Effects of Increased Salinity and Inundation on Inorganic Nitrogen Exchange and Phosphorus Sorption by Tidal Freshwater Floodplain Forest Soils, Georgia (USA)

• Published in: Estuaries and coasts Vol. 36; no. 3; pp. 508 - 518
• Main Authors: Jun, Mihee, Altor, Anne E., Craft, Christopher B.
• Format: Journal Article
• Language: English
• Published: New York Spring Science + Business Media 01.05.2013; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish water ecosystems; Cations; Coastal Sciences; Cores; Earth and Environmental Science; Ecology; Environment; Environmental changes; Environmental Management; Estuaries; Eutrophication; Floodplains; Forest soils; Fresh water; Fresh water ecosystems; Freshwater & Marine Ecology; Freshwater ecology; Fundamental and applied biological sciences. Psychology; Inorganic chemistry; Marine; Mineralization; Nitrogen; Nutrient cycles; Organic matter; Phosphorus; Rainforests; Saline water; Saline water intrusion; Salinity; Sea level rise; Soils; Sorption; Synecology; Tides; Water and Health; Water column; Georgia; United States; North America; America; United States > US; ASW, USA, Georgia; Sea level rise; N exchange; P sorption and precipitation; Tidal freshwater floodplain forest; Saltwater intrusion; Inundation; Exchange; Freshwater environment; Sorption; Brackish water environment; Flood plain; Flood; Inorganic nitrogen; Environmental factor; Phosphorus; Forest soil; Tides; Salinity
• ISSN: 1559-2723; 1559-2731
• DOI: 10.1007/s12237-012-9499-6

We investigated the effects of increasing salinity and inundation on inorganic N exchange and P sorption/precipitation in soils of tidal freshwater floodplain forests (TFFF) of coastal Georgia, USA. Our objectives were to better understand how sea level rise, increasing inundation, and saltwater intrusion will affect the ability of TFFFs to retain nitrogen (N) and phosphorus (P). We collected soil cores (0–5 cm) from three TFFFs that do not currently experience saltwater intrusion and from one TFFF currently experiencing saltwater intrusion and measured NH 4 -N exchange and PO 4 -P removal over five simulated 6-h tidal cycles using nutrient-enriched freshwater (30 μM NH 4 -N and 5 μM PO 4 -P). In a second experiment, we exposed soil cores to three salinities (0, 2, and 5) and two inundation depths (5 and 10 cm) using the same nutrient enrichment. When flooded with nutrient-enriched freshwater, soils from the three TFFFs that do not experience saltwater intrusion removed inorganic N and P in amounts ranging from 5.2 to 10.7 and 2.3 to 4.4 mg/m 2 , respectively, and the TFFF soils experiencing saltwater intrusion removed 2.1 to 3.8 mg P/m 2 . However, TFFF soils experiencing saltwater intrusion released inorganic N to the water column in amounts ranging from 7.1 to 67.5 mg/m 2 . In the second experiment, soils from TFFFs not experiencing saltwater intrusion released NH 4 -N to the water column when exposed to 2 and 5 salinity, and the amount of N released increased with salinity and number of tidal cycles. In contrast, the same TFFF soils sorbed two and three times more PO 4 -P when exposed to 2 and 5 salinity than when exposed to 0 salinity. P removal on a mass basis was greater under 10 cm of inundation, but the efficiency of removal was greater under the 5 cm flooding depth. Our findings suggest that saltwater intrusion caused by sea level rise will promote N release into the water column through organic matter mineralization and/or ion exchange and may promote P sorption, or precipitation of P with metal cations. In addition, release of N and resulting increased N/P could exacerbate eutrophication of estuaries in the future.