Flood and drought risk assessment for agricultural areas (Tagus Estuary, Portugal)

Estuaries are coastal systems particularly vulnerable to climate change. Within these systems, agriculture is one of the most potentially affected sectors. This paper proposes a risk assessment approach for helping the decision-making process at a local level, addressing two risks that affect agricultural areas located in estuarine margins: the unavailability of freshwater for irrigation resulting from the upstream propagation of estuarine brackish water during droughts and land inundation by high water levels associated with high tides and storm surges. For each risk, quantitative consequence descriptors are proposed to support risk level determination and evaluation through a continuous consequence–probability diagram. The approach applicability is discussed through its application to the Lezíria Grande de Vila Franca de Xira, located in the Tagus Estuary (Portugal). Results indicate that the approach is appropriate to support risk owners in taking actions to mitigate the risk. Examples of risk control measures for the risks addressed are presented. The main strengths of the proposed approach are its flexibility to be adapted to local conditions and updated through time, as well as the ease of its application by the risk owner.

Tidal and Physicochemical Effects on Phytoplankton Community Variability at Tagus Estuary (Portugal)

The Tagus Estuary is one of the largest estuaries in Europe and merges large urban and industrial areas. Understanding phytoplankton community variability is key for an appropriate assessment of the estuarine ecological status. The objective of the present study was to assess the importance of the tidal influence over the phytoplankton community and to evaluate its main drivers of variation. Weekly sampling was performed at two stations on the Tagus Estuary with different anthropogenic pressures (Alcântara and Barreiro). The sampling covered periods with different tidal amplitude. Alcântara presented both the lowest and highest concentrations of dissolved inorganic nitrogen (DIN) and orthophosphate concentration (DIP), depending on the tidal height. Such high variability in this sampling station is probably due to its proximity to a sewage treatment station outfall and to the estuary mouth. In the present study, both seasonal and tidal variations influenced the chlorophyll a concentration of which the tidal cycle explained up to 50% of the chlorophyll a variations. Chlorophyll a displayed a seasonal trend with two peaks of phytoplankton biomass between spring and mid-summer. The main drivers of chlorophyll a variation were radiation, water temperature, tidal amplitude, salinity, river discharge, and the inorganic nutrients DIN and DSi. The estuarine phytoplankton community was mainly dominated by Bacillariophyceae, especially at Alcântara. Bacillariophyceae were less important at Barreiro, where communities had a higher representation from other phytoplankton groups, such as Cryptophyceae and Prasinophyceae. The drivers of variability in the community composition were similar to those influencing the total biomass. In conclusion, the spring-neap tidal cycle strongly influenced the phytoplankton community, both in terms of biomass and community composition. Of the several tidal conditions, spring tides were the tidal condition that presented both higher biomass and higher Bacillariophyceae representativity in the community.

Integrative Taxonomy Reveals That the Marine Brachyuran Crab Pyromaia tuberculata (Lockington, 1877) Reached Eastern Atlantic

Pyromaia tuberculata is native to the north-eastern Pacific Ocean and currently established in distant regions in the Pacific Ocean and southwest Atlantic. Outside its native range, this species has become established in organically polluted enclosed waters, such as bays. The Tagus estuary, with a broad shallow bay, is one of the largest estuaries in the west coast of Europe, located in western mainland Portugal, bordering the city of Lisbon. In this study, sediment samples were collected in the estuary between 2016 and 2017. Several adult specimens of P. tuberculata, including one ovigerous female, were morphologically and genetically identified, resulting in accurate identification of the species. The constant presence of adults over a 16-month sampling period suggests that the species has become established in the Tagus estuary. Moreover, their short life cycle, which allows for the production of at least two generations per year, with females reaching maturity within six months after settlement, favours population establishment. Despite being referred to as invasive, there are no records of adverse effects of P. tuberculata to the environment and socio-economy in regions outside its native range. However, due to its expanding ability, its inclusion in European monitoring programmes would indeed be desirable.

Estimating the conservation cost of the projected new international Lisbon airport for migratory shorebirds of the Tagus estuary, Portugal

Summary The increasing pressure of anthropogenic development in areas with high natural value poses a huge challenge for wildlife conservation worldwide. The Tagus estuary in southern Portugal is among the most important wetlands for migratory shorebirds in the East Atlantic Flyway (EAF). However, in 2020 the Portuguese government approved the construction of the new Lisbon international airport at the heart of the Tagus estuary. Intense aircraft traffic, flying at low altitudes during both approach and take-off, is expected to cross the estuary, overlapping to a great extent the important intertidal foraging areas. Here, we aim to quantify the potential loss of conservation value of the intertidal areas of the Tagus estuary for shorebirds resulting from the disturbance (noise) caused by overflying aircraft. Using a comprehensive dataset of wintering shorebird abundance and distribution in the whole intertidal estuarine area we first identified priority areas for conservation using a spatial prioritization approach. We then performed a replacement cost analysis by excluding the areas likely to become unsuitable or severely underused by birds due to intense air traffic noise. Our results suggest that the implementation of the new Lisbon airport may lead to a loss of up to 30% of the conservation value of the Tagus estuary in terms of intertidal feeding areas of wintering birds alone. The global impact will likely be greater when effects on supratidal roosts, as well as on passage birds, are also considered. The Tagus estuary, which is internationally important for six of the 10 species included in our analysis, is just one of a network of already depleted sites along the EAF. Thus, negative impacts on bird populations on the Tagus estuary will have repercussions and undermine conservation efforts elsewhere. The plight of shorebirds at the Tagus estuary is thus a matter of international conservation concern.

