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Environmental and Biological Consequences of Microplastic Within Marine Habitats

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ENVIRONMENTAL AND BIOLOGICAL CONSEQUENCES OF MICROPLASTIC WITHIN MARINE HABITATS by MARK ANTHONY BROWNE A thesis submitted to the University of Plymouth in partial fulfilment for the degree of DOCTOR OF PHILOSOPHY School of Biological Sciences October 2007 Frontispiece. Plastic debris on a beach in Looe, Cornwall, UK. Copyright Statement This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived fr om it may be published without the author's prior consent. f:D . Item No loo Sl0 8ýka b ý..ý ý'rZwrk "(klýSlS363,73441301" Mark Anthony Browne October 2007 ii Environmental and biological consequences of microscopic plastic within marine habitats Mark Anthony Browne Abstract Large pieces of plastic greater than a millimetre in diameter contaminate marine habitats worldwide and the associated environmental problems are well documented. In addition tiny fragments of plastic debris less than a millimetre in size have recently been reported. This thesis examines the distribution and environmental consequences of microscopic particles of plastic within marine habitats. To quantify the relative influence of wind and depositional environment on the accumulation of plastic debris, a mensurative experiment was conducted in a macrotidal Estuary. The overall trend was that material accumulated in down-wind sites. However, the relative importance of wind as a transport agent depended on the size and density of the plastic. Natural sediments are transported according to their size; but the extent to which models of sediment dynamics could be applied to the transport of plastic debris remains untested. I examined relationships between the abundance of microplastic debris and sediment particle size, latitude and human population density using samples from sandy shores worldwide. Microplastic was found at every location, showing the global extent of this contamination and there was a significant positive correlation between human population density and microplastic abundance. Sewage sludge disposal grounds were examined as potential sources of microplastic. Replicate sediment grab samples showed that disposal grounds near Plymouth and Newcastle (UK) had greater abundance of microplastic debris compared to reference sites. To investigate the biological consequences of ingesting clean microplastic particles the mussel, Mytilus edulis (L. ) was used as a model organism. The fate of ingested plastic was tracked within the body tissues using a laboratory trial. Mussels were exposed to 3.0 and 9.61Lm microplastic particles in seawater for 3 hours and then transferred to clean conditions. After 3 days ingested microplastic had accumulated in the circulatory fluid of M edulis. Smaller particles 3.0 nn were present in the haemolymph in consistently higher numbers than larger particles, and both sizes were still present after 48 days. There were no measurable changes in organismal health from ingestion of this material. However, it has been frequently suggested that plastics debris may transfer chemical contaminants to marine life. To test this, the sorption-affinity of candidate environmental hydrophobic contaminants from aqueous solution onto microscopic particles of polyvinylchloride and similar sized particles of sand was compared. Chemical analysis confirmed that polyvinylchloride absorbed more contaminants than sand. A second experiment examined the bioavailability of sorbed contaminants and chemical additives that are incorporated into plastic during manufacture. Laboratory trials using Arenicola marina (L. ) showed that the sorbed contaminants and additives bioconcentrated in gut tissues leading to deleterious biological effects. In conclusion, microplastic debris is a ubiquitous form of contamination and when ingested, this material can translocate from the gut to the circulatory system and haemocytes, and can transfer chemicals into animal tissues, and reduce the health of animals near the base of the food chain. The implications of these findings are discussed in relation to potential measures to improve the management of plastics in society and to reduce the amount of plastic entering the environment. iii List of contents Abstract iii ..................................................................................................................................... List figures viii of .......................................................................................................................... List xi of tables............................................................................................................................... Acknowledgements xii .................................................................................................................. Chapter 1. Microplastic an emerging contaminant of potential concern? 1.1 Abstract 2 ........................................................................................................................... 1.2 What is 3 plastic? ............................................................................................................... 1.3 Brief history 5 of plastic .................................................................................................... 1.4 Global disposal 9 plastic production, use and subsequent ................................................. 1.5 Degradation 10 and persistenceof plastic ......................................................................... 1.6 What in the 14 are the sourcesof microplastic environment?........................................... 1.7 Contamination habitats by debris 15 of marine plastic ...................................................... 1.8 What is in habitats? 16 the extent of microplastic contamination marine ......................... 1.9 Environmental in 17 consequencesof microplastic the environment ............................... have for 19 1.10 Does ingestion of microplastic any toxicological consequences animals? .... 1.11 Aims 21 of thesis ................................................................................................................ Chapter 2. Influence of wind, depositional environment, and size and density of plastic debris on patterns of accumulation in the Tamar Estuary, UK 2.1 Abstract 24 ......................................................................................................................... 2.2 Introduction 25 ................................................................................................................... 2.2.1 Hypothesestested 27 ............................................................................................. 2.3 Materials 28 and methods .................................................................................................. 2.3.1 Field 28 sampling.................................................................................................. 2.3.2 Extraction identification debris 30 and of plastic ................................................... 2.3.4 Sediment 31 particle size analysis.......................................................................... 2.3.5 Statistical 31 analyses............................................................................................. 2.4 Results 33 ........................................................................................................................... 2.4.1 Characterisation debris Tamar Estuary (UK) 33 of plastic within the ................... 2.4.2 Influence of wind, depositional environment and plastic density on debris 35 patterns of plastic accumulation ............................................................. 2.4.3 Influence of wind and depositional environment on the composition of debris 38 plastic ...................................................................................................... 2.4.4 Relationship between sediment grain composition and the abundanceof microplastic debris 41 2.5 Discussion ............................................................................................41 ..................................................................................................................... 2.5.1 Implications for habitats 43 marine ........................................................................ iv Chapter 3. Global trends in microplastic abundance and the possible role of sewage disposal sites as sources of microplastic debris to marine habitats 3.1 Abstract 48 ......................................................................................................................... 3.2 Introduction 49 ................................................................................................................... 3.2.1 Hypothesestested 53 .............................................................................................. 3.3 Materials 53 and methods.................................................................................................. 3.3.1 Global 53 sampling ............................................................................................ .... 3.3.2 Sewagedisposal 55 site sampling .......................................................................... 3.3.3 Statistical 56 analyses............................................................................................. 3.4 Results 57 ..........................................................................................................................
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