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Jacob, J.; Correia, C.; Torres, A.F.; Xufre, G.; Matos, A.; Ferreira, C.; Reis, M.P.; Caetano, S.; Freitas, C.S.; Barbosa, A.B., and Cravo, A., 2020. Impacts of decommissioning and upgrading urban wastewater treatment plants on the water quality in a shellfish farming coastal lagoon (Ria Formosa, South Portugal). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 45–50. Coconut Creek (Florida), ISSN 0749-0208. Ria Formosa is a productive coastal lagoon, located on the south coast of Portugal, and represents the largest national producer of shellfish bivalves (ca. 90% production). This ecosystem is subjected to various anthropogenic pressures, including the discharge of urban wastewater treatment plants (UWWTP), which impacts the lagoon water quality. This study aimed to assess the impact of alterations in the functioning of two UWWTP on the water quality of Ria Formosa, based on chemical variables, phytoplankton composition (including potential harmful species) and faecal contamination. During the period September 2018 - October 2019, water sampling was conducted along dominant longitudinal gradients of the effluent dispersion from the discharge point (1-2 km), for two sites: a decommissioned (OP) and a modified (FO) UWWTP. After modification, the later started receiving a higher influent volume (ca. 40%), under an innovative technology system (biological treatment in aerobic granular sludge). Based on chemical water quality variables, phytoplankton and indicators of faecal contamination, a significant improvement along the longitudinal gradient from the discharge point was observed after OP decommissioning. This improvement was fast, being detected two months after decommissioning, positively affecting areas used as shellfish farming grounds. However, distribution patterns of bacteriological indicators and regular shellfish harvesting interdictions suggested an alternative source of faecal contamination after OP decommissioning. At FO, both chemical variables and bacteriological indicators of faecal contamination revealed a slower improvement, only six-months after the UWWTP alteration. Before that, increased and highly variable ammonium, chlorophyll a concentration, phytoplankton abundances and Escherichia coli densities, revealed an unstable phase. Overall, a lower water quality at FO in respect to OP reflected not only a higher effluent volume but also more restricted water circulation for the former. [ABSTRACT FROM AUTHOR]

Costa, S.; Picado, A.; Vaz, N.; Coelho, C.; Portela, L., and Dias, J.M., 2018. Climate change effects on suspended sediment dynamics in a coastal lagoon: Ria de Aveiro (Portugal). In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 521–525. Coconut Creek (Florida), ISSN 0749-0208. Coastal systems are very important interface areas between land and sea, subject to constant changes motivated by both natural and anthropogenic factors. In addition to the increasing modifications imposed by human activities, natural processes are also being altered as a result of climate change. Important consequences of climate change in coastal systems are sea level rise (SLR) and changes in freshwater discharge, due to modifications in rainfall patterns and air temperature. The aim of this work was to assess the impact of climate changes on the suspended sediment dynamics in a coastal system (the Ria de Aveiro, Portugal). A sediment transport model was implemented for this system and results used to investigate the impact of SLR and rivers discharge, separately and combined, considering a reference and five future scenarios. Maps of suspended sediment concentration (SSC) and sediment fluxes along the tidal cycle were analysed for each future scenario and compared with the reference scenario. In general, the highest changes on net sediment balance (difference between flood and ebb fluxes) are predicted for the scenario that only considers changes in river discharges, with a decrease of 33% relatively to the reference scenario. Combining changes in both river discharges and mean sea level (MSL), differences are attenuated, with a decrease of 6% in net sediment balance. However, for scenarios with changes only in MSL an opposite behaviour is expected, with an increase of 15%. [ABSTRACT FROM AUTHOR]

