A quantitative analysis of

microplastic pollution along the

south-eastern coastline of South

AfricaDr Holly Nel

Prof. William Froneman

Sources of microplastics

• Large items (Plastic

cup, polystyrene

chunks etc)

• Land or sea-based

sources

• Deliberately or

accidently

introduced

• Degrade (UV, wind

action etc)

• Secondary

microplastic

(microplastic

fragments)

• Primary

microplastics

• Nurdles/virgin

pellets

• Microbeads

(cosmetics, air-

blasting etc)

• Deliberately or

accidentally

introduced

• Land or sea-basedhttps://journeytotheplasticocean.wordpress.com/tag/nurdles/

Sources of microplastics

• Microfibres

• Secondary microplastics

• Large items (i.e garments, carpets etc)

• Land or sea-based source

Browne et al. (2011)

1 mm

500 µm

Effect• Attachment of diatoms and hydroids (Carpenter and Smith,1972)

• Small size – potential to be ingested by organism

– Originally thought to be inert

• Absorption and concentration of Persistent Organic Pollutants (POPs)

– Transportation as microplastics are transported

– Concentrated when ingested by organisms

– Bio-magnify up the food chain, until possibly reaching our plates

• Leaching causing contamination to surrounding areas (toxic monomers

released)

Microbeads by Steve Greenberg

• Ryan (1988) – Sea-surface off south-western Cape Province

– Mean 3 640 particles/km2

• Lamprecht (2013)– Milnerton beach in Table Bay

– Mean 30.9 (±17.2) articles/L1

– (30 900 articles/m3)

• Naidoo (2015)– 5 estuaries along Kwa-Zulu Natal

– Highest at Durban Harbour 745.4 ± 129.7 particles per 500 mL (sediment)

– 1 490 800 particles per m3

Extent (South Africa)

• Ryan (1988)

– Sea-surface off south-western Cape Province

– Mean 3 640 particles/km2

• Lamprecht (2013)

– Milnerton beach in Table Bay

– Mean 30.9 (±17.2) articles/L1

– (30 900 articles/m3)

• Naidoo (2014)

– 5 estuaries along Kwa-Zulu Natal

– Highest at Durban Harbour 745.4 ± 129.7 particles per 500 mL (sediment)

– 1 490 800 particles per m3

• Nel and Froneman (in prep.)

– 21 beaches along south-eastern coastline

– Range in sediment: 72 222 ± 34 820 and 334 167 ± 144 970 particles.m-3

– Range in water column: 279.1 ± 53.36 to 1237 ± 276.7 particles.m-3

Extent (South Africa)

• Hypothesis:

Bays, which are largely retention systems, are

characterised by higher densities of microplastics in

comparison to open stretches of coastline.

• Objectives:

Determined the distribution, density and composition

of microplastic particles collected from beach sediment

and surf-zone water from 21 beaches (11 within bays

and 10 along the open coast) on the south-eastern

coastline of South Africa.

Methodology• Sediment

– (3 samples)

• Water

– (3 samples)

• 21 beaches

– 11 bay sites

– 10 open coast

sites

Methodology

Hidalgo-Ruz et al. (2012)

Results

Sediment range: 72 222 – 334 167 particles.m-3

Water range: 279 – 1 236 particles.m-3

1 mm

500 µm

1 mm

500 µm500µm

Polystyrene Blue fibres

Red fibresPossible fragment

Fibres

Results• One-way ANOVA (assumptions met)

• Sediment

– No significant difference between sites

– F = 1.236; df = 20; p = 0.2748

• Water

– Significant difference between sites

– F = 2.288; df = 20; p = 0.0119

– Tukey HSD test: Oyster Bay was significantly different to Cannon Rocks;

Kleinbrak; Danabaai 2 ( p= 0.02328; p = 0.00936; p = 0.00894 respectively)

• Independent t-test (assumptions met)

• Sediment

– No significant difference between bay and open coast sites

– t = 1.752826; df = 19; p = 0.095753

• Water

– No significant difference between bay and open coast sites

– t = 0.891416; df = 19; p = 0.383856

Discussion• There are many factors that determine the fate of microplastics in the

marine environment

Individual• Size, shape, density, lifespan

Population• Flocculation

Ecosystem• Wind (South-easterly vs

North-westerly)

• Currents (Agulhas Current)

• Seasons (Tourism)

• Human interaction Sources

= waste disposal sites)

Community• Ingestion by mussels, fish etc

• Association with microbial

aggregations

• No difference between bay and open coastline sites

• Port Elizebeth sites were not different to other sites

• Sediment is a major sink

• Synthetic fibres is a major source of pollution

• However, there still needs to be a lot of work done on this topic and

these conclusions are just preliminary

Conclusion

Future:Filter-feeders (e.g. mussels)

• Left to evacuate guts

• Left overnight in Nitric Acid

• Heated for 1hr at 60oC and then for 1hr at 100oC

• Mixture diluted in distilled water (80oC)

• Filtered over 5µm filter

Solutions• Recognising the problem and getting the community to recognise it

• 2013 addition of microplastics to beach clean-up data form

Thank you

• Ryan (1988)

– Sea-surface off south-western Cape Province

– Mean 3 640 particles/km2

• Lamprecht (2013)

– Milnerton beach in Table Bay

– Mean 30.9 (±17.2) articles/L1

– (30 900 articles/m3)

• Naidoo (2014)

– 5 estuaries along Kwa-Zulu Natal

– Highest at Durban Harbour 745.4 ± 129.7 particles per 500 mL (sediment)

– 1 490 800 particles per m3

• Nel and Froneman (in prep.)

– 21 beaches along south-eastern coastline

– Range in sediment: 72 222 ± 34 820 and 334 167 ± 144 970 particles.m-3

– Range in water column: 279.1 ± 53.36 to 1237 ± 276.7 particles.m-3

Extent (South Africa)