Cone Bay proves reliable for acoustic recordings of humpback dolphins

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

The initial ship-based expedition to Camden Sound was conducted under the auspices of WAMSI’s Kimberley Benthic Biodiversity Project, which aims to provide a better knowledge base about what occurs where in the Kimberley’s diverse marine environments, especially in areas of management priority such as the state government’s proposed marine parks and reserves.

Cruise leader on board the RV Solander, Dr Andrew Heyward from AIMS in Perth, said that the vessel operated 24/7 during its 18-day itinerary. “Scientists and staff worked in shifts, doing towed video and sediment sampling during daylight, and multibeam sonar surveys during the night,” he said.

Although the weather was generally very good, extreme tides, strong currents, turbid waters and some uncharted areas provided plenty of challenges for researchers. They successfully completed more than 200 km of towed video and thousands of km of multibeam seafloor mapping, in the first of two expeditions to the Camden Sound area.

“We’ve seen large areas of dynamic sand across the open Sound, including some patches with underwater sand dunes,” commented Andrew, “but also rocky ground covered in a large variety of marine invertebrates, in particular sponges and soft corals.”

The turbid waters of Camden Sound prevent sunlight from penetrating more than ~10 m in depth, so organisms that need light – such as corals and seaweeds – appear to be restricted to the shallowest parts of rocky ground and the upper edges of fringing reefs around islands. As depth increases and light fades the filter feeding sponges, soft corals, ascidians and bryozoans become the dominant components of the seabed communities.

“Thanks to the combined efforts of the Solander and the Linnaeus this month,” said Andrew, “we’re beginning to understand a lot more about what the seafloor of the Lalang-garram-Camden Sound Marine Reserve looks like, and the benthic biodiversity that lives there.”

Dr Iain Parnum from Curtin University is busily compiling all the gathered multibeam sonar data now. “In terms of outputs, first of all, we’ll deliver some much-needed improved bathymetry information for Camden Sound,” he explained. “Secondly, sonar backscatter data – both from the seafloor and the water column – will give us good insights into the kinds of underwater terrain and ecosystems at each sampled location.”

In addition, Dr John Keesing from CSIRO took advantage of the presence of the RV Solander in the Kimberley to advance another WAMSI project investigating historic changes in water quality. He collected sediment cores (each ~1.5 m long) at ~20 m depth from two locations in Roebuck Bay. “These cores will be used to reconstruct a time series of water quality in the Bay, which is expected to go back about 100 years,” he said.

As with all WAMSI projects, the data and outputs will be freely available to everyone with an interest in the marine environments of the Kimberley.

Map showing sites in Camden Sound where towed video surveys were conducted in November 2014 

A still image from one of the towed video surveys showing mixed filter-feeding community (including bryozoans, sponges and soft corals) growing on a rock outcrop (Photo courtesy of AIMS)

Kimberley Marine Research Program

It’s an amazing journey for most tropical fish starting out life as larvae floating in the open ocean to making it back to the coast to settle down and live out the rest of their days.

During this process many species undergo rapid and often radical changes in their appearance changing from transparent larvae to the beautiful diversity of shapes and colours we are most familiar with.

Understanding when, where and how many tropical fish settle into different Kimberley habitats will provide an important management tool to help protect essential nursery areas and ensure there are plenty of reproductive adults to resupply following generations.

Alongside the Bardi-Jawi Marine Rangers and Traditional Owners, a WAMSI team from the Australian Institute of Marine Science (AIMS), CSIRO, Western Australian Museum and Departments of Fisheries and Parks and Wildlife, began surveys of fish recruitment in April.

Diversity of larval fish (and other) forms captured from the open ocean. Image from Robert Cowen Laboratory, University of Miami, USA.

“The first stage was to develop the right technique to do this accurately in the challenging Kimberley environment,” AIMS researcher Martial Depczynski explained.

