Tufa stromatolite ecosystems on the South African south coast

  • Renzo Perissinotto DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
  • Tommy G. Bornman 1 South African Environmental Observation Network, Elwandle Node, Grahamstown, South Africa 2 Coastal & Marine Research Unit, Department of Botany, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
  • Paul-Pierre Steyn Coastal & Marine Research Unit, Department of Botany, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
  • Nelson A.F. Miranda DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
  • Rosemary A. Dorrington DST/NRF Research Chair in Marine Natural Products, Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa
  • Gwynneth F. Matcher DST/NRF Research Chair in Marine Natural Products, Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa
  • Nadine Strydom Department of Zoology, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
  • Nasreen Peer DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
Keywords: tufa stromatolites, microbialites, South Africa, barrage pools, waterfall deposits

Abstract

Following the first description of living marine stromatolites along the South African east coast, new investigations along the south coast have revealed the occurrence of extensive fields of actively calcifying stromatolites. These stromatolites have been recorded at regular distances along a 200-km stretch of coastline, from Cape Recife in the east to the Storms River mouth in the west, with the highest density found between Schoenmakerskop and the Maitland River mouth. All active stromatolites are associated with freshwater seepage streams flowing from the dune cordon, which form rimstone dams and other accretions capable of retaining water in the supratidal platform. Resulting pools can reach a maximum depth of about 1 m and constitute a unique ecosystem in which freshwater and marine organisms alternate their dominance in response to vertical mixing and the balance between freshwater versus marine inflow. Although the factors controlling stromatolite growth are yet to be determined, nitrogen appears to be supplied mainly via the dune seeps. The epibenthic algal community within stromatolite pools is generally co-dominated by cyanobacteria and chlorophytes, with minimal diatom contribution.

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Published
2014-09-22