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Tidal dynamics of shallow estuaries and lagoons is a complex matter that has attracted the attention of a large number of researchers over the last few decades. The main purpose of the present work is to study the intricate tidal dynamics of the Tagus estuary, which states as the largest estuary of the Iberian Peninsula and one of the most importan...
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... In open coastal lagoons, tides can dominate hydrodynamics over river flows although the associated dynamics is very complex. Tidal wave propagates in a shallow medium and because of non-linear interactions, deforms and becomes asymmetrical, modifying the intervals between the flood and the ebb as well as tidal currents (Dias et al. 2013). The interaction of a tidal constituent with itself or with others fundamental constituents generates overtides (e.g., M 4 ) and fortnightly (e.g., MsF) constituents. ...
Very complex aquatic ecosystem, the mangrove forest colonizes coastal lagoons, estuaries and deltas in tropical and subtropical zones. This study investigates the impact of mangrove vegetation on tidal propagation in the Somone Coastal Lagoon, located on the Senegalese small coast. The analysis of new field data is complemented with the application of a 3D circulation model accounting for vegetation. The analysis of well-reproduced water levels and currents over the whole lagoon make it possible to spatially study the amplitudes of the main tidal harmonics, semi-diurnal (M2), diurnal (K1) and the major overtide (M4). The comparison between our baseline model accounting for vegetation and a configuration without vegetation reveals firstly that the mangrove strongly attenuates tidal propagation in the lagoon, whit a stronger impact on semi-diurnal waves than diurnal waves. Tidal currents are also strongly reduced when the mangrove is accounted for, even close to the inlet mouth, far away from vegetation areas. The mangrove also enhances tidal asymmetry and promotes ebb dominance, both in terms of duration (ebbs last from 0.5 up to 3 h more than floods) and current magnitude (ebb currents are about 50% stronger). Spring tides accentuate ebb-dominance compared to neap tides, where tidal asymmetry is weaker.
... It is a mesotidal system with semidiurnal tides and with a complex geomorphology: its main channel comprises a narrow inlet with 4 km width and depths from 25 to 30 m, linking the Atlantic Ocean to a broad inner basin of 10 km width at its maximum, and depths ranging from 0 to 12 m in the mixing region. At the upper reaches, where the large intertidal mudflats and salt marsh areas are located, the estuary's depth is lower than 1 m [41][42][43], making the overall estuarine mean depth lower than 10 m. The river flow varies markedly either seasonally and interannually, presenting a mean value of 400 m 3 s −1 . ...
Estuaries are extremely productive ecosystems, providing habitats for numerous aquatic species and crucial ecological services. The Tejo estuary, one of the largest European estuaries, has been thoroughly studied, and its important functional role as a nursery for several commercially important fish species is already established. In the present work, a trait-based approach was applied to functionally describe the fish community structure of the Tejo estuary and to enlighten potential changes in the ecosystem functioning at this level, following environmental changes expected to occur. To predict the distribution of species from the two most representative ecological guilds of the Tejo estuary, estuarine residents and marine migrants, species distribution models were built using an ensemble technique (combining forecasts of single models). The predictions obtained were more accurate for the marine migrants and the species distribution was strongly related with salinity, whereas estuarine species, were also influenced by depth, habitat type and river flow. The potential distributions of these ecological guilds showed that marine migrants will tend to use upstream areas in the estuary, where salinity is lower. Nonetheless, salinity is expected to increase as extreme weather events such as droughts tend to occur more frequently, decreasing favorable habitat availability for these species, and thus threatening the crucial role this ecosystem plays for these species.
... Portanto, é fulcral selecionar adequadamente a ferramenta numérica mais adequada para os problemas específicos que se pretendem resolver. Essa seleção deve ser feita estabelecendo um compromisso entre os dados disponíveis para calibração e validação do modelo, os objetivos das simulações e os recursos computacionais disponíveis (Iglesias et al., 2019b Existe, portanto, uma ampla gama de modelos numéricos que podem ser aplicados, como revelam alguns dos muitos estudos implementados em áreas estuarinas (Avilez-Valente e Seabra- Dias et al., 2013;Jones e Davies, 2010;Gomes et al., 2015;Horritt e Bates, 2002;Iglesias et al., 2016Iglesias et al., , 2018Mesquita et al., 2009;Monteiro et al., 2011;Peixoto e Pinho, 2013;Pinho e Vieira, 2007;Pinho et al., 2015;Robins e Davies, 2010;Sutherland et al., 2004;van Maren et al., 2015). No entanto, cada modelo numérico tem as suas próprias vantagens e limitações, e as suas soluções contêm incertezas. ...
