Dissecting by hand a ~cm-thick biomat that covers the bottom of saline ponds near Bahiret El Bibane, south of Zarzis (Tunisia), on 2010-09-28. Microscopic algal-microbial filaments bind various organic debris together with fine-grained sediments. Microbial activity in both the biomat and underlying sediments generates methane - the gas pressure causing the mat to bend out of shape (wrinkles, domes...)