To quantify wave attenuation by (introduced) Spartina alterniflora vegetation at an exposed macrotidal coast in the Yangtze Estuary, China, wave parameters and water depth were measured during 13 consecutive tides at nine locations ranging from 10 m seaward to 50 m landward of the low marsh edge. During this period, the incident wave height ranged from <0.1 to 1.5 m, the maximum of which is much higher than observed in other marsh areas around the world. Our measurements and calculations showed that the wave attenuation rate per unit distance was 1 to 2 magnitudes higher over the marsh than over an adjacent mudflat. Although the elevation gradient of the marsh margin was significantly higher than that of the adjacent mudflat, more than 80% of wave attenuation was ascribed to the presence of vegetation, suggesting that shoaling effects were of minor importance. On average, waves reaching the marsh were eliminated over a distance of ∼80 m, although a marsh distance of ≥100 m was needed before the maximum height waves were fully attenuated during high tides. These attenuation distances were longer than those previously found in American salt marshes, mainly due to the macrotidal and exposed conditions at the present site. The ratio of water depth to plant height showed an inverse correlation with wave attenuation rate, indicating that plant height is a crucial factor determining the efficiency of wave attenuation. Consequently, the tall shoots of the introduced S. alterniflora makes this species much more efficient at attenuating waves than the shorter, native pioneer species in the Yangtze Estuary, and should therefore be considered as a factor in coastal management during the present era of sea-level rise and global change. We also found that wave attenuation across the salt marsh can be predicted using published models when a suitable coefficient is incorporated to account for drag, which varies in place and time due to differences in plant characteristics and abiotic conditions (i.e., bed gradient, initial water depth, and wave action).

Accelerating sea-level rise and decreasing riverine sediment supply are widely considered to lead to global losses of deltaic marshes and their valuable ecosystem services. However, little is known about the degree to which the related erosion of the seaward delta front can provide sediments to sustain salt marshes. Here, we present data from the mesomacrotidal Yangtze Delta demonstrating that marshes have continued to accrete vertically and laterally, despite rapid relative sea-level rise ($10 mm yr −1) and a > 70% decrease in the Yangtze River sediment supply. Marsh progradation has decelerated at a lower rate than fluvial sediment reduction, suggesting an additional source of sediment. We find that under favorable conditions (e.g., a mesomacrotidal range, strong tidal flow, flood dominance, sedimentary settling lag/scour lag effects, and increasing high-tide level), delta-front erosion can actually supply sediment to marshes, thereby maintaining marsh accretion rates in balance with relative sea-level rise. Comparison of global deltas illustrates that the ability of sediment remobilization to sustain marshes depends on coastal processes and varies by more than an order of magnitude among the world's major deltas. Salt marshes are among the world's most valuable ecosystems (Costanza et al. 1997). They sequester carbon, protect shorelines from storm impacts, transform nutrients, contribute to fisheries production, and maintain biodiversity (Barbier et al. 2011; Kirwan and Megonigal 2013; Temmerman et al. 2013; Möller et al. 2014). Unfortunately, many salt marshes have disappeared due to reclamation and waste disposal during the past century (Gedan et al. 2009; Ma et al. 2014). Deltaic marshes are one of the most dynamic landscapes on Earth's surface (Wagner et al. 2017) and are threatened by accelerating sea-level rise and decreases in fluvial sediment supply. Decreasing fluvial sediment supply reduces the ability of salt marshes to accumulate sediments and to build up their soil elevation in balance with the rising sea level (Kirwan et al. 2010; Weston 2014). Although the morphology and evolution of deltas are influenced by various factors (Paola et al. 2011), such as riverine water and sediment discharges (Besset et al. 2019), sediment properties (Caldwell and Edmonds 2014), flow patterns (Shaw et al. 2016), vegetation height and density (Nardin et al. 2016), marine hydrodynamics (waves, tides, and longshore currents) (Caldwell and Edmonds 2014; Besset et al. 2017), land subsidence and sea-level changes (Jerolmack 2009; Syvitski et al. 2009), changes in the fluvial sediment supply and relative sea level are usually the most important for the long-term morphological evolution of deltaic marshes. The rate of global mean sea-level rise increased from 1.

No abstract

To delineate temporal and spatial variations in suspended sediment concentration (SSC) in the Yangtze (Changjiang) Estuary and adjacent coastal waters, surfacewater samples were taken twice daily from 10 stations over periods ranging from 2 to 12 years (total number of samples >28,000). Synoptic measurements in 2009 showed an increase in surface SSC from 0.058 g/l in the upper sections of the estuary to ∼0.6 g/l at the Yangtze River turbidity maximum at the river mouth, decreasing seaward to 0.057 g/l. Annual periodicities reflect variations in the Yangtze discharge, which affect the horizontal distribution and transport of SSC, and seasonal winds, which result in vertical resuspension and mixing. Over the past 10-20 years, annual surface SSC in the lower Yangtze River and the upper estuary has decreased by 55%, due mainly to dam construction in the upper and middle reaches of the river. The 20-30% decrease in mean surface SSC in the lower estuary and adjacent coastal waters over the same period presumably reflects sediment resuspension, in part due to erosion of the subaqueous Yangtze Delta. SSCs in the estuary and adjacent coastal waters are expected to continue to decline as new dams are constructed in the Yangtze basin and as erosion of the subaqueous delta slows in coming decades.

Cartilage tissues have limited capacity for repair after damage and then cause osteoarthritis, so finding alternative treatment is ongoing. Mesenchymal stem cells (MSCs) have become a promising therapy for cartilage damage and diseases due to the advantages of easy separation, high proliferative potentiality, and genetic stability. Synovium-derived MSCs (SMSCs) have been recognized as an ideal source for cartilage repair. In our previous study, we found that Sox4 promoted proliferation and chondrogenesis of SMSCs through upregulation of long noncoding RNA (lncRNA) DANCR. However, the exact molecular mechanism by which DANCR promotes proliferation and chondrogenesis of SMSCs remains unknown. In the present study, we investigated the effect of lncRNA DANCR on the proliferation and chondrogenesis of SMSCs. We found that overexpression of DANCR could promote proliferation and chondrogenesis of SMSCs, while knockdown of DANCR had the opposite effect. Moreover, our data demonstrated that DANCR directly interacted with myc, Smad3, and STAT3 mRNA to regulate their stability. Finally, we found that the promotion of SMSC proliferation induced by DANCR depended on myc. Also, DANCR activated chondrogenesis of SMSCs via upregulation of Smad3 and STAT3 expression. Our growing knowledge of the role of DANCR is pointing toward its potential use as a novel therapeutic approach for cartilage damage and diseases.

No abstract

No abstract

No abstract