An asymmetry in wave scaling drives outsized quantities of coastal wetland erosion

Wetland shorelines around the world are susceptible to wave erosion. Previous work has suggested that the lateral erosion rate of their cliff-like edges can be predicted as a function of intercepting waves, and yet numerous field studies have shown that other factors, for example, tidal currents or mass wasting of differing soil types, induce a wide range of variability. Our objective was to isolate the unique effects of wave heights, wavelengths, and water depths on lateral erosion rates and then synthesize a mechanistic understanding that can be applied globally. We found a potentially universal relationship, where the lateral erosion rates increase exponentially as waves increase in height but decrease exponentially as waves become longer in length. These findings suggest that wetlands and other sheltered coastlines likely experience outsized quantities of erosion, as compared to oceanic-facing coastlines.

Hydro-morphodynamics triggered by extreme riverine floods in a mega fluvial-tidal delta

Maintaining accretion and progradation in a mega delta is crucial to its geomorphic stability and ecology. Extreme riverine floods can disturb hydro-sediment dynamics with great damage to the deltaic landscape, as for instance deltaic erosion. Nowadays, most mega deltas suffer from sediment starvation. Understanding the impact of extreme floods is a priority to determine the long-term fate of deltaic systems. Herein, we used the Delft 3D model and field data to study the hydraulics and morphodynamics of the 2016 extreme riverine floods in the South Passage (SP) of the Yangtze Delta. Results reveal that extreme floods can increase water levels, velocities, and bed shear stresses in an inner estuarine channel and mouth bar, while the flood has a weak effect in offshore areas. High-energy floods trigger strong tidal asymmetry and Euler residual currents, which intensifies downstream suspended sediment transport and bottom riverbed erosion. In comparison with those during extreme floods in 2016, net erosion after floods passed away was generated with seaward weakened magnitudes, the corresponding mean bathymetric erosion thickness was 19.97 cm, 12.71 cm and 4.62 cm in inner estuarine channel, mouth bar and offshore area, respectively. Even though the seaward deposition patches were due to lower scouring effect and converged sediment. Hydrodynamic increments in deeper channels were more significant, while shoals and deeper areas were strongly eroded with the lowest erosion between -5 m to -6 m isobath. These results further clarified the bathymetric patterns with highlights of extreme riverine floods that can amplify the sediment-insufficient risks in such mega fluvial-tidal delta.

Bedrock erosion in subglacial channels

The Labyrinth in the McMurdo Dry Valleys of Antarctica is characterized by large bedrock channels emerging from beneath the margin of Wright Upper Glacier. To study the morphodynamics of large subglacial channels cut into bedrock, we develop herein a numerical model based on the classical theory of subglacial channels and recent results on bedrock abrasion by saltating bed load. Model results show that bedrock abrasion in subglacial channels with pressurized flow reaches a maximum at an intermediate distance up-ice from the glacier snout for a wide range of sediment grain sizes and sediment loads. Close to the snout, the velocity is too low and the sediment particles cannot be mobilized. Far from the snout, the flow accelerates and sediment is transported in suspension, thus limiting particle impacts at the channel bottom and reducing abrasion. This non-monotonic relationship between subglacial flow and bedrock abrasion produces concave up bottom profiles in subglacial channels and potential cross-section constrictions after channel confluences. Both landforms are present in the bedrock channels of the Labyrinth. We therefore conclude that these geomorphic features are a possible signature of bedrock abrasion, rather than glacial scour, and reflect the complex interplay between transport rate, sediment load, and transport capacity in subglacial channels.

Efficient tidal channel networks alleviate the drought-induced die-off of salt marshes: Implications for coastal restoration and management

Massive die-off in salt marshes is one of the most common examples of widespread degradation in marine and coastal ecosystems. In salt marshes, tidal channel networks facilitate the exchange of water, nutrients, sediments and biota with the open marine environments. However, quantitative analyses of the role of channel networks in alleviating vegetation die-off in salt marshes are scarce. Here we quantified the spatial-temporal development of marsh vegetation die-off in the northern Liaodong Bay by analyzing aerial images before, during, and after a drought (from 2014 to 2018). We found that Suaeda salsa marshes have recently experienced large-scale die-off. The extent of vegetation die-off increases with increasing distance from the channel network. Moreover, our results suggested that efficient tidal channel networks (high drainage density, low mean unchanneled path length) can mitigate die-off at the watershed scale. We presented possible abiotic & biotic processes in channel networks that explain this spatial dynamic. Our study highlights the importance of efficient tidal channel networks in mitigating die-off and enhancing the resistance of marshes to droughts, and call for incorporating theses dynamics in coastal restoration and management.

