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A two-dimensional, non-linear, finite difference, hydrodynamic model was applied to the San Pedro channel (Cadiz bay) to study the changes on tidal current asymmetries along its course due to the reconnection of its main channel to a wide tidal lagoon that was artificially desiccated in the mid of 20th century. Results of both experimental in-situ data and model simulations show changes from a flood-dominance of current asymmetries when the channel was isolated, to a stronger and ebb-directed asymmetry after the reconnection to the upper lagoon. The influence of the upstream intertidal flats is revealed on the configuration of tidal current asymmetries induced by the mutual phase-lags between the M2 and M4 tidal constituents, as well as in the tide-induced residual currents. These effects were found to be stronger during spring tides. The impacts of current asymmetry reversal on the morphodynamics of coastal tidal environments and on water quality and pollutants transport are discussed. • Changes in tidal currents asymmetries are analyzed in a human-modified creek. • A real case is evaluated by field measurements and hydrodynamic modeling. • The isolation of the creek from upper marshes causes weak flood-asymmetry. • The creek re-connected to upper tidal flats presents stronger ebb-asymmetry. [ABSTRACT FROM AUTHOR]

The rapid decline in both quality and availability of freshwater resources on our planet necessitates their thorough assessment to ensure sustainable usage. The growing demand for water in industrial, agricultural, and domestic sectors poses significant challenges to managing both surface and groundwater resources. This study tests and proposes a hybrid evaluation approach to determine Groundwater Quality Indices (GQIs) for irrigation (IRRI), seawater intrusion (SWI), and potability (POT), finalized to the spatial distribution of groundwater suitability involving water quality indicator along with hydrogeological and socio-economic factors. Mean Decrease Accuracy (MDA) and Information Gain Ratio (IGR) were used to state the importance of chosen factors such as level of groundwater above the sea, thickness of the aquifer, land cover, distance from coastline, silt soil content, recharge, distance from river and lagoons, depth to water table from ground, distance from agricultural wells, hydraulic conductivity, and lithology for each quality index, separately. The results of both methods showed that recharge is the most important parameter for GQI IRRI and GQI POT , while the distance from the coastline and the rivers, are the most important for GQI SWI. The spatial modelling of GQI IRRI and GQI POT in the study area has been achieved applying three machine learning (ML) algorithms: the Boosted Regression Tree (BRT), the Random Forest (RF), and the Support Vector Machine (SVM). Validation results showed that RF has the highest prediction for GQI IRRI , while the SVM model has the highest prediction for the GQI POT index. It is worth to mention that the future utilization and testing of new algorithms could produce even better results. Finally, GQI IRRI and GQI POT were combined and compared using two combine and overlay methods to prepare a hybrid map of multi-GQIs. The results showed that 69% of the study area is suitable for irrigation and potable use, due to both geogenic and anthropogenic activities which contribute to make some water resources unsuitable for either use. Specifically, the northern, western, and eastern portions of the study area are in the "very high and high quality" classes while the southern portion shows "very low and low quality" classes. In conclusion, the developed map and approach can serve as a practical guide for enhancing groundwater management, identifying suitable areas for various uses and pinpointing regions requiring improved management practices. [Display omitted] • Groundwater suitability for human utilization has been assessed in the Campania region (South Italy) using a combined approach. • Three machine learning methods (RF, BRT, and SVM) have been tested to identify the areas related to potable and irrigation indicators. • The results show as almost 80% of resources are suitable for human utilization while the remaining 20% could benefit a preliminary treatment. [ABSTRACT FROM AUTHOR]

