New Report Highlights Delayed, Inconsistent Recovery For Marine Life Devastated By Natural Disasters

Sydney waterways have serious biodiversity loss along with a delayed and inconsistent ecosystem recovery following the mass devastation caused by the series of record-breaking natural disasters (drought, bushfires, floods) according to researchers at the Abyss Project, a marine research team based in Sydney. The research team has joined forces with sovereign elders of The Gweagal/Bidjigal Tribal Elders Council, the traditional custodians of Botany Bay to share knowledge to complete the historical picture of the waters they study. The La Perouse (Guriwal) Aboriginal community are the longest functioning and only discreet community in Sydney with unbroken ancestral ties to country.

Aunty Yvonne Simms (Bidjigal Sovereign Elder) expressed her concerns, saying "We can’t eat anything from the bay anymore and we fear this event is much greater than just seasonal storm damage. With the amount of industry surrounding the bay, chemical pollutants and dredging, there are already many animals gone and this extreme event may just be the tipping point for others."

“We are concerned by the way our waterways are recovering. Following the near-complete loss of life in many areas, some study sites are yet to start regenerating 4 months later. In contrast, other areas have early pioneering species completely dominating the landscape with some invasive species appearing to outcompete indigenous species which is greatly altering community structures. We just don’t know what the new normal will look like in the future.”, said Carl Fallon, Founder and scientific diver at the Abyss Project.

In March 2020 just before the COVID lockdown was announced, the group discovered a ‘Mass Mortality Event’ within Sydney waterways that devastated marine life within inshore shallow areas 0-8 metres following the worst storms in 20 years. The group have been studying and collecting observational and photographic records of change in the waters from the Hawkesbury to Port Hacking Rivers for over 10 years. The group continued to investigate the area throughout the COVID lockdown and have been recording their findings. They now call for further investigation with shared studies from other research groups in other, effected coastal areas throughout NSW.

Most severely impacted were shallow-water habitats with no adjacent deep-water locations that could help flush and dilute the deadly runoff. The lockdown stopped the release of the independent report and the groups observations have not been included in the Royal Commission into the bushfires.

Carl Fallon, Co-Founding Director and Scientific Diver at The Abyss Project, said, "The whole ocean's chemistry changed for that window of time, creating mayhem underwater which kicked off a mass mortality event. We will only know the full impacts in the coming years that the bushfires had on the marine environment through continuous scientific research. Any species relying on these shallow regions for milestones in their lifecycle, such as breeding or recruitment, will have been affected in some capacity. Right now, no one knows the extent of the impact. We will need to continue monitoring the ecosystem’s recovery."

Carl Fallon said, "The ocean was black with ash and suspended debris, combined with flood waters which changed the ocean chemistry creating mayhem underwater that kicked off the mass mortality event. We will only know the full impacts in the coming years that the bushfires had on the marine environment through continuous scientific research.

Nathalie Simmonds Director and Head of Marine Science at the Abyss Project who prepared the report said “The unique and unprecedented sequence and scale of the 3 natural disasters have resulted in ecosystem collapse mirroring terrestrial images of the devastated firegrounds. Shallow inshore coastal waters have been transformed. Our initial observations following the mortality event have shown; these events have caused a serious imbalance in the ecosystem with inconsistent rates of regeneration between sites. Our major concerns are the observations of some individual species completely dominating entire habitats while other species are failing to recruit where they previously flourished. Opportunistic species which more often than not are introduced, or invasive are exhibiting monodominance, outcompeting slower growing native species. This prevents the capability for various soft body ecosystem engineering species such as tunicates, sponges and corals from returning or thriving in a previously biodiverse and balanced ecosystem."

Several points have contributed to the extent of devastation found in the waterways. They include:

• The two-year drought that proceeded the bushfires contributed to the hardened ground so that the initial rain ran off the ground, carrying ash to Sydney waterways.
• The storms immediately following the bushfires were the worst reported in 20 years. This culminated in extremely hard ground with a sudden influx of heavy rain. Ash from the unprecedented fires was washed away by the stormwater and deposited into the surrounding waterways.

David Booth, Fish Ecology Expert from UTS. “Whilst there wasn't devastation to the fish in the areas the Abyss Project studied, we know there were significant numbers who died closer to the water entry points where ash concentration was highest.”

Gary Hamer, renowned retired NSW Fisheries Researcher has contributed scientific evidence of the Mass Mortality Event to the Abyss Projects Report. This evidence shows inshore shellfish species (Conch’s - Turban Snails) that were devastated with reports of close to 90% mortalities recorded, are now missing recruitment milestones which points to a collapsed community.

Conch’s are a culturally significant species to the Bidjigal People and have been collected from the foreshore of Botany Bay for millennia.

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