title: Environmental influences on living marine stromatolites: insights from benthic microalgal communities.
abstract: Extant marine stromatolites act as partial analogues of their Achaean counterparts, but are rare due to depleted ocean calcium carbonate levels and suppression by eukaryotic organisms. Unique, peritidal tufa stromatolites at the interface between marine and freshwater inputs were discovered in South Africa in the past decade. Our aim was to investigate the benthic microalgal community (green algae, diatoms and cyanobacteria) of these stromatolites to assess succession and dominance patterns using real-time, in situ measurements of algal concentrations and composition. These biological measurements were modelled using generalized linear modelling (GLM) multivariate statistics against water physical and chemical parameters measured at regular monthly intervals, from January to December 2014. Salinity peaked and temperature dipped in winter, with both correlated to microalgal community change (GLM: P < 0.01). Diatoms and cyanobacteria, which construct the stromatolites, were consistently the dominant groups within the algal community, with minimal green algae present throughout the year. Importantly, this demonstrates a unique, relatively stable microalgal stromatolite community as opposed to those of other marine stromatolites, which likely require seasonal and stochastic disturbance to persist. This has implications in terms of interpreting community succession and differential layering in modern and fossilized stromatolites respectively.
authors.affiliation: DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa.
authors.forename: Gavin M
authors.initials: GM
authors.lastname: Rishworth
authors.affiliation: DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa.
authors.forename: Sean
authors.initials: S
authors.lastname: van Elden
authors.affiliation: DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa.
authors.forename: Renzo
authors.initials: R
authors.lastname: Perissinotto
authors.affiliation: DST/NRF Research Chair in Shallow Water Ecosystems, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa.
authors.forename: Nelson A F
authors.initials: NA
authors.lastname: Miranda
authors.affiliation: Coastal and Marine Research Institute, Department of Botany, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa.
authors.forename: Paul-Pierre
authors.initials: PP
authors.lastname: Steyn
authors.affiliation: Coastal and Marine Research Institute, Department of Botany, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa.|South African Environmental Observation Network, Elwandle Coastal Node, Port Elizabeth, 6031, South Africa.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Bornman
mesh_terms: D002119:Calcium Carbonate / Q000378:metabolism*; D000460:Chlorophyta / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D004777:Environment; D004781:Environmental Exposure; D005580:Fossils; D058086:Microalgae / Q000378:metabolism*; D009792:Oceans and Seas; D054712:Salinity
chemical_list: D002119:Calcium Carbonate