Standard and innovative methods of biomonitoring marine pollution using mussels
Creators: name: SHEN, Hao
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 4104
subject: Environmental management
classificationCode: 410404
subject: Environmental management

description: Coastal and estuarine areas have a great biodiversity with very active cycles of matter and energy and are inevitably under the threat of pollution from increasing human activities. Multiple types of contaminants, including heavy metals, organic contaminants such as polycyclic aromatic hydrocarbons (PAHs), and contaminants of emerging concern such as microplastics and pharmaceutical residues, in coastal areas, have been attracting increasing attention and concern. Although, environmental laws, regulation, and policies have been introduced by authorities globally, pollution control compared to the increased production of pollutants, and the legacy pollutants left in the environment are still a great challenge for human civilisation.

In this research project, the Mediterranean mussel (Mytilus galloprovincialis), with its wide distribution, high adaptability, robust physiological activity patterns, and abundant history for pollution research, was used as the model organism for biomonitoring and impact evaluation of multiple types of contaminants in the coastal and estuarine ecosystem. Field studies focused on Port Philip Bay, Victoria, Australia were conducted. Standard biomonitoring methodologies were used, and innovative methodologies were developed and applied by me.
 
Trace metals and PAHs represent the major types of environmental contaminants. In Chapters 2 and 3, the wild mussels were collected from multiple coastal and estuarine areas of Port Phillip Bay, Australia, and their body burdens of trace metals and PAHs were measured and compared using standard methodologies. In Chapter 2 artificial mussels that accumulated trace metals were also deployed at 14 sites around Port Phillip Bay and results were comparable with wild mussels.  Spatial and temporal variations between different trace metals, and PAHs were observed. Generally, the body burdens of contaminants were higher for the mussels from estuarine areas, and the areas close to industries, urban areas, and yacht sports areas, including the effects of legacy emissions. The activities of selected enzymes involved in oxidative stress were measured using the mussel gills, and results were compared to the body burdens of trace metals and PAHs. The results showed decreased activities of the enzymes which were highly correlated to high trace metal and PAH body burdens. The threats of contaminant accumulation in mussels with respect to food safety were also discussed, as wild Mediterranean mussel collection as seafood is one of the local recreation activities. The results showed that the bioaccumulation of trace metal and PAHs in the mussels from most of the areas caused moderate health risks, and it was recommended that wild mussels as seafood should be consumed with caution. In Chapter 5, the wild mussels collected from a relatively clean site were exposed to sub lethal levels of trace metals, and the trends of the bioaccumulation and the metabolites in mussel bodies and gills were measured and analysed. The results showed various accumulation patterns between different types of trace metals and the interruptions of multiple metabolic pathways including the synthesis and metabolism of amino acids, tricarboxylic acid (TCA) cycle, the synthesis of fatty acids, the metabolism of neurotransmitters, and hormone regulation.
 
In addition, innovative methodologies were developed and applied in this project. In Chapter 2, the innovative "artificial mussel" devices were deployed in the same sites where the wild mussels were collected, and accumulation of trace metals in the devices were measured and compared to the body burdens of wild mussels. The results showed proportional accumulation patterns to the wild mussels for most of the trace metals in the artificial mussels, and thus the devices were considered a good replacement for wild mussels for monitoring trace metal pollutants. In Chapter 4, real-time automated monitoring of mussel behavioural responses during trace metal and microplastic pulse exposure were conducted using an improved microcontroller based device that was constructed in the lab. The device has low cost, high throughput, and high portability, and can be applied to conduct real-time preliminary automatic data processing. The results demonstrated unique patterns of the cardiac activities and valve movements at the beginning of exposure and during the gradual removal of the toxicant exposure. The device has the potential to measure and establish behavioural responses in mussels and other bivalves, to the stress of exposure from environmental contaminants.

This research study provided extensive knowledge on the current status of multiple types of contaminants in the coastal and estuarine ecosystem in Port Phillip Bay, and provides information for the authorities to introduce new policies and regulations for the environmental protection of Port Phillip Bay. Additionally, it developed new methodologies that help to establish a deeper understanding of the physiological effects of contamination on marine biota.