Project background
After years of interest but limited on-ground activity, the seaweed industry is beginning to gain momentum in southern Australia. Until recently, most operations have focused on harvesting beach-cast material through a few established enterprises.
There is now particular interest in farming Asparagopsis for its methane-reducing properties in ruminants, along with several other species such as golden kelp (Ecklonia radiata) for human consumption and a range of commercial uses. While much of the current effort centres on aquaculture development, a sustainable wild harvest sector is also needed to support industry growth.
However, the tools and knowledge available to guide sustainable harvest and regulation are limited. This project will help fill critical gaps by developing methods to rapidly assess potentially harvestable biomass, understanding how much seaweed can be harvested without compromising ecological sustainability, and building an initial understanding of biosecurity risks associated with seaweed aquaculture.
Objectives
This project aims to support sustainable wild harvest and aquaculture of seaweeds by achieving the following objectives:
- Develop a rapid assessment tool for species-specific subtidal macroalgal biomass, focusing initially on Asparagopsis armata, A. taxiformis and Ecklonia radiata.
- Develop harvesting methods for these species that protect local populations and maintain ecosystem function.
- Review existing literature on macroalgal diseases, pests, health management strategies and population genetics.
- Identify information and approaches to help define seaweed health management units.
- Collate existing knowledge to develop an initial framework for seaweed translocation.
Research approach
Rapid biomass assessment
Following a national workshop to explore biomass assessment methods for wild seaweed stocks, the team conducted experimental surveys at multiple reef sites across South Australia. These trials compared a range of techniques including diver video assessments, photo-quadrats, towed underwater cameras, ROV transects, and diver harvest.
Image-based photo-quadrat methods using machine learning showed strong correlation with diver harvest results—the current gold standard—while offering lower costs and faster turnaround. Based on these findings, the team is adapting this technique for use with remotely operated vehicles (ROVs), aiming to further automate the process, reduce cost and, increase survey coverage.
Harvest methodology
To test recovery from harvesting, experimental plots were set up off the coast of Glenelg. For Asparagopsis species, researchers permanently marked 1m² quadrats and removed varying proportions of seaweed (from 0% to 100%). These quadrats are being monitored over 2 years via photographic records to measure regrowth.
For Ecklonia radiata, a larger species, researchers removed different proportions of the plant’s thallus from individual specimens. These are also being tracked over 2 years to assess the speed and extent of recovery.
Biosecurity
The team conducted an international review of seaweed pests, diseases, and biosecurity management strategies, including available treatments. To inform health management unit definitions, researchers analysed patterns in macroalgal population genetics.
They also hosted a national workshop with industry, government and scientific stakeholders to explore translocation risks, drivers, and challenges. Based on this input, they developed a draft framework for supporting seaweed translocation decisions; integrating genetics, disease risks, and health management units. This work lays the foundation for future national policy and translocation guidelines.
Expected outcomes
- A rapid, cost-effective method will be developed to estimate the biomass of Asparagopsis armata, A. taxiformis and Ecklonia radiata. Designed for use by researchers and industry, it will be adaptable to other species with additional ground-truthing.
- The project will improve understanding of how different harvesting patterns affect recovery rates, helping to ensure local populations remain healthy and ecosystems remain intact.
- New insights into seaweed disease, genetics, and health management will support the definition of management units and guide best-practice translocation protocols for the emerging industry.
- The ability to rapidly assess biomass at harvest sites will help place permit applications in the context of local availability—supporting better-informed regulatory decisions.
- The project will provide the knowledge base for setting science-backed permit or licence conditions that prevent overharvesting and localised depletion.
- By identifying biosecurity challenges early, the project aims to reduce the likelihood of disease outbreaks and associated production crashes as the seaweed aquaculture industry expands.
Project team
- A/Prof. Jason Tanner – Sub-program Leader, Environmental Assessment & Rehabilitation, SARDI
- Dr Sasi Nayar – Program Leader, Aquaculture, SARDI
- Dr Kathryn Wiltshire – Acting Sub-program Leader, Marine Biosecurity, SARDI
- Dr Matthew Bansemer – Manager, Aquatic Animal Health Unit, PIRSA Fisheries & Aquaculture
