Tidal marshes play an important role in climate change mitigation through natural coastal protection. The effectiveness of the natural coastal defense by tidal marshes is closely related to their ...channel network which is in turn greatly influenced by their vegetation cover and shape. Previous research suggests a dual effect of vegetation on marsh topography; stabilizing sediment on the one hand versus promoting erosion and channel incision on the other hand. This study links these effects to different vegetation species, Salicornia procumbens, Spartina anglica, and Puccinellia maritima (further referred to as Salicornia, Spartina, and Puccinellia), by means of a coupled bio‐hydromorphodynamic modeling study. Single species, species‐assemblages, and species shifts were studied, incorporating both species‐specific physical plant properties and spatiotemporal growth strategies. The results indicate the influence of vegetation on the marsh topography to be highly species‐dependent, but also of a very complex nature. Both the presence of Spartina and Puccinellia resulted in significant channel development, whereas Salicornia did not induce topographic change. The combination of several species promoted or reduced channel development depending on the included species. Species‐shifts linked with climatic changes resulted in increased erosion of the existing channel network potentially reducing the protective capacity of the marsh.
Plain Language Summary
Located on the boundary between land and sea, tidal marshes serve as natural protection of the coast. These marshes typically consist of vegetation patches that are intersected by tidal channels. The latter mainly determine the degree of protective capacity, as they induce wave damping and facilitate sediment distribution across the marsh. Where prior research indicates that vegetation plays an important role in the development of tidal channels, our study relates this process to vegetation species. By means of a modeling study, we showed that the influence of vegetation on channel development varies greatly among different species and combinations of species. Here the species' biomass directly relates to channel size and density, while seasonal variation in growth is especially important in case of multiple species. Our results also imply that a shift in dominant species, a likely result of climate change, can have a significant impact on the existing channel network. Such shifts could eventually lead to reduced protection of our coasts.
Key Points
Rate and properties of intertidal channel emergence depend on marsh species, with significant interspecies variation
Channel initiation by species‐assemblages follows the most dominant species, with reduced dimensions in case of species competing for space
ABSTRACT
The Tunka Advanced Instrument for Gamma- and cosmic-ray Astronomy (TAIGA) is a multicomponent experiment for the measurement of TeV to PeV gamma- and cosmic rays. Our goal is to establish a ...novel hybrid direct air shower technique, sufficient to access the energy domain of the long-sought Pevatrons. The hybrid air Cherenkov light detection technique combines the strengths of the HiSCORE shower front sampling array, and two ∼4 m class, ∼9.6° field of view Imaging Air Cherenkov Telescopes (IACTs). The HiSCORE array provides good angular and shower core position resolution, while the IACTs provide the image shape and orientation for gamma-hadron separation. In future, an additional muon detector will be used for hadron tagging at ≥100 TeV energies. Here, only data from the first IACT of the TAIGA experiment are used. A randomforest algorithm was trained using Monte Carlo (MC) simulations and real data, and applied to $85\, \mathrm{h}$ of selected observational data tracking the Crab Nebula at a mean zenith angle of 33.5°, resulting in a threshold energy of 6 TeV for this data set. The analysis was performed using the gammapy package. A total of 163.5 excess events were detected, with a statistical significance of 8.5 σ. The observed spectrum of the Crab Nebula is best fit with a power law above 6 TeV with a flux normalization of (3.20 ± 0.42) · 10−10 TeV−1 cm−2 s−1at a reference energy of $13\, \mathrm{TeV}$ and a spectral index of −2.74 ± 0.16.
Mangrove forests are valuable ecosystems, but their extent and diversity are increasingly threatened by sea-level rise and anthropogenic pressures. Here we develop a bio-morphodynamic model that ...captures the interaction between multiple mangrove species and hydro-sedimentary processes across a dynamic coastal profile. Numerical experiments are conducted to elucidate the response of mangrove assemblages under a range of sea-level rise and sediment supply conditions, both in the absence and presence of anthropogenic barriers impeding inland migration. We find that mangrove coverage can increase despite sea-level rise if sediment supply is sufficient and landward accommodation space is available. Tidal barriers are mainly detrimental to mangrove coverage and result in species loss. Importantly, we show that bio-morphodynamic feedbacks can cause spatio-temporal variations in sediment delivery across the forest, leading to upper-forest sediment starvation and reduced deposition despite extended inundation. As such, bio-morphodynamic feedbacks can decouple accretion rates from inundation time, altering mangrove habitat conditions and causing mangrove diversity loss even when total forest coverage remains constant or is increasing. A further examination of bio-morphodynamic feedback strength reveals that vegetation-induced flow resistance linked to mangrove root density is a major factor steering the inundation-accretion decoupling and as such species distribution. Our findings have important implications for ecosystem vulnerability assessments, which should account for the interactions between bio-morphodynamics and mangrove diversity when evaluating the impacts of sea-level rise on species assemblages.