Lencart e Silva, J. D., Lopes, C. L., Picado, A., Sousa, M. C., Dias, J. M., 2014. Tidal dispersion and flushing time in a multiple inlet lagoon. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 598-603, ISSN 0749-0208. The Ria Formosa is a tidal multi-inlet shallow-water coastal lagoon located in the south of Portugal, subjected to the dry Mediterranean climate. The tide controls the Ria's exchange with the adjacent shelf for most of the hydrological year except for isolated torrential run-off events. Episodes of low hypoxia reported in the literature may be related to the lagoon's flushing time, affecting its shellfish production valued at 20 - 50 million €y−1. Over the past decades several observational and modelling studies presented values for the capacity of the tide to renovate the water inside the Ria. However, these studies lack either the spatial resolution to yield results unaffected by numerical diffusion or analyze a very limited part of the lagoon's territory. In this work, we use a very-high resolution hydrodynamic model to assess the flushing time exclusively due to tidal forcing inside the Ria Formosa. A bi-dimensional implementation of the finite-volume/finite-difference Eulerian Lagrangian hydrodynamic and transport model (ELCIRC) was used, allowing for the local refinement of the computational domain, which best suits the lagoon's complex morphology. The present model configuration was validated for tidal propagation with sea surface elevation collected in 1979/80 at 11 lagoon stations. The validation results show a good agreement between predicted and observed elevations, with root mean square errors lower than 20 cm and skill values higher than 0.98. A set of experiments were carried out by releasing a conservative tracer at different stages of the tide at discrete points of the Ria, where possible environmental hazard hot-spots are located and the flushing e-folding time calculated from the tracer's dilution. The results are discussed taking into account the propagation of the tide in this multi-inlet, meandering topography. Evidence is presented of topographic trapping due to the complex spatial distribution of the phase lags of the semi-diurnal tidal constituents. This evidence explains the significant increase of the flushing time from the inlets to the head of the channels, thus justifying the use of detailed spatial resolution when modelling such a complex system. [ABSTRACT FROM AUTHOR]

Cravo, A., Cardeira, S., Pereira, C., Rosa, M., Madureira, M., Rita, F., Luís, J. and Jacob, J., 2013. Nutrients and particulate matter exchanges through the Ria Formosa coastal lagoon. The Ria Formosa lagoon (south coast of Portugal) is a highly productive shallow mesotidal system of high water renewal through six permanent connections to the ocean. The three inlets in the western sector represent ~ 90% of the total tidal prism. To understand spatial and temporal dynamics of nutrients, chlorophyll a (proxy of phytoplankton) and particulate matter, data acquisition of these parameters along with current velocity was conducted hourly during two consecutive semi-diurnal spring and neap tidal cycles (~12.5 h) in the three inlets of Ria Formosa western sector, in late autumn of 2011. In all three inlets, nutrients ranges were typical for this time of the year, varying in antiphase relative to tidal signal, although less evident during the neap tide. Chlorophyll a and suspended solids concentrations were lower during the neap tidal cycle with less evident tidal variation than for nutrients. Net transport results show that Ria Formosa plays an important role in the mass export of nutrients to the adjacent coastal area, particularly during spring tides, with a greater contribution by the Faro-Olhão inlet, followed by the Armona and Ancão inlets. These two, regardless of the residual tidal prism, export nutrients while suspended solids were imported. The Faro-Olhão inlet presented different behaviour: it acts as a flood dominated inlet importing chlorophyll a and nitrate, and exporting ammonium and suspended solids. Nonetheless, values can change due to tidal variability, asymmetry and distortion, and interconnection of inlets inside the lagoon. To further understand the seasonal variation of this system more surveys will be conducted. [ABSTRACT FROM AUTHOR]

The late Holocene evolution of the former coastal lagoon of Vilamoura was reconstructed according to sediment cores and geophysical profiles. According to sedimentological analyses of the cores, five palaeoenvironmental stages were defined. (1) The pretransgression stage is represented by an erosive surface formed during incision of the river into the basement because of a lower sea level. This palaeosurface was retraced by refraction seismic profiles, showing that the marine transgression took place on a wide plain with several incised channels. (2) The development of an estuary started by transgression into the river valley corresponding to the postglacial sea level rise. Radiocarbon dating indicates a sea level not lower than -4 m at a minimum age of 4716 ± 72 Cal BP. After the transgressive maximum, infilling of the estuary started, beginning with (3) subtidal infilling related to the formation of a sandy barrier followed by (4) supratidal infilling with further accretion of the barrier, changing the previous open bay into a coastal lagoon. (5) Finally, the lagoon was fluvially filled with terrestrial sediments, changing the marine to a fluvial milieu with floodplain deposition. Analysis of benthic foraminiferal and ostracod assemblages revealed additional information about the environmental conditions during evolution of the estuary, which led to a further subdivision of the marine facies into stages with mainly estuarine, lagoonal, or marine influence. The end of the marine stage was dated at 2895 ± 48 Cal BP, indicating a pre-Roman onset of human-induced soil erosion. [ABSTRACT FROM AUTHOR]

