Bert graduates!

Big congratulations are in order for Bert Anderson. Bert graduated this summer with his M.S. in Biology. Bert’s master’s thesis is entitled “The Distribution and Biogeochemistry of Subtropical Intertidal Microbial Mats”.

Microbial mats can be several millimeters thick, and form through a diverse assemblage of microorganisms cohering in an extracellular matrix. Photo: Bert Anderson.

Biological and ecological zonation are quintessential to our models of intertidal communities and ecosystems. In the low-wave energy, depositional intertidal environments of the U.S. Southeast, zonation is typically described as bands of various plant foundation species and growth forms, such as a variety of mangroves, gramminoids, and succulents spread across a low, flat landscape. Often overlooked are unvegetated salt pans. Yet these habitats are biologically rich, as well, hosting a taxonomically and metabolically diverse array of microbiota that are interwoven into cohesive mats that are several millimeters thick and sit atop the sandy surface. These life forms have yielded some of Earth’s oldest fossils and sequestered deposits of recalcitrant carbon.

Salt pans can be sinuous landscape elements, covered with dark microbial mat, nested within the intertidal landscape. The perimeter of this salt pan in west-central peninsular Florida, presents a band of generally unmatted sandy soil, exemplifying structure in the distribution microbial mats. Drone photo by Bert Anderson.

Bert investigated geographical factors that explained variation in the distribution of these mats, as well as biogeochemical footprints created by the mats in the carbon and nitrogen pools of the sand they lie on. Bert found that salt pan boundaries mattered a lot! Mats tended to be found disproportionately toward the sides of salt pans that were close to one of the many tidal creeks that cut up through the intertidal landscape, yet mats tended to stop short of actually reaching the salt pan edges—there seems to be a track of largely unmatted sand that defines the salt pan perimeter. These microbial mat distributional properties then affect spatial variation in soil biogeochemical pools, as the sandy substrate beneath mats tended to be warmer, more saline, and richer with deposits of largely recalcitrant carbon when compared with unmatted salt-pan soil. Bert used a nice mix of photo-interpretation, paired-plot sampling, and lab C and N fractionation techniques to shed light on a little-studied ecological zone, thereby enriching our overarching model of the intertidal landscape.