A série Estudos Cindínicos, lançada em 2018, pretende compilar contributos diversos, provenientes tanto de autores de diferentes nacionalidades, cujas realidades estão sujeitas a vários tipos e graus de riscos, como de distintas áreas de investigação, cobrindo assim uma vasta diversidade de regiões e de temas, dentro das ciências cindínicas.
... The nonlinear effects associated with these factors transform tides and tidal currents into an asymmetric form, characterized by the periodic gap between the duration of tidal ebb and flood and the growth of higher harmonics within the system (Boon and Byrne, 1981;Speer et al., 1991). Tidal asymmetry, while serving as an important mechanism for sediment transport and erosion processes in coastal areas (Dias et al., 2013;Prandle, 2009), exerts effects on both the geological evolution of shallow estuaries and the navigability of estuarine channels (Aubrey and Speer, 1985). ...
... Understanding the tidal dynamics in the Wouri estuary is critical to gain insight into the different uses of this coastal system primarily governed by tidal flow and forcing (Olivry, 1986). Although many studies have focused on tidal distortion in different estuaries around the world (Dias et al., 2013;Toublanc et al., 2015;Yoon and Woo, 2013;Yu et al., 2020), information on African estuaries remains very patchy and poorly known (Capo et al., 2006). The case of the Wouri estuary is very evocative. ...
... This index is not a calculation of correlation in the strict sense of the term, but rather an estimate of the degree to which the model's output is error-free. A skill scores equal to 1 corresponds to a perfect prediction; excellent, when Skill> 0.65; very good, 0.5 <Skill <0.65; good, 0.20 <Skill <0.5; poor, Skill <0.2 (Allen et al., 2007;Wu et al., 2011;Dias et al., 2013). In additions to skill score, the correlation coefficient ® between the model and in observation is also used to quantify the model results. ...
Understanding tidal dynamics in shallow estuaries is of paramount importance to assess the influence of the parameters control them. In the present study, a comprehensive analysis of the tides in the Wouri estuary (Cameroon) was carried out with a high resolution two-dimensional numerical model. Non-stationary harmonic analysis (S_TIDE) and spatio-temporal variation of tidal asymmetry allowed us to quantify changes and tidal asymmetry metrics in the Wouri estuary. A relative sensitivity coefficient (RSC) was introduced to decompose the contribution of tidal amplitude variations to multiple tidal asymmetries. The result reveal an attenuation of the tidal wave as it propagates inland, with a notable reduction in tidal range. This phenomenon is also amplified by the increase in river flow. The positive values of the asymmetry factor confirm a flood dominance in the upper part of the estuary with a pronounced increase upstream. Conversely, ebb dominance with negative values in the lower part of the estuary. The two tidal combinations M2/M4 and M2/S2/MS4 are identified as the main contributors to the tidal asymmetry in the Wouri estuary. These results allowed the Wouri estuary to be qualified as tidal in its lower part and fluvial in its upper part. The evolution of the tidal amplitude and asymmetry may depend significantly on the variations of the river flow and the morphology of the estuary.
... This study case calculates the sound transmission loss (TL, henceforward) in a region around the Tagus estuary's inlet. The inlet channel of the Tagus estuary is a deep, straight, and narrow inlet located on the west coast of mainland Portugal, connecting the Tagus estuary basin to the Atlantic Ocean (see Fig. 2 complex bathymetry [46][47][48] and marked seasonal sediment transport and morphological changes [49]. ...
Underwater sound modeling is applied in several environmental studies, from assessing underwater noise induced by offshore wind farms to the influence of climate change on ocean temperature. One of the most well-known underwater acoustics models is KRAKEN, an open-source code requiring a mesh to simulate 3D environments. This paper presents OMesh2KRAKEN, a software toolkit that uses OceanMesh2D to generate unstructured meshes for KRAKEN based on realistic environmental data. Two practical study cases in the North Atlantic are presented and discussed. In addition, an idealized 3D shallow water wedge was simulated. Practically, OMesh2KRAKEN can assist in implementing underwater acoustic modeling studies from deep waters to nearshore regions where, for instance, sound propagation maps are required. Indeed, higher mesh resolutions may be required for areas with complex bathymetric features. In these cases, the new tool presents several advantages as it automatically implements different mesh resolutions in areas of interest and prepares the respective environmental files for acoustic computations.
