Identifying the Presence of Microplastics in Maputo Bay Quantifying Microplastic Debris in a Field Setting
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Identifying the presence of microplastics in Maputo Bay Quantifying microplastic debris in a field setting Maja Karlsson Degree project for Bachelor of Science in Biology BIO603 Biology: Degree project 30 hec Spring-summer 2015 Department of Biological and Environmental Sciences University of Gothenburg Examiner: Catharina Olsson Department of Biological and Environmental Sciences University of Gothenburg Supervisor: Bethanie Carney Almroth Department of Biological and Environmental Sciences University of Gothenburg External supervisor: Daniela de Abreu Department of Biological Sciences Eduardo Mondlane University Front page image: Beach debris surrounding a ‘no littering’ sign in Catembe, Mozambique. Photographed by Sandra Toivio, used with permission. Contents Abstract – Swedish ...................................................................................................................... 5 Abstract – English ........................................................................................................................ 6 1. Introduction............................................................................................................................... 7 2. Materials and methods ......................................................................................................... 9 2.1 Study area ........................................................................................................................ 9 2.2 Biotic sampling .............................................................................................................. 9 2.3 Digestion of biotic tissues ....................................................................................... 10 2.4 Beach surveys ............................................................................................................... 10 2.5 Sediment sampling .................................................................................................... 11 2.6 Visual identification .................................................................................................. 12 2.7 Statistical analysis ..................................................................................................... 12 3. Results ....................................................................................................................................... 12 3.1 Beach transects ........................................................................................................ 12 3.2 Sediment samples ....................................................................................................... 15 3.3 Biological samples .................................................................................................. 16 4. Discussion ................................................................................................................................ 17 4.1 Beach transects ........................................................................................................... 18 4.2 Sediment samples .................................................................................................... 18 4.3 Biological samples .................................................................................................. 19 4.4 Performing the study on Inhaca Island .......................................................... 21 5. Conclusion ............................................................................................................................... 21 Acknowledgements .................................................................................................................. 21 References .................................................................................................................................... 22 Appendix ....................................................................................................................................... 25 3 4 Abstrakt – Svenska Under de senaste åren har medvetenheten hos forskare angående förekomsten av mikroplast i den marina miljön ökat nämnvärt och likaså intresset beträffande dess potentiellt skadliga effekter. “Mikroplast” är en samlingsterm för alla plastpartiklar som är mindre än 5 mm i storlek, oavsett ursprung, och kan således innefatta allt från tillverkade pellets, som används t.ex. i kosmetika eller som råmaterial vid tillverkning av plastartiklar, till fragment av större föremål som slitits ner. Denna studie undersöker förekomsten av mikroplastpartiklar i Maputo Bay i södra Moçambique. En jämförelse görs även mellan ett “förorenat” och två “oförorenade” områden, för att se om de skiljer sig åt. Varje område undersöktes ur tre aspekter: ”beach surveys” (direkt översatt ”strandinspektioner”), för att se mängden makroplast närvarande, sedimentprover, för att undersöka mikroplasten på stranden samt biologiska prover, för att se hur mycket mikroplast som intagits av marina djur. Resultaten visade en relativt jämn fördelning av mikroplast på alla tre platser och de enda signifikanta skillnaderna syntes hos makroplasten i strandinspektionerna, där det ”förorenade” området hade betydligt högre mängder (p<0,001). Mikroplast återfanns i totalt 32 % av de biologiska proverna och i 100 % av sedimentproverna. Resultaten måste dock tolkas i enlighet med förutsättningarna för studien, vilka begränsade utförandet något då de var relativt primitiva. Det råder dock inte mycket tvivel om att mikroplast i viss mån förekommer i Maputo Bay, till och med på den oexploaterade och ekologiskt värdefulla ön Inhaca. 5 Abstract – English In recent years, the awareness of microplastic pollution in the marine environment has spiked in the scientific community, and with it the interest and concern for its potential effects. ‘Microplastics’ is a collective term for any plastic particle less than 5 mm in size, whether being a fragment of a larger item or a pellet manufactured to be this size for use in factories or cosmetics. This study investigates the presence of microplastics in Maputo Bay in southern Mozambique, and compares the abundance in a ‘polluted’ area to that of a ‘pristine’ one. Three locations were chosen – one ‘polluted’ and two ‘pristine’, and three aspects were considered: beach surveys, for identifying macro-sized plastic debris, sediment samples, for quantifying micro-scale particles, and biological sampling by examining the GI-tracts of marine organisms to see how much microplastic they have ingested. Results showed a relatively even distribution of microplastics in all three sites. The only significant differences regarded macrodebris where the ‘polluted’ site was substantially higher in abundance than the others (p<0.001). Microplastics was found in 32 % of the biological samples and 100 % of the sediment samples in this study. The conditions under which it was performed put some constraints on the methodology and so some results have to be considered accordingly. There is however little doubt that microplastic pollution is to some degree present in Maputo Bay, even at the pristine and ecologically valuable island of Inhaca. 6 1. Introduction While it is well known that there are vast quantities of plastic garbage in the marine environment (Cozar et al., 2014; Eriksen et al., 2014; Gregory, 2009), much is still unclear about its ultimate fate in oceans and seas. Plastic debris can be found in almost every part of the ocean, from the deep sea to coastlines and surface water (Barnes et al., 2009), with a major accumulation point at the subtropical surface gyres (Cozar et al., 2014). It is also common to find marine animals entangled in discarded fishing gear, six- pack yokes or other plastic litter, as well as stranded marine animals that died from starvation after ingesting plastic items (Gregory, 2009). These types of debris, known as macroplastics, have received the most attention from the public due to the ethical and aesthetic problems they pose. As a result, many scientific studies have been performed to evaluate the harmful effects of macroplastics, particularly concerning marine birds, turtles and sea mammals (Gall & Thompson, 2015; van Franeker et al., 2011). However, marine debris is a difficult thing to monitor as it is patchy (Barnes et al., 2009), covers large areas, and is extremely time consuming to document. Therefore, knowledge about plastic quantities in the ocean is subject to much uncertainty. Though it has been reported that the levels of plastic debris in the open oceans seem to have stabilized, they have simultaneously increased on shorelines and in the deep sea (Barnes et al., 2009). Furthermore, as large items break down into smaller particles they become even harder to quantify and monitor since quite sophisticated equipment is needed for reliable identification (Hidalgo-Ruz et al., 2012). These small plastic fragments, pellets or fibres are known as microplastics and can be found in many parts of the ocean (Barnes et al., 2009; Browne et al., 2010; Cole et al., 2011; Collignon et al., 2012; Shaw & Day, 1994). Although the presence of microplastics has been recognised since the 1970’s (Carpenter & Smith, 1972), there has been no clear definition of the term until 2009, when the NOAA International Research Workshop on the Occurrence, Effects, and Fate of Microplastic Marine Debris suggested that it should be defined as “plastic particles smaller than 5 mm” (Arthur et al., 2009, page 10). There is, however, no lower size limit to the term and this has led to scientific reports differing in the