Abstract The study results describe the hydrogeochemical and the hydrodynamic characterization, and the evolution compounds in the water in the Nichupté Lagoon System (NLS). This is the most representative lagoon of Quintana Roo State and hosts the Natural Protected Area "Manglares de Nichupté" and borders the Punta Cancún-Punta Nizuc National Park. Sampling was performed during rainy and cold-front seasons to asses the distribution and variability of temperature, pH, dissolved axygen salinity, nutrients and major elements. Significant differences were detected for temperature and salinity but not for dissolved oxygen between the seasons. The dissolved oxygen values have considerably diminished in a decade. NO x and PO 4 concentrations were high, and did not show significant differences between seasons. NH 4 + concentration was an order of magnitude higher in the rainy season. Two types of water occur in the study area (Cl) and (Cl-SO 4 -Na-Ca-Mg). A strong predominance of Na-Cl, classifies the lagoon system as a brackish lake. Evaporation was the dominant process and the lagoon behaves like a salty lake, with an evolution in the chemical composition of the water, which became enriched in calcium during the cold-front season, and in sulfates during the rainy season. No precipitation of calcite or gypsum was identified, but this could occur during the cold fronts due to the geochemical evolution observed in the Spencer diagram. Nutrient concentrations have increased in ten years, but some are still below Mexican water quality criteria (CE-CCA-001/89). Some sites present high nutrients concentrations like Bojorquez lagoon sites. The results obtained underline: a) high temperature records vis-à-vis of previous studies measurements (historical records), b) decreasing dissolved oxygen concentrations, c) increasing NO 3 − and PO 4 3− concentrations. These factors combination shows eutrophication signs that should already be taken as an alert. The circulation of the water in the two analyzed periods was qualitatively similar but the magnitudes of the currents were remarkably different between each other. The rainy season (August 2015) showed near-coastal mean currents of magnitude ∼2–3 cm s−1, while the cold-front season (March 2016) showed mean currents about twice stronger (∼5–6 cm s−1). The circulation pattern result in relatively short residence times of the water bodies of the Lagoon System, with values from 3 to 6 weeks in the rainy season; these values can be decreased by 30–50% in the cold-front season. Graphical abstract Image 1 Highlights • The dominant process is the evaporation, two water types (Cl−) and (Cl−-SO 4 2--Na+-Ca2+-Mg2+). • Water is enriched in Ca2+ (cold-front season), and in SO 4 2− (rainy season). • High temperature records vis-à-vis of previous studies measurements. • Decreasing dissolved oxygen concentrations, increasing NO 3 −, PO 4 3− concentrations. • Circulation qualitatively similar in both seasons but magnitudes remarkably different. [ABSTRACT FROM AUTHOR]

Eutrophication is a major driver of the degradation of transitional waters worldwide, especially in environments with a restricted connection to the sea, such as coastal lagoons. In recent decades, intensive agriculture and urban water inputs around the Mar Menor coastal lagoon (Western Mediterranean) have disturbed this originally oligotrophic aquatic system. The nutrient input into the lagoon has triggered its eutrophication, leading to dystrophic crises and mass mortality events for aquatic biota, transforming it into one of the most eutrophication-impacted transitional waters in the Mediterranean basin. In this study, we applied a fish-based indicator to assess the ecological quality of shallow waters under different eutrophication-mediated environmental stress scenarios (from pre-eutrophic reference periods to critical eutrophic periods), as well as to explore the role of confinement (i.e., water renewal time) and shoreline anthropogenic pressure as factors modulating the indicator response. Despite the high magnitude of the eutrophication impact on the lagoon, the ecological quality of the shallow waters decreased only slightly after the mass mortality events. The level of confinement also had slight effects on the ecological quality of the most confined shallow areas in the summer during eutrophic periods. Hence, shallow waters could play a critical role as refuge habitats, both for fish assemblages and other aquatic taxa, by buffering euxinic conditions during eutrophication processes.". In fact, shallow waters could act as critical habitats, allowing for the recolonisation of aquatic biota from more impacted areas in the lagoon. This attribute further reinforces the need to properly manage and protect the shoreline areas of transitional waters, particularly under eutrophication scenarios. • A fish-based index was applied to assess the ecological quality of the Mar Menor. • No major temporal changes were found between reference and eutrophic periods. • The ecological quality of more confined areas was particularly affected in warmer seasons. • Shallow waters buffered eutrophication-mediated impacts by providing refuge habitats. • This alternative role should be considered into coastal lagoon restoration. [ABSTRACT FROM AUTHOR]