Ria de Aveiro, a Portuguese coastal lagoon that exchanges water with the Atlantic Ocean, received the effluent from a chlor-alkali industry for over 50 years; consequently several tons of mercury had been buried in the sediments of an inner basin. To assess the importance (and seasonal variation) of the lagoon waters as carriers of mercury to the nearby coastal area, we measured total mercury levels in several compartments: in surface sediments, in surface and deep waters (including dissolved and particulate matter), and in biota. Dissolved (reactive and total) mercury concen- trations both in surface and deep waters were low (<1 to 15 ng L-1). Mean mercury values in suspended particulate matter varied between 0.2 and 0.6 μg g-1 and in sediments between 1 and 9 ng g-1. Aquatic organisms displayed levels below regulatory limits but exhibited some bioaccumulation of mercury, with concentrations ranging from 0.05 to 0.8 μg g-1 [dry weight (dw)]. No seasonal pattern was found in this study for mercury-related determinations. Levels found in the estuary mouth during ebb tide provide evidence for the transport of mercury to the coastal zone. No significant changes in the partition of mercury between dissolved and particulate phases were found in the coastal waters in comparison with the values found in the estuary mouth. In spite of the high levels of mercury found inside some areas of the lagoon, the wide web of islands and channels allows some spreading of contaminants before they reach the coastal waters. Moreover, the low efficiency of local marine sediments in trapping mercury contributes to a dilution of mercury transported in suspended particulate matter over a broader area, reducing the impact in the nearby marine coastal zone. [ABSTRACT FROM AUTHOR]

The Portuguese coastline has a high diversity of coastal types, which will react differently to an accelerated sea-level rise. Estuaries and coastal lagoons will be most affected by a rising sea level. Amongst these, the Sado and Tagus estuaries and the Ria de Aveiro and the Ria Formosa coastal lagoons are probably the ones where socioeconomic impacts resulting from accelerated sea-level rise would be greatest. Sandy shores will face increased erosion.However, it is likely that at this type of coast other factors, such as sand deficiency caused by damming river basins, will continue to play a larger role in erosion than accelerated sea-level rise. Hard rocky coasts will be the least affected by accelerated sea-level rise. Specific adaptation policies for accelerated sea-level rise impacts do not presently exist in Portugal. However, existing laws can be used to prevent and/or reduce socioeconomic impacts if they are strictly applied. A strong commitment to coastal management by Portuguese authorities is therefore necessary in order to prevent and minimise future implications of accelerated sea-level rise. [ABSTRACT FROM AUTHOR]

The Cacela Peninsula on the south coast of Portugal was, previous to nourishment operations, extremely vulnerable to overwash events. During the 1995-96 winter, extensive overwashing led to the opening of a new inlet. Simultaneously, the lagoon channel in the backbarrier was silting up with the overwash deposits, inlet flood delta sands, and accretion of fine sediments. Between October 1996 and February 1997 the channel was dredged, and the sediments were deposited on the western 2,000 meters of the Cacela Peninsula, forming an artificial dune ridge. The sediment characteristics of the dredge spoils were in contrast with the natural dune sand. The spoils had higher silt and clay content, lower mean grain size, and poorer sorting. In January 1998, three washover breaches were infilled, with sand removed from the foreshore, on the eastern part of the Cacela Peninsula. These sands were coarser and more poorly sorted than the original dune sediments. A 2-year monitoring program, consisting of beach/dune profiling, topographic surveys in specific areas, and sediment analysis, was established to observe the morphological evolution of these areas. The total eroded volume recorded for the dune nourishment project after 2 years was about 106,500 cubic meters, corresponding to 33% of the total 325,000 cubic meters of sediment that was deposited. The washover infilling showed little or no variation. However, the downdrift. beaches and foredunes experienced severe erosion. Both protective measures accomplished their purposes in terms of preventing erosion; however, a natural landscape was only created where dune development by aeolian processes was possible. [ABSTRACT FROM AUTHOR]

