Evaluating Restored Tidal Freshwater Wetlands

Baldwin, Andrew H.; Hammerschlag, Richard S.; Cahoon, Donald R.

doi:10.1016/b978-0-444-63893-9.00025-3

Cited by 14 publications

(11 citation statements)

References 71 publications

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“…Conflicts between water supply and species management have therefore led to major efforts to improve the status of state-and federally-listed Delta fishes. The restoration of tidal wetlands has become a major focus of resource managers (Baldwin et al 2009b), based on an extreme long-term loss of tidal wetland habitat (Nichols et al 1986;Cloern and Jassby 2012;Whipple et al 2012). Our study provides insight into both the potential benefits of freshwater tidal sloughs, as well as the importance of flow and nutrient inputs.…”

Section: Management Implicationsmentioning

confidence: 99%

Physical and Biological Responses to Flow in a Tidal Freshwater Slough Complex

Frantzich¹,

Sommer²,

Scheier³

2018

SFEWS

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Although brackish marsh has been the subject of decades of research, tidal freshwater regions are still poorly understood. To provide insight into spatial and temporal dynamics of nutrients, physical conditions, and the plankton community in freshwater tidal habitat, we investigated from 2011 to 2014 a remnant freshwater tidal slough complex located in the Sacramento-San Joaquin Delta region of the San Francisco Estuary. Our results suggest that the tidal slough complex showed different seasonal nutrient, physical, and biological conditions when compared to a relatively homogenous adjacent large river channel, the Sacramento River. The tidal slough complex also showed substantial spatial variability in habitat conditions compared to nearby main river channels. Nutrient dynamics in the tidal slough complex appear to be driven by a complex suite of factors, including inflow from upstream tributaries and tidal flows from the downstream reach of the Sacramento River. Chlorophyll a in the tidal sloughs responded more strongly to upstream flow pulses than other environmental variables. The tidal slough complex generated significantly higher levels of chlorophyll a than other freshwater regions of the Delta. The 2011 and 2012 results were especially notable because unusually large flow pulses through the tidal slough complex appear to have contributed to rare phytoplankton blooms in downstream areas of the Delta during the fall months. Moreover, the 2012 flow pulse stimulated higher trophic levels, because significantly higher levels of zooplankton were in the tidal slough complex after the flow event. These results have important implications for our understanding of the functioning of freshwater tidal habitat, and for the design of potential restoration projects in these regions.

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Section: Management Implicationsmentioning

confidence: 99%

Physical and Biological Responses to Flow in a Tidal Freshwater Slough Complex

Frantzich¹,

Sommer²,

Scheier³

2018

SFEWS

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“…TFW typically do not have salinities high enough to cause the death of terrestrial or freshwater wetland vegetation, but vegetation dynamics are largely unknown in the context of ecological restoration of these systems located in northeastern North America. Restoration efforts in tidal brackish or fresh systems elsewhere in North America often involve sediment augmentation using dredged or otherwise externally sourced material (Baldwin and Hammerschlag, 2019). In the Upper Bay of Fundy suspended sediment concentrations in tidal rivers can be high (>500 mg•L −1 ; van Proosdij et al, 2006), but it is not clear if sediment supply will be adequate to restore marsh platform elevations.…”

Section: Introductionmentioning

confidence: 99%

High sedimentation rates lead to rapid vegetation recovery in tidal brackish wetland restoration

Proosdij

Graham²,

Lemieux

et al. 2023

Front. Ecol. Evol.

