Incidence of microplastics in coastal inshore fish species and surface waters in the Hauraki Gulf, New Zealand

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dc.contributor.advisor Parsons, Darren
dc.contributor.author Shetty, Devina
dc.date.accessioned 2021-02-15T00:18:21Z
dc.date.available 2021-02-15T00:18:21Z
dc.date.issued 2020 en
dc.identifier.uri https://hdl.handle.net/2292/54455
dc.description Full Text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Plastics make up to 90% of marine litter. Microplastic contamination has emerged as one of the most serious environmental issues over recent years. Fish are an important source of protein for many New Zealanders, yet there is little information on contamination of marine fish species by microplastics. The principal aim of this thesis was to assess the occurrence of microplastics in coastal inshore fish species and surface waters at the Hauraki Gulf Marine Park, New Zealand. This study has been structured in two parts. First, it provides baseline information on plastic ingestion by fish species commonly consumed by New Zealanders, in order to gain a better understanding of the number of fish species affected by plastic ingestion and to estimate the average ingestion rate. Secondly, it assesses the abundance and spatial distribution of microplastic debris in the surface waters. Lastly, it quantifies and characterizes the composition of recovered plastics by size, form and color. Samples of six inshore fish species (N = 305) were collected from eleven different sites within the Hauraki Gulf in 2019. All tissue and other organic material were dissolved using a solution of 10% potassium hydroxide (KOH), incubating for 48 hours at 40°C. The remaining homogenate was filtered, and visual analysis was performed to identify suspected plastic particles. In addition, this study also quantified the amount of floating plastic debris in surface waters. Sampling was carried out through surface trawls using a zooplankton net with a 330μm pore size. Microplastics were found in 70 out of a total of 305 specimens examined. Plastic ingestion rate (PIR) was expressed as the percentage of fish of the same species that ingested plastic. Average microplastics (AM) per fish is the arithmetic mean of the total number of microplastic pieces found in each fish. Plastic load (PL) per individual fish is the arithmetic mean of the total number of microplastics found in each individual fish that contained microplastics. The average plastic ingestion rate across all six species was 22.95% with an average of 0.397 pieces per fish and a plastic load of 1.73 pieces per individual fish. Yellowbelly founder recorded the highest rate of ingestion at 52.6% while the red gurnard recorded the lowest rate of ingestion at 6.81%. The gills from pilchards were also separately dissected to investigate the occurrence of microplastics in the gills as they are filter-feeding fish. Microplastic uptake by the gills of fish were observed in 4.9% of pilchard samples confirming that filter-feeding fish are at a risk of consuming plastics. If whole prey were found in the gut, the entire prey item was removed and analysed for secondary ingestion. Plastic was found in prey, which suggests the trophic transfer of microplastics from prey to predator. Incidence of microplastics in fish caught at locations closer to Auckland (inshore) and at locations further from Auckland (offshore) were compared to evaluate if proximity to urban areas influenced the concentrations of microplastic in fish. Sixty snapper were collected from offshore locations and 43 were collected from locations closer to Auckland. No significant statistical difference in plastic ingestion rates were observed between the inshore and offshore locations. Floating microplastic debris were found in 36 out of 38 sampling stations in the Gulf. In total, this study identified 500 plastic particles with varying abundances and characteristics. The average number of plastic particles per site was found to be 13.15 pieces/sample. The total average concentration of plastics across all sites was estimated at 931.32 plastic pieces/km2. This study constitutes the first report of floating microplastic debris in New Zealand thus helping advance the knowledge on plastic pollution in this sparsely sampled region. Considering that knowledge on microplastic contamination in New Zealand fish and waters is largely limited, this research has revealed important information on the occurrence of microplastics in fish helping provide more insight about the safety of seafood products and their potential impact on human health.
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA en
dc.rights Restricted Item. Full Text is available to authenticated members of The University of Auckland only. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/nz/
dc.title Incidence of microplastics in coastal inshore fish species and surface waters in the Hauraki Gulf, New Zealand
dc.type Thesis en
thesis.degree.discipline Marine Science
thesis.degree.grantor The University of Auckland en
thesis.degree.level Masters en
dc.date.updated 2021-02-11T18:25:14Z
dc.rights.holder Copyright: the author en


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