Durban - Nearly 70 percent of small fish collected from Durban Harbour and nearby river estuaries have fragments of plastic in their guts.
This is one of the findings by researchers at the University of KwaZulu-Natal’s school of life sciences who collected several fish species from the harbour and Vetch’s Pier, as well as the Isipingo, uMngeni, uLovu and Mdloti river mouths to study the effects of plastic pollution on sea life.
Reporting on the preliminary results at a recent conservation symposium near Pietermaritzburg, researcher Trishan Naidoo said plastic pollution levels had increased across the world since the 1950s.
While the microscopic fragments from plastic could potentially harm fish by blocking their intestines and other organs, or by acting as carriers of toxic compounds and alien species, Naidoo said the research project had focused so far on collecting fish, sediment and water samples for laboratory analysis.
Initial samples showed that there were tiny plastic fibres, fragments and beads in 77 percent of the fish gut samples from horse mackerel (Trachurus species) caught near Vetch’s Reef. Overall, 69 percent of fish sampled from other areas had microplastics in their guts
Naidoo noted that microplastic fibres were ubiquitous and, because these fish filtered the water column for plankton, it was likely that they picked up microplastics via their gill rakers.
Horse mackerel filtered zooplankton from the water, increasing the risk of swallowing tiny particles of plastic by mistaking the plastic for a food source.
Mullet and other fish species had not been analysed yet, although small fish specimens had “significantly more plastic in their guts” than larger fish, according to joint research by Naidoo, Michael Staegemann, Stacey Buitendyk, Kelly Brown, Megan Clarkson, David Glassom and AJ Smit.
“The manner in which microplastics affect organisms ingesting plastic contaminants and organisms living in the sediment is still to be determined.”
Naidoo and his colleagues stressed that more samples, sites and species would have to be analysed to make “more informed and justified conclusions on the abundance and effects of microplastics around the eThekwini coastline”. - The Mercury