Effects of Abnormal Flooding Events on Microbial Mat Communities and Aragonitic Stromatolites, Laguna Mormona, Baja California, Mexico: ABSTRACT

Laguna Mormona (Baja California, Mexico) is a coastal sabkha that contains a variety of microbial (cyanophycean and bacterial) mat communities. Studies conducted during 1971-76 concentrated on the microstructure, macrostructure, and degradation of these microbial mats and aragonitic stromatolites and the information they provide that is relevant to the interpretation of Proterozoic stromatolites, silicified microbial mats, and their contained microfossils. Abnormally high rainfall in 1979-80 flooded the sabkha to depths exceeding 1 m and profoundly affected these microbial communities by lowering the salinity of the water and depositing 5-10 cm of very fine grained, organic-rich mud over most of the microbial mats. The water level has returned to normal, and diatoms, cyan phytes, and bacteria locally form millimeter-thick mats upon this mud in areas that previously contained well-developed mats; however, it is unclear whether these mats will eventually attain the thickness (up to 30 cm) of their predecessors. End_of_Article - Last_Page 267------------