Chronic toxicity of the diatom Rhizosolenia amaralis and its role in bitter mussel syndrome

Supervisory Team:

Primary supervisor: Assoc. Prof. Christopher Bolch

Co-supervisor: Dr Mark Adams

Additional supervisors: (Kim Lee Chang, CSIRO) Research advisor

Location of student: Launceston only

Brief project description:

In 1987 a diatom bloom caused by the diatom Rhizosolenia cf. chunii (now known as R. amaralis) occurred in Port Phillip Bay Victoria that was associated with a strong bitter taste and subsequent mortality (from 30-95%) in range of shellfish including, oysters, scallops and mussels. Mussels in in particular became so unpalatable, that they were unmarketable for several months following the bloom (Parry et al. 1989), suffered extensive inflammation, lesions and degeneration of the digestive gland, and high mortality up to 8 months after the bloom. Despite the event being well documented, the suspected causative diatom, Rhizosolenia amaralis has never been successfully cultured and the thus the cause of bitter mussel syndrome remains unconfirmed and the toxic compounds involved unknown. The bitterness and toxicity also coincided with the presence of unusual long chain (C30) highly branched isoprenoid (HBI) alkenes in affected mussels that have been suggested to be resonsible for the bitterness (Volkman et al. .1994) - hypothesis that remains untested.

In late 2020, Rhizosolenia amaralis was successfully isolated and cultured by IMAS (Christopher Bolch) from intake water of an aquaculture facility suffering extended periods of high stock mortality. Now more than 30 years after the first “bitter-mussel” event, there is opportunity for a motivated research student to establish and confirm the toxicity of R. amaralis, the compounds involved in bitter mussel syndrome, and investigate the role of this diatom in chronic shellfish mortality.

Using controlled shellfish feeding experiments with R. amaralis cultures, the project aims to:

  1. Confirm the identity and relationship of R. amaralis to other Rhizosolenia species.
  2. Determine whether R. amarlis is the source of shellfish bitterness and chronic mortality.
  3. Establish the concentrations of R. amaralis that lead to bitterness of shellfish.
  4. Assess the nature of chronic shellfish mortality and associated pathological changes.

The student will also work with CSIRO-based lipid biochemists to establish whether HBI alkenes are produced by R. amaralis and whether these compounds are involved in bitter mussel syndrome.

Skills students will develop during this research project:

The student will learn the following skills during this project. Algal culture techniques, DNA sequencing and phylogenetics; Experimental methods/design for shellfish feeding experiments; histopatholgical methods.

Authorised by the Executive Director, Institute for Marine and Antarctic Studies
February 15, 2021