In this paper, we discuss the "black box" model of microbial activity in the environment with regards to the biogeochemistry of trace elements. We highlight the limitations of this conceptual model, with a focus on the different variables and processes that can impact microbial activity in the environment. We then highlight microbial transformations of arsenic and mercury as an example of how these processes can influence contaminant biogeochemistry. Finally, we discuss methods and strategies that can be employed to investigate and untangle the complex microbial processes that mediate key trace element biogeochemical pathways.

This was a fun paper to work on as it grew out of endless discussions with my postdoc PI Brett Poulin, many of them while conducting field work, as we grappled with how to put together solid experimental designs to "illuminate" the mechanisms underlying microbial transformations of mercury. As we've learned it is not trivial to do these types of experiments (especially in remote Alaska!), but the value in doing so is very high. I hope you enjoy the paper as much as we enjoyed discussing it and putting it together.

(Ben Peterson, Assistant Professor UW-Milwaukee)