Blue-green algal mats of the salinas in San-ya, Hai-nan Island (China): structure, taxonomic composition, and implications for the interpretation of Precambrian stromatolites

Abstract

The study of the algal mats in salinas used for salt production on Hai-nan Island (China) revealed the presence of five morphological types, which are dominated by different blue-green algae: (1) Orange high pinnacle mats dominated by Phormidium hypersalinum and P. hypolimneticum; (2) Pale green, low pinnacle mats dominated by P. hypolimneticum, P. hypersalinum and Aphanothece sp.; (3) Pale green spongy mats dominated by the unicellular blue-green algae Aphanothece sp., Chroococcus minutus, Aphanocapsa concharum; (4) Yellow green gelatinous mats dominated by P. hypolimneticum and Microcoleus tenerrimus; (5) Blue-green flat mats with finger-like projections dominated by M. tenerrimus and M. chthonoplastes. The distribution of these different mats is correlated to the main ecological parameters monitored: salinity, temperature and water depth. The role of the constituent blue-green algae and of the ecological parameters in the control of the composition and morphology of algal mats, as well as the implications of these findings for the interpretation of Precambrian stromatolites are discussed.