Indian Ocean creates its own flow-on effect

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New research led by CSIRO has described how heavy rainfall caused the top layer of the southeast Indian Ocean to be less salty, creating a barrier layer which trapped the heat during the deadly marine heatwave – La Niña and the ‘Ningaloo Niño’ of 2010-11. The result was a larger volume of warmer water being driven by a stronger current down the WA coastline.

The finding, which is part of WAMSI’s Kimberley Marine Research Program, provides further scientific knowledge to help predict responses to climate change, and adds another layer to consider when forecasting extreme marine heatwave events.

Surface salinity anomalies (psu) derived from gridded Argo product (relative to 2005–2012 monthly climatology) in February 2011.

According to CSIRO’s physical oceanographer Dr Ming Feng, the change in salinity levels on the top 100 metres of the ocean also raises more questions, such as how it will affect some marine species.

“In the past we have followed the Pacific Ocean climate closer in evaluating WA marine environment. We haven’t focused much attention on the Indian Ocean variables and the effect on the WA environment,” Dr Feng said. “It seems that the more we find out about the Indian Ocean, the more we realise it operates very differently to any other ocean on earth.”

The Leeuwin Current, the eastern boundary current of the southeast Indian Ocean, carries warm fresh tropical water southward along the west coast of Australia. The current is stronger in Australia’s winter and weaker in summer; it also tends to be stronger during La Niña events.

Surface currents in the Indian Ocean during austral summer, adapted from Schott et al. [[1]] and Menezes et al. [[2]]. The background shading shows the sea surface temperature anomalies (°C) in February 2011 derived from the Argo float data. ITF: Indonesian throughflow; LC: Leeuwin Current; SJC: South Java Current; SEC: South Equatorial Current; SECC: South Equatorial Counter Current; SC: Somali Current; NMC: Northern Monsoon Current; NEMC: North East Madagascar Current; SEMC: South East Madagascar Current; SICC: South Indian Countercurrent.

The latest research compared salinity observations at the CSIRO/Integrated Marine Observing System (IMOS) Rottnest National Reference Station collected during the past 60 years. Analysis of these observations revealed the unusual, but significant, freshening of the ocean’s top layer during 2010-2011.

Dr Feng suspects this may not be the first or last time we experience such an event.

“Something similar probably happened in 1999/2000, so it might happen in the future, especially as we experience more frequent warmer conditions,” he said.

It’s thought that the change in salinity can take a few years to return to normal but the El Niño forecast for 2015, which was to result in a weakening in the Leeuwin Current and cooler water temperatures along the coast of WA, has not rung true.

“Typically we should be experiencing cooler temperatures off the west coast this year but the temperatures have still been warmer than normal, so this is an unusual year, and it shows we don’t fully understand the impact of the Indian Ocean,” Dr Feng said.

Ming Feng, Jessica Benthuysen, Ningning Zhang and Dirk Slawinski (October 2015) Freshening anomalies in the Indonesian throughflow and impacts on the Leeuwin Current during 2010–2011 Research Letters DOI: 10.1002/2015GL065848

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. 

 

Category:

Kimberley Marine Research Program

Kimberley reefs based on ancient history

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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.

Category:

Kimberley Marine Research Program

James Price Point data to support Kimberley program

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The Browse liquefied natural gas (LNG) Development investigated a major onshore processing facility 52 kilometres north of Broome on the Dampier Peninsula, in Western Australia’s Kimberley region. The Browse Joint Venture (JV) participants commissioned numerous studies and rigorous environmental management planning for the proposed onshore LNG development.

In April 2013, the Browse JV completed its technical and commercial evaluation of the proposed Browse LNG Development near James Price Point and determined that the development concept did not meet the company’s commercial requirements for a positive final investment decision.

Even so, the research and technical work gathered during this time represents a significant and comprehensive collection of unreleased information on the local areas’ marine environment including, habit and species assessments, aerial and vessel megafauna surveys as well as benthic and seagrass habitat surveys.  Woodside, on behalf of the Browse JV, has shared this data with WAMSI for the Kimberley Marine Research Program.

