Results released on seagrass responses to dredging in northwest Australia

Three new reports have been released on the primary producer responses to dredging.

There is almost no knowledge of how seagrass primary producers in the northwest of Australia will respond to the environmental changes produced by dredging. Consequently, it is difficult to predict and then manage the impacts of dredging on these critical habitats with an acceptable level of certainty.

Research within the Western Australian Marine Science Institution (WAMSI) Dredging Science Node focuses on two of the most significant stresses produced by dredging: the reduction in light availability to plants; and the smothering of seagrass and algae as suspended sediments settle.

Project leader Kathryn McMahon from Edith Cowan University and team members from The University Australia, Department of Parks and Wildlife WA and The University of Adelaide have looked at three key areas:

  1. Seagrasses of the northwest of Western Australia: biogeography and considerations for dredging-related research;
  2. The current state of knowledge regarding the effects of dredging-related ‘pressure’ on seagrasses using information compiled from unpublished industry data, as well as published reports, articles and books; and
  3. Genetic variability within seagrass of the northwest of Western Australia

The first project identified five dredging related stressors that are likely to directly impact seagrass habitat and prioritised the top three in the following list that are of most interest for impact prediction and management of dredging events:

  • reduced benthic light quantity;
  • burial by sediment;
  • sediment anoxia and increased hydrogen sulfide production;
  • altered benthic light quality (i.e. spectral characteristics); and
  • increased suspended sediment

It identified knowledge gaps in three key areas:

  • How dredging affects environmental conditions that are likely to impact seagrass.
  • Thresholds for dredging-related stressor beyond which seagrasses will be affected; and
  • Monitoring during dredging campaigns.

The second project identified the seagrass species Halophila ovalis, Halodule uninervis and Cymodocea serrulata, as the focus of subsequent research into thresholds and indicators of response to dredging-related pressures.

The third study is the first of its kind to examine the patterns of genetic diversity in seagrasses in the Pilbara region which strongly influences their ability to adapt to, resist or recover from these pressures.

This study identified  that:

  1. Most meadows examined  had  relatively  high  clonal  diversity  (i.e.  many  unique  individuals in the meadow), so both sexual reproduction and vegetative growth are important for maintaining these populations; and
  2. There was a reasonably high level of migration of genes over distances of 2−5km, but lower levels over  greater  distances. The  study  also  showed  that  not  all  seagrass  meadows  and  species  in NW Australia  have  a  similar  level  of  genetic  diversity. This information should be incorporated into management decisions as the level of genetic diversity has implications for the ability of populations to resist and recover from disturbance.

The WAMSI Dredging Science Node is one of the largest single issue research programs in Australia meeting the needs of the State Government and industry to improve their understanding of how key primary producers are affected by dredging-related pressures.

The full reports can be found on the WAMSI DSN Primary Producer project page

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.



Dredging Science

Scientists learn more about Kimberley dolphin populations

Australian snubfin dolphins in the Kimberley appear to form at least three genetic populations that require careful management, according to new research.

The snubfin and humpback dolphin are unique to shallow, coastal waters of northern Australia and southern New Guinea. Both species are found off the coast of the Kimberley, though little is known of their numbers, key habitats and movements.

Over the past three years, a Western Australian Marine Science Institution, Kimberley Marine Research Program project has been working to answer some of these questions, by surveying local populations, collecting genetic samples, and developing new tools to help monitor these elusive species.

The research team from Murdoch and Curtin universities found that both snubfin and humpback dolphins occurred at all sites surveyed, although in varying numbers.


The team conducted different fieldwork in a number of locations across the Kimberley, and presented data on dolphin relative abundance (R), population genetic structure (G) and/or passive acoustic monitoring (A).


Humpback dolphins were observed in similarly low numbers at most sites, while snubfin dolphins appeared to occur in greater numbers at a few discrete locations.

Small local populations of snubfins were apparent at Cone Bay and the Prince Regent River; however, previous research showed the Dampier Peninsula sites of Roebuck and Cygnet Bay to support greater numbers, highlighting these sites as key habitats for snubfin dolphins.

Genetic analyses, led by Murdoch University’s Dr. Alex Brown, showed that not all snubfin dolphins in the Kimberley could be considered the same population.


Using the biopsy darting system to collect dolphin genetic samples in Cone Bay, with assistance from Dambimangari Ranger Edmund Jungine. Photo: Alex Brown.


Evidence suggests that there is very limited movement of snubfin dolphins between Roebuck Bay and King Sound, and that animals sampled further north and east may represent a third genetic population.

Analyses of humpback dolphin genetic samples revealed a lack of gene flow between animals sampled in the Kimberley and the Pilbara regions.

“It’s important for decision makers to recognise this genetic structure in order to minimise any threats to small, isolated, local populations,” Dr. Brown said. “For both species, more genetic samples are required in the north/east of the Kimberley to better understand the connectivity of local populations.”

“However, monitoring these species can be tricky, particularly in areas where they are unfamiliar with and shy of boats,” Dr Brown said.

