the Kimberley.

“Through collaboration with the Bardi Jawi Rangers we have been able to build up detailed seasonal understanding of seagrass productivity through the year,” Dr Vanderklift said. “We also have a better understanding of the importance of this productivity for green turtles and herbivorous fish like rabbitfish.”

Seagrass habitat with a sea cucumber in the Bardi Jawi IPA (Mat Vanderklift)

“The key findings are that the main plants that we have found in the lagoon habitats (the seagrasses Thalassia and Enhalus, and the large brown algae Sargassum) all have high growth rates throughout the year, with growth rates sometimes exceeding a centimetre a day,” Dr Vanderklift said. “We have also found that microscopic algae are very abundant in some places, but not everywhere, and bacteria are particularly abundant in the sediment under mangroves and seagrasses.”

The project has found that herbivores are abundant in the area and that they eat a lot of the seagrass. One of the main herbivores in the area, rabbitfish (Siganus lineatus), is a highly sought after food source by the Bardi Jawi people.

The project is also finding that the seagrasses are living at the limit of their temperature tolerances and further studies of their vulnerability to climate change are needed.

James McLaughlin on Jologo beach talking about microalga with kids from One Arm Point Remote Community School. (Mat Vanderklift)

“Collaborations with the Bardi Jawi Rangers have added enormous value to the research,” Dr Vanderklift said. “We have been able to exchange knowledge and learn from each other – for example, the discovery of the importance of seagrass to rabbitfish would not have happened if we had not worked closely together. The success of this project is because of the collaboration we have built together.”

The latest trip also gave the researchers an opportunity to present to children from the local One Arm Point Remote Community School.

James McLaughlin wowed the high school “Bush Rangers” with real-life chemistry on the beach, while Mat Vanderklift talked to dozens of excited children about turtles at their Culture Day. “They all enjoyed the game of guessing where the tagged turtles had travelled,” he said.

The project group is now completing the measurements and analysing the data, and will return to show the community and the rangers the results next year, with the aim of informing the ranger’s activities under their Indigenous Protected Area management plan.

Josh Setting up Benthic chamber module. (Mat Vanderklift)

 

 

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’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