Study shows pattern of litter on beaches
RIVERS are assumed to be one of the major conduits for plastics entering the sea, but little is known about the interchange of plastic litter between rivers and coastal waters.
In a study recently published in Estuarine, Coastal and Shelf Science journal, researchers from UCT’s FitzPatrick Institute of African Ornithology recorded the amounts of litter washing ashore along 2.4km of beach on the northern shore of False Bay.
The study was conducted from April to June during the initial Covid19 lockdown, when beaches were closed to the public.
The study found that when the Zandvlei estuary was closed, litter washed ashore more or less evenly along the coast with only a slight concentration in Muizenberg corner, presumably due to local currents in False Bay. However, when Zandvlei was opened to the sea for the first winter storm, litter was concentrated within a few hundred metres of the estuary mouth.
“We were surprised by how little litter from the Zandvlei dispersed more than 500m from the estuary mouth,” said Professor Peter Ryan, director of FitzPatrick Institute of African Ornithology.
“To get an idea of the proportion of litter from the Zandvlei washing ashore, we deployed marked plastic and wood blocks where the river entered the sea.
“On a falling tide, 99% of blocks were recovered from the beach close to the river mouth. On a rising tide, most blocks were carried back into Zandvlei, where they travelled up to 1.2km inland.
“In the long term, we need to rethink the way we manage our plastic waste, but for now, removing large plastic items from rivers and beaches prevents them breaking up into microplastics, which are much harder to deal with,” Ryan said. |