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Mangrove-forest sustainability hinges upon propagule recruitment and seedling retention. This study evaluates biophysical limitations to mangrove-seedling persistence by measuring anchoring force of two mangrove species (Rhizophora mangle L. and Avicennia germinans (L.) L.). Anchoring force was measured in 362 seedlings via lateral pull tests administered in mangrove forests of two subtropical estuaries and in laboratory-based experiments. Removal mechanism varied with seedling age: newly established seedlings failed due to root pull-out while seedlings older than 3 months failed by root breakage. The anchoring force of R. mangle seedlings was consistently and significantly greater than A. germinans (p = 0.002); however, force to remove A. germinans seedlings increased with growth at a faster rate (p < 0.001; A. germinans: 0.20–0.23 N/g biomass; R. mangle: 0.04–0.07 N/g biomass). Increasing density of surrounding vegetation had a positive effect (p = 0.04) on anchoring force of both species. Critical velocities at which seedlings become susceptible to instantaneous uprooting estimated from anchoring forces measured in the field were 1.20 m/s and 1.50 m/s, respectively, for R. mangle and A. germinans. As estimated critical velocities exceed typical flow magnitudes observed in field sites, removal of established seedlings likely occurs following erosion of sediments from the seedling base. 

Mean flow and turbulence measurements collected in a shallow Halodule wrightii shoal grass fringe highlighted significant heterogeneity in hydrodynamic effects over relatively small spatial scales. Experiments were conducted within the vegetation canopy (~4 cm above bottom) for relatively sparse (40% cover) and dense (70% cover) vegetation, with reference measurements collected near the bed above bare sediment. Significant benthic velocity shear was observed at all sample locations, with canopy shear layers that penetrated nearly to the bed at both vegetated sites. Turbulent shear production (P) was balanced by turbulent kinetic energy dissipation (ϵ) at all sample locations (P/ϵ≈1), suggesting that stem-generated turbulence played a minor role in the overall turbulence budget. While the more sparsely vegetated sample site was associated with enhanced channel-to-shore velocity attenuation (71.4 ± 1.0%) relative to flows above bare sediment (51.7 ± 2.2%), unexpectedly strong cross-shore currents were observed nearshore in the dense canopy (VNS), with magnitudes that were nearly twice as large as those measured in the main channel (VCH; VNS/VCH¯ = 1.81 ± 0.08). These results highlight the importance of flow steering and acceleration for within- and across-canopy transport, especially at the scale of individual vegetation patches, with important implications for nutrient and sediment fluxes. Importantly, this work represents one of the first hydrodynamic studies of shoal grass fringes in shallow coastal estuaries, as well as one of the only reports of turbulent mixing within H. wrightii canopies. 

Hydrodynamic experiments were conducted on reference and restored oyster reefs in Mosquito Lagoon, Florida (USA) between June and November 2018. Measurements were collected on intact, degraded, and restored (restoration age: 6month, 2years, 4years) oyster reefs (Crassostrea virginica) to investigate differences in flow and turbulence characteristics related to restoration age. The dataset presented herein includes hydrodynamic observations (timeseries) from experiments conducted on five different oyster reefs (Reference, R-2017, R-2016, R-2014, Degraded), with measurements that include: (1) forcing characteristics (wave heights, water depths, wind speeds, channel velocities), (2) reef characteristics (oyster densities, solid volume fractions), and (3) near-bed flow and turbulence observations (flow speeds, turbulent energy, turbulent kinetic energy dissipation, shear production) from within and above the oyster canopy on sample reefs. Data are presented as timeseries (column vectors) in nine .txt files, with one file for each experiment.