Microbialite formation in seawater of increased alkalinity, Satonda Crater Lake, Indonesia - Reply

Our paper (Arp et al. 2003) revises previous studies of Kaz´mierczak and Kempe (1990, 1992), Kempe and Kaz´mierczak (1990a, 1990b, 1993), and Kempe et al. (1996, 1997) on Lake Satonda reefs with regard to biofilm calcification and microbialite formation. We confirm that the transfer of bottom waters of increased alkalinity (due to sulfate reduction) to shallow water layers (mixolimnion) principally can support or cause biofilm calcification and microbialite formation in shallow waters (as suggested by Kempe 1990). However, their two-stage model of microbialite formation in Lake Satonda, which claims that superficial in vivo permineralization of coccoid cyanobacterial colonies by high-Mg calcite is followed by internal fibrous aragonite growth due to anaerobic decay of the entombed colonies to form microstromatolites (Kaz´mierczak and Kempe 1990) as well as Wetheredella-like structures (Kaz´mierczak and Kempe 1992) is a theoretical construct without supporting evidence from data and observations from Satonda crater lake. Also, the comparison of Lake Satonda stromatolitelike encrustations on green algae with early Paleozoic stromatoporoids by Kaz´mierczak and Kempe (1990) lacks—in our opinion—any supporting evidence. In their discussion, Kaz´mierczak and Kempe reiterate allegations seemingly supported by images and data. At a closer look, results obtained from inadequately treated samples (air drying, etching fractures, or cutting planes), a tendentious identification of coccoid structures, analytical failures (basic mineralogy from EDX measurements), and biased consideration of data (supersaturation) results in theoretical misconceptions of post-mortem calcification of degrading cyanobacterial colonies. Our positions and arguments follow.