The missing metric: an evaluation of microorganism importance in wetland assessments

In growing recognition of the importance of preserving wetland ecosystem function, federal and state agencies have developed assessment procedures to manage and preserve remaining wetland areas. Currently, wetland assessments do not consider microorganisms when determining wetland quality. This is notable, because fungi are the primary decomposers of organic material in many wetlands making them important players in nutrient cycling. The objective of this study is to quantify how the quality of freshwater depressional marshes, as measured using the Ohio Rapid Assessment Method (ORAM), relates to fungal community composition as a first step in determining if current assessment methods need to be adjusted to account for microorganism communities. To achieve this objective, we sampled soils from six depressional emergent marshes in the state of Ohio belonging to each of the three ORAM quality categories. From these soils we assessed soil physicochemical properties and recovered fungal DNA. We then compared these metrics across wetland types to determine if wetland quality as expressed by the ORAM reflects soil health. Our results indicate that the current ORAM scoring methodology significantly explains differences in fungal community composition between wetlands. We also found that soil physicochemical properties not currently included in the ORAM are strong drivers of fungal community composition, particularly bulk density, pH, soil organic matter, soil moisture, and percent total nitrogen and carbon.