Particle size characterization of historic sediment deposition from a closed estuarine lagoon, Central California

Recent studies of estuarine sediment deposits have focused on grain size spectra as a tool to better understand depositional processes, in particular those associated with tidal inlet and basin dynamics. The key to accurate interpretation of lithostratigraphic sequences is establishing clear connections between morphodynamic changes and the resulting shifts in sediment texture. Here, we report on coupled analysis of shallow sediment profiles from a closed estuarine lagoon in concert with recent changes in lagoon morphology reconstructed from historic sources, with a specific emphasis on the ability of suite statistics to provide meaningful insights into changes in sediment transport agency. We found that a major reorganization in lagoon morphology, dating to the 1940s, was associated with a shift in sediment deposition patterns. The restricted inlet was associated with deposition of sediments that were finer, less negatively skewed, and less leptokurtic in distribution than sediments deposited while the lagoon had a more open structure. These shifts are associated with a change in transport process from fluvial (through-flow) to closed basin (trapping). We also found other chemostratigraphic changes accompanying this shift in sediment texture, reflecting changes in organic matter source, wetland species composition, and an increase in sediment organic content, as presumably coarse, well-ventilated floodplain sediments tend to result in mineralization rather than sequestration of organic matter. In conclusion, we found that grain size analysis, in concert with the suite statistics technique, reflected changes in coastal configuration supported by historic maps and photos, however, we also recognize that this analysis was more informative given further context through additional sedimentary analyses. These findings provide a basis for the interpretation of particle size distribution in lithostratigraphic sequences associated with bar-built estuaries, where understanding natural and anthropogenically-modified inlet dynamics may help shape conservation management where concerns exist with respect to fish passage, water quality, and sediment transport.KEYWORDS: Lagoon sedimentation, Granulometry, ICOLL, Sediment texture, Sediment sorting, Intermittently open estuarie

Evaluating Thin-Layer Sediment Placement as a Tool for Enhancing Tidal Marsh Resilience: a Coordinated Experiment Across Eight US National Estuarine Research Reserves

Thin-layer sediment placement (TLP) is a promising management tool for enhancing tidal marsh resilience to rising seas. We conducted a 3-year experiment at eight US National Estuarine Research Reserves using a standardized implementation protocol and subsequent monitoring to evaluate effects of sediment placement on vegetation in low and high marsh, and compared this to control and reference plots. Sediments added to experimental plots were sourced from nearby quarries, were sandier than ambient marsh soils, and had more crab burrowing, but proved effective, suggesting that terrestrial sources can be used for tidal marsh restoration. We found strong differences among sites but detected general trends across the eight contrasting systems. Colonization by marsh plants was generally rapid following sediment addition, such that TLP plot cover was similar to control plots. While we found that 14-cm TLP plots were initially colonized more slowly than 7-cm plots, this difference largely disappeared after three years. In the face of accelerated sea-level rise, we thus recommend adding thicker sediment layers. Despite rapid revegetation, TLP plots did not approximate vegetation characteristics of higher elevation reference plots. Thus, while managers can expect fairly fast revegetation at TLP sites, the ultimate goal of achieving reference marsh conditions may be achieved slowly if at all. Vegetation recovered rapidly in both high and low marsh; thus, TLP can serve as a climate adaptation strategy across the marsh landscape. Our study illustrates the value of conducting experiments across disparate geographies and provides restoration practitioners with guidance for conducting future TLP projects

Investigating Word Learning in Fragile X Syndrome: A Fast-Mapping Study

Fast-mapping paradigms have not been used previously to examine the process of word learning in boys with fragile X syndrome (FXS), who are likely to have intellectual impairment, language delays, and symptoms of autism. In this study, a fast-mapping task was used to investigate associative word learning in 4- to 10-year-old boys with FXS relative to younger typically developing boys and age-matched boys with autism spectrum disorders (ASD). Task performance exceeded chance levels for all groups; however, boys with FXS outperformed boys with ASD, despite having lower levels of nonverbal cognition. Memory task demands significantly impacted performance only for boys with typical development. For boys with FXS or ASD, fast-mapping uniquely accounted for small but significant variance in concurrent levels of vocabulary comprehension as did chronological age and nonverbal IQ, but not autism severity. Understanding the fast-mapping process has implications for designing interventions to support word learning and language acquisition in these populations