Application of seaweeds to integrated multi-trophic aquaculture in southern Australia: identifying and investigating suitable native species
Date
2020
Authors
Wiltshire, Kathryn Helen
Editors
Advisors
Tanner, Jason
Deveney, Marty
Gurgel, Fred
Deveney, Marty
Gurgel, Fred
Journal Title
Journal ISSN
Volume Title
Type:
Thesis
Citation
Statement of Responsibility
Conference Name
Abstract
Integrated multi-trophic aquaculture (IMTA) involves strategic co-culture of organisms so
that wastes from one species are used to grow another. Seaweeds can be used in IMTA
systems to remove and utilise dissolved inorganic nutrients from fish aquaculture, improving
environmental performance and providing economic benefits through diversification and
increased productivity.
IMTA with seaweed could be applied to assist sustainable expansion of fish farming in South
Australia (SA), where dissolved nitrogen (N) wastes limit environmental carrying capacity.
Seaweed farming is also of interest in Australia to meet increasing demand for seaweed
products, of which Australia is a net importer. Several native seaweeds have been identified
as potential candidates for aquaculture in SA based on general knowledge of their biology and
potential economic value, but specific knowledge of their suitability for cultivation was lacking.
I investigated eight candidate seaweeds, comprising four red (Solieria robusta, Gelidium
australe, Pterocladia lucida, Plocamium angustum) and four brown (Ecklonia radiata,
Cystophora subfarcinata, Sargassum linearifolium, Scytothalia dorycarpa) species, to
determine which species were most suitable for farming, with specific emphasis on application
to IMTA in SA. I assessed feasibility of cultivation and potential for nutrient remediation of the
eight species in two field trials and in laboratory experiments, and applied species distribution
modelling (SDM) to identify the most suitable candidate species for aquaculture in the vicinity
of current SA fish farms. My research identified the red seaweed Solieria robusta and the brown seaweed
Ecklonia radiata as the most suitable species for aquaculture. The red Gelidium australe
showed promising growth in a pilot field trial and removed the most N in a 4-week laboratory
trial, but S. robusta grew best in laboratory trials and would remove more N over time due to
its faster growth. Solieria robusta tolerated a wider temperature range and grew better at
higher temperatures than G. australe. SDM results demonstrated that S. robusta has high
environmental suitability in aquaculture zones throughout Spencer Gulf, where all SA finfish
farming currently occurs, while G. australe was poorly suited to most existing aquaculture
zones. Pterocladia lucida and Plocamium angustum had slower growth rates, and SDMs
indicated low suitability in aquaculture zones. There was little difference in field performance
of the brown seaweeds, apart from Scytothalia dorycarpa, which performed poorly, but
Ecklonia radiata was most amenable to hatchery reproduction and cultivation. SDM showed
that several aquaculture zones in southern Spencer Gulf had good suitability for E. radiata.
Seedstock production methods used for commercially farmed relatives were successfully
applied to S. robusta and E. radiata, and I developed protocols that can be employed to upscale
production of these seaweeds. Solieria robusta and E. radiata demonstrated the ability
to accumulate tissue N, and N uptake rates comparable to other IMTA seaweeds, supporting
the suitability of these species for IMTA. Data from my experiments help to inform suitable
depths, locations and seasons for cultivation of these seaweeds, and to incorporate N removal
by seaweeds into biogeochemical models. These experiments provide the foundation for
developing seaweed aquaculture in southern Australia, including IMTA.
School/Discipline
School of Biological Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2020
Provenance
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals