From people to reefs: marine debris and plastic pollution in North Queensland

Bauer-Civiello, Anne Marie (2019) From people to reefs: marine debris and plastic pollution in North Queensland. PhD thesis, James Cook University.

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Marine debris, also known as marine litter, is defined as any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment. Mostly consisting of plastic, marine debris is polluting global oceans at an increasing rate. Plastic items of all shapes and sizes can have detrimental impacts on marine fauna, and increases the stress on marine organisms. Beach clean-ups are one way to reduce plastic pollution but such actions only remove a small fraction of the debris currently present in the ocean, and they will need to occur frequently and indefinitely with existing levels and the current rates of use and production of plastics in society. Instead, identifying preventative techniques for reducing the inputs of debris in the environment or stopping it before it reaches ocean is the key to successfully reducing marine debris pollution in the long-term. Doing this will require multidisciplinary research, including understanding human behaviours, monitoring plastic loads from specific sources, and implementing a wide range of infrastructure and policy to create change.

My overall thesis aim is to provide meaningful insights into plastic pollution management using inter-disciplinary research on marine debris abundance, education and source reduction in Queensland, Australia. To do this, my thesis is split into four research themes. Theme 1 is to understand the distribution patterns of marine debris on Queensland reefs to narrow down potential sources (Chapter 2). Theme 2 is to identify exactly how plastic is entering the aquatic environment (Chapter 3 and 4). Theme 3 is to identify ways to monitor macroplastics (>5mm in size) and microplastics (plastics <5mm in size) to identify impacts, create baselines, and monitor change (Chapter 3, 4 and 5). Lastly, theme 4 is to understand community awareness and concern about marine debris to reduce land based sources, such as that from littering (Chapter 6).

In my first data chapter, I use citizen science data to determine the distribution of subtidal marine debris on reefs in Queensland coastal waters. Using this dataset, I identified the average debris loads collected during reef-health impact surveys completed since 2001. Results showed that debris is present in the highest abundances on the reefs near urban communities, particularly in South East Queensland. Debris loads near the Gold Coast were the highest with a maximum of 27 items per surveys (400m²). There was a wide range of items recorded on surveys, however fishing and boating related debris were among the highest observed. This suggests that debris effecting subtidal reefs are more likely to be sourced by fishing and boating, and therefore, targeted messaging and source-reduction plans, specifically for recreational fishers and boaters are needed to reduce debris on the reef itself.

In my second data chapter, I monitored debris loads adjacent to and outside stormwater effluents after rainfall events to determine how much plastic was originating from urban sources, using Ross River in Townsville, Queensland as a case study. No seasonal differences in debris abundance were observed, however, I found that even during below-average rainfall years, there was a relatively high and constant flow of debris items entering the river system year-long. In addition, I found that the likely origin of debris items was site dependent. For example, in one of the monitored sites the proportion of the most common plastic debris items in the river matched those found in the nearby park. Whereas, in the other site, the proportion of debris items varied from the types of items found in nearby parks, suggesting that debris may be traveling longer distances via storm drains to enter the river system. These results suggest that the placement of infrastructure, such as drain socks and river booms may be more helpful in some sites, but not others. As a result, this data chapter provides insight into the pathways in how debris can enter aquatic systems, which ultimately flush into the ocean. Most importantly, my chapter suggest relatively small cities, such as Townsville, can contribute to plastic loads in the ocean.

In my third data chapter, I monitored microplastic loads (plastics <5mm) within Ross River, to identify potential sources in local aquatic systems. Sediment and water samples were collected throughout the freshwater section of the river, within the estuary, and within Cleveland Bay both before and after the wet season. Similar to my 2nd data chapter, I did not find any seasonal difference in plastic loads within any section of the river. However, the abundance of plastics within the freshwater sediments was high, with highest concentrations matching levels found in rivers and lakes in Europe. As a result, this data chapter suggests that even in low rainfall years, the Ross River retains a high abundance of plastics in the sediments. Since the rainfall that occurred did not show measurable differences of microplastic abundances within the bay after the wet season, I hypothesise that after heavy rainfall (in excess of the 687 mm that occurred during the sampling period) a proportion of these plastics will be flushed to into sea. In addition, this chapter identifies that the majority of the plastic particles were fragments from degraded larger plastic items, indicating that the reduction of macro debris in the river long term would likely reduce the amount of microplastics in the system.