... In open coastal lagoons, tides can dominate the hydrodynamics over river ows although the associated dynamics is very complex. Tidal wave propagates in a shallow medium and because of non-linear interactions, deforms and becomes asymmetrical, modifying the intervals between the ood and the ebb as well as tidal currents (Dias 2013). The interaction of a tidal constituent with itself or with others fundamental constituents generates overtides (e.g. ...
Very complex aquatic ecosystem, the mangrove forest colonizes coastal lagoons, estuaries and deltas in tropical and subtropical zones. This study investigates the impact of mangrove vegetation on tidal propagation in the Somone Coastal Lagoon, located on the Senegalese small coast. The analysis of new field data is complemented with the application of a 3D circulation model accounting for vegetation. The analysis of well-reproduced water levels and currents over the whole lagoon make it possible to spatially study the amplitudes of the main tidal harmonics, semi-diurnal (M 2 ), diurnal (K 1 ) and the major overtide (M 4 ). The comparison between our baseline model accounting for vegetation and a configuration without vegetation reveals firstly that the mangrove strongly attenuates tidal propagation in the lagoon, whit a stronger impact on semi-diurnal waves than diurnal waves. Tidal currents are also strongly reduced when the mangrove is accounted for, even close to the inlet mouth, far away from vegetation areas. The mangrove also enhances tidal asymmetry and promotes ebb dominance, both in terms of duration (ebbs last from 0.5 up to 3 h more than floods) and current magnitude (ebb currents are about 50% stronger). Spring tides accentuate ebb-dominance compared to neap tides, where tidal asymmetry is weaker.
... Constituent M2 is the dominant semidiurnal lunar constituent, while constituent M4 is the fourth daytime constituent. In this way, the M4 and M2 amplitude ratios (which corresponds to the amplitude ratio values -AR) can be analyzed to determine the magnitude of the tidal asymmetry generated within the estuary (Dias et al., 2013;Siegle et al., 2019). The relative phases of M2 and M4 determine the type of asymmetry (Dias et al., 2013). ...
... In this way, the M4 and M2 amplitude ratios (which corresponds to the amplitude ratio values -AR) can be analyzed to determine the magnitude of the tidal asymmetry generated within the estuary (Dias et al., 2013;Siegle et al., 2019). The relative phases of M2 and M4 determine the type of asymmetry (Dias et al., 2013). ...
... For the 2014 scenario, the main semidiurnal component amplitude, M2, remained higher than that in the other scenarios, especially in the Santos channel, where it fluctuated between 0.36 m at the inlet and 0.39 m in the upper estuary. Usually, in estuaries, a decrease in tidal propagation is expected due to energy dissipation caused by bottom friction (Dias et al., 2013;Iglesias et al., 2019). The Table 3 Average cross-section integrated instantaneous discharge for the Santos, São Vicente and Bertioga channels for the period from 10/June to 30/June. ...
We assess changes in estuarine hydrodynamics due to the deepening of navigation channels by dredging. A validated numerical hydrodynamic model (Delft3D) was used to analyze scenarios (historical bathymetry data from 1876 to 2014) and applied to assess the hydrodynamic evolution of the Santos estuarine system (SES), Brazil. During the studied period, the SES underwent significant morphological changes, mainly related to the dredging of the Santos harbor navigation channel. The unprecedented results of the hydrodynamic evolution of the SES show that the gradual process of deepening the channels by dredging resulted in modified estuarine circulation parameters such as tidal propagation and stratification of the water column, as well as the residual water and materials transport through the SES channels. Channel deepening resulted in greater saline intrusion, a decrease in the volume of water transported through the Santos channel, an increase in the influence of the tide in the system and an increase in its asymmetry over the years in the upper estuary.
... The rivers Tagus and Sado have meso-tidal estuaries, with a mean tidal amplitude of 2.4 m. Detailed characterizations are available of the geography and hydrodynamics of the Tagus (Dias et al., 2013) and Sado (Biguino et al., 2021) estuaries. Roughly 3 million people live in the region, mainly around the Tagus estuary, where the Portuguese capital, Lisbon, is located. ...
