Page 49 - Research & Innovation Report 2020

SCIENCE

Microbialite pools along the Seaview coastline near Gqeberha

are flagships of freshwater sites. Any modern human utilising the years ago the ocean would have had a much higher calcium
coastline for food resources would have needed a reliable source carbonate level and so they would have been forming in most
of freshwater to survive, so was likely to have relied on these pools. shallow seas, hence current ocean acidification is a threat to them.”
The value of these systems was described in an article, “Peritidal
stromatolites as indicators of stepping-stone freshwater resources Their position at the convergence of groundwater seepage
on the Palaeo-Agulhas Plain landscape”, published in a special is also critical as they are efficient at absorbing the nutrients in
issue on the region’s Palaeo-Agulhas Plain in the Quarternary groundwater and they therefore form a pollution buffer for the
Science Reviews in 2020. coastline. They also function similarly to estuaries along the coast,
attracting estuarine-dependent fish into their vicinity, which might
Similar supratidal coastal zone SSLiME habitats have subsequently help to connect important biological populations up and down the
been documented in southwestern Australia, Northern Ireland and coast. Their connectivity value along the coastline is an important
the Scottish Hebrides, as recently as 2018, revealing that supratidal area of knowledge that is a future SSLiME research priority.
microbialites have a global distribution. To further this research, Dr
Rishworth is part of an international team of researchers called the To support this research, in 2020 Dr Rishworth applied for
Extant Peritidal Stromatolite Network (EPStromNet) that received and received an NRF CSUR (Competitive Support for Unrated
a grant at the end of 2020 through UKRI - the United Kingdom Researchers) grant of R686 812 for 2021 – 2023. He received his
Research and Innovation (UKRI) government-funded body. The PhD at Nelson Mandela University in 2017 and will apply for an
other recipients are Ulster University and the University of Essex in NRF rating in 2021.
the UK and the University of Wollongong in Australia.

Dr Rishworth leads the overall SSLiME research project on these
habitats to understand what their drivers are, their local and
global importance and how meaningful they are to the scientific
understanding of the coast. These findings were published in
2020 in a paper he co-authored in one of the top international
geosciences journals, Earth-Science Reviews, titled Modern
supratidal microbialites fed by groundwater: functional drivers,
value and trajectories.

“The current SSLiME forming are about 6000 years old and they
appear to grow two to five mm per year. Some of those in Nelson
Mandela Bay are up to a metre thick but they can start and stop
growing depending on sea-level or groundwater conditions,”
Dr Rishworth explains. “They only form when pH conditions are
towards the alkaline extreme – the calcium carbonates on which Dr Gavin Rishworth at the Schoenmakerskop microbialites,
their growth depends only precipitates at that point. Half a billion close to the Nelson Mandela University’s South Campus

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