Salt Marshes as Potential Indicators of Global Climate Change

Abstract

Coastal scientists postulate that salt marshes are significantly affected by dynamics of global climate. However, few studies have explicitly proposed a perspective that regards salt marshes as potential indicators of climate change. This review article evaluates the possibility of salt marshes as indicators of global climate change, focusing upon three major aspects: sedimentary, vegetation, and biogeochemical dynamics. The previous literature concerned with these aspects commonly argues that the primary impact of climate change on salt marshes occurs via sea‐level variations, because hydrologic fluctuations regulate the frequency, duration, and depth of over‐marsh flooding events. Sedimentary, floristic, and biogeochemical dynamics prove to be significantly influenced by sea‐level changes regardless of climate zones, and hence, undoubtedly possess a potential for indicating climate signatures. However, where plant‐plant interactions such as facilitation and competition are important, vegetation dynamics in salt marshes may not be an immediate, sole function of sea‐level and climate variations. Also, specifically in the field of salt marsh biogeochemistry, enough long‐term data have not been collected to convincingly conclude that biogeochemistry is a useful indicator of climate change. Therefore, while this review is concerned mainly with the possibility of salt marshes as indicators of climate change, their suitability or usefulness is a different matter to be resolved through further data collection and discussion in future investigations.

Salt Marsh Bacterial Communities before and after the Deepwater Horizon Oil Spill

“…Significant deterioration of salt marshes along the Louisiana coastline has been linked to natural stressors (in many cases exacerbated by anthropogenic activities), such as hurricanes, sea-level rise, subsidence, and diminishing sediment supply (4)(5)(6)(7)(8) and to direct anthropogenic stressors from canal development, introduction of invasive species, pervasive nutrient pulses, pollutant accumulation, and freshwater flooding due to river diversions (9)(10)(11), as well as from accidents such as chemical and oil spills (12 and 13-16). The Deepwater Horizon (DWH) explosion and Macondo Prospect well blowout in the Mississippi Canyon Block 252 (MC252) on 20 April 2010 released an estimated 4.9 million barrels of Louisiana sweet crude oil into the Gulf of Mexico (17).…”

“…However, although microorganisms are known to regulate marsh biogeochemical reactions (6,23,24), predicting whether and how marsh microbial communities would respond to the DWH oil spill was a challenge because diversity had been understudied (8,16,25,26), and almost nothing was known about community functional redundancy that could enhance response and resistance (20,21,(27)(28)(29)(30). Initially, some DWH spill researchers proposed a swift microbial response (16,17) because microbes have the capacity to degrade constituent carbon compounds in oil (31)(32)(33)(34)(35) and earlier nutrient enrichment, metal exposure, and oiling experiments provided evidence that marsh communities could withstand low levels of disturbance from an oil spill (25,36).…”

The impacts of land-use changes on the recovery of saltmarshes in Portugal

“…Many studies have assessed the causes and consequences of saltmarsh loss (Eliot et al, 1999, Miller et al, 2001, Wu et al, 2002, Cahoon et al, 2006, Marfai and King, 2008, including in Portugal (Moreira, 1986;Ferreira et al, 2008). Degradation and loss of saltmarshes have major implications to their capacity of delivering ecosystem services, including: sediment accumulation; nutrients cycling; filtering of contaminants; wildlife habitat; flood regulation and storm protection (Simas et al, 2001;Currin et al, 2008;Feagin et al, 2008;Gedan and Bertness, 2010;Kim et al, 2011). The extension, exposure and orientation of the saltmarsh in relation to the coast, and the vegetation cover and maturity level of the plant communities influence the capacity to provide ecosystem services.…”

Modeling the long-term vegetation dynamics of a backbarrier salt marsh in the Danish Wadden Sea

“…Due to our rapidly warming climate, increasing attention is being paid to the future fate of salt marsh vegetation and the stability of marshes themselves (Bakker et al 1993;Bertness et al 2002;Feagin et al 2010;Kim et al 2011a;Kirwan et al 2010;Reed 1995). This warming trend induces the thermal expansion of oceans and the melting of polar and alpine ice, causing the mean sea level to rise along many coastlines worldwide.…”