Several scientists in the dolphin project team have been working on this problem by exploring the use of passive acoustic monitoring to detect and monitor dolphin presence and use of particular areas.


Acoustic data loggers, developed by Curtin University, were deployed for up to three weeks at Cygnet and Roebuck Bay, recording dolphin vocalisations and allowing the Curtin researchers to characterise the natural soundscape of the two areas. Photo: Alex Brown.


This new technology was able to pick up the whistles and clicks that dolphins make as they travel, forage and socialise, and the research team uncovered several new whistle types to add the species’ repertoire. However, more work is required before the two species can be efficiently distinguished and the number of animals present can be identified.


An audiogram of echolocation clicks, pulsed ‘buzz’ sounds, and tonal whistles
recorded in the presence of snubfin dolphins.


A key part of this research was collaborating with local stakeholders. The research team collected data alongside Yawuru, Bardi-Jawi, Dambimangari and Balanggarra Traditional Owners, as well as regional Parks and Wildlife staff, generating valuable training opportunities.


Murdoch University researchers work alongside Balanggarra Rangers Wesley Alberts and Wayne Moore to collect individual identification photos of humpback dolphins in the Cambridge Gulf. Photo: Alex Brown.


The data collected, along with the improved local collaboration, will help with future research and monitoring in the region.

The full research findings presentation is available on the WAMSI dolphin project webpage.    


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

Saltwater crocodile populations continue to grow in Prince Regent River

Population growth rates of estuarine (saltwater) crocodiles in the West Kimberley region of Western Australia do not appear to be slowing, with steady increases in total numbers observed, along with a more gradual increase in the number of large crocodiles (> 3m ~ 10 ft).

There has been a 259% increase in non-hatchling crocodile numbers since the last survey of the Prince Regent system in 1986, some 30 years ago.

The presence of large creek systems adjacent to the main river are allowing sub-adult crocodiles (1.5 – 2m ~ 5-7 ft) to remain near the river of their birth, rather than having to undergo migrations or increased rates of mortality from competition by larger crocodiles. This results in sub-adults making up ~ 20% of the resident crocodile population, compared to 8% in the Adelaide River in the NT, where the crocodile population is considered stable.

Lead researcher for the Western Australian Marine Science Institution’s (WAMSI) saltwater crocodile project, Dr Andy Halford (Parks and Wildlife), when comparing the crocodile recovery in the Kimberley with that in the Northern Territory (NT) said: “Continuous research and surveys in the Northern Territory since the 1980s showed the NT population was considered to have recovered from hunting (outlawed in 1971) by 2000 and we would expect a similar pattern in WA.”

However, comparison of results with established crocodile population patterns in the NT’s Adelaide River indicates that the West Kimberley crocodile populations are still recovering from the large-scale hunting that prevailed pre 1970.

“We counted a total of 5 crocodiles >3m in length in comparison with 63 counted in the Adelaide River and we estimated a biomass density of 91.4 kg/km compared with 274.02 kg/km in the Adelaide River,” Dr Halford said.

“These findings confirm the likelihood of increasing interactions between crocodiles and humans.


“The interesting difference is that, while a lot of crocodiles between  (1.5-2m ~ 5-7 ft) long are usually eaten or killed by larger crocodiles or forced to move into new territory, the percentage of young adults entering the West Kimberley system is up to three times that seen in the NT,” he explained.


“What this study has told us is that while crocodile populations are healthy and recovering well, because of the unique environment and the considerably smaller amount of appropriate nesting habitats in the West Kimberley, exactly how the future recovery will pan out is unclear.

“What we do know is that there will be increased interactions between crocodiles and humans, and in order to provide advice on managing this, we need to learn more about the amount of available nesting habitat throughout the region, as well as updating our surveys of other river systems,” Dr Halford said.

Dr Halford’s full presentation is available on the WAMSI saltwater crocodile project webpage


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

Vale Professor Susan Moore

Professor Susan Amanda Moore. Born: Finley NSW 5th April 1960. Died: Perth WA 22nd December 2016.

Professor Susan (Sue) Moore was an environmental scientist who was regarded as an expert voice in natural-area tourism, both in Australia and overseas.

A first class honours graduate in Natural Resources from the School of Natural Resources at the University of New England, Professor Moore joined the former Western Australian Department of Fisheries and Wildlife in 1982 as its first female scientist. Community participation in the planning process – a new concept at the time – was integral to her role in helping develop the first nature reserve and national park management plans for the Swan Coastal Plain. She also pioneered a new approach to preparing management plans for groups of nature reserves located within Wheatbelt local government boundaries.

Transitioning to the Department of Conservation and Land Management (CALM), Professor Moore became involved in surveying flora and fauna, ensuring ecological knowledge was included in field activities such as prescribed burning, weed control and development of roads and trails.

Her deft stakeholder engagement skills came to the fore when developing the management plan for the World Heritage-listed Fitzgerald River National Park, one of the largest and most botanically significant national parks in Australia. This work became an integral part of her PhD in natural resource sociology in the College of Forest Resources, University of Washington, where, as a prestigious Harkness Fellow from 1991-94, she compared park planning in WA with that in the US. Her research was also supported by a CALM Executive Director’s scholarship, the United States Department of Agriculture (Forest Service) Pacific Northwest Research Station at Portland, Oregon and the Commonwealth Fund, New York.