Worldwide, many tidal basins associated with barrier coasts have infilled over the past millennia due to the combination of sediment supply, wave‐tidal sediment transport, and eco‐engineering effects ...of vegetation. However, the biogeomorphological interactions between saltmarsh and the morphodynamics of an entire coastal barrier system are poorly understood, especially under sea level rise (SLR). Here, we study the evolution of a barrier coast for combinations of mud availability, presence of vegetation, and SLR. We developed a novel biogeomorphological model of an idealized barrier coast enclosing a tidal basin with sandy‐clayey sediments that was subjected to tides and waves for a century. The morphodynamic Delft3D model was coupled to a vegetation code which accounts for the dynamics of marsh‐type vegetation. Initially, vegetation contributed to reducing the tidal prism while sediment was imported. However, with SLR this trend was reversed and the tidal basins started to export sediment for vegetated runs after about 50–60 years while the unvegetated scenarios continued to infill in pace with the SLR. The sediment export was caused by cascading biomorphodynamic feedback effects triggered by vegetation which modified channel and shoal dynamics. Even under higher mud supply, the SLR resulted in vegetation collapse. The hypsometries, similar to natural systems, showed that vegetated systems converge to an alternative stable state condition. We conclude that the long‐term resilience of the tidal basin associated with sediment infilling under SLR can be reduced by cascading large‐scale effects of vegetation on the morphodynamics of barrier coasts.
Plain Language Summary
Tidal basins occur along coasts worldwide and are important environments for nature and human activities. Tidal basins develop under a balance of tides, waves, sea level variations, the availability of sand and mud, and the interactions with vegetation. We know that tidal basins are under pressure due to human interventions and climate change. However, little is known about the long‐term development, in the range of decades–century, of these coastal areas as a whole. Our new comprehensive model produced simulations with the combined effects of sea level rise (SLR), sediment supply, and vegetation in a schematized tidal basin under the effects of both tides and waves over a century. We found that vegetation changes the long‐term morphological development and sediment balance of tidal basins. This allows for a rapid increase of tidal currents and erosion that pose stress for vegetation specially under SLR. This caused a runaway effect of drowning of the tidal basin. The previously vegetated basin underwent a major reconfiguration towards a drowned landscape. These findings show that projects to raise coastal environments by promoting vegetation growth could backfire under fast SLR as vegetation may reduce the tidal basin resilience against SLR.
Key Points
Vegetation modifies the local and basin‐scale morphodynamics and alters the equilibrium state and the basin response to sea level rise (SLR)
Vegetation limits basin infilling despite sediment supply, reducing resilience to SLR and accelerating drowning compared to unvegetated basins
A multidecadal lag between initial basin drowning and vegetation response may exist, allowing for delayed but rapid saltmarsh loss
To describe the clinical workup and laparoscopic treatment of ovarian remnant syndrome in dogs and cats.
After confirming the diagnosis with some or all of the following tests - vaginoscopy with ...cytology, hormonal tests, and ultrasound - laparoscopic removal of the ovarian remnants was performed. A three-portal technique was used in the four dogs and a two-portal technique in the two cats.
All patients recovered well and were discharged the same day. No post-operative complications occurred in any patient.
Overall, in the hands of an experienced laparoscopic surgeon, laparoscopic removal of ovarian remnants appears to be a safe procedure in dogs and cats. In addition, laparoscopy offers the advantages of excellent visualization and a reduced morbidity for the patient. Careful case selection and complete pre-operative workup to rule out co-morbidities or underlying neoplasia are important. As with any laparoscopy the surgeon should always be prepared to convert to an open laparotomy if necessary.