The impact of coastal water quality and its interaction with business results is still an unexplored field. This study uses a probit model and estimates marginal effects to investigate the impact of chlorophyll a concentration in the Mar Menor (Spain) coastal waters on the probability of business failure of firms located in this area. This coastal area has been in a critical ecological condition since 1980 when intensive irrigation agriculture expanded to the surroundings of this salted lagoon. Therefore, identifying the most damaging productive activities is crucial to convince companies and policymakers to overcome this situation. The most remarkable findings of our study are the following. First, we find opposing geographical impacts on the probability of business failure for companies located on the Mar Menor coast: A location effect showing a decreasing probability of business failure for companies located near the Mar Menor and a pollution effect indicating an increased probability of failure due to proximity to water pollution. Second, we further identify the economic sectors in which the pollution effect outweighs the location effect. We find that most of the examined productive activities seem to be negatively affected by the pollution effect , overcoming the positive effect of being located near the Mar Menor. Third, marine eutrophication increases the probability of business failure for some economic activities but not for others. Concretely, agricultural and transport activities benefit from being near the coast despite the quality of the water. These firms' probability of failure decreases when they are located near the sea), whereas a 1 mg/m3 increase of chlorophyll a raises the probability of business failure for accommodation services (8.4%), minor trade (9.5%), financial and real estate services (11%), and industrial and building activities (14.4%). This paper highlights the need to design effective environmental regulations to preserve the area of Mar Menor, considering the specific productive characteristics of the different agents. We highlight the sectors requiring additional incentives to implement pro-environmental strategies and reduce their contribution to environmental pollution. The main insights from this analysis are applicable to other coastal areas around the world that suffer from marine eutrophication due to human activities. • This study provides evidence about the relevance of environmental characteristics on business behaviour. • Two opposing and significant effects have been found: geographical location and marine water pollution. • This study helps evaluate the sectors impacted by the deterioration of water pollution in Mar Menor. • These sectors require additional incentives to implement strategiesc to reduce environmental pollution. [ABSTRACT FROM AUTHOR]

Bar-built estuaries (BBEs) or intermittently closed/open lagoons (ICOLs) are common to coastal regions experiencing episodic river flows and seasonal precipitation changes along the US West Coast. Unique to Mediterranean climates, BBEs have a hydrologic mixing regime and variation in water chemistry characteristics resulting from seasonal breaches and closures of their mouth and watershed inputs. This study observes spatiotemporal variability in dissolved oxygen (DO) in a small bar-built estuary in Carmel, CA during variable morphological states. For this study, field measurements were collected using dissolved oxygen loggers during a seasonal transition from fully open to fully closed states to determine the spatiotemporal variability of dissolved oxygen within the three main branches of Carmel River Lagoon. The data collected spanned a 6-month (February to August 2020) period, covering several transitions from fully open to intermittently closed to fully closed mouth state. This study did not document any periods within the lagoon when dissolved oxygen concentrations were uniformly below water quality objective levels (5 mg/L) suggesting that during the entire period of this investigation, portions of the lagoon supported high oxygen conditions while also supporting a variety of other water chemistry characteristic zones, unique to BBEs. The dissolved oxygen fluctuations were closely tied to the temporal effects of environmental forcing (river discharge) on the seasonal transition of river mouth morphological state from fully open to fully closed. The main conclusion is that during open mouth states, relative DO variability in the bottom of the main channel is low and more similar to surface waters, indicating mixing, and during closed mouth states vertical location in the water column matters more. Furthermore, variability between sites suggests single point observations of DO cannot accurately represent the distribution of DO within a BBE. • Bar-built estuarine dissolved oxygen levels depend on mouth morphological state (open vs. closed) in well-connected regions. • Locations with less connectivity to the river channel have low dissolved oxygen periods even when river discharge is high. • Low variance in dissolved oxygen is associated with well-connected regions of the lagoon. • Despite small separation distances (<325 m), there is spatial variability of dissolved oxygen levels within the lagoon system. [ABSTRACT FROM AUTHOR]

