A Levels-of-Evidence Approach for Assessing Cumulative Ecosystem Response to Estuary and River Restoration Programs

Vavrinec

et al. 2011

Estuaries and Coasts

An objective of many ecological restoration projects is to establish resilience to disturbances. Eelgrass (Zostera marina L.) represents a useful model to evaluate resilience because the plant community is dominated by one species and the estuarine environment is dynamic. Our studies of planted and reference plots used shoot density monitoring data from three projects spanning 3 to 12 years. Data show that eelgrass can recover from major shifts in pond position and shape on sandflats, as well as natural disturbances causing >20-fold change in density. However, cumulative effects of multiple stressors on unestablished plantings suggest algal blooms of unusual magnitude can tip normally marginal conditions to unfavorable. Thus, potential resilience appears to depend on landscape conditions. A dynamic equilibrium was evinced in even the deepest, lowest-density plantings, probably associated with lightmediated carrying capacity and vegetative belowground production characteristic of the Pacific Northwest. We recommend eight resilience-related planning elements to reduce uncertainties in eelgrass restoration.

Section: Resilience In Restoration Planningmentioning

confidence: 99%

Restoring Resiliency: Case Studies from Pacific Northwest Estuarine Eelgrass (Zostera marina L.) Ecosystems

Thom

Vavrinec

et al. 2011

Estuaries and Coasts

“…This study incorporated two typical reference-site applications used by the programmatic restoration assessment approach for the LCRE (Diefenderfer et al, 2011) where (1) each restoration site was paired with a single reference site to assess restoration targets and monitor change: Vera Slough and Vera Slough reference site, Kandoll Farm and Seal Slough reference site, Crims Island and Gull Island reference site, and the historically breached marsh and reference swamp on Karlson Island; and (2) to broaden understanding of acceptable restoration targets, a group of reference sites was used to evaluate the range of natural conditions in a plant community, in this case Sitka spruce swamps: Seal Slough, Karlson Island, Crooked Creek, and Secret River. Differences among the swamps become evident in the fundamental relationship between WSE and inundated area (Fig.…”

Section: Comparing Restoration and Reference Sitesmentioning

confidence: 99%

“…Typical for large rivers globally (Tockner and Stanford, 2002), diking and flow reduction have significantly reduced the shallow-water habitat area available to juvenile salmon (Kukulka and Jay, 2003). Thus, the reconnection of lateral floodplain and estuarine habitat with the main-stem river by breaching dikes and removing or replacing culverts and tide gates is a primary activity of the landscape-scale Columbia Estuary Ecosystem Restoration Program (CEERP) (NMFS, 2008;Diefenderfer et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

A spatially based area–time inundation index model developed to assess habitat opportunity in tidal–fluvial wetlands and restoration sites

Coleman

Ward

et al. 2015

Ecological Engineering

A B S T R A C T A geographic information system (GIS)-based Area-Time Inundation Index Model (ATIIM) was developed to predict and evaluate availability of hydrologically connected habitats in estuarine and tidal-fluvial regions. The model establishes and describes patterns in the spatial and temporal relationships of the land and water including non-dimensional area-time and volume-time inundation indices. The processing integrates in situ or modeled water-surface elevation (WSE) data with high-resolution elevation data, using established terrain generation and spatial hydrologic analysis methods which are applied in a new geographic domain: the low-relief microtopography characteristic of coastal wetlands. The ATIIM links these data to newly developed, spatially continuous wetted-area algorithms in a GIS module and determines site average bankfull elevation, two-and three-dimensional inundation extent, and other spatial, tabular, and graph-based metrics. It is a cost-effective, rapid assessment tool suitable for the desktop planning environment, and represents an advance over methods that estimate inundation but do not enforce hydrological connectivity. Example model outputs for 11 tidal wetland areas in the lower Columbia River floodplain and estuary illustrate habitat opportunity for threatened and endangered salmon. Outputs for wetland reference sites (tidal marshes and tidal forested wetlands) are compared with river-restoration sites where objectives include increasing salmon access to beneficial habitats by hydrologically reconnecting channels in diked areas of the floodplain. Hydrological process metrics produced by the model, both new and commonly used, support the prioritization of proposed restoration sites, pre-construction planning, and post-construction evaluation. For example, the model can help determine relationships between WSE and habitat opportunity, contrast alternative restoration designs, predict impacts of altered flow regimes, estimate nutrient and biomass fluxes, and provide standardized site comparisons to support effective monitoring of the developmental trajectories of restoration sites.

“…Using the framework described by Diefenderfer et al. (, ), we hypothesized that restoring hydrological interconnection would allow for a material exchange process and we investigated how much material would leave the system and whether that material could reach the broader estuary from sites located in tidal freshwater portions of tributary streams and rivers.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, our study addressed the following question: Does restoring hydrological connection facilitate the export of quantities of endogenously produced POM that could fuel the food web of the broader ecosystem? Using the framework described by Diefenderfer et al (2011Diefenderfer et al ( , 2016, we hypothesized that restoring hydrological interconnection would allow for a material exchange process and we investigated how much material would leave the system and whether that material could reach the broader estuary from sites located in tidal freshwater portions of tributary streams and rivers.…”

Section: Introductionmentioning

confidence: 99%

Storm‐driven particulate organic matter flux connects a tidal tributary floodplain wetland, mainstem river, and estuary

Thom

Breithaupt

Ecological Applications

et al. 2018

The transport of terrestrial plant matter into coastal waters is important to regional and global biogeochemical cycles, and methods for assessing and predicting fluxes in such dynamic environments are needed. We investigated the hypothesis that upon reconnection of a floodplain wetland to its mainstem river, organic matter produced in the wetland would reach other parts of the ecosystem. If so, we can infer that the organic matter would ultimately become a source for the food web in the mainstem river and estuary. To accomplish this, we adapted numerical hydrodynamic and transport modeling methods to estimate the mass of particulate organic matter (POM) derived from the annually senescent aboveground parts of herbaceous marsh plants (H-POM). The Finite-Volume Community Ocean Model (FVCOM), parameterized with flow, tide, and aboveground biomass data, simulated H-POM mobilization from fluid shear stress during tidal exchange, flooding, and variable river flow; entrainment into the water column; transport via channel and overland flow; and entrapment when wetted surfaces dry. We examined export from a recently reconnected, restoring tidal emergent marsh on the Grays River, a tributary to the Columbia River estuary. Modeling indicated that hydrologically reconnecting 65 ha at the site resulted in export of about 96 × 10 kg of H-POM, primarily during pulsed storm flooding events in autumn and early winter. This exported mass amounted to about 19% of the summer peak aboveground biomass measured at the site. Of that 19%, about 48% (47 × 10 kg) was deposited downstream in the Grays River and floodplain wetlands, and the remaining 52% (50 × 10 kg) passed the confluence of the Grays River and the mainstem estuary located about 7 km from the study site. The colonization of the restoring study site largely by nonnative Phalaris arundinacea (reed canarygrass) may have resulted in 18-28% lower H-POM mobilization than typical marsh plant communities on this floodplain, based on estimates from regional studies of marshes dominated by less recalcitrant species. We concluded that restored floodplain wetlands can contribute significant amounts of organic matter to the estuarine ecosystem and thereby contribute to the restoration of historical trophic structure.