Mud plays a pivotal role in estuarine ecology and morphology. However, field data on the lateral and vertical depositional record of mud are rare. Furthermore, numerical morphodynamic models often ...ignore mud due to long computational times and simplifications of mixed depositional processes. This study aims to understand the spatial distribution, formative conditions and preservation of mud deposits in the intertidal zone of bars in high‐energy sand‐dominated estuaries, and to elucidate the effects of mud on morphology, ecology and stratigraphic architecture. To meet these objectives, field data (historic bathymetry, bio‐morphological maps and sediment cores of the shoal of Walsoorden, Western Scheldt estuary, the Netherlands) were combined with complementary hydro‐morphodynamic numerical modelling (Delft3D). Based on the field observations, two types of mud deposits were distinguished: (1) mudflat deposits, which are thick (>10 cm) mud beds at the surface associated with high elevations and low accumulation rates; and (2) mud drapes, which are thin (millimetre to centimetre) buried laminae that form and preserve at a wide range of elevations and energy conditions. Model results show that deposition on mudflats occurs just after high‐tide slack water in areas shielded from high flood velocities, suggesting that mud accumulation is mostly controlled by elevation, flow velocity and flow direction. Mud accumulation increases shoal elevation, sometimes to supratidal levels. This reduces flow over the shoal, which in turn reduces chute channel formation, stabilises bar morphology and decreases local tidal prism. These effects further promote mud deposition and vegetation settling. Although observations show that mud cover at the surface is relatively high (20%–40% of the intertidal area), mud constitutes only a small percentage of the total estuary volume (ca 5%) revealing that only a small fraction is preserved in the stratigraphy. Due to this mismatch between surface and subsurface expression of mud, interpretations of estuarine stratigraphy risk underestimating the influence of mud at the surface on morphodynamics and habitats.
We investigated the formative conditions, preservation and spatial distribution of mud deposits in the intertidal zone of a tidal bar in a high‐energy sand‐dominated estuary by combining field observations and hydro‐morphodynamic modelling. Mud is dominantly deposited at high elevations just after high water slack shielded from high flood velocities. Because mud deposits on top of the sand, the surface cover is relatively high (20‐40% of intertidal area), but it is more easily reworked and difficult to preserve in stratigraphy (5% of volume). Due to this mismatch between surface and subsurface, interpretations of estuary stratigraphy risk underestimating the importance of mud at the surface for morphodynamics and habitats.
Mud accretion and establishment of biostabilizers, such as microphytobenthos and saltmarsh vegetation, govern the development of estuarine morphology. Mud facilitates saltmarsh survival and ...microphytobenthos growth, which in turn promotes sedimentation and reduces mud erosion. Consequently, an increasing extent and thickness of mud cover might lead to a stabilization of large‐scale estuarine morphology. To disentangle the interactions between saltmarsh establishment, microphytobenthos colonization, and mud layer formation, we use our novel eco‐morphodynamic model applied to the Western Scheldt estuary. Our model shows that presence of dynamic saltmarsh vegetation and microphytobenthos enhances predictions of mud location in the computations compared to field data. Saltmarsh establishment is partly determined by the antecedent mud content in the bed, resulting in varying emerging vegetation coverage between model experiments of a generic saltmarsh and a saltmarsh species that requires prior mud for establishment. In contrast to microphytobenthos enhancing seasonal mud accretion during their growth period, saltmarshes promote largest accretion when lower biomass and high water levels are present. Interestingly, thick long‐term mud is enhanced despite the biostabilizers seasonal growth. The combination of saltmarsh and microphytobenthos leads to expanding saltmarsh cover and mud area. Generally, mud layer thickness is governed by the ratio of hydroperiod and maximum flow velocity that is mediated by the biostabilizers. On estuary scale, the presence of intertidal vegetation leads to increased mud volumes in the intertidal. Mud layers are enhanced in extent by a mud‐dependent species and in thickness by a generic species. Thus, local biostabilization alters large‐scale morphology controlling long‐term estuarine development.
Key Points
Saltmarsh colonization is partly determined by antecedent mud content in the bed which provides a geomorphological window of opportunity
Mud layer thickness depends on the presence of biostabilizers that change the ratio between hydroperiod and flow velocity
Considering the estuary scale, a mud‐dependent saltmarsh species mainly increases mud area and a generic saltmarsh species mud thickness
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