Water quality fluctuations are influenced by natural and artificial openings of ICOLLs. In this study artificial opening resulted in a greater degradation of water quality than natural openings. Artificial openings are commonly undertaken in response to flood risk to human assets but often cause fish kills. We assessed water quality (parameters: temperature, dissolved oxygen, pH, salinity) within two ICOLLs before and after natural openings and two ICOLLS before and after artificial openings. Natural openings caused only a slight decline in water quality and no fish kills, whereas the artificial openings triggered poor water quality and fish kills. Decline of dissolved oxygen concentrations were observed following two artificial opening events associated with fish kills. We conclude that there are multiple drivers and sources contributing to low dissolved oxygen concentrations that are unique to individual ICOLLs and the type of opening. • Water quality fluctuations occur during natural and artificial openings. • Low DO is driven by physical, chemical and biological factors. • Dissolved oxygen (DO) depletion was a major driver of fish kills in ICOLLs. • Natural openings of ICOLLs did not cause fish kills. • ICOLLs require site specific water quality guidelines for management. [ABSTRACT FROM AUTHOR]

The development, protection, and restoration of bays require works in scientific research and applications, and the success of which depends on a well deployment of monitoring stations for marine water quality. However, for bays without historical data, it is difficult to carry out related research on deployment of the monitoring stations, resulting in very few research works. This paper has introduced the affinity propagation (AP) clustering algorithm and achieved good results by correcting the preferences. The results show that under the given preference, that is, when the value of M is −6800, the number of monitoring stations in the Xincun lagoon area is 24. Simultaneous the sensitivity analysis of preferences shows that the number of exemplars decreases with lower preferences, that is, when M decreased from −4000 to −12000, the number also decreased from 70 to 36. However, some exemplars remain unchanged or being changed to adjacent positioning. This shows the stability of computation results and the rationality of AP. The research results can be well applied to other bays, even open waters. • AP clustering can be used to layout seawater monitoring stations. • Multi-dimensional feature parameters is used to modify the bias parameters of the algorithm. • Sensitivity analysis shows that AP clustering can be applied in bays lacking historical data. [ABSTRACT FROM AUTHOR]

In recent decades animal agriculture in the U.S. has moved from small, distributed operations to larger, concentrated animal feeding operations (CAFOs). CAFOs are defined by federal regulations based on animal numbers and confinement criteria. Because of the size of these operations, the excessive amount of manure generated is typically stored in lagoons, pits, or barns prior to field application or transport to other farms. Water and air quality near CAFOs can be impaired through the overflow of lagoons, stormwater runoff, lagoon seepage or emissions, motivating the following research question: what manure lagoon parameters impact pollutant fate and transport across multiple mechanisms? To address this question, a CAFO lagoon module was developed to assess lagoon overflow risk, groundwater quality, and ammonia emissions of a dairy lagoon. The results from 10,000 Monte Carlo simulations indicated that lagoon overflow is a rare occurrence for simulated environmental conditions in Washington (3.17%). Second, we developed a groundwater module to complete a groundwater quality assessment of a Dairy Lagoon in Washington using analytical and semi-analytical solutions for groundwater solute transport. The long-term effects of this lagoon on water quality were explored as well as the effectiveness of improving the lagoon lining to reduce seepage. Doubling the lagoon liner thickness attenuated peak groundwater ammonia-N concentrations by 2.8. Lastly, we constructed an air quality module and found that ammonia emissions were not sensitive to changes in lagoon liner construction, but small reductions in lagoon pH significantly reduced yearly average ammonia emissions. The combined model can be used to improve understanding of the impacts of CAFO lagoon overflow and seepage and develop sustainable management practices at the field scale for these key components of the agricultural landscape. [Display omitted] • A point-source model of a CAFO dairy lagoon was developed. • Overflow was a rare occurrence for simulated dairy CAFOs. • Groundwater quality was affected by the soil liner construction. • Ammonia emissions were sensitive to lagoon pH. • We highlight the importance of this hydrologically-relevant agricultural feature. [ABSTRACT FROM AUTHOR]