Consumer control and abiotic stresses constrain coastal saltmarsh restoration

Die-off of coastal wetlands has been reported worldwide. Planting habitat-forming species is an important strategy to reverse the decline of coastal wetlands. However, how abiotic environmental stresses and consumers affect the establishment of the planted vegetation species is unclear. We reported a large-scale restoration project in the Liaohe estuary, China, where native pioneer plant Suaeda salsa was planted. We evaluated the growth performance of the planted S. salsa, and identified the constraints on the establishment of planted S. salsa. Results showed that the growth performance (density, coverage and survival rate) of planted S. salsa was better in the low restored marsh than that in the high restored marsh. The death of planted S. salsa was primarily driven by crab herbivory, followed by abiotic stresses (low soil moisture and high salinity) in the high restored marsh, whereas plant death was only driven by crab herbivory in the low restored marsh. Herbivory strength in the high marsh was significantly higher than that in the low marsh. Our findings challenge the bottom-up paradigm used as the foundation for coastal restoration, and highlight the overlooked role of consumers. Therefore, protection measures against consumer pressure, especially in physically harsh conditions, should be considered to enhance the success of coastal wetland restoration.

Improving Predictions of Salt Marsh Evolution Through Better Integration of Data and Models

Salt marshes are recognized as valuable resources that are threatened by climate change and human activities. Better management and planning for these ecosystems will depend on understanding which marshes are most vulnerable, what is driving their change, and what their future trajectory is likely to be. Both observations and models have provided inconsistent answers to these questions, likely in part because of comparisons among sites and/or models that differ significantly in their characteristics and processes. Some of these differences almost certainly arise from processes that are not fully accounted for in marsh morphodynamic models. Here, we review distinguishing properties of marshes, important processes missing from many morphodynamic models, and key measurements missing from many observational studies. We then suggest some comparisons between models and observations that will provide critical tests and insights to improve our ability to forecast future change in these coastal landscapes.

Climate change leads to a doubling of turbidity in a rapidly expanding Tibetan lake

Recent climate change is causing most lakes on the Tibetan Plateau to grow at an unprecedented rate. Changes in the physical properties and water storage of the lakes are now relatively well documented. Yet the impacts on their water quality remain poorly understood. Turbidity is a well-established optical water-quality indicator related to suspended particulate matter concentration which can affect vertical light attenuation and ecosystem functioning. Here, we use remotely sensed data to assess the seasonal and long-term variations in turbidity in Siling Lake, one of the fastest growing lakes on the Tibetan Plateau, and to identify potential driving mechanisms of this change. The lake experiences two distinct peaks of turbidity during the year: one in August (warm season) caused by the seasonal influx of sediments from the Zagya Zangbo River, and one in December (cold season) caused by the wind-driven resuspension of sediments along the lakes' shorelines. The analysis further revealed a persistent increasing trend that doubled the average lake turbidity between 2000 and 2017. Evidence suggests this rise in turbidity results from a climate-driven increase in sediment supply from the Zagya Zangbo River, and from sediment resuspension associated with the erosion of shorelines recently submerged during the rapid expansion of the lake (paleoshorelines). Our results highlight the vulnerability of the Tibetan Lakes' water quality to climate change.

Sea-level rise and storm surges structure coastal forests into persistence and regeneration niches

The retreat of coastal forests as sea level rises is well documented; however, the mechanisms which control this retreat vary with the physical and biological setting of the interface between tidal marsh and forest. Tidal flooding and saltwater intrusion as well as flooding and wind associated with storms can kill trees. Even if these processes do not kill stands, they may halt regeneration because seedlings are more sensitive to stress. We present a case study of a coastal pine forest on the Delmarva Peninsula, United States. This forest contains a persistent but nonregenerating zone of mature trees, the size of which is related to the sea level rise experienced since forest establishment. The transgression of coastal forest and shrub or marsh ecosystems is an ecological ratchet: sea-level rise pushes the regeneration boundary further into the forest while extreme events move the persistence boundary up to the regeneration boundary.

Thermal balloon ablation versus transcervical endometrial resection: evaluation of postoperative pelvic pain in women treated for dysfunctional uterine bleeding

PURPOSE OF THE STUDY

To evaluate postoperative pain after mini-invasive surgical treatment for dysfunctional uterine bleeding (DUB) with transcervical endometrial resection or thermal ablation balloon.