Valorisation of cost-effective wastes and underused soils through Technosols construction for the Suaeda vera Forssk. ex J. F. Gmel. cultivation: a valued marine halophyte

<p>Salinization is one of the major causes of soil degradation and salt-affected soils have been underused due to their physical and chemical properties. Although most conventional crops are non-salt tolerant plants (glycophytes), halophytes can develop under high salinity concentrations and provide food, fodder and other uses, such as remediation and pharmaceuticals. Among them, Suaeda vera can be used for human consumption as forage and in phytoremediation. This study aims to optimize the cultivation of this species by producing a Technosol (TEC) using wastes as amendments to improve the properties of a Fluvisol (FLU). The amendments were constituted by cost-effective wastes: sludge and waste kieselguhr from breweries, medium sand, gravel limestone and biomass obtained from pruning. The FLU used in a microcosm assay was collected in the Tagus Estuary, close to Lisbon, Portugal. The soils properties, plants growth in Fluvisol and Technosol under the estuarine water (Ew) irrigation also collected in Tagus Estuary, were assessed. The microcosm assay was set up with four replicates and the substrata were incubated at 70% of the maximum water-holding capacity for 28 days, in the dark. After, seedlings obtained by germination in wet filter paper with deionised water were transplanted. The amendments, the FLU and the TEC were analysed for: pH, electrical conductivity (EC), concentrations of C<sub>organic</sub>, P<sub>extractable,</sub> K<sub>extractable</sub> and N<sub>total</sub>. The chemical characteristics of Ew were also analysed for pH, EC, Cl<sup>–</sup>, HCO₃<sup>–</sup>, Na, Ca, Mg, and the SAR was calculated. The plant growth parameters like stem length and biomass were determined. The FLU was slightly alkaline (pH 8), with a high EC (5.6 mS/cm) and low values of C<sub>organic</sub> (20 g/kg), N<sub>total</sub> (1.7 g/kg), P<sub>extractable</sub> (1x10<sup>-3</sup> g/kg) and K<sub>extractable</sub> (0.9 g/kg). Due to the wastes’ properties, the TEC showed a significant increase in C<sub>organic </sub>(28 g/kg), N<sub>total </sub>(2.5 g/kg), P and K<sub>extractable</sub> (0.1 and 1.2 g/kg, respectively), in comparison with the FLU. The Ew was strongly saline (EC 22.1 mS/cm), had a neutral pH (7.78) and high concentration of Cl<sup>-</sup> (7330 mg/L), HCO₃<sup>-</sup> (267 mg/L), Na<sup>+</sup> (4305 mg/L), Ca<sup>2+</sup> (210 mg/L) and Mg<sup>2+</sup> (538 mg/L). The Ew SAR value was high (157) but tolerated by halophytes. The individuals grown in the TEC presented a larger stem (18 cm) and a higher fresh biomass value (23 g) than individuals grown in the FLU. These results indicate that the wastes improved the Fluvisol properties being S. vera cultivation favoured if carried out in TEC. In a circular economy perspective, this study reveals that it is possible to cultivate a halophyte species with economic potential from underused resources as saline soils, wastes and brackish water.</p>

Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged between 1.08–18.15 ng m−3 in CN and 1.18–3.53 ng m−3 in ALC. In CN, most of the high Hg(0) levels occurred during nighttime, while the opposite was observed at ALC, suggesting that photoreduction was not driving the air Hg(0) concentrations at the contaminated site. Vegetation–air Hg(0) fluxes were low in ALC and ranged from −0.76 to 1.52 ng m−2 (leaf area) h−1 for Hp and from −0.40 to 1.28 ng m−2 (leaf area) h−1 for Sf. In CN, higher Hg fluxes were observed for both plants, ranging from −9.90 to 15.45 ng m−2 (leaf area) h−1 for Hp and from −8.93 to 12.58 ng m−2 (leaf area) h−1 for Sf. Mercury flux results at CN were considered less reliable due to large and fast variations in the ambient air concentrations of Hg(0), which may have been influenced by emissions from the nearby chlor-alkali plant, or historical contamination. Improved experimental setup, the influence of high local Hg concentrations and the seasonal activity of the plants must be considered when assessing vegetation–air Hg(0) fluxes in Hg-contaminated areas.

Flood and drought risk assessment for agricultural areas (Tagus Estuary, Portugal)

Estuaries are coastal systems particularly vulnerable to climate change effects and within these systems, agriculture is one of the most potentially affected sectors. This paper proposes a risk assessment approach for helping the decision-making process at a local level, addressing two risks that affect agricultural areas located in estuarine margins: the unavailability of fresh water for irrigation resulting from the upstream propagation of estuarine brackish water during droughts, and land inundation by high water levels associated with high tides and storm surges. For each risk, quantitative consequence descriptors are presented to support risk level determination and evaluation through a continuous consequence/probability diagram. The approach applicability is discussed through its application to the Lezíria Grande de Vila Franca de Xira, located in the Tagus Estuary (Portugal). Results indicate that the approach is appropriate to support risk owners in taking actions to mitigate the risk. The flexibility of the approach to be adapted to local conditions and updated through time, and the ease of its application by the risk owner can be pointed out as the main strengths.