In my fourth data chapter, I identify ways to monitor microplastic pollution on reef systems by using bioindicators. Currently, there is little information on the degree to which microplastics interact with benthic organisms. Therefore, in this Chapter, I assess new ways to monitor plastic loads by performing experiments using two filter feeders, a sponge, Carteriospongia foliascens and a soft coral species, Lobophytum sp. In this experiment, I fed two different concentrations of fluorescent microspheres to both species for three days, and determined how much plastic was ingested, how long it was retained, and whether or not the organisms can detect differences in concentration loads. In addition, I observed how plastics interact with the organism, finding that much of the microspheres adhere to the surface of the organism, which is then removed via mucus production. I found that ingestion rates for both species were low, with neither able to detect differences in concentration loads. Sponge species, C. foliascens ingestion rates were higher (>1% of the total exposed particles), and able to retain the microspheres up to 7 days. Alternatively, the coral species, Lobophytum sp. was low (less than 1% of the total exposed particles), but retained the small amount of ingested particles for the full 14 day experiment. Interestingly, differences in plastic concentrations found on the surface of the organism shed by mucus was detected. Therefore, to monitor microplastic loads on reef systems, it is possible to collect mucus off of benthic species to monitor plastic loads. This has broad implications on potential non-invasive monitoring techniques.

Lastly, my fifth data chapter uses social surveys to understand the community knowledge and perception of marine debris and its sources, again using Townsville, Queensland as a case study. Previous research has shown that the increased awareness, knowledge, concern, and feelings of responsibility for environmental issues have been found to directly link to the likelihood for people to show pro-environmental behaviour such as responsible plastic use and disposal. Therefore, these themes were used to provide information on the current understanding of marine debris and its sources from Townsville residents. Questionnaires distributed online and in-person identified that approximately 70% of Townsville residents had a relatively high awareness of marine debris, and its sources. In addition, a large portion of participants were able to correctly identify that litter occurring inland, such as that from storm drains and within the river system can contribute to marine debris. My results also showed that over 70% of residents believed that individuals had the most responsibility regarding reducing the inputs of marine debris into the environment, and I found a strong connection between people and the Great Barrier Reef. Therefore, in this chapter, I suggest that future messaging to focus on the individual responsibility, pride, and identity to reduce litter in the urban environment, and ultimately, reduce debris from arriving to the ocean.

Overall, in this thesis, I use interdisciplinary research to make a novel contribution to science which can be directly useful to local managing agencies in Australia. For the first time, I collected data of plastic abundances on the Great Barrier Reef, and a local river system, creating baselines for future research, and provided new insights on the possible pathways in which plastic enters the aquatic environment. I identified ways to improve local management, by providing advice on the placement of infrastructure, and identifying the current views and perspectives of marine debris and littering in Townsville.

Item ID: 63755
Item Type: Thesis (PhD)
Keywords: marine debris, litter, pollution, fishing line, subtidal, coral reefs, river, storm drains, rainfall, run-off
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Copyright Information: Copyright © 2019 Anne Marie Bauer-Civiello.
Additional Information:

Two publications arising from this thesis are stored in ResearchOnline@JCU, at the time of processing. Please see the Related URLs field. The publications are:

Chapter 2: Bauer-Civiello, Anne, Loder, Jennifer, and Hamann, Mark (2018) Using citizen science data to assess the difference in marine debris loads on reefs in Queensland, Australia. Marine Pollution Bulletin, 135. pp. 458-465.

Chapter 3: Bauer-Civiello, Anne, Critchell, Kay, Hoogenboom, Mia, and Hamann, Mark (2019) Input of plastic debris in an urban tropical river system. Marine Pollution Bulletin, 144. pp. 235-242.

Date Deposited: 15 Jul 2020 00:52
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 50%
16 STUDIES IN HUMAN SOCIETY > 1608 Sociology > 160802 Environmental Sociology @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 30%
97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 40%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960807 Fresh, Ground and Surface Water Flora, Fauna and Biodiversity @ 30%
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