Sediment export and impacts associated with river delta channelization compound estuary vulnerability to sea-level rise, Skagit River Delta, Washington, USA

Grossman, Eric E.; Stevens, Andrew W.; Dartnell, Peter; George, Doug A; Finlayson, David P.

doi:10.1016/j.margeo.2020.106336

Cited by 11 publications

(6 citation statements)

References 38 publications

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“…These factors are associated with the global ‘flattening of kelp forests,’ through altering competitive interactions with turf algae [ 21 ]. In SPS, widespread deforestation began in the mid-1850s, and extensive clear-cut logging and river channelization radically altered sediment delivery to nearshore marine areas and sediment dynamics [ 153 ]. Fishing pressure often alters grazer populations by decreasing top-down controls from predation [ 4 , 16 , 17 ].…”

Section: Discussionmentioning

confidence: 99%

Long-term changes in kelp forests in an inner basin of the Salish Sea

Berry

Mumford²,

Christiaen

et al. 2021

PLoS ONE

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Kelp forests form an important biogenic habitat that responds to natural and human drivers. Global concerns exist about threats to kelp forests, yet long-term information is limited and research suggests that trends are geographically distinct. We examined distribution of the bull kelp Nereocystis luetkeana over 145 years in South Puget Sound (SPS), a semi-protected inner basin in a fjord estuary complex in the northeast Pacific Ocean. We synthesized 48 historical and modern Nereocystis surveys and examined presence/absence within 1-km segments along 452 km of shoreline. Compared to the earliest baseline in 1878, Nereocystis extent in 2017 decreased 63%, with individual sub-basins showing up to 96% loss. Losses have persisted for decades, across a range of climate conditions. In recent decades, Nereocystis predominantly occurred along shorelines with intense currents and mixing, where temperature and nutrient concentrations did not reach thresholds for impacts to Nereocystis performance, and high current speeds likely excluded grazers. Losses predominated in areas with elevated temperature, lower nutrient concentrations, and relatively low current velocities. The pattern of long-term losses in SPS contrasts with stability in floating kelp abundance during the last century in an area of the Salish Sea with greater wave exposure and proximity to oceanic conditions. These findings support the hypothesis that kelp beds along wave-sheltered shorelines exhibit greater sensitivity to environmental stressors. Additionally, shorelines with strong currents and deep-water mixing may provide refugia within sheltered systems.

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Section: Discussionmentioning

confidence: 99%

Long-term changes in kelp forests in an inner basin of the Salish Sea

Berry

Mumford²,

Christiaen

et al. 2021

PLoS ONE

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“…Restoration may be expected to take longer for terrestrial invertebrates dependent on marsh vegetation than for benthic invertebrates because terrestrials must wait for vegetation to establish (Woo et al, 2018). In the Refuge, after dike emplacement the land behind the dikes subsided due to reduced drainage and compaction by farming activities (Grossman et al, 2020), and salt marsh was slow to colonize after dike removal because elevation remained low. Greater sediment input would speed elevation increase and vegetation reestablishment.…”

Section: Management Implicationsmentioning

confidence: 99%

“…Other management actions and human-caused disturbances affecting sedimentary processes on deltas will also affect benthic invertebrates. River channelization can change sediment routing patterns, in some cases resulting in delta progradation, export of mud beyond the delta, and destabilization of sediments (Grossman et al, 2020). Sea level rise, in conjunction with fine sediment bypassing the marsh due to river channelization, can cause decreased marsh accretion rates and increased marsh erosion (Hood et al, 2016).…”

Section: Management Implicationsmentioning

confidence: 99%

Benthic macroinvertebrate response to estuarine emergent marsh restoration across a delta-wide environmental gradient

Rubin,

Davis,

Grossman

et al. 2024

Front. Ecol. Evol.

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Benthic invertebrates play vital roles in estuarine ecosystems, but like other taxa they have been excluded from former marshlands by diking and land use conversion. Dike removal is one way of restoring marsh, but the response of benthic invertebrates has been little studied. Also understudied is variation in benthic invertebrate communities across entire deltas, particularly in the Pacific Northwest of North America where deltas receive high flows and sediment loads for their size. Our goals were to evaluate invertebrate response to large-scale dike removal on the Nisqually River Delta in Puget Sound, Washington, U.S.A., characterize delta-wide invertebrate community variation, and relate invertebrate response and spatial variation to environmental conditions. We sampled invertebrates annually from one year before to three years after dike removal in restoring marsh, previously restored marsh, undisturbed reference marsh, and adjacent tidal flats. Marine taxa immediately colonized the area recently restored to tidal inundation and population size grew exponentially thereafter for several of them. Community composition and diversity recovered completely, and density and biomass were approaching recovery three years later. Invertebrate communities converged between restoring and pre-existing marsh (previously restored and reference), suggesting an influence of reestablished connectivity. Just offshore from the dike line, invertebrates declined one year after dike removal but then rebounded indicating resilience to short-term disturbance. Dike removal effects were not detected farther offshore. Near the offshore edge of the delta, invertebrate biomass and body size were greater than elsewhere and a diverse assemblage of crustaceans, polychaetes, and bivalves was present. Farther inshore, tidal flats were dominated by a few species of small-bodied polychaetes and had higher density but lower biomass and diversity. Facultative detritivores, which can also filter feed, were the dominant feeding guild everywhere on the tidal flats. Density, biomass, diversity, and community composition on the marsh were more similar to the inner than outer tidal flats. Environmental variables most associated with invertebrate community variation were elevation, salinity, and sediment grain size and organic content. Our results are relevant to assessing performance and setting expectations for future restorations and have broad implications for the role of benthic invertebrates in estuarine ecosystems.

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“…Del mismo modo, la modificación de las estructuras naturales o construidas para el control de las inundaciones puede reducir los efectos adversos aguas abajo de los cambios en la hidrología, la sedimentación y la erosión de las costas y mejorar la calidad del agua y la capacidad de drenaje de las aguas subterráneas en los sistemas agrícolas 191 . Estos esfuerzos pueden generar beneficios en cascada para los hábitats, lo que favorece a los salmónidos, otros peces, mariscos y aves costeras 192,193 .…”

Section: Capacidad De Adaptación De Los Ecosistemas Y Las Especies Al...unclassified

“…Existe amplia evidencia de que la conservación de la diversidad genética y la protección y restauración ecológicas pueden beneficiar los procesos de los ecosistemas y aumentar la capacidad de adaptación de las especies 120,121,122,192,193,194,195,196 . Por ejemplo, la restauración mediante la eliminación de presas y estructuras infranqueables en todo el Noroeste ha restablecido algunos procesos ecológicos e hidrológicos naturales que permiten a los peces anádromos acceder a su hábitat histórico 194,197,198,199,200 .…”

Section: Mensaje Clave 272 Los Ecosistemas Cambian En Respuesta a Los...unclassified

Cap. 27: Noroeste. En: La Quinta Evaluación Nacional del Clima

2023

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Sediment export and impacts associated with river delta channelization compound estuary vulnerability to sea-level rise, Skagit River Delta, Washington, USA

Cited by 11 publications

References 38 publications

Long-term changes in kelp forests in an inner basin of the Salish Sea

Long-term changes in kelp forests in an inner basin of the Salish Sea

Benthic macroinvertebrate response to estuarine emergent marsh restoration across a delta-wide environmental gradient

Cap. 27: Noroeste. En: La Quinta Evaluación Nacional del Clima

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