Sediment chemistry associated with native and non-native emergent macrophytes of a Hudson River marsh ecosystem

Abstract

In tidal freshwater marshes of the Hudson River, coverage by Phragmites australis and Lythrum salicaria has increased greatly over the past twenty years, although Typha angustifolia is still the predominant vegetation. Prior to any attempts at marsh restoration via removal of exotic/invasive plant species, we wanted to describe the current relationship between these plants and sediment nutrient pools. Extant stands (n=3 of each) of T. angustifolia, L. salicaria, and P. australis were sampled with porewater equilibrators in the spring and summer of 1995 and summer 1996 to measure porewater ammonium, nitrate, and phosphate. Porewater pools of phosphate were significantly lower (p<0.05) in stands of L. salicaria in summer, with concentrations only half those measured in stands of P. austral& and T. angustifolia. Porewater ammonium did not differ among plant communities, and nitrate was undetectable in sediments associated with all three communities. Sequestration of nutrients in above-ground biomass differed significantly among plant species, indicating differential demand on sediment nutrient pools. There were significant decreases in porewater ammonium from spring to summer. Growing season estimates of nitrogen incorporation into above-ground plant tissue are more than adequate to explain the removal of ammonium from porewater for all plant communities. Similarly, plant uptake of porewater phosphate was several times greater than springtime standing stocks of dissolved inorganic P. Concentrations of porewater phosphate remained high in the summer, indicating rapid replenishment from other sediment phosphorus pools. Depletion of porewater ammonium in the summer and low N : P in plant tissues suggest N limitation of these marsh plants. Our data suggest that marsh management practices intended to shift the relative vegetation coverage towards native and non-invasive species should consider the subtle but ecologically significant effects on nutrient cycling.

Nitrogen Uptake by Native and Invasive Temperate Coastal Macrophytes: Importance of Dissolved Organic Nitrogen

“…In addition, these plants could take up significantly more N (both DON and DIN) than S. alterniflora, which is evidenced by our field experiment and greater N assimilation by introduced Phragmites. Numerous studies have shown that Phragmites demands in introduced Phragmites and S. alterniflora marsh zones Estuaries and Coasts (2010) 33:784-797>50% more N than the species it displaces in salt, brackish, and tidal fresh marshes (Templer et al 1998, Windham 2001, Windham and Ehrenfeld 2003, Windham and Meyerson 2003. The high affinity and greater uptake of N could reduce N availability in sediment porewater for the other species.…”

Influence of emergent vegetation on nitrate cycling in sediments of a groundwater-fed river

“…Nitrogen cascading into riverine sediments from upwelling groundwater, may be attenuated in the hyporheic zone through immobilization (sorption, and plant and microbial uptake) (Howard-Williams et al 1982;Clarke 2002;Strauss and Lamberti 2002), and through reduction to N 2 gas by denitrification before the reactive N joins river flows (Pretty et al 2006;Krause et al 2009;Trimmer et al 2009;Stelzer et al 2011;Forshay and Dodson 2011;Harrison et al 2012). In addition to research looking at the influence of classic geomorphic features of rivers on nutrient cycling in riverine sediments, a number of researchers have also noted the importance of evaluating the influence of different vegetation types on nutrient cycling including those growing in riverbeds (Templer et al 1996;Wigand et al 2001;Clarke and Wharton 2001;Groffman et al 2005;Trimmer et al 2009;Lefebvre et al 2006;Forshay and Dodson 2011).…”

“…3-10 cm below river bed) in the rooting zones of vegetation (Templer et al 1996;Wigand et al 2001;Groffman et al 2005;Forshay and Dodson 2011). However, the stimulation of the activity of microbes, including those responsible for NO 3 -attenuation, by vegetation may extend beyond typical rooting depths (from 5 to 12 cm) in the sediments: this possibility needs investigation to be able to account for sediment NO 3 -attenuation more accurately in and beyond the rooting depth.…”

Effects of the invasive, nonindigenous seagrass Zostera japonica on nutrient fluxes between the water column and benthos in a NE Pacific estuary

“…Some of these studies have linked changes in nutrient cycling in estuarine oligohaline zones to nonindigenous plants (e.g. Posey et al 1993, Templer et al 1998, Meyerson et al 1999. In contrast, the effects of nonindigenous plants on nutrient cycling in lower (mesohaline and marine) estuary zones have not been reported.…”