Investigating the Australian glass shrimp Paratya australiensis as a biomonitoring tool for microplastics in freshwater waterbodies

© 2021 Bingxu NanMicroplastics are ubiquitous anthropogenic pollutants in ecosystems globally and have become a major concern in the environment. Recent studies have used standard organisms to biomonitor microplastic pollution. There would not be a single species available everywhere, so a regionally widespread organism could be a good option as the biomonitoring tool. The Australian glass shrimp Paratya australiensis (Family: Atyidae) are commonly found in south-eastern Australia; they are sensitive to anthropogenic stressors but have a wide tolerance range to environmental conditions. The aim of this thesis is to explore if P. australiensis could become an ideal biomonitoring tool for microplastic pollution, and the results could possibly be comparable with other atyid shrimp studies. This thesis presents four data chapters. The first data chapter investigated the population patterns of P. australiensis in central Victoria, to explore their seasonal population dynamics. The study found male, female and juvenile shrimp were distributed across all study sites, and the breeding seasons could extend to cooler seasons. Unnatural flow regimes may be detrimental to shrimp populations and possibly impact juvenile development. The second data chapter explored the occurrence and types of microplastics in surface waters and P. australiensis. Results show a relatively low concentration of microplastics in comparison with global studies, but microplastics were regularly detected from all sites. Fibre was the most common shape, and blue was the most frequent colour in both water and shrimp. Compared with water samples, shrimp contained a wider variety of plastic types. Since shrimp will reflect a prior history of microplastics exposure, biomonitoring these organisms could provide better information on microplastic pollution than traditional point sampling methods. The third data chapter explored the ingestion trends and consumption pathways of microplastics for different age groups of P. australiensis. Results have shown that adult shrimp could ingest more microbeads than the other age groups; shrimp of all age could ingest higher numbers of smaller microbeads than larger ones. This study surprisingly found that shrimp in all ages could digest larger microbeads. From this study, large adult shrimp can ingest more microplastics within a certain time period and should be chosen as the standard biomonitoring tool. Instead of monitoring larger sizes of microplastics, shrimp could be more appropriate to capture microplastics in smaller sizes. The fourth data chapter investigated selective uptake of microplastics based on shape and colour by P. australiensis under environmentally relevant concentrations. When all types and colour combinations were provided simultaneously in tanks, there were no significant differences across time, concentrations or tanks. When each type and colour of microplastics was provided separately in beakers, no significant differences were found across time and types of microplastics. Blue microfibres were the most common present in shrimp. The lengths of microfibres detected in beaker groups were generally shorter than those in tank groups. This study suggested that P. australiensis could still be able to ingest microplastics under environmentally relevant concentrations. However, the numbers, colours and types of microplastics they ingest may not be able to indicate the pollution conditions accurately