Columnar stromatolites from intertidal zone of Hamelin Pool, Shark Bay, Aus.
(Awramik, 1984)
The environments for stromatolites are very wide ranging.  They are not only able to live in intertidal and supratidal environments but also in deep water environments

Marine supratidal microbial mat from the Yucatan, Mexico (Awramik, 1984)

Stromatolites at lowtide, Hamelin Pool, Australia (www.calm.wa.gov.au)
They can survive exposure during low tide, therefore they are resistent to dessication, high temperature and solar radiation.
Cyanobacteria can range to depths of 100m because of their photosynthetic capabilities.

Stromatolites at high tide, Hamelin Pool, Aus. (www.calm.gov.ca)