Proposed FLNG location in 2010

“The Browse JV has invested more than A$55 million in environmental research and studies, often in conjunction with leading academic and research organisations, to better understand the offshore marine environment in the vicinity of the three Browse gas fields,” Woodside’s Senior Vice President Projects, Steve Rogers said.

“By sharing our research and collaborating with WAMSI scientists, the valuable data collected over the past two decades can directly improve how the marine environment is managed,” Mr Rogers said.

WAMSI CEO Patrick Seares described the James Price Point data as key to helping the Kimberley Marine Research Program link information developed through its fieldwork focus further to the north, with more studies in the areas of Roebuck Bay and the Browse Basin.

“This enormous marine science program is all being done to improve the understanding and management of the Kimberley marine environment. The Browse JV data will allow us to fill in some of the gaps off the Dampier Peninsula and provide an even more complete picture to marine park and fisheries managers, traditional owners, regulators and future proponents,” Mr Seares said.

“We’ve been working to build both trust and the business case to support broader data sharing with industry on a number of fronts, including the agreements supporting the dredging science node and working with the energy sector on the IGEM system,” Mr Seares said.

“Opening up this data for the Kimberley program is another great step in that process and evidence that leading groups within the energy sector are increasingly working with the science sector to share knowledge. Long may it continue! ”

At this stage the raw data is limited to use for the WAMSI Kimberley Marine Research Program.

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.

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Kimberley Marine Research Program

Groundbreaking tidal study optimises export capacity at the world’s largest bulk export port

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By Albina Skender, PPA

A groundbreaking tidal model developed by the Pilbara Ports Authority is receiving industry acclaim for achieving extra depths in shipping channels.

Results from the study, conducted at Port Hedland harbour, when combined with maintenance dredging targeting high spots, achieved an extra depth of 71 centimetres in the shipping channel.

The project has been recognised by industry leaders, and its survey work has been acknowledged as the methodology that should be applied internationally.

The project also won a prestigious Premier’s Award in the Developing the Economy category, which recognises projects that maximise opportunities for the future through stimulating the economy to support employment and growth in Western Australia.

PPA’s Marine Department conducted the tidal study after discovering data inconsistencies with previous hydrographic surveys carried out in the shipping channel. The tidal study was an opportunity to accurately identify existing, deeper channel depths, and resulted in the creation of a Lowest Astronomical Tide (LAT) Model or ‘Hydroid’ unique to Port Hedland.

In short, the study determined the actual levels of LAT measured to ‘the ellipsoid’, a geospatial reference datum. A hydrographic survey conducted to this new LAT model (Hydroid) was consequently fed into the port’s Dynamic Under Keel Clearance (DUKC©) system, allowing for a deeper draft for draft restricted vessels transiting the channel.

The study and the survey, combined with the improved depths of a maintenance dredging campaign in 2013, resulted in an extra 71cms of draft availability in the shipping channel.

Dredging Manager Frans Schlack, who led the project, said the increased draft has provided port customers the opportunity to safely load more product onto vessels, and has potentially extended sailing windows for cape size vessels from six to eight on a tide.

“These developments have enabled PPA to significantly increase its export capacity and allow the port to more safely manage increasing vessel movements in the Port Hedland shipping channel,” he said.

Port Hedland inner harbour (Photo: Pilbara Ports Authority)

The port now regularly facilitates the export of more than a million tonnes on a tide. In February 2015, the port set a new record tonnage of more than 1.5 million tonnes on a single tide that was achieved with eight cape size vessels departing in one convoy. Up to the end of September 2015, the port has achieved one million tonnes on a tide more than 30 times this year.

PPA’s customers are now able to load more product on vessels to a deeper sailing draft, enabling higher volumes of commodities to depart the port in a safe and efficient manner while simultaneously reducing transport costs.

“This not only generates greater export capacity, but it has been achieved without the need to conduct capital dredging (equivalent to three million m³ of material that would otherwise have to be dredged), avoiding significant costs and environmental impacts,” Mr Schlack said.