Estuarine food webs are complex, as marine, freshwater, and terrestrial inputs combine and contribute variable amounts of organic material. Seasonal fluctuations in precipitation amplify the dynamism inherent to estuarine food webs, particularly in lagoonal estuaries, which can be seasonally closed and disconnected from the ocean in low-runoff periods (bar-built lagoons). Despite their abundance along coastlines in Mediterranean climates, the organic matter sources fueling bar-built lagoon food webs are poorly understood, particularly with respect to seasonal hydrologic variability, episodic marine connections, and internal nutrient cycling. In this study, we evaluate the food web of a bar-built lagoon with respect to seasonal differences in lagoon water quality, the sources of organic matter which support consumers, and the trophic ecology of resident fishes. Observed water quality conditions reflected biogeochemical processes associated with salinity-driven stratification and high lagoon residence times and were associated with strong seasonal differences in the contribution of different organic matter sources to lagoon consumers. A variety of organic matter sources supported consumers; marine inputs were important to lagoon food webs in spring when the lagoon was open, while summer food webs were largely driven by phytoplankton which was likely fueled by internal nutrient cycling. Fish diets were largely comprised of crustaceans and fish eggs, with clearly defined trophic niches in spring but high overlap in summer. This study demonstrates that the seasonal changes in bar-built lagoon food webs are largely dependent on ocean connectivity and internal cycling within the lagoon, rather than watershed processes as is typical for many estuaries. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Long-term non-linear ecosystem-scale changes in water quality and biotic communities in coastal lagoons have been associated with intensification of anthropogenic pressures. In light of incipient changes in Johnson Bay (an embayment of Chincoteague Bay, Maryland-Virginia, USA), examination of nitrogen sources was conducted through synoptic water quality monitoring, stable nitrogen isotope signatures (δ15N) of in situ bioindicators, and denitrification estimates. These data were placed in the context of long-term and broader spatial analyses. Despite various watershed protection efforts, multiyear summer time studies (2004–2007) suggested that high levels of terrestrially derived nutrients still enter Johnson Bay. Total nitrogen concentrations in Johnson Bay were 132% the concentrations in the broader Chincoteague Bay during the late 1970s (mean 2004–2007 was 40.0 – 73.2 μM). Comparing total nitrogen concentrations in Johnson Bay to St. Martin River (consistently the most eutrophic region of these coastal bays), Johnson Bay has increased from 62.5% to 82.5% of the concentrations in St. Martin River during the late 1970s. Though specific sources of nitrogen inputs have not yet been definitively identified, the long-term increase in total nitrogen concentrations occurred despite increased and continued conservation and protection measures. We suggest that investigating nutrient sources can reveal potentially ineffective nutrient policies and that this knowledge can be applied towards other coastal lagoons. [Copyright &y& Elsevier]

Abstract: In the present study the annual variability of the physico-chemical parameters of four coastal lagoons subjected to intense human activity was characterised. The trophic state indices (TSI) of Carlson (1977) and the water quality index TRIX of Vollenweider et al. (1998) were tested and compared with the water quality categories proposed by the European Environmental Agency (2009). All the parameters were sampled monthly from May 2004 to July 2005. There were important differences in the annual variability of the physico-chemical parameters between the lagoons, reflecting the importance of human-induced pressures and the heterogeneity of these environments. The lagoons were in a eutrophic/hypereutrophic state most of the year. Trophic state indices classified the lagoons in a bad or poor trophic state most of the year, and they were not able to discriminate the effect of secondary variables such as freshwater releases, ground waters fluxes or water renewal. Nitrogen was the limiting factor in the lagoon with a higher exchange rate with the sea, while phosphorous was the limiting factor in the other lagoons, due to the high nitrogen external loads and the poor water renewal. The need for developing indices specifically designed for coastal lagoons in order to asses their trophic state is discussed. [Copyright &y& Elsevier]

