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Data from: Multitrophic responses to tidal marsh restoration: Early effects of channel configuration on water quality, aquatic food web structure, and fish communities

Merz, Joseph12; Dean, Cheryl1; Flores, Bobbie1; Karpenko, Katie1; Ross, Kai1; Veary, Andrew1

Published May 13, 2026 on Dryad. https://doi.org/10.5061/dryad.p2ngf1w61

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May 13, 2026 version files 51.47 MB

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Abstract

Introduction: Tidal wetland restoration is critical for reversing habitat loss and enhancing estuarine resilience under accelerating sea‑level rise and climate variability. Dutch Slough in the San Francisco Estuary served as a living laboratory for adaptive management and ecosystem recovery.

Objectives: We assessed early ecological outcomes of a tidal wetland restoration design, focusing on how channel length, complexity, connectivity influence functional recovery and habitat quality across variable climate.

Methods: Two constructed tidal channels and one large open-water feature were monitored from 2021 to 2023 using a Before–After–Reference–Impact (BA:RI) framework. Mixed-effects BA:RI models isolated restoration effects. Data collection integrated continuous water-quality sensors, machine-learning-based zooplankton imaging, and video sampling and environmental DNA (eDNA) for fish.  Here, we evaluate aquatic food‑web responses using coordinated indicators spanning primary producer biomass, zooplankton assemblages, and fish abundance and composition during early restoration.

Results: Pre‑breach (2021): Three isolated aquatic food webs formed, and water quality differed significantly from reference sites. Post-breach (2022–23): Conditions shifted toward reference states, with improved dissolved oxygen, dynamic turbidity, and reduced chlorophyll-a linked to shorter residence times and enhanced tidal mixing. Despite lower chlorophyll-a concentrations, observed patterns were consistent with our expectation of altered production pathways characterized by rapid turnover rather than reduced production, suggesting a shift from biomass accumulation toward rapid export and trophic transfer rather than diminished productivity. Longer, more complex channels supported greater habitat heterogeneity, higher zooplankton and juvenile fish densities, especially near vegetated margins, and increased species richness. eDNA and video surveys detected rapid fish taxa increases post-breach, including seasonal expansion of native taxa amid persistent non-native dominance.

Conclusions: Channel length, complexity, and connectivity strongly influence ecological rehabilitation. Adaptive management accelerates functional restoration and improves nursery habitat quality.

Implications for Practice: Restoration designs should prioritize structural complexity, dendritic channels, and vegetated margins to enhance food web support and fish recruitment. Connectivity reduces residence time and drives measurable shifts in water‑quality conditions toward reference states (e.g., dissolved oxygen, turbidity variability, salinity gradients, and chlorophyll‑a), while potentially enhancing nutrient exchange. These strategies increase ecological return on investment by fostering biodiversity and resilience in subsided, highly invaded landscapes. Adaptive management (integrating monitoring with iterative design refinements) remains essential for sustaining benefits under climate change. Practitioners should pair physical complexity with long-term data collection to ensure restored wetlands deliver ecosystem services such as carbon sequestration, flood protection, and fisheries support.