Biogeochemical Effects of Simulated Sea Level Rise on Carbon Loss in an Everglades Mangrove Peat Soil

Saltwater intrusion and inundation can affect soil microbial activity, which regulates the carbon (C) balance in mangroves and helps to determine if these coastal forests can keep pace with sea level rise (SLR). This study evaluated the effects of increased salinity (+15 ppt), increased inundation (−8 cm), and their combination, on soil organic C loss from a mangrove peat soil (Everglades, Florida, USA) under simulated tides. Soil respiration (CO2 flux), methane (CH4) flux, dissolved organic carbon (DOC) production, and porewater nutrient concentrations were quantified. Soil respiration was the major pathway of soil organic C loss (94–98%) and was approximately 90% higher in the control water level than the inundated treatment under elevated salinity. Respiration rate increased with water temperature, but depended upon salinity and tidal range. CH4 flux was minimal, while porewater DOC increased with a concomitant, significant decline in soil bulk density under increased inundation. Porewater ammonium increased (73%) with inundation and soluble reactive phosphorus increased (32%) with salinity. Overall, the decline in soil organic C mineralization from combined saltwater intrusion and prolonged inundation was not significant, but results suggest SLR could increase this soil’s susceptibility to peat collapse and accelerate nutrient and DOC export to adjacent Florida Bay.

Effect of Water Management on Interannual Variation in Bulk Soil Properties from the Eastern Coastal Everglades

We examined interannual variation in soil properties from wetlands occurring in adjacent drainage basins from the southeastern Everglades. Triplicate 10-cm soil cores were collected, homogenized, and analyzed during the wet season 2006–2010 from five freshwater sawgrass wetland marshes and three estuarine mangrove forests. Soil bulk density from the Taylor Slough basin ranged from 0.15 gm-cm−3 to 0.5 gm-cm−3, was higher than from the Panhandle basin every year, and generally increased throughout the study period. Organic matter as a percent loss on ignition ranged from 7 % to 12 % from freshwater marshes and from 13 % to 56 % from estuarine mangroves. Extractable iron in soils was similar among drainage basins and wetland types, typically ranging from 0.6 to 2.0 g Fe kg−1. In contrast, inorganic sulfur was on average over four times higher from estuarine soils relative to freshwater, and was positively correlated with soil organic matter. Finally total soil phosphorus (P) was lower in freshwater soils relative to estuarine soils (84 ± 5 versus 326 ± 32 mg P kg−1). Total P from the freshwater marshes in the Panhandle basin rose throughout the study period from 54.7 ± 8.4 to 107 ± 17 mg P kg−1, a possible outcome of differences in water management between drainage basins.