Abstract: Santo André is an enclosed brackish water coastal lagoon with temporary connections to the sea by a man-made channel. The exchange and mixture of saltwater and freshwater is irregular and the lagoon may show daily and seasonal fluctuations, but also long-term variation. Different benthic communities may be present along the annual cycle according to the magnitude of episodic freshwater and sea water inputs. In the last 30 years the communication with the sea has followed different regimes from year to year and, as a consequence, macrobenthic communities, assessed several times during the period before the opening to the sea, shifted from freshwater to marine affinities. Major differences were found between 1979 and 2010, with a preponderance of species with marine affinity, and the 1980s in which the organisms with freshwater affinity prevailed. Benthic communities are frequently used to assess aquatic environmental condition. Metrics used in the indices currently under discussion to assess ecological status of aquatic ecosystems within the scope of European Water Framework Directive were applied to Santo André data and the applicability of these metrics to assess quality in this coastal land-locked lagoon was discussed. [Copyright &y& Elsevier]

Abstract: The Atlantic western coast of Portugal includes several shallow coastal lagoons, such as Óbidos, Albufeira and Santo André, that are intermittently closed to the ocean by sand barriers. Their physico–chemical characteristics, as well as their residence time and tidal influence, are highly dependent on the open/closed periods and on the inter-annual raining/dry season''s variability with important impacts on the phytoplankton community structure, abundance and dynamics. Furthermore, the number of coastal ecosystems with identified eutrophication symptoms is increasing worldwide due to the increasing anthropogenic pressures. Eutrophication is one of the greatest threats to water quality in coastal lagoons and a major concern for the European water quality regulators. One of the first symptoms of eutrophication is enhanced algal biomass. Thus, phytoplankton is generally one of the most important biological indicator of these processes. In this study, all available phytoplankton (chlorophyll and taxa blooms) and nutrient data from a period of more than 50 years were gathered. During the periods of closure, these lagoons have favoring conditions for phytoplankton growth, which can reach high levels of chlorophyll a (chl a, 290 μg L−1), as observed in Óbidos lagoon during the 80''s. At that time, during the open periods, the highest chl a concentration registered was about one fifth lower (64 μg L−1). At present, this lagoon is artificially maintained open during almost all the time and the highest observed chl a concentration was 7 μg L−1. Comparatively, the lagoon of Albufeira still presents high phytoplankton biomass levels during the closed periods (e.g. 55 μg L−1, during winter 2004). In these semi-enclosed systems, phytoplankton blooms are recurrent and HAB species are frequently observed. Significant linear relationships were found between nutrient and chlorophyll concentration, during the open and closed periods, for the lagoon of Óbidos. This assessment was performed to validate the use of phytoplankton as an indicator of anthropogenic pressures. A tool for the classification, under the WFD, of the ecological quality of water bodies within these coastal lagoons is also described based on two different situations: open vs closed lagoon. A set of reference conditions and boundaries are also proposed. This tool was tested and validated against a scale of risk. In addition, the usefulness of specific species as ecological quality indicators is discussed, highlighting the occurrence of frequent Prorocentrum minimum blooms and its association with nutrient enrichment events worldwide. [Copyright &y& Elsevier]

