The west coast of South Africa is a key area for mining, trawling and the oil and gas industry – yet very little is known about the thousands of animals living in the sand at the bottom of the ocean, which could potentially be affected by these activities.
Over the past five years, Natasha Karenyi, a PhD student with the South African National Biodiversity Institute (SANBI) has been exploring these sandy ecosystems in selected areas stretching from the Namibian border all the way to Cape Point – and in parts of the ocean as far out to sea as 160 km and as deep as 500 m.
This ambitious large-scale project – the first of its kind along the west coast – formed the basis of her doctoral research at Nelson Mandela Metropolitan University in Port Elizabeth.
She also drafted the country’s first conservation plan for the submerged sea floor sediment ecosystems in this area, taking into account selected priority areas and the industries that operate in these areas. Her work will feed into SANBI's next National Biodiversity Assessment.
“One of the major issues with studying these ecosystems is that we are limited in terms of our understanding by the accessibility of the ecosystems – the deeper we go, the less we know. You need to go out on ships to get the deepest samples,” she says.
The research involved nine trips out to sea ranging from three days to two weeks, where samples were gathered from the far-off continental shelf.
The PhD student – one of a handful of benthic (bottom of the ocean) ecologists in South Africa – also collected samples from the beach, and utilised divers to collect samples from shallow areas. In all, she collected more than 44 000 sand-dwelling animals representing over 450 species from 200 samples collected at 48 different sites during the course of her research. Her collection will be sent to a museum to identify any new species.
Karenyi explained her sampling in more detail: “I looked at animals bigger than 1 mm that live in the sediment. These were mostly polychaetes (marine worms) and crustaceans (e.g. prawns and crabs). There were also some anemones and a few other organisms, like starfish and sea urchins.”
Karenyi is hoping that similar large-scale research studies currently underway or in the pipeline will produce comparable information for South Africa’s other coastlines. This will provide national scale data essential for the conservation and management of these ecosystems.
“Marine unconsolidated sediments (the sandy sea floor) constitutes the largest sea floor ecosystem on earth. Because it’s such a large ecosystem, you can’t sample the whole thing. Most people focus on a particular area – a bay or a harbour – and work on that. A large-scale study requires lots of resources and is very difficult to do.”
Karenyi’s study was funded by the National Research Foundation (NRF) and the Andrew Mellon Foundation in the United States.