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IntroductionTidal wetland restoration in the Bay of Fundy involves restoring tidal hydrology to sites with tidal restrictions. Most have focused on salt marsh sites close to the mouth of estuaries, but there are also many tidally restricted wetlands closer to the freshwater end of tidal rivers. Recovery of salt marsh vegetation has been rapid in past projects, but little is known about sediment and vegetation dynamics post restoration in tidal brackish or freshwater environments.MethodsWe implemented tidal wetland restoration projects on two tidal rivers near the inland limit of saltwater. Hydrological restoration involved breaching (St. Croix) or realigning agricultural dykes (Belcher Street). We monitored hydrology, sediment accretion and vegetation at replicated plots on restoration sites and nearby reference tidal marshes; and conducted habitat mapping and elevation surveys using drones.ResultsAfter re-establishing tidal flow, sediment accretion was very rapid, leading to a deep layer of new sediments. Plant colonization at both sites resulted in a high diversity of halophytes in the first 2 years post restoration, but the St. Croix site transitioned to freshwater wetland species dominating by the fifth year post- restoration. The Belcher St. site has a mix of freshwater and brackish wetland species after the fourth-year post-restoration.DiscussionHigh suspended sediment concentrations at both sites suggest that each site was positioned closed to the estuarine turbidity maximum within its river. Tidal wetland restoration at the head of estuaries may benefit from the large ecological disturbance associated with rapid sediment accretion, providing a productive substrate with little competition from prior vegetation. However ultimate vegetation patterns may take longer to develop as elevation gains alter tidal flooding frequency. Low salinities suggest that the physical disturbance of sediment burying prior vegetation is the main mechanism creating a clean slate for plant recolonization, rather than mortality of terrestrial vegetation due to salt water. The majority of elevation change was due to allochthonous sediment deposition, with belowground processes playing a minor role. The wetlands restored showed substantial net elevation gains in the first years following tidal hydrological restoration, but long-term monitoring is required to track their overall resilience in the face of sea level rise.

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“…Previous research into long‐term accumulation rates at the Tivoli Bays, NY utilized both simple hydrodynamic models and sedimentary observations to predict rapid sediment accretion and marsh area expansion under future sea level rise scenarios (Benoit et al, 1999; Tabak et al, 2016; Yellen et al, 2020). While much emphasis has been placed on sedimentation rates in marsh restoration projects, variable marsh establishment at these bays demonstrates that a high sediment supply is not the dominant factor driving marsh evolution, nor is the pace of sea level rise (Baldwin et al, 2019; Ganju et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Invasive water chestnut hinders tidal wetland development

McKeon

Woodruff

Yellen

et al. 2022

Earth Surf Processes Landf

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Consistent shoreline development and urbanization have historically resulted in the loss of wetlands. However, some construction activities have inadvertently resulted in the emergence of new tidal wetlands, with prominent examples of such anthropogenic wetlands found within the Hudson River Estuary. Here, we utilize two of these anthropogenically created tidal wetlands to explore the sedimentary and hydrologic conditions driving wetland development from a restoration perspective. Tivoli North is an emergent freshwater tidal marsh, while Tivoli South is an intertidal mudflat with vegetation restricted to the seasonal growth of invasive water chestnut during summer months. Using a combination of sediment traps, cores, and tidal flux measurements, we present highly resolved sediment budgets from these two protected bays and parameterize trapping processes responsible for their divergent wetland evolution. Utilizing a 16‐year tidal flux dataset, we observe net sediment trapping in Tivoli North for most years, with consistent trapping throughout the year. Conversely, flux measurements at Tivoli South reveal net sediment loss over the study period, with trapping constrained to the summer months. Here, we explore potential mechanisms responsible for these contrasting accumulation regimes, including initial geological differences, sediment loading, and human land use changes, with a focus on the invasion of emergent aquatic vegetation. Results suggest that water chestnut is contributing to these divergent morphologies by inhibiting sediment trapping and facilitating erosion, thereby preventing marsh nucleation in Tivoli South. The longevity of this dataset highlights the capacity of aquatic vegetation to regulate sediment exchange and geomorphology in enclosed bays when provided with an opportunity to colonize. The results of this project provide evidence to inform the management of restoration projects in river systems with tidal wetlands, especially those affected by invasive species of aquatic vegetation.

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Evaluating Restored Tidal Freshwater Wetlands

Cited by 14 publications

References 71 publications

Physical and Biological Responses to Flow in a Tidal Freshwater Slough Complex

Physical and Biological Responses to Flow in a Tidal Freshwater Slough Complex

High sedimentation rates lead to rapid vegetation recovery in tidal brackish wetland restoration

Invasive water chestnut hinders tidal wetland development

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