Abstract: Intermittently closed and open lakes and lagoons (ICOLLs) are shallow barrier lakes which are intermittently connected to the sea and experience saline intrusions. Many ICOLLs are mechanically opened to prevent flooding of surrounding agricultural and urban land and to flush water of poor quality. In this study, the effects of modified opening regimes (frequency and duration of barrier openings and closures) on water quality and phytoplankton in two New Zealand ICOLLs were investigated over a number of opening/closure cycles. Water quality in Lake Ellesmere (Te Waihora) responded weakly to both opening and closing events, indicating that sea–ICOLL exchange did not markedly improve water quality. Conversely, water quality in Waituna Lagoon responded rapidly to barrier openings; water level decreased to near sea level within days of opening and subsequent seawater exchange resulted in rapid decreases in nitrate and chlorophyll a concentrations. The closure of Waituna Lagoon resulted in rapid rise in water level and a pulse of nitrate and phosphorus in the water column and phytoplankton chlorophyll a concentrations increased with increasing closed-period duration. Based on data on the underwater light climate and nutrient dynamics, phytoplankton in Lake Ellesmere was probably light-limited, whereas phytoplankton in Waituna Lagoon was rarely light-limited, and appeared to be predominately P-limited. The marked differences in responses of Lake Ellesmere and Waituna Lagoon to barrier openings and closures reflected differences in ICOLL water levels and morphological characteristics, which dictated the degree of tidal flushing when the barriers were open. The inter-ICOLL differences observed in this study indicate that unless the effects of ICOLL openings/closures on phytoplankton and nutrient dynamics are understood, changes to ICOLL opening regimes may have unintended consequences for the water quality and ecology of these systems. [Copyright &y& Elsevier]

Abstract: The dynamics of the Lesina coastal lagoon (Italy) in terms of nutrients, phytoplankton and chemical–physical parameters were evaluated, together with their functional relationships with freshwater inputs, in order to identify ecosystem responses to changes in driving forces in a Mediterranean non-tidal lentic environment. Lesina Lagoon is a shallow coastal environment characterised by limited exchange with coastal waters, which favours enrichment of nutrients and organic matter and benthic fluxes within the system. Lagoon–sea exchanges are influenced by human management. There is a steep salinity gradient from East to West. High nitrogen and silica values were found close to freshwater inputs, indicating wastewater discharges and agricultural runoff, especially in winter. Dissolved oxygen was well below saturation (65%) near sewage and runoff inputs in the western part of the lagoon during summer. Classification in accordance with guidelines suggests the system is of “poor” or “bad” quality in terms of nitrogen concentrations in the eastern zone during the winter rainy period. In terms of phosphate concentrations, the majority of the stations fall into the “good” category, with only two stations (close to the sewage and runoff inputs) classed as “bad”. In both cases, the raw nitrogen levels make the lagoon a P-limited system, especially in the eastern part. There was wide space–time variability in chlorophyll a concentrations, which ranged from 0.25 to 56μgl−1. No relationships between chlorophyll a and nutrients were found, suggesting that autotrophic biomass may be controlled by a large number of internal and external forcing factors driving eutrophication processes. Water quality for this type of environment depends heavily on pressure from human activities but also on the management of sewage treatment plants, agricultural practices and the channels connecting the lagoon with the sea. [Copyright &y& Elsevier]

Abstract: Drana Lagoon, located at the NW site of Evros River Delta, was drained in 1987 and re-flooded in 2004 within the framework of an integrated wetland restoration project. This study presents the results of a monitoring program of the lagoon''s oceanographic, water quality and fish fauna characteristics, during the pre- and post-restoration period. Results depict the presence of high salinity water (up to 41) due to seawater intrusion, strong evaporation in its interior and inadequate freshwater inflows. Overall, nutrient levels were low depicting local changes. Tidal variability at the mouth was approximately 0.2m, producing high velocity tidal currents (up to 0.75m/s). Eleven fish fauna species were collected; seven species were caught in both the inlet channel and the lagoon during the pre-restoration period and nine species in the post-restoration period. Atherina boyeri (37.6%) and Pomatoschistus marmoratus (31.7%) dominated the lagoon during the post-restoration period. Most of the A. boyeri specimens (88.5%) were caught inside the lagoon, while P. marmoratus had an almost equal distribution in the inlet channel and the lagoon (56.3% and 43.7% respectively). The presence of species of the Mugilidae family (5.2% total average catches after lagoon re-flooding) was mainly in the inlet channel (12.6% of the average catches) and not inside the lagoon (only 1.3% of the average catches). The small number of fish species inhabiting the lagoon might be the result of the recent restoration or it could be related with the increased water flow observed at the lagoon mouth during the flood and ebb tidal phases, and also in the presence of a smooth bank in the concrete waterspout that connects the entrance channel with the lagoon. The limited presence of the Mugilidae juveniles inside the lagoon could be related to the prevailing tidal inlet dynamics (i.e. strong ebb flow at lagoon inlet), thus preventing the species to enter the lagoon. In order to restore the lagoon environment, careful and gradual steps should be undertaken under the basis of continuous monitoring of hydrologic, environmental and fisheries system''s status. [Copyright &y& Elsevier]