“The initiative has also given PPA a more precise understanding of the channel, enhancing safety and the port’s ability to manage risk within the uni-directional channel.”

The establishment of the Port Hedland ‘Hydroid’ corrects the long held assumption that LAT is a datum for chart depths and tide readings. LAT is an astronomical event, not a datum.

The establishment of a port’s ‘Hydroid’ creates the correct datum to reference both chart depths and tide heights from which mariners can reliably determine safe navigable depth for their vessels.

“The depths were always there, we just found a better way of measuring them,” Mr Schlack said.

The work has also been acknowledged and commended by the regulator, the Royal Australian Navy Hydrographic Office, which provides leadership, coordination and standards for surveying, mapping and national datasets.

In April 2014, the Permanent Committee on Tides and Mean Sea Level and Ports Australia Hydrographic Surveyors Working Group visited Port Hedland and commended PPA’s work on determining the real tide at the world’s biggest bulk export port.

The Royal Australian Navy Hydrographic Office has also acknowledged the port’s tidal study and survey work as the standard that should be applied internationally, by means of a submission by the office’s Deputy Hydrographer to the Intergovernmental Committee on Surveying and Mapping (ICSM).

Mr Schlack believes other ports can significantly benefit from the model and targeted dredging.

 “A new LAT model will also be created for all other PPA ports, with each port having its own unique Hydroid established through individual tidal studies in combination with PPA’s recognised high standard of hydrographic surveying,” he said.

WAMSI/CSIRO partner with Kimberley Aboriginal groups to manage dugong

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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. 

Category:

Kimberley Marine Research Program

Cone Bay proves reliable for acoustic recordings of humpback dolphins

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Blog By: Josh Smith PhD, MUCRU

For what could be the last field trip in a project to determine the feasibility of conducting passive acoustic monitoring of snubfin and humpback dolphins, the research team headed to Cone Bay on the northeast tip of King Sound in the Kimberley to focus on recording humpback dolphins specifically.

I was fortunate enough to have the aid of fellow Murdoch University Cetacean Research Unit (MUCRU) researcher, Alex Brown, to help me in the field to focus on getting the recordings of the sounds that humpback and snubfin dolphins are making.

We were also fortunate to be joined and helped out by Dambimangari Rangers during several days of the fieldwork, who provided excellent dolphin spotting skills and assisted in photo-identification of the dolphins we encountered.

In September 2014, Alex and fellow MUCRU researcher Dr Simon Allen and Dr Stephanie King undertook a WAMSI trip to Cone Bay to determine the size of the dolphin populations there and reported consistent sightings of humpback dolphins around the Marine Produce Australia barramundi sea farm, in Cone Bay at Turtle Island.

Not only did Cone Bay provide consistent sightings of snubfin and humpback dolphins, it also provided an elevated land based platform that could provide information on the dolphins detection thresholds by comparing the dolphins location relative to the acoustic recorders.

The acoustic data that we are collecting will help to develop a better understanding of the acoustic repertoire of these species, whether there are geographical differences in the sounds they make within a species, and understand over what type of ranges these dolphins are using their sound.

The main objective is to determine the feasibility of conducting passive acoustic monitoring for these species, which is being conducted as a Bill Dawbin Fellowship and part of the Western Australian Marine Science Institution (WAMSI) Kimberley Marine Research Program dolphin project.

The trip to Cone Bay was a great success with encounters of humpback dolphins engaged often in very interesting social behaviour. The trip was divided up in effort with land based hilltop observations over the sea farm and boat-based recordings.

For the hilltop observations, we deployed several SoundTrap acoustic recorders around the farm and waited for humpback dolphins to come in around the sea farm. This did not always happen regularly and was difficult to determine exactly when during the day this would happen.

