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Biogeochemical Recovery of Oligohaline Wetland Soils Experiencing a Salinity Pulse
Author(s) -
Kiehn Whitney M.,
Mendelssohn Irving A.,
White John R.
Publication year - 2013
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2013.05.0202
Subject(s) - saltwater intrusion , wetland , salinity , biogeochemical cycle , biogeochemistry , environmental science , soil water , hydrology (agriculture) , soil salinity , ecology , groundwater , oceanography , soil science , geology , biology , aquifer , geotechnical engineering
Oligohaline wetlands exist at a dynamic interface along a river‐to‐estuary gradient where salinity changes frequently due to fluctuating tidal cycles and weather events. Large storms can cause short‐term saltwater intrusion into these low‐lying coastal areas, exposing oligohaline wetland plants and soils to above‐normal salinities and severe stress on wetland organisms. The objective of this study was to determine how oligohaline wetland soils respond to a single pulse saltwater intrusion, similar to what may occur during hurricane‐associated storm surge. Soil response variables were measured in intrusion‐Impacted and Reference soils before, during, and after a 6‐wk saltwater intrusion event to determine potential impacts on microbial biomass and activity and associated nutrient dynamics. We observed no significant change in basal CO 2 or CH 4 production in oligohaline soils (interstitial salinity = 1.3 ± 0.1 practical salinity units [psu]; mean ± 1 SD) exposed to 20 psu saltwater, while substrate‐induced methanogenesis was negatively correlated with salinity. Microbial biomass C (MBC) responded positively to saltwater intrusion by doubling in concentration at the 0‐ to 5‐cm depth interval. Saltwater intrusion had no impact on porewater nutrient concentrations; however, extractable NH 4 + decreased as salinity increased. Although some significant changes in microbial activity, abundance, and nutrient availability occurred due to saltwater intrusion, these impacts were generally transient, with post‐intrusion conditions resembling pre‐intrusion conditions. These results suggest that short‐term and transient saltwater intrusion may have little longer‐term effect on wetland soil biogeochemistry. However, compounding effects of frequent saltwater intrusion pulses due to strong, regularly occurring storm events could cause longer‐lasting shifts in biogeochemical functioning of these wetlands.