Seagrasses are declining globally, in large part due to increased anthropogenic coastal nutrient loads that enhance smothering by macroalgae, attenuate light, and are toxic when in excessive concentrations of inorganic nitrogen and phosphorus. However, as sanitation is improved many seagrass meadows have been observed to recover, with a few studies suggesting that they may even benefit from mild anthropogenic nutrient additions. Monitoring seagrass demography and health has faced difficulties in establishing the adequate variables and metrics. Such uncertainty in the methods has caused uncertainty of the significance of results presented and compromised extrapolations to other seasons, areas, or species. One solution has come from within the plant self-thinning theories. During the 1980s, an interspecific boundary line (IBL) was determined as the upper limit of the combination of plant density and above-ground biomass for any stand on Earth, setting their maximum possible efficiency in space occupation. Recently, two meta-analyses to determine specific IBLs for algae and for seagrasses have been performed. The recently updated seagrass dataset comprises 5,052 observations from 78 studies on 18 species. These IBLs opened new perspectives for monitoring: the observed distance of a stand to the respective IBL (i.e., each stand’s relative efficiency of space occupation) was demonstrated to be a valuable indicator of a population’s health. Thus, this metric can be used to determine the impact of nutrients and pollutants on algae and seagrass populations. Furthermore, because the IBLs are common to all species, they may be used to compare all species from any location worldwide. This novel approach showed that Halodule wrightii, Halodule beaudettei, Halophila baillonii, Zostera marina, and Zostera noltei meadows benefit from anthropogenic additions of nitrogen and phosphorus, as long as these additions are moderate. In fact, the healthier Z. noltei meadows in Portugal (and among the healthiest meadows worldwide) were the ones exposed to effluents from wastewater treatment plants (WWTP) and a food factory. We conclude that those effluents are providing water with enough quality and that their optimal management should coordinate the technological solutions of the WWTP with the natural potential of seagrass meadows as water purifiers and biomass producers.
... Paço de Arcos (Q) shows the highest RMSE and ∆E disagreement, with 40 cm and ∆E of 16%, respectively, which may be explained by the time lag between the bathymetry and the tidal observational data. These results are in agreement with previous studies at the Tagus estuary [39] and other similar systems [40,41]. The model's accuracy correctly predicts the spring-neap cycle. ...
During the winter of 2013, the Tagus estuary was under the influence of intense winds and extreme freshwater discharge that changed its hydrodynamics and, consequently, the salt and heat transport. Moreover, the dynamics of the estuary may change due to climate change which will increase the frequency of heat waves and increase the mean sea level. Therefore, it is of utmost importance to study the impact of the future increase in air temperature and mean sea level under extreme events, such as that in the winter of 2013, to ascertain the foreseen changes in water properties transport within the estuary and near coastal zone. Several scenarios were developed and explored, using the Delft3D model suite, considering the results of the CMIP6 report as forcing conditions. Before the event, the mixing region of the estuary presented well-mixed conditions and its marine area a slight stratification. During the event, the estuary was filled with freshwater and the mixing region migrated toward the coast, leading to lower water temperature values inside the estuary. SLR has a higher impact on the salinity and stratification patterns than the air temperature increase. The response of water temperature is directly related to the increase in air temperature. The estuary mouth and the shallow regions will be more prone to changes than the upstream region of the estuary. The projected changes are directly linked to the future CO2 emissions scenarios, being intensive with the highest emission scenario.
... Zn is dispersed within the aquatic environment may from high traffic density (tire wear particles) (Callender and Rice, 2000), and Ni is the primary source from the use of liquid and solid fuels, as well as municipal and industrial waste (Genchi et al., 2020). They were settled as sediment at the estuarine bottom, and water currents and tidal fluctuation have carried out the dispersion of heavy metals towards the estuarine mouth (Dias et al., 2013). ...
Ulhas River estuary is one of the most significant estuarine systems situated western coast of India. This estuary has been polluted by several point and nonpoint source and therefore, the multivariate statistical methods were used to determine sediments parameter concentrations, their distributions, and their relationship. In the present study, sediment samples were collected from five different stations and analyzed eight heavy metals' concentrations with seven other parameters. The multivariate statistical methods (PCA, nMDS, and ANOSIM) were used to determine sediments parameter concentrations, their distributions, and their relationship. The PCA results showed that the concentrations of N%, H%, S%, C/N, C/H, EC, and OC% were significant contributors to PC1 (36%) while the heavy metals such as Cu, Pb, Cd, Ni, Si, and Hg concentration were major contributor to PC2 (20%). Both PCs are indicated anthropogenic pollutant deposition towards the mouth of the estuary. Other results of nMDS showed a high degree of similarities within the stations such as 2, 3, and 4. Moreover, analysis of similarities (ANOSIM) results also support them at a significant level of 0.01% with a global R-value (0.6). The observed level of heavy metals contamination in the sediment samples was in the order of Cr >Pb >Cu > Ni >Zn > Hg >Si>Cd. Industrial discharges within the catchment area may be the potential source of sediment pollution and warrants immediate targeted actions to protect this vital ecosystem and its biodiversity.