Hilltop observations using SLR camera and binoculars overlooking the barramundi sea farm
Hilltop observations using SLR camera and binoculars overlooking the barramundi sea farm

A humpback dolphin jumping not far from an acoustic recorder
A humpback dolphin jumping not far from an acoustic recorder

The hilltop observations (using a Canon SLR and mounted GPS unit along with Vadar software) allows information on the range that sounds can be detected by the acoustic recorders to determine detection thresholds. This is done by the SLR camera recording many attributes of the camera and lens settings and the GPS function being capable of determining the bearing the camera is pointed.

The software Vadar takes the elevation of the land based platform along with the camera settings and is capable of geo-referencing the dolphins’ location which is corrected for the tide. This is then related back to the known positions of the acoustic recorders.

Alex on the water as we pursure mobile acoustic recordings

Alex on the water as we pursue mobile acoustic recordings

It wasn’t long before Alex and I realised the humpback dolphins were not around the farm for the entire day and we needed to increase encounter rates. So, remaining within VHF radio contact of workers at the farm who could radio us if they saw dolphins, we went out on the six metre research boat to increase our dolphin encounters. Generally, we were quite successful, coming across either a group of snubfin or humpback dolphins.

The other objective of this trip to Cone Bay was to see whether we could increase the number of genetic samples of the dolphins from that obtained in September 2014 and from photo identification we could see whether many of the previously identified dolphins were still in Cone Bay. Almost straight away it became apparent that many of the same dorsal fins of the dolphins were being sighted from the photo ID, although there were also some new fins that Alex could not recognise.

Being on the boat meant that we could get close to the dolphins and use the mobile acoustic recorder, which was a SoundTrap attached to a rope on a float. When we had sighted a group of dolphins we would establish the type of behaviour they were exhibiting ie foraging, socialising or travelling, which would largely determine the possibility of getting acoustic recordings. When the dolphins are socialising, they are less worried about the boat and will often not travel as far, providing a better opportunity for good acoustic recordings.

The main objective of the mobile recordings was to increase our understanding of the different types of social sounds they were making to identify their acoustic repertoire. The boat recordings provided some interesting sound recordings, particularly from a mixed group of four humpback dolphins in what appeared to be attempted mating of a single snubfin dolphin.

A group of humpback dolphins socialising near the mobile acoustic recorder attached to the float
A group of humpback dolphins socialising near the mobile acoustic recorder attached to the float

Finally, after almost three weeks of what was pretty good weather and almost 12-hour days, we left Cone Bay for Cygnet Bay and eventually Perth, having collected as much data as the weather would allow.

In total, there is now approximately five hours of mobile recordings and 23 groups of humpback dolphin positional data to process to help with previous fieldwork to assess the feasibility of passive acoustic monitoring for humpback and snubfin dolphins.

Cone Bay definitely proved to be more reliable for acoustic recordings of humpback dolphins than previous Cygnet Bay fieldwork and provided a pretty amazing backdrop to this research.

This fieldtrip would not have been as successful or viable without the support of Marine Produce Australia and we are extremely grateful for their support.

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. 

Category:

Kimberley Marine Research Program

Giant corals reveal WA’s heatwave history

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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. 

Category:

Kimberley Marine Research Program

Groundbreaking research to build instruments to measure net sediment deposition

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Researchers in the WAMSI Dredging Science Node are developing new automated scientific instruments to measure sediment deposition in the field with prototypes deployed and tested.

Sediment deposition and subsequent smothering of marine habitats such as corals and seagrasses is one of the mechanisms by which dredging can impact on the environment.

This pressure parameter is incorporated into sediment transport models by proponents during the Environmental Impact Assessment (EIA) process to make predictions of the likely extent, severity and duration of their impacts on the environment.

However, according to Dr James Whinney from James Cook University there are no scientific instruments that can actually measure net deposition in the field.

“Measuring net sediment deposition is quite challenging” Dr Whinney said. “When sediment falls out of the water column and deposits on the seafloor, not all of it will stay there with the energy from waves and currents causing some of those sediments to resuspend and be transported elsewhere. This is what we mean by net deposition and is the actual pressure that will be exerted on an organism.

Deposition sensor deployed in laboratory experiments alongside traditional sediment traps and sedpods.

