## 4 Discussion  
### The Enzyme Activity as Affected by Soil Horizons and Microsites  
Microbial extracellular enzyme activity is a crucial step in heterotrophic decomposition of SOC [1; 3]. As such, understanding how land-use affects enzyme activity rates is essential to predicting potential changes in SOC storage and cycling, particularly in deep, organic soils of coastal wetlands which store large amounts of C in saturated soils [48]. In this study, we measured the activity of a suite of C- and N-degrading extracellular enzymes and environmental variables across organic and mineral soil horizons to better understand how wetland drainage and spatial variability (microtopography and soil depth) influence enzyme activity, and which C compounds soil microorganisms will breakdown under the different land-use scenarios. We also leveraged previously collected data from the same soil sample collection ([PERSON] et al., 2019) to normalize enzyme rates by SOC and MBC, along with the more widespread normalization by soil weight, in order to elucidate how enzymes normalized using different parameters influenced trends in enzyme activity with drainage and soil depth. In the organic and mineral soil horizons sampled in this study, activity of hydrolytic and oxidative enzymes fell within the range of the global average of 40 ecosystems [49]. Generally, enzyme activity rates (except PER) were in line with those measured in other freshwater wetlands [36; 38; 50; 51], excluding the Oi which exhibited an order of magnitude higher enzyme activity rate. For PER, activity normalized by SOC showed the greatest differences compared to previous studies, with rates ranging approximately 1-90 \(\upmu\)mol g\({}^{-1}\) SOC h\({}^{-1}\) compared to approximately 4 \(\upmu\)mol g OM\({}^{-1}\) h\({}^{-1}\) (which would be even lower if we assume half of organic matter is C and adjust [PERSON] et al. [36] measurements accordingly). Similarly, rates of BG (0.1-8 \(\upmu\)mol g\({}^{-1}\) SOC h\({}^{-1}\)) and CBH (0.1-2 \(\upmu\)mol g\({}^{-1}\) SOC h\({}^{-1}\)) normalized by SOC from organic and mineral horizons (excluding the Oi) were similar to those found in a tidal freshwater wetland (BG: 3-13 \(\upmu\)mol g OM\({}^{-1}\) h\({}^{-1}\); CBH: \(<\) 1 \(\upmu\)mol g OM\({}^{-1}\) h\({}^{-1}\); [50]). Rates of BG (0-24 \(\upmu\)mol g\({}^{-1}\) h\({}^{-1}\)) normalized by soil weight in our study were also similar to those measured in Minnesota peatlands (BG: 2-25 \(\upmu\)mol g\({}^{-1}\) h\({}^{-1}\); [51; 52]), while activity of POX (0-6.5 \(\upmu\)mol g\({}^{-1}\) h\({}^{-1}\)) was lower (POX: 6-3-12.7 \(\upmu\)mol g\({}^{-1}\) h\({}^{-1}\); [51]). In comparison to surface soil horizons of many upland sites [33; 51; 53], surface horizons of wetland soils, including those of our sites, have much higher enzyme activity. Soil depth has been demonstrated to influence enzyme activity in a wide range of upland soils [33; 54; 55; 53], and to a lesser extent in wetland soils [34; 36; 51] as conditions affecting enzyme activity (e.g., water table depth, SOC quantity and quality, oxygen, pH, temperature, microbial community structure) shift with soil depth. In our study, soil depth effects on enzyme activity was dependent on how the data were normalized, with exponential decreases in enzyme activity measured with soil depth when normalized per unit soil weight [52; 54; 55], as compared to either no change or increases with soil depth when normalized per unit SOC or MBC (particularly in the AB and B mineral soil horizons) [33; 53]. Higher enzyme activity per unit SOC or MBC at depth may result from proportionally greater enzyme production by soil microorganisms, as well as the presence of relic extracellular enzymes sorbed to soil mineral particles at depth which may desorb from mineral components and interact to decompose soil organic matter [53].