MATERIALS AND METHODS

A longitudinal observational study, analyzing 47 women affected by DUB who underwent endometrial ablation was conducted. The authors collected evaluation of pelvic pain at one and four hours after intervention and the individual necessity of analgesics. After 30 days, all patients underwent a gynecological visit to evaluate postoperative outcome.

RESULTS

Pelvic pain was higher one and four hours after procedure in thermal balloon ablation group, and patients in the same group required more analgesic rescue dose. There were no complications such as uterine perforation, heavy blood loss or thermal injuries with both the procedures.

CONCLUSION

Thermal balloon ablation appears a more painful procedure than endometrial resection, both in the immediate postsurgical time and 30 days after surgery. Ad hoc anaesthesiologic and analgesic protocol should be adopted to ensure quick recovery and good acceptance of the procedure.

Pregnancy outcome after laparoscopic myomectomy

PURPOSE OF INVESTIGATION

Main purpose of this study was to analyze the reproductive and obstetrical outcome as delivery mode and incidence of major complications (uterine bleeding and uterine rupture) after laparoscopic myomectomy.

MATERIALS AND METHODS

The authors conducted an observational study in patients who underwent laparoscopic myomectomy. Inclusion criteria were: surgery performed for single and or multiple myomas sized between five and 15 cm and pregnancy desire. Exclusion criteria were: surgery for pedunculated myomas and male or tubal infertility. Collected data on pregnancy desire, success in obtaining pregnancy surgical interval time before pregnancy, performing assisted reproductive medicine, gestational weeks, mode of delivery, indicating a possible cesarean section, and complications. On collected data the authors calculated pregnancy and abortion rates.

RESULTS

Among patients aged between 19 and 42 years who answered a telephonic questionnaire, the authors selected 185 patients with pregnancy willing. A total number of 426 myomas were removed; 115 (62.2%) patients reported 151 pregnancies, nine in a total of 17 patients achieved it with reproductive assistance, 38 pregnancy ended in abortion, and two had an ectopic implantation. The authors finally reported 111 successful pregnancy, with seven preterm deliveries (6.3%). Mode of delivery had been cesarean section in 69 cases (63.4%) and vaginal delivery in 42 cases (36.6%), with a respective mean interval time between surgery and delivery of 24.6 +/- 20.0 months and 19.2 +/- 13.3 months.

CONCLUSION

Laparoscopic myomectomy proved to be an effective procedure feasible for women who wish to become pregnant with a subsequent good reproductive outcomes, both in terms of pregnancy and abortion rates that were comparable with the literature. If laparoscopic suturing of the fovea myometralis is adequate, there are no contraindications for vaginal delivery, regardless of the patient's age, the number, size, and location of the myomas removed.

Laparoscopic hysterectomy: really so risky to a vaginal cuff dehiscence?

PURPOSE OF INVESTIGATION

The authors report their experience with vaginal vault suturing procedure in patients that underwent total laparoscopic hysterectomy (TLH) for benign diseases. Vaginal vault colpotomy and closure were only laparoscopically carried out.

MATERIALS AND METHODS

Longitudinal retrospective study was conducted in 550 patients, affected by gynaecological benign pathologies, that underwent TLH were enrolled. Information about age, body mass index, parity, corticosteroid therapy, previous pelvic surgery, smoking, diabetes, menopausal status, and procedure characteristics (operating time, blood loss, uterus weight, postoperative recovery time, and adverse outcomes) were collected. Postoperative complications and adverse outcomes were recorded.

RESULTS

Only one case (0.2%,) of vaginal cuff dehiscence (VCD) occurred four weeks after surgery, which was quickly laparoscopically repaired with interrupted intracorporeal knots. The trigger event was sexual intercourse in a patient affected by systemic lupus erythematosus (SLE). No cases of VCD presented in patients with other considered comorbidities.

CONCLUSION

A careful technique could further decrease the incidence of postoperative vaginal cuff dehiscence, regardless of laparoscopic or vaginal suture approach.

Critical bifurcation of shallow microtidal landforms in tidal flats and salt marshes

Shallow tidal basins are characterized by extensive tidal flats and salt marshes that lie within specific ranges of elevation, whereas intermediate elevations are less frequent in intertidal landscapes. Here we show that this bimodal distribution of elevations stems from the characteristics of wave-induced sediment resuspension and, in particular, from the reduction of maximum wave height caused by dissipative processes in shallow waters. The conceptual model presented herein is applied to the Venice Lagoon, Italy, and demonstrates that areas at intermediate elevations are inherently unstable and tend to become either tidal flats or salt marshes.