In shallow highly productive coastal environments intense biogeochemical activity is concentrated in the upper sediment layers. However, pore water composition of permeable inter-tidal sediments change as water flows over the areas during ebb and flood tides. In order to examine metal post-mobilisation, inter-tidal sediment cores of 4 cm length and particles settled in sediment-traps over several periods during 10 months were collected in Ria Formosa (SW Iberian Peninsula). Concentrations of Al, Fe, Mn, Cu and Cd, loss on ignition and the proportion of fine fraction were determined in sediment layers of 0.5 cm thickness and in sediment-trap material. Levels of Mn in sediments were similar to those in sediment-trap material, although enrichment in the topmost sediment layer (0.1 mm) was observed as MnO2 is formed. Although Fe in sediments and sediment-trap material ranged within similar intervals, two relationships with Al were found showing that sediment-trap material are impoverished in Fe in comparison to sediments. This suggests that Fe is mainly cycled inside the sediment. Copper and Cd exhibited different patterns. Levels in sediment-trap material were not correlated to Al or LOI, probably due to local contamination or uptake by plankton. These values were lower than levels in the topmost sediment layer, suggesting that Cu and Cd that reach the sediment surface are rapidly released to the water column. Concentrations in sediments, including the topmost layer, exhibited two relationships to Al, for both Cu and Cd. One corresponding to background values and the other found in stations closer to the anthropogenic sources. In these cases Cu and Cd are incorporated into the sediments that is facilitated by AVS values close to the sediment surface. [ABSTRACT FROM AUTHOR]

Examines the pollen diagram of the Doninos coastal lagoon in Iberian Peninsula. Degree of pollinic signal recorded in the sediments of coastal lagoons; Development of a lacustrine system at the bottom of the sequence; Diatom facies; Sedimentology.

Sousa, M. C. and Dias, J. M., 2007. Hydrodynamic model calibration for a mesotidal lagoon: the case of Ria de Aveiro (Portugal). Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 1075 – 1080. Gold Coast, Australia, ISSN 0749.0208 Ria de Aveiro is a shallow vertically homogeneous mesotidal lagoon, located in the Northwest of Portugal. It has a very intricate morphology and large tidal flats areas that cover and uncover along the tidal cycle. A two-dimensional vertically integrated hydrodynamic model was considered to be adequate to simulate its hydrodynamics and a model developed from the SIMSYS2D model was applied. The purpose of this study is to describe the implementation and calibration of this model which is able to predict tide-induced water level and depth integrated velocity for the entire lagoon. The numerical bathymetry used was developed from data concerning depth obtained from a general survey carried out in 1987/88 and actualised for several channels in the last years. The Monte Carlo method was used to generate the rectangular computational grid, which has 409 cells in the eastward direction and 966 cells in the northward direction (dimensions of 40×40 m). The model calibration was performed adjusting the bottom friction coefficient for the entire lagoon, through the comparison between measured and predicted time series of sea surface elevation (SSE) for a large number of stations distributed along the main channels of the lagoon. The relative mean absolute error, the root-mean square and a skill assessment of the difference between those SSE values were determined to quantify the models performance. Harmonic analysis was also performed in order to evaluate the model accuracy. According to the results the hydrodynamic model was successfully calibrated, reproducing accurately the barotropic flows in this complex lagoon. [ABSTRACT FROM AUTHOR]

Fortunato, A.B. and Oliveira, A., 2007. Improving the Stability of a Morphodynamic Modeling System. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 486 – 490. Gold Coast, Australia, ISSN 0749.0208 Coastal area morphodynamic modeling systems couple modules for tidal hydrodynamics, wave propagation, sediment transport and bottom update. The non-linear coupling between these modules generates spurious oscillations and stability problems that are still poorly understood. This paper assesses and compares various methods to avoid the oscillations and improve the stability of a coastal area morphodynamic modeling system (MORSYS2D). The model is assessed with a simple case, the propagation of a sinusoidal bedform, and a complex natural system (Óbidos Lagoon, Portugal), whose exceptional dynamics enhances numerical problems in the morphodynamic models. The best results are obtained with a combination of methods: a predictor-corrector method to improve the implicitness of the solution, along-flux diffusion in the Exner equation to control oscillations, and a morphological factor below unity to reduce the Courant number. With these methods, the modeling system can be used with Courant numbers well above unity. [ABSTRACT FROM AUTHOR]