Abstract Benthic microbial mats are a major component of modern and ancient global ecosystems, and their morphologies are often linked to specific ecological or environmental factors. This is especially true of pustular microbial mats that form in supratidal environments where microbes must cope with subaerial exposure and ultraviolet (UV) radiation stress. The pustular morphology of modern and ancient mats may be linked to these stresses. However, the extent to which subaerial exposure and UV radiation stress drive the pustular morphology has not been tested, and the mechanisms by which stresses influence microbial ecosystems are not well constrained. To make more robust environmental and ecological interpretations from pustular mat textures in the sedimentary record, we need to determine how UV radiation stress and subaerial exposure drive the pustular morphology. Here, we use laboratory growth experiments to test the role of subaerial exposure and UV radiation stress on the morphology of microbial mats. We characterize community composition, internal organization, and stress responses of the communities to constrain the mechanisms by which these conditions contribute to the pustular morphology. Our experimental results demonstrate that UV radiation stress contributes to the pustular mat morphologies and this morphology can be attributed to the unstructured distribution of diverse resident microbes and the production and heterogenous distribution of extracellular polymeric substances (EPS). These experimental findings help us better constrain the environmental controls and ecological dynamics that drive supratidal pustular mat morphologies and help us better interpret the diversity, ecology, and preservation potential of microbes in ancient supratidal communities.
Moore et al. (Sun,) studied this question.