“The most common technique currently used to measure deposition is to use a sediment trap which typically comprise of vertical PVC tubes that are closed at the bottom and open at the top and mounted on a frame on the seafloor. These are generally deployed for months at a time before they are retrieved and the amount and characteristics of the sediment in the tube can be measured.” Dr Whinney said.

“The problem with this is that once sediments have settled in the tube, they get trapped there and can’t be resuspended by wave energy. So while they can accurately tell you the total amount of sediment that settles, they can’t tell you what the net deposition would be after some of this has been resuspended and transported elsewhere. “Another problem is that they can’t tell you how much settles each day. Just averaging the total amount of sediment by the number of days it was deployed is not accurate as on calm days more sediment would settle out of the water column whereas on rough and windy days less would settle.

This is important to know for organisms like corals as they can actively remove sediment that has deposited on them but only up to a point. If the rate of deposition becomes too great, they will not be able to keep up and begin to get buried by that sediment.

To address this problem Dr Whinney and his colleagues have been developing an automated deposition sensor that can measure net deposition as well as provide accurate information of the amount settling each day.

“The deposition sensor we are developing uses optical back scatter allowing readings to be taken every few minutes and uses a perforated plate on top of the sensors to mimic the surface of a coral so that deposition occurring on the instrument is similar to that on a coral.”

“During the development of this sensor it has been tested at AIMS, used in experiments at SEASIM and also deployed off Townsville and on the site of the Wheatstone Project, off Onslow. The data from the sensor is promising, measuring expected levels of sedimentation in the laboratory and gathering interesting data from the field which compares well with wave and turbidity data.”

Calibrating deposition sensor in laboratory by adding known quantity of sediment.

Dr Ray Masini from the Office of the Environmental Protection Authority and the Node Leader – Policy, said developing an instrument that can accurately measure net sediment deposition will be a major step forward and improve confidence during the EIA process.

“While proponents use sediment transport models to make predictions of the amount of sediment deposition that will occur, because we can’t actually measure net sediment deposition in the field, there is no way to verify and refine the sediment deposition rates that were predicted by those models” Dr Masini said. “This reduces confidence for both the Environmental Protection Authority and project proponents in the prediction of impacts during the EIA process.”

“It is also important for scientists conducting experiments to establish thresholds of response to dredging-related pressures.  To accurately define the sediment deposition rates that led to mortality, sub-lethal impact and first observable effect, you have to be able to accurately measure this in the first place.”

“Therefore the development of this deposition sensor will be an important step forward and provide both the Environmental Protection Authority and project proponents a greater level of confidence in the prediction of impacts during the EIA process,” Dr Masini said. “Which is what the Dredging Science Node is designed to do – to increase the confidence, timeliness and efficiency of the assessment, approval and regulatory processes associated with dredging projects.”

The WAMSI Dredging Science Node is made possible through $9.5 million invested by Woodside, Chevron and BHP as environmental offsets. A further $9.5 million has been co-invested by the WAMSI Joint Venture partners, adding significantly more value to this initial industry investment. The node is also supported through critical data provided by Chevron, Woodside and Rio Tinto Iron Ore.

Category:

Dredging Science

Can dredging sediments affect the reproductive cycle of corals?

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A new review has found that turbidity and sedimentation, two of the most widely recognised threats to coral reefs, can have an effect on coral reproduction before, during and after spawning.

Elevated turbidity regularly occurs in shallow, tropical marine environments driven primarily by wind-driven waves but this can be exacerbated by anthropogenic activities such as dredging. The effects on adult corals and the sensitivity of their early life-history stages has been well documented, but the review, published in Marine Pollution Bulletin highlights new potential mechanisms that suspended sediments can have on the reproductive cycle including gametogenesis, spawning synchrony and on gametes in the water column.

The WAMSI study, conducted by researchers from the Australian Institute of Marine Science (AIMS) and The University of Western Australia (UWA), is working to help environmental managers predict how corals will react to changing pressures on their environment.

