Complete Genome Sequence of Methanobacterium electrotrophus Strain YSL, Isolated from Coastal Riverine Sediments

Methanobacterium electrotrophus strain YSL was isolated from enriched microbial aggregates from a coastal riverine sediment sample from Shandong Province, China. The genome of YSL was sequenced with the PacBio Sequel platform and contained three plasmids in addition to the chromosome. A total of 2,521 protein-coding genes and 58 RNA genes were predicted.

Median bed-material sediment particle size across rivers in the contiguous U.S.

Bed-material sediment particle size data, particularly for the median sediment particle size (D50), are critical for understanding and modeling riverine sediment transport. However, sediment particle size observations are primarily available at individual sites. Large-scale modeling and assessment of riverine sediment transport are limited by the lack of continuous regional maps of bed-material sediment particle size. We hence present a map of D50 over the contiguous U.S. in a vector format that corresponds to millions of river segments (i.e., flowlines) in the National Hydrography Dataset Plus (NHDplus) dataset. We develop the map in four steps: 1) collect and process the observed D50 data from 2577 U.S. Geological Survey stations or U.S. Army Corps of Engineers sampling locations; 2) collocate these data with the NHDplus flowlines based on their geographic locations, resulting in 1691 flowlines with collocated D50 values; 3) develop a predictive model using the eXtreme Gradient Boosting (XGBoost) machine learning method based on the observed D50 data and the corresponding climate, hydrology, geology and other attributes retrieved from the NHDplus dataset; 4) estimate the D50 values for flowlines without observations using the XGBoost predictive model. We expect this map to be useful for various purposes such as research in large-scale river sediment transport using model- and data-driven approaches, teaching of environmental and earth system sciences, planning and managing floodplain zones, etc. The map is available at http://doi.org/10.5281/zenodo.4921987 (Li et al., 2021).

Effect of decreasing sediment supply and sea level rise on the long-term morphodynamics of a large estuary

<p>Globally the riverine sediment supply to estuaries is decreasing and the mean sea level is rising, while the effects of these changes on the long-term estuarine morphodynamics have not been fully investigated. An idealized numerical model was used to explore the long-term morphodynamics of a large estuary subject to these changes. In the model, a funnel-shaped channel with fixed banks, constant riverine water and sediment fluxes, a single grain size and a semi-diurnal tide were used. A range of values of changes in the sediment supply (50-90% reduction) and sea level (1-5~mm/yr increase) were considered. Starting from an equilibrium state for an initial sediment supply, the estuary shifts to a new equilibrium for the considered changes on a timescale of millennia. Half of the bed level change occurs within several hundreds of years. A larger decrease in the sediment supply leads to a stronger bed erosion, while the corresponding adjustment time has minor changes in its range for the considered settings. When combined with sea level rise, the erosion is weakened and the adjustment time is shortened. The equilibrium state under sea level rise is characterized by a bed level keeping pace with the sea level and a significant amount of sediment being trapped in the estuary. Additional numerical experiments that use more realistic geometry and forcing of the Yangtze Estuary show that overall erosion of the estuary is expected for centuries.</p>

Potential Morphologic Responses of Tropical River Deltas in Colombia to Future Sediment Supply Scenarios

<p>Riverine sediment yield changes by human-induced catchment alterations can have important implications for river delta morphology. Here, we assess the potential response of 99 tropical deltas along the Caribbean and Pacific coasts of Colombia to projected human land use intensifications by deforestation and river damming. We assess delta morphology through the balance of wave, tidal, and (modern and future) river sediment transport processes at their mouths. We find that most Colombian deltas along the Caribbean coast are wave-dominated, except for large catchments with high riverine sediment load, which are river-dominated. Most deltas are wave-river dominated along the Pacific coast, with few examples of river-tide and wave-tide dominance. We predict Colombian deltas to become more wave and tide-dominated under river damming scenarios. In contrast, deforestation scenarios suggested virtually no future morphological changes.</p>