Vegetation death and rapid loss of surface elevation in two contrasting Mississippi delta salt marshes: The role of sedimentation, autocompaction and sea-level rise

It is predictable that salt marshes in regions, where sediment loads are high, should be stable against a broader range of relative sea level scenarios than those in sediment-poor systems. Despite extensive theoretical and laboratory studies, additional syntheses of marsh &#8216;persistence&#8217; indicators under human interventions and accelerated sea-level rise rates are still needed. This study investigates the recent lateral changes occurring in lagoon-type marshes of the Ria Formosa lagoon (south Portugal) in the presence of human interventions and sea-level rise, to identify the major drivers for past marsh evolution and to estimate potential future trends. The conducted analysis assessed the past geomorphological adjustment based on imagery analysis and assessed its potential future adjustment to sea-level rise (~100 years) based on modelled land cover changes (by employing the SLAMM model within two sea-level rise scenarios).Salt marshes in the Ria Formosa showed slow lateral growth rates over the last 70 years (<1 mm&#8729;yr-1), with localized erosion along the main navigable channels associated with dredging activities. Higher change rates were noted near the inlets, with stronger progradation near the natural inlets of the system, fed by sediment influx pulses. Any potential influence of sea-level increase to an intensification of marsh-edge erosion in the past, could not be distinguished from human-induced pressures in the area. No significant sediment was exchanged between the salt marshes and tidal flats, and no self-organization pattern between them was observed in past. The related analysis showed that landcover changes in the salt marsh areas are likely to be more prominent in the future. The obtained results showed evidence of non-linearity in marsh response to high sea-level rise rates, which could indicate to the presence of critical thresholds and potential negative feedbacks within the system, with significant implications to marsh resilience.

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Salt Marshes and sea level rise: marsh dynamics in relation to accretion processes and accretion enhancement techniques

Studies in Environmental Science - Climate Change Research - Evaluation and Policy Implications, Proceedings of the International Climate Change Research Conference ◽

10.1016/s0166-1116(06)80111-1 ◽

1995 ◽

pp. 823-826 ◽

Cited By ~ 1

Author(s):

Erik-Jan Houwing ◽

Joost H.J. Terwindt

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

And Sea Level

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Differential Effects of Increasing Salinity on Germination and Seedling Growth of Native and Exotic Invasive Cordgrasses

Plants ◽

10.3390/plants8100372 ◽

2019 ◽

Vol 8 (10) ◽

pp. 372 ◽

Cited By ~ 2

Author(s):

Infante-Izquierdo ◽

Castillo ◽

Grewell ◽

Nieva ◽

Muñoz-Rodríguez

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Fresh Water ◽

Seedling Growth ◽

Salt Marshes ◽

Germination Percentage ◽

Tidal Elevation ◽

Exotic Invasive ◽

Specialist Species ◽

And Sea Level

Soil salinity is a key environmental factor influencing germination and seedling establishment in salt marshes. Global warming and sea level rise are changing estuarine salinity, and may modify the colonization ability of halophytes. We evaluated the effects of increasing salinity on germination and seedling growth of native Spartina maritima and invasive S. densiflora from wetlands of the Odiel-Tinto Estuary. Responses were assessed following salinity exposure from fresh water to hypersaline conditions and germination recovery of non-germinated seeds when transferred to fresh water. The germination of both species was inhibited and delayed at high salinities, while pre-exposure to salinity accelerated the speed of germination in recovery assays compared to non-pre-exposed seeds. S. densiflora was more tolerant of salinity at germination than S. maritima. S. densiflora was able to germinate at hypersalinity and its germination percentage decreased at higher salinities compared to S. maritima. In contrast, S. maritima showed higher salinity tolerance in relation to seedling growth. Contrasting results were observed with differences in the tidal elevation of populations. Our results suggest S. maritima is a specialist species with respect to salinity, while S. densiflora is a generalist capable of germination of growth under suboptimal conditions. Invasive S. densiflora has greater capacity than native S. maritima to establish from seed with continued climate change and sea level rise.

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Salt marsh resilience to sea-level rise and increased storm intensity

10.5194/egusphere-egu21-1294 ◽

2021 ◽

Author(s):

Natascia Pannozzo ◽

Nicoletta Leonardi ◽

Iacopo Carnacina ◽

Rachel Smedley

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Storm Surge ◽

Salt Marshes ◽

Sediment Budget ◽

Geophysical Research ◽

Storm Intensity ◽

Combined Impact ◽

And Sea Level

Salt marshes are widely recognised as ecosystems with high economic and environmental value. However, it is still unclear how salt marshes will respond to the combined impact of future sea-level rise and possible increases in storm intensity (Schuerch et al. 2013). This study investigates marsh resilience under the combined impact of various storm surge and sea-level scenarios by using a sediment budget approach. The current paradigm is that a positive sediment budget supports the accretion of salt marshes and, therefore, its survival, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as test case, and the hydrodynamic model Delft3D was used to simulate the response of the salt marsh system to the above scenarios. We conclude that the resilience of salt marshes and estuarine systems is enhanced under the effect of storm surges, as they promote flood dominance and trigger a net import of sediment.&#160; Conversely, sea-level rise threatens marsh stability, by promoting ebb dominance and triggering a net export of sediment. Ultimately, when storm surge and sea-level scenarios are combined, results show that storms with the highest intensities have the potential to counteract the negative impact of sea-level rise by masking its effects on the sediment budget.AcknowledgementsWe acknowledge the support of the School of Environmental Sciences, University of Liverpool.ReferencesGanju, N.K., Kirwan, M.L., Dickhudt, P.J., Guntenspergen, G.R., Cahoon, D.R. and Kroeger, K.D. 2015. &#8220;Sediment transport-based metrics of wetland stability&#8221;. Geophysical Research Letters, 42(19), 7992-8000.Schuerch, M., Vafeidis, A., Slawig, T. and Temmerman, S. 2013. &#8220;Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise&#8221;.&#160;Journal of Geophysical Research-Earth Surface, 118(1),&#160;84-96.

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