Recovery of freshwater marsh vegetation after a saltwater intrusion event

Abstract

Greenhouse mesocosms of freshwater marsh vegetation were exposed to a simulated saltwater intrusion event followed by a recovery period during which water levels and interstitial water salinity were adjusted over a range of conditions. Virtually all above-ground vegetation, including the three dominant species, Sagittaria lancifolia L., Leersia oryzoides (L.) Swartz, and Panicum hemitomon Schultes, was killed by the initial saltwater intrusion event. P. hemitomon did not recover, but S. lancifolia and L. oryzoides, as well as many of the other species initially present, exhibited some ability to recover depending on post-saltwater intrusion conditions. Increasingly harsh recovery conditions (for freshwater marsh vegetation), including more reduced soil conditions, higher interstitial salinities, and higher interstitial sulfide concentrations were associated with decreased live above-ground biomass and species richness. The effect of elevated salinity on vegetative recovery became more pronounced under flooded conditions. This experiment illustrates that the response of a freshwater marsh community to the long-term disturbance effect of a transient saltwater intrusion event will be strongly influenced by post-intrusion salinity and water levels.

A global perspective on wetland salinization: ecological consequences of a growing threat to freshwater wetlands

“…McKee and Mendelssohn (1989) suggested that gentle increases in salinity were tolerated, while abrupt increases caused dieback. Flynn et al (1995) showed that, in coastal Louisiana (USA) marshes, salinity induced aboveground mortality and, while vegetation recovered from short pulses, seeds and rhizomes did not re-grow after longer flooding times with high salinity which resulted in low redox and high H 2 S concentrations.…”

“…Altered hydrology may also play a role in mitigating or aggravating salinity stress, but no clear pattern has been established (Flynn et al 1995, Spalding and Hester 2007, Sharpe and Baldwin 2012. Depending on a wetland's elevation relative to mean high tide, moderate increases in inundation can either stimulate or depress rates of primary production (Morris et al 2002, Kirwan et al 2010.…”

Salt Marsh Monitoring in Jamaica Bay, New York from 2003 to 2013: A Decade of Change from Restoration to Hurricane Sandy

“…Saltwater intrusion into freshwater ecosystems is a major source of storm event derived vegetation loss; evident in both coastal wetland environments [51] and forests [52]. The survival and recovery of freshwater wetland vegetation depends on the species [53] and replanting of coastal forests can be limited by the increased soil salinity and herbivory [54]. These long-term impacts emphasize the importance of monitoring the West Pond breach.…”

Bodies of Water Along the Coast of a Tideless Sea in Areas with Young Pleistocene Accumulation from Scandinavian Glaciers (Baltic Sea)

“…Seawater intrusions are some of the most common events taking place during extreme weather conditions. The effects of seawater intrusions have been observed in coastal lakes (Saeijs, Stortelder, 1982;Tiruneh, Motz, 2003), lagoons (Ishitobi et al, 1999;Tanaka et al, 2005), wetlands (Glover, 1959;Flynn, McKee, 1995) and mouth sections of rivers (Foster, 1980;Giambastiani et al, 2007). Seawater intrusions cause an increase in water salinity (van der Thuin, 1990) and abruptly increased water levels (Haslett, 2008).…”