Evaluating the Aquatic Habitat Potential of Flooded Polders in the Sacramento–San Joaquin River Delta

Durand, John R.

doi:10.15447/sfews.2017v15iss4art4

Cited by 3 publications

(2 citation statements)

References 40 publications

(58 reference statements)

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“…Habitat loss and fragmentation result in myriad negative effects on the structure, function, and productivity of nearshore marine ecosystems and their fisheries (Valentine-Rose et al 2007;Rypel and Layman 2008). In severely human-dominated aquatic ecosystems, the ability to fully restore habitat can be limited by land ownership, funding, dams and other water infrastructure, flood control projects, water diversions, subsidence, and invasive species (Lund et al 2007;Durand 2017). In these circumstances, ecological rehabilitation may be needed to help re-establish functional nursery habitats (Nagelkerken et al 2015), but studies needed to inform rehabilitation efforts are often lacking.…”

Section: Introductionmentioning

confidence: 99%

Managed Wetlands Can Benefit Juvenile Chinook Salmon in a Tidal Marsh

Aha

Moyle

Fangue

et al. 2021

Estuaries and Coasts

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Loss of estuarine and coastal habitats worldwide has reduced nursery habitat and function for diverse fishes, including juvenile Chinook salmon (Oncorhynchus tshawytscha). Underutilized off-channel habitats such as flooded rice fields and managed ponds present opportunities for improving rearing conditions and increasing habitat diversity along migratory corridors. While experiments in rice fields have shown enhanced growth rates of juvenile fishes, managed ponds are less studied. To evaluate the potential of these ponds as a nursery habitat, juvenile Chinook salmon (~ 2.8 g, 63 mm FL) were reared in cages in four contrasting locations within Suisun Marsh, a large wetland in the San Francisco Estuary. The locations included a natural tidal slough, a leveed tidal slough, and the inlet and outlet of a tidally muted managed pond established for waterfowl hunting. Fish growth rates differed significantly among locations, with the fastest growth occurring near the outlet in the managed pond. High zooplankton biomass at the managed pond outlet was the best correlate of salmon growth. Water temperatures in the managed pond were also cooler and less variable compared to sloughs, reducing thermal stress. The stress of low dissolved oxygen concentrations within the managed pond was likely mediated by high concentrations of zooplankton and favorable temperatures. Our findings suggest that muted tidal habitats in the San Francisco Estuary and elsewhere could be managed to promote growth and survival of juvenile salmon and other native fishes.

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Section: Introductionmentioning

confidence: 99%

Managed Wetlands Can Benefit Juvenile Chinook Salmon in a Tidal Marsh

Aha

Moyle

Fangue

et al. 2021

Estuaries and Coasts

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“…Although we evaluated the potential effects of a future increase in open water associated with tidal wetland restoration, we did not analyze the effects of increases that would result from levee failures and permanent flooding of lands below sea level. This scenario is worthy of additional study because the land below sea level is quite extensive (approximately 1,400 km 2 ) and flood risks are expected to increase into the future with additional land subsidence and sea level rise (Durand 2017).…”

Section: Potential Future Scenarios Not Evaluatedmentioning

confidence: 99%

Landscape Transformation and Variation in Invasive Species Abundance Drive Change in Primary Production of Aquatic Vegetation in the Sacramento–San Joaquin Delta

Boyer¹,

Safran²,

Khanna³

et al. 2023

SFEWS

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Conversion of wetlands in the Sacramento–San Joaquin Delta beginning in the mid-1800s resulted in a pronounced shift from a wetland-dominated food web to one driven by open-water primary producers. Submersed and floating aquatic vegetation (SAV and FAV) now rank highest in potential net primary production (NPP) among producer groups, and provide a comparable amount of carbon to the detrital food web as marshes. However, important details of this contribution that relate to shifts in species composition and habitat extent were not understood. Here, we review how changes in aquatic vegetation influence NPP and trophic support from the historical to modern periods, within the modern period (the last 2 decades), and under future management and climate scenarios. We estimate that NPP of SAV and FAV during the historical period was approximately half that of today, before increases in open water and introduction of the highly productive water primrose. During the modern period (the last 20 years), high interannual variability in the extent and relative composition of aquatic vegetation species has driven significant variation in total NPP. This recent temporal variation is 6 to 13 times larger than projected changes in production from the potential future scenarios we modeled, including a reduction in FAV by 20% through control measures, substantial wetland restoration (and thus increased channel area that could support SAV and FAV), and increased salinity intrusion in the western Delta with climate warming, which favors native species with greater salinity tolerance. Large temporal swings in NPP of SAV and FAV cascade to influence the degree of carbon that flows to consumers through detrital pathways and herbivory. This volatility and interannual inconsistency in aquatic vegetation support of food webs make achieving wetland restoration goals for the Delta—which could lead to recovery of a portion of the NPP lost since historical times—even more imperative.

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Impacts of human modifications on material transport in deltas

Hariharan,

Wright,

Moodie

et al. 2023

Earth Surf. Dynam.

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Abstract. As humans continue to inhabit and modify river deltas, the natural processes governing material transport through these landscapes are altered. Two common engineering projects undertaken on deltas are the dredging of channels to enable shipping and the construction of embankments to reduce flooding. While the impact of these topographic modifications has been studied at a local level for specific sites, there is a gap in our generalized understanding of how these landscape modifications impact material transport. To narrow this gap, we conduct exploratory numerical modeling to develop deltaic landscapes with different input sediment compositions, modify their topography to mimic dredging and embankments, simulate different flow conditions, and then model the transport of passive particles. We find that human modification of topography lowers hydrological connectivity by reducing the area visited by fluvial inputs. The amount of time particles spend within the delta is reduced by the construction of polders and is lengthened by dredging. Material buoyancy has a greater impact on nourishment areas and exposure times than flow regime or topographic modification, with positively buoyant particles spending longer and visiting a greater area of the delta than neutral and negatively buoyant material. The results of this study can help guide the design of future engineering projects by providing estimates of their likely impact on transport processes.

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Evaluating the Aquatic Habitat Potential of Flooded Polders in the Sacramento–San Joaquin River Delta

Cited by 3 publications

References 40 publications

Managed Wetlands Can Benefit Juvenile Chinook Salmon in a Tidal Marsh

Managed Wetlands Can Benefit Juvenile Chinook Salmon in a Tidal Marsh

Landscape Transformation and Variation in Invasive Species Abundance Drive Change in Primary Production of Aquatic Vegetation in the Sacramento–San Joaquin Delta

Impacts of human modifications on material transport in deltas

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