Page 48 - Research & Innovation Report 2020

SCIENCE

Windows into life’s

earliest habitat

Living microbialites and stromatolites in coastal pools provide a glimpse into the early
conditions that allowed complex life to evolve on Earth.

Along the coast of South Africa, extensive distributions of “Microbialites and stromatolites resemble the first types of living
unique habitats called Supratidal Spring-fed Living Microbialite ecosystems we have in the fossil record on earth – they first arose
Ecosystems (SSLiME) and their layered forms, stromatolites, have 3.45 billion years ago and they have been continuous in the fossil
been discovered and described since the early 2000s. record since,” says Dr Rishworth. “Half a billion years ago they
started to decline in the world’s oceans and the reason could be
In 2012 they were discovered along the southern Nelson Mandela that when animals developed 540 million years ago they started
Bay coastline (close to Nelson Mandela University’s South Campus) burrowing into and disrupting the calcium carbonate biofilm layer
by Professor Renzo Perissinotto – then holder of the SARChI that forms these microbialites.
Chair in Shallow Water Ecosystems – as well as Professor Tommy
Bornman from the South African Environmental Observation “They are seen as evidence of the first life on Earth and are windows
Network (SAEON) – a coastal and marine research partner of into understanding life’s earliest habitat and how it changed and
Mandela University – who started mapping them. evolved into what it is today. They are also a proxy of past and
present sea levels because one of the unique features of the South
“SSLiME occur along other parts of the South African coastline but African microbialites is that they only occur in the supratidal coastal
the Nelson Mandela Bay area is the hotspot for them globally by zone at the convergence of emergent groundwater seepage.”
far,” says Dr Gavin Rishworth, senior lecturer in the Department of
Zoology, who has focused his research on these ecosystems. Because they only form where fresh groundwater flows into the
SSLiME pools along the South African coastline, microbialites

Underwater photograph of the microbialites at Cape St Francis. Photo: Gavin Rishworth

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