Salt marsh ecosystem biogeochemical responses to nutrient enrichment : a paired 15N tracer study
Drake, Deanne C.
Peterson, Bruce J.
Galvan, Kari A.
Deegan, Linda A.
Hopkinson, Charles S.
Johnson, J. Michael
LeMay, Lynsey E.
MetadataShow full item record
KeywordBiogeochemistry; Eutrophication; New England; USA; Nitrogen processing efficiency; Salt marsh; Stable isotopes
We compared processing and fate of dissolved NO3− in two New England salt marsh ecosystems, one receiving natural flood tide concentrations of 1–4 μmol NO3−/L and the other receiving experimentally fertilized flood tides containing 70–100 μmol NO3−/L. We conducted simultaneous 15NO3− (isotope) tracer additions from 23 to 28 July 2005 in the reference (8.4 ha) and fertilized (12.4 ha) systems to compare N dynamics and fate. Two full tidal cycles were intensively studied during the paired tracer additions. Resulting mass balances showed that essentially 100% (0.48–0.61 mol NO3-N·ha−1·h−1) of incoming NO3− was assimilated, dissimilated, sorbed, or sedimented (processed) within a few hours in the reference system when NO3− concentrations were 1.3–1.8 μmol/L. In contrast, only 50–60% of incoming NO3− was processed in the fertilized system when NO3− concentrations were 84–96 μmol/L; the remainder was exported in ebb tidewater. Gross NO3− processing was 40 times higher in the fertilized system at 19.34–24.67 mol NO3-N·ha−1·h−1. Dissimilatory nitrate reduction to ammonium was evident in both systems during the first 48 h of the tracer additions but <1% of incoming 15NO3− was exported as 15NH4+. Nitrification rates calculated by 15NO3− dilution were 6.05 and 4.46 mol·ha−1·h−1 in the fertilized system but could not be accurately calculated in the reference system due to rapid (<4 h) NO3− turnover. Over the five-day paired tracer addition, sediments sequestered a small fraction of incoming NO3−, although the efficiency of sequestration was 3.8% in the reference system and 0.7% in the fertilized system. Gross sediment N sequestration rates were similar at 13.5 and 12.6 mol·ha−1·d−1, respectively. Macrophyte NO3− uptake efficiency, based on tracer incorporation in aboveground tissues, was considerably higher in the reference system (16.8%) than the fertilized system (2.6%), although bulk uptake of NO3− by plants was lower in the reference system (1.75 mol NO3−·ha−1·d−1) than the fertilized system (10 mol NO3−·ha−1·d−1). Nitrogen processing efficiency decreased with NO3− load in all pools, suggesting that the nutrient processing capacity of the marsh ecosystem was exceeded in the fertilized marsh.
Author Posting. © Ecological Society of America, 2009. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecology 90 (2009): 2535-2546, doi:10.1890/08-1051.1.
Showing items related by title, author, creator and subject.
Effects of regular salt marsh haying on marsh plants, algae, invertebrates and birds at Plum Island Sound, Massachusetts Buchsbaum, Robert N.; Deegan, Linda A.; Horowitz, Julie; Garritt, Robert H.; Giblin, Anne E.; Ludlam, John P.; Shull, David H. (2008-10)The haying of salt marshes, a traditional activity since colonial times in New England, still occurs in about 400 ha of marsh in the Plum Island Sound estuary in northeastern Massachusetts. We took advantage of this haying ...
Distribution of hydrocarbons in a salt marsh ecosystem after an oil spill and physiological changes in marsh animals from the polluted environment Burns, Kathryn A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1975-06)The studies described in this thesis were designed to answer several problems relating to the recovery of a salt marsh heavily polluted by an accidental spill of Number 2 fuel oil. Field and laboratory studies were ...
Forbrich, Inke; Giblin, Anne E. (John Wiley & Sons, 2015-09-29)We studied marsh-atmosphere exchange of carbon dioxide in a high marsh dominated salt marsh during the months of May to October in 2012–2014. Tidal inundation at the site occurred only during biweekly spring tides, during ...