“We assessed nine different methods among seagrass, coral reef, inter-tidal and mangrove habitats typical of the Kimberley region.

“We found in most cases that different nursery habitats were best quantified using different methods but that one single method was sufficiently efficient, easy, cost-effective and safe to use in all four habitats,” Dr Depczynski said.

Lifecycle of a juvenile reef fish. Fish begin their lives in the open ocean as semi-transparent larvae before recruiting and settling into their juvenile and adult coastal habitat often for the rest of their lives. During recruitment, they undergo metamorphosis losing their larval features to take on their characteristic shape and colouration. Image from Reefkeeping South Africa.

The investigators found that remote underwater video, although new to the task of recording small juvenile fishes, was able to provide robust relative estimates of abundance and diversity in fish nursery habitats and was the best option among the nine methods.

“Now that the correct methodology has been developed, our next trip in October, which will run in conjunction with a team investigating the same recruitment process in corals, will concentrate on getting a solid data set together to answer questions such as; what nursery habitats are important to what fish species, are there hotspots of fish recruitment activity and what is the strength of fish recruitment in dry versus wet seasons,” Dr Depczynski said.

“We will continue to work in with the Bardi-Jawi Marine Rangers and the Traditional Owners on the Cape Leveque – Sunday Island – Cygnet Bay area to better understand the processes that govern fish recruitment processes in this area.

“The main aim and best possible outcome from this WAMSI project is to have definitive quantitative data on fish and coral nursery areas which identify nursery hotspots and can feed into both State and Indigenous management plans such as the next Bardi-Jawi Indigenous Area Management Plan.

Remote underwater video unit deployed to record newly recruited fishes in an intertidal rock pool during low spring tides on Sunday Island.

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

As the annual humpback whale migration begins from the Antarctic to the Kimberley coast, one WAMSI project, working to model their spatial distribution, is looking to combine satellite imagery and bathymetric LiDAR (Laser or Light Detection and Ranging) for the first time as an efficient and safe means to monitor these giants of the sea.

The number of humpback whales travelling the coast of Australia from their feeding grounds in the Antarctic to their breeding grounds in the Kimberley has increased from around 300 in 1963 to some 30,000 today since hunting was outlawed.

The challenge now for lead researcher on the WAMSI project Michele Thums, from the Australian Institute of Marine Science, is to map habitats that are important to them when they are on their breeding grounds in the Kimberley which, in turn, could help to manage marine park boundaries and the potential to overlap with human activities such as boating and industry.

“We already understand quite a lot – timing of the migration, spatial extent of the calving area, and general distribution of migrating whales but there has been very little attempt to bring this data together and synthesise it to get a quantitative understanding of their habitat requirements and the specific habitats that breeding humpbacks rely on,” Dr Thums said.

The project is analysing data from some of the extensive aerial and vessel line transect surveys gathered over the last 25 years mostly on behalf of industry. This study is predominantly relying on data released by WAMSI research collaborator Curt Jenner, Inpex and Woodside.

“It’s very expensive to do these surveys,” Dr Thums said. “Collecting data from aerial and boat surveys is especially prohibitive in the Kimberley because it is so remote. So we’re fortunate to get access to this rich source of data collected by industry as part of their legislative requirements to operate.”

In September the project team is going to take an opportunity to head out into the field and test the reliability of monitoring whales using a scanning laser fixed to an aircraft that is capable of generating precise 3-dimensional information about the characteristics on the earth’s surface (bathymetric LiDAR system), in this case whales.

“We’re still developing this project but, if successful, it doesn’t require observers on the flight, so it’s safer and it could still allow us to analyse the data later to count the whales,” Dr Thums said. “We’re also hoping to get satellites tasked to capture high resolution images so we can compare the satellite data with LiDAR and, if it’s a good match, we might be able to rely on monitoring the Kimberley humpback whales with satellite in the future.”

The findings for the WAMSI Humpback project are expected to be released by early next year.

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

Kimberley Marine Research Program