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Sea level rise impacts on estuarine salt marshes - a multi-disciplinary approach

Bernardo Duarte1*, João C. Marques2 and Isabel Caçador1
  • 1 MARE - Marine and Environmental Sciences Centre, University of Lisbon, Portugal
  • 2 MARE - Marine and Environmental Sciences Centre, University of Coimbra, Portugal

One particular aspect that acquired a great meaning in the last years is the vulnerability of the coastal areas to SLR, especially salt marshes. Gathering a multidisciplinary approach form geochemistry, to hydrodynamics and ecophysiology, a holistic point of view on this problematic could be attained. Although salt marshes maintain positive sedimentation rates having the mean SLR as comparison, this might not be true in the future do to the increased anthropogenic pressures in the estuarine systems. Additional studies (Valentim et al., 2013) showed that SLR scenario could lead to changes in nutrients and sediments patterns around the salt marshes and thus vegetation coverage percentage would be affected. Additionally, as a consequence of flood duration increase, sediment moisture will increase causing a stress condition to plants. Hence, the ratio below/aboveground biomass might increase, becoming critical to plants survival under conditions of accelerated SLR. Accordingly, both SLR and expected changes in vegetation coverage percentage in controlling salt marshes evolution have important implications in their stability and consequently in coastal management. This was lately confirmed by the finding presented in this chapter. Gathering a multidisciplinary approach form geochemistry, to hydrodynamics and ecophysiology a more holistic point of view on this problematic could be addressed. The pioneer S. maritima undergoes periods of stress when exposed to prolonged tidal submersion (Duarte et al., 2014a). Thus this will have serious implications on its primary production, corroborating the hypothesis advanced by Valentim et al. (2013). This has serious implications not only on the ecosystems services provided on land by salt marsh halophytes but also for the entire estuarine system, as these are important areas with several functions for the whole ecosystem. Some examples of these functions are the contaminant remediative capacity of the salt marshes (Duarte et al., submitted) and its nutrient recycling role and food sources for secondary production (Duarte et al., 2014b). Due to the increasing stress conditions to which the halophytes are exposed under SLR, the senescence mechanisms will be more evident. Results from these studies point out an increasing number of necromass particles exported to the oceanic waters adjacent to the estuarine areas, as a combined result of the increased senescence and altered hydrodynamical features. If by one side, this will increase the fuelling of the secondary production of the coastal shelf by supplying higher amounts of particulate organic C and N (Duarte et al., 2014b), on the other hand will also contribute to an increasing contamination of these oceanic waters, due to a higher number of contaminated detritus that will not be retained within the estuarine remediative area. (Duarte et al., under revision). Thus becomes important to address SLR from a multidisciplinary approach, as these processes impacts on the halophyte vegetation will condition the whole system at several and different levels. Being trapped between the sea and the urbanized lands, this data points out to a reduction of the salt marshes foundations (by reduction of its pioneer species) with enormous impacts on the coastal erosion, possible eutrophication events and reduced remediative capacity of the ecosystem, making it prone to a possible collapse.

Acknowledgements

To authors would like to thank the “Fundação para a Ciência e Tecnologia (FCT)” for funding the research in the Marine and Environmental Sciences Centre (MARE) throughout the project UID/MAR/04292/2013 and by supporting B.Duarte PhD workplan with a National PhD Grant (SFRH/BD/75951/2011) and throughout the ECOSAM project (PTDC/AAC-CLI/104085/2008).

References

Valentim, J.M., Vaz, N., Silva, H., Duarte, B., Caçador, I. and Dias, J.M., 2013. Tagus Estuary and Ria de Aveiro Salt Marsh Dynamics and the Impact of Sea Level Rise. Estuarine, Coastal and Shelf Science 130, 138-151.
Duarte, B., Santos, D., Marques, J.C. and Caçador, I., 2014. Biophysical probing of Spartina maritima Photo-system II changes during increased submersion periods: possible adaptation to sea level rise. Plant Physiology ad Biochemistry 77, 122-132.
Duarte, B., Valentim, J.M., Dias, J.M., Silva, H., Marques, J.C. and Caçador, I., 2014b. Modelling Sea Level Rise (SLR) impacts on salt marsh detrital outwelling C and N exports from an estuarine coastal lagoon to the ocean (Ria de Aveiro, Portugal). Ecological Modelling 289, 36-44.
Duarte, B., Vaz, N., Valentim, J.M., Dias, J.M., Silva, H., Marques, J.C. and Caçador, I. (under revision). Revisiting the Outwelling Hypothesis: Modelling Salt Marsh Detrital Metal Exports under Extreme Climatic Events. Marine Chemistry.

Keywords: sea level rise, salt marsh, hydrodynamic modelling, sediment dating, plant physiology

Conference: IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016.

Presentation Type: Oral presentation

Topic: Biodiversity, Conservation and Coastal Management

Citation: Duarte B, Marques JC and Caçador I (2016). Sea level rise impacts on estuarine salt marshes - a multi-disciplinary approach. Front. Mar. Sci. Conference Abstract: IMMR | International Meeting on Marine Research 2016. doi: 10.3389/conf.FMARS.2016.04.00101

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Received: 22 Mar 2016; Published Online: 13 Jul 2016.

* Correspondence: Dr. Bernardo Duarte, MARE - Marine and Environmental Sciences Centre, University of Lisbon, Lisbon, Lisbon, 1749-016, Portugal, baduarte@fc.ul.pt