Port Phillip Bay Seafloor Integrity Project

Fathom Pacific has partnered with universities, industry partners and laboratories to complete the Seafloor Integrity Project, funded by the Department of Energy, Environment and Climate Action (DEECA). The Seafloor Integrity Project is the largest Victorian marine monitoring program since the Port Phillip Bay Environmental Study (1992-1996). The Project involves sampling of sediments within Port Phillip Bay to study biological, physical, and chemical properties of sediments and associated biogeochemistry processes, as well as undertaking ecotoxicological studies and underwater imaging surveys of benthic ecosystem. The objective of the Seafloor Integrity Project is to understand the condition of the benthic ecosystem within Port Phillip Bay and identify biological, physical, and chemical monitoring indicators of seafloor integrity.

The Seafloor Integrity Project involves studies which target several benthic habitats, from coastal coarse sand to deep muddy sediments. Study sites were placed in areas influenced by different types of anthropogenic activities at different intensities, and in ‘good conditions’ areas, where sediment habitats are expected to be less exposed to anthropogenic pressures. Sources of pressure on sediments and benthic ecosystem include shipping, pollution, nutrient input, and industrial discharge.

Photos of sediment samples collected from a range of sites across Port Phillip Bay.

To study physical and chemical sediment properties, Fathom Pacific collected 45 sediment samples in July 2022 using a Ponar Grab, a device designed to collect sediment samples from the seafloor. These samples were analysed to characterise grain size, a physical property that provides a way to classify sediments and to understand processes such as bioavailability and toxicity of contaminants. Typically, concentration of contaminants within fine sediments is greater than coarse sediments because contaminants can bind more readily to smaller grain sizes. These sediment samples were also analysed for presence of inorganic and organic compounds and nutrients, revealing distribution of contaminants across Port Phillip Bay. Specifically, the presence of persistent contaminants like pesticides and emerging contaminants such as PFAs (per- and poly-fluoroalkyl substances) and PBDEs (polybrominated diphenyl ethers) was studied, as well as the presence of common pollutants, including metals and nutrients.

To study biogeochemistry processes associated with sediments in Port Phillip Bay, Fathom Pacific has partnered with the Centre for Coastal Biogeochemistry (Southern Cross University). This involves measuring biogeochemical processes at the sediment-water interface including benthic metabolism, and nutrient and N2 (net denitrification-nitrogen fixation) fluxes. Biogeochemistry processes play a critical role in mediating the impacts of nutrient loads into Port Phillip Bay and influence benthic ecosystem community composition and production. In October 2022, sediment biogeochemistry was investigated in the laboratory through sediment core incubation experiments collected at 6 sites and monitored in the field using benthic chambers installed at 2 different sites across Port Phillip Bay. Fathom Pacific divers also collected small sediment cores that Southern Cross University analysed for concentration of pigments, the results of which are used as a proxy for productivity at these sites. A second round of sampling for this part of the project has been planned for October 2023.

To investigate how contaminated sediments interact with other elements of the benthic ecosystem in Port Phillip Bay, Fathom Pacific has partnered with the Neuroecology Group at La Trobe University to undertake ecotoxicological studies. Ecotoxicological analysis allows the investigation of bioavailability of contaminants to marine fauna and bioaccumulation across the food web. Studying the concentration of harmful contaminants in marine species is key to understanding whether pollutants found in sediments and water can be transferred to marine organisms. Fathom Pacific, in partnership with La Trobe University, are undertaking analyses on fish and benthic invertebrate species representative of multiple structural and functional groups to understand bioaccumulation and toxicological stress from the molecular to the morphological level. In April 2023, fish and invertebrates were collected across 10 different zones, 7 of which represent impacted sites and the remaining 3 represent control areas.

Underwater imaging surveys of the benthic ecosystem will inform the identification of biological indicators of seafloor integrity in Port Phillip Bay. These studies involve image-based morphospecies and biotope surveys using AUV (autonomous underwater vehicle) and ROV (remotely operated vehicle) imagery techniques. AUV surveys were led by the University of Sydney’s Australian Centre for Robotics and were completed at 35 sites in January 2023. ROV surveys are planned for late 2023. To support the exploration, management and annotation of georeferenced images and video data collected as part of the benthic imaging surveys, Fathom Pacific has partnered with Greybits Engineering. Underwater imagery is analysed using SQUIDLE+, a software platform developed by Greybits Engineering for video and image annotation, to study benthic community composition and target morphospecies abundance scoring. These results can be used to assess the condition of the seafloor and classify biotopes within Port Phillip Bay.

To facilitate data management for the Seafloor Integrity Project, Fathom Pacific has engaged Nordinson Studios. They have also developed a web portal to view project data stored in the qCore database. This provides visibility on completed field activities and accessibility to project data.

The Seafloor Integrity Project involves significant collaboration across multiple organisations. To achieve this, Fathom Pacific has partnered with several stakeholders across industry and academia,  who were involved in the planning phase and have informed the project plan.

Our Partners

This Project is funded by the Victorian Government, Department of Energy, Environment and Climate Action.