Co-author from UWA’s Centre for Microscopy, Characterisation and Analysis, Gerard Ricardo, said the review highlighted the need to be able to quantify the extent of the changes in the environment in order to accurately predict how coral spawning would be affected.

WAMSI researcher Gerard Ricardo (UWA) collecting freshly spawned eggs for laboratory experimentation. (AIMS)

“This review was partly motivated by the recent resources boom in tropical Australia, the need for dredging for coastal infrastructure and shipping channels to export mineral and petroleum products, and current environmental regulations around protecting coral spawning events during dredging campaigns,” Gerard explained. “However, the findings are equally as applicable to natural events in turbid-zone communities driven by wind-wave induced resuspension.”

Lead author AIMS’ Dr Ross Jones said that while sediments can act as an energy source for adult corals, there are overwhelmingly more than 30 possible causal pathways whereby turbidity-generating activities can negatively affect reproduction and early life-cycle stages.

“We know that it is only very subtle changes in light quantity and quality that trigger spawning,” Dr Jones explained. “A loss in natural synchronicity could ultimately affect the arrival of the gametes at the surface, which could affect the separation for each species, a process which prevents or reduces hybridization between closely-related species by spawning at slightly different times.

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Reproductive cycle of the broadcast spawning Acropora species with indicative timings based on the studies of Hayashibara et al. (1997), Okubo and Motokawa (2007), Okubo et al. (2008) and Ball et al. (2002).

In recognition of the sensitivity of the early life-cycle stages of corals, and their importance to the marine community, policy makers have attempted to protect coral spawning periods from sediments generated by dredging-related activities. Since 1993, dredging projects in Western Australia that are close to reefs are required to temporarily stop when corals are spawning five days before spawning and up to seven days afterwards.

This management approach has also been adopted in some dredging projects on the Great Barrier Reef and the possibility of introducing this practice to other locations such as Singapore has been suggested but it’s a contentious issue internationally because it can significantly inflate costs.

One of the most contested issues is the length of the window and also whether dredging-related turbidity-generating activities need to cease entirely or whether dredging can continue but must adhere to more conservative water quality guidelines.

Sperm tangled in sediment particles. WAMSI scientists are examining whether this impacts on the reproductive success of corals (Image: AIMS)

“The successful use of a coral spawning environmental window as a management tool depends on a shutdown period which encompasses the entire period that turbidity-generating activities could have an effect on spawning and ultimately the successful recruitment of juveniles into the next generation,” Dr Ross Jones said. “The window needs to contain sensitive stages such as settlement and early post-settlement survival.”

In Western Australia there is a well-known main autumn spawning period, but more recently a significant spring spawning period has been identified.

“The presently applied 12 days coral spawning shutdown period is too short to fully encompass the full settlement period, especially settlement and early post-settlement survival,” Dr Jones said.

“Extending the window before and after the predicted spawning date seems an obvious next step to also accommodate effects on gametogenic and spawning synchrony and to fully cover the settlement period. This may however significantly limit time that turbidity-generating activities could occur near coral reefs in any given year.

“Although the approach seems logical, the question is whether this approach is reasonably practicable and whether the resulting intermittent and protracted dredging operation would result in a better net environmental benefit than a shorter campaign.

“What we do know is that conducting dredging activities at a time that avoids coral spawning periods and settlement periods constitutes a best management practice,” Dr Jones said

[R. Jones,,G.F. Ricardo,,A.P. Negri, (2015) Effects of sediments on the reproductive cycle of corals. Marine Pollution Bulletin doi:10.1016/j.marpolbul.2015.08.021]

This project was funded by the Western Australian Marine Science Institution as part of the WAMSI Dredging Science Node, and made possible through investment from Chevron Australia, Woodside Energy Limited, BHP Billiton as environmental offsets, and by co-investment from the WAMSI Joint Venture partners. This research was also enabled by data and information provided by Chevron Australia. The commercial investors and data providers had no role in the data analysis, data interpretation, the decision to publish or in the preparation of the manuscript.

Category:

Dredging Science