Tufa stromatolite ecosystems on the South African south coast

• Published in: South African Journal of Science 2014-09, Vol.110 (9-10), p.1-1
• Main Authors: Perissinotto, Renzo, Bornman, Tommy G, Steyn, Paul-Pierre, Miranda, Nelson A F, Dorrington, Rosemary A, Matcher, Gwynneth F, Strydom, Nadine, Peer, Nasreen
• Format: Article
• Language: English
• Subjects: Algae; Aquatic ecosystems; Aquatic plants; barrage pools; Chlorophyll; Dunes; Ecosystems; Environmental aspects; Freshwater organisms; Marine ecosystems; Marine organisms; microbialites; River mouth; Rivers; Salinity; South Africa; Streams; Studies; Tufa; tufa stromatolites; Water depth; Water inflow; waterfall deposits
• ISSN: 0038-2353; 1996-7489
• DOI: 10.1590/sajs.2014/20140011

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.