On her return from the US she developed the first directory of nature based tourism opportunities on WA’s conservation lands.

Her academic career at Murdoch University began in 1995 and spanned 21 years. She was the co-founder and leader of the university’s Nature Based Tourism Research Group, utilising her practical experience as a park planner and scientist to create and develop this undergraduate unit. She was made a Professor at Murdoch University in 2013.

With her close colleagues, she established an international research reputation in areas such as eco-tourism, visitor experiences in protected areas, measuring and managing visitor impacts and understanding and managing interactions between wildlife and tourists.

She championed social research and its important role in protected area management. Her continuing motivation was her belief that parks need visitors in order to gain advocates and community and political support.

University research projects coordinated by Professor Moore included governance of protected areas, improving ecosystem-based management of the Vasse Wonnerup Estuary; assessing the visitor experience swimming with humpback whales; visitor profiles and activities for the Pilbara Islands and human values and aspirations for coastal waters of the Kimberley.

The WAMSI funded project on ‘Human values and aspirations for coastal waters of the Kimberley’ was the last major project Professor Moore led and saw through to its completion. Her leadership saw the team across three academic institutions (Murdoch University, The University of Western Australia and Queensland University) successfully collaborate on a novel investigation across this vast region.

Professor Moore was highly regarded by her peers as an innovative multi-disciplinary researcher. Her research coupled well-considered theory with work of a great practical value in nature tourism management.

She was prolific, publishing more than 100 articles, papers, reports and books, co-authoring two editions of the popular Natural Area Tourism: Ecology, Impacts and Management and Wildlife Tourism. She contributed to environmental policy development through membership of the WA Bushcare Reference Group, WA Natural Resource Management Council, and the WA State Salinity Reference Group and as an expert evaluator for the WA Premier’s Awards for Excellence in the Public Sector.

Professor Moore received a number of awards for her research and teaching achievements at Murdoch, including the Vice Chancellor’s Award for Excellence in Research in 2012. She was responsible for supervising and lecturing thousands of students in environmental science, nature based tourism and protected area management.

She mentored and inspired many students who went on to be successful conservation managers, resource agency staff and academics. These former students, many of whom received her support long after her postgraduate supervision role ended, and her body of work over a distinguished career, are her enduring legacies in environmental science.

Professor Moore’s intelligence, humour, passion for the environment and her collegial and inclusive approach were universally admired by her current and former workmates.

Her work ethic continued while she had cancer. She completed more than 12 journal articles in the final year of her life, the most she had ever completed in a 12-month period.

Sue Moore is survived by her husband Warren and children Jess and Sam, sisters Terry and Miranda and father Neil.


Kimberley Marine Research Program

Light limitation affects coral health more than sediment

Researchers have compared the impact low light and suspended sediment particles have on coral and found that, of the two events associated with dredging, several coral species are more likely to be affected by the loss in light intensity.

The results, undertaken as part of the Western Australian Marine Science Institution’s Dredging Science Node at the AIMS National Sea Simulator in specially developed tank systems, have been published in the Marine Pollution Bulletin.

Lead researcher, Pia Bessell-Browne from The University of Western Australia Oceans Institute, Centre for Microscopy, Characterisation and Analysis and Australian Institute of Marine Science, said corals face increasing pressures from coastal development, particularly through dredging for ports.

“In order to appropriately manage these pressures, we need to improve our understanding of the key impacts of dredging on corals,” Ms Bessell-Browne said. “Sediments released from dredging activities can reduce or block light, clog feeding and smother coral. The sediments can also affect many aspects of coral reproduction and recruitment processes.

“High light levels are considered key to the health of corals as it allows for photosynthesis by algae that live within the coral. The products of this photosynthesis provide the coral with a food source.”

A range of light and suspended sediment concentrations were tested to determine their impacts on coral health.

Representative coral colonies from experimental manipulations that were exposed to no, low and high light, showing decreased colour in no and low light treatments (AIMS)


Exposure to low light conditions was found to result in coral bleaching, where algae that contribute to the nutrition of their partners, leave their coral host. Mortality of corals was only observed in low light levels, regardless of the amount of suspended sediment in the water column.

“When comparing experimental treatments with conditions experienced during dredging and natural sediment re-suspension events, such as storms and tidal currents, the results suggest that light reduction resulting from increased suspended sediments poses more of a risk to corals than suspended sediments alone,” Ms Bessell-Browne said.

Further work will determine the low light thresholds for corals.


PhD Completion Presentation: Lethal and sub-lethal impacts of dredge related stressors on corals, Thursday 02 March, IOMRC Auditorium, 4pm

Bessell-Browne P, Negri A.P., Fisher R, Clode P.L., Duckworth A, Jones R, Impacts of turbidity on corals: The relative importance of light limitation and suspended sediments Marine Pollution Bulletin 2017

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.


Dredging Science