Cadiz Bay is a shallow mesotidal lagoon with extensive populations of the seagrass Cymodocea nodosa at intertidal and shallow subtidal elevations. This work aims to understand the mechanisms behind the resilience of this species to gradual sea level rise by studying its acclimation capacity to depth along the shallow littoral, and therefore, to gradual variations in the light environment. To address this objective, these populations have been monitored seasonally over a 10 year period, representing the longest seasonal database available in the literature for this species. The monitoring included populations at 0.4, −0.08 and −0.5 m LAT. The results show that C. nodosa has a strong seasonality for demographic and shoot dynamic properties – with longer shoots and larger growth in summer (high temperature) than in winter (low temperature), but also some losses. Moreover, shoots have different leaf morphometry depending on depth, with small and dense shoots in the intertidal areas (0.4 m) and sparse large shoots in the subtidal ones (−0.08 and 0.5 m). These differences in morphometry and shoot dynamic properties, combined with the differences in shoot density, explain the lack of differences in meadow production balance (i.e. meadow growth – meadow losses) between the intertidal (0.4 m) and the deepest population (−0.5 m), supporting the long term resilience of Cymodocea nodosa in Cadiz Bay. This study contributes to the understanding of the mechanisms behind seagrass stability and resilience, which is particularly important towards predicting the effects of climate change on these key coastal ecosystems, and also highlights the value of continuous long-term monitoring efforts to evaluate seagrass trajectories. • This work presents the longest seasonal database available in literature for Cymodocea nodosa. • C. nodosa acclimates to differences in light availability through morphometric changes. • C. nodosa morphotypes have different growth rate and shoot density. • Morphometric acclimation supports the long-term resilience of C. nodosa meadows in shallow environments. • Water quality and accommodation space are going to be crucial for the adaptation of this species to Sea Level Rise. [ABSTRACT FROM AUTHOR]

Abstract: Coastal lagoon ecosystems are particularly vulnerable to eutrophication due to often restricted water exchange with the adjacent ocean, leading to an accumulation of nutrients from the surrounding watershed. The coastal areas of the northern Yucatán (SE Mexico) show similar geological characteristics: carbonate soils, and strong groundwater discharges (SGD), which are a source of fresh water and dissolved inorganic nutrients. However, due to differences in land use and human impact, these coastal lagoons have different water quality characteristics. To determine the variables and processes that influence water quality and eutrophic status of these tropical coastal lagoons with different hydrological regimes and human impacts, bimonthly samplings were carried for a year at 11 stations in Celestún and Chelem lagoons. The results indicate that Celestún is influenced by bioturbation (resuspension and nutrients inputs from waterfowl) and SGD with high concentrations of nitrate and silicate, leading to oligo-mesotrophic conditions. Chelem had high ammonium and phosphate concentrations, reflecting impacts by wastewaters from the surrounding urban area, resulting in meso-eutrophic conditions. Forcing functions such as climatic patterns, water residence time and local aquifer pollution are probably the main variables that explain the observed patterns. [Copyright &y& Elsevier]

Dzilam Lagoon, located in the central coast of Yucatan, Gulf of Mexico, is a shallow water body with average depth of 0.6 m and area of 9.4 km2. Numerous groundwater inputs are distributed along the system representing a continuous source of nitrates and silicates. Due to scarce anthropogenic activity, it is well preserved. Such pristine conditions suggest that changes on nutrient dynamics are mostly related to natural behavior. Monthly samples were taken from September 1998 to August 1999. Physicochemical parameters, inorganic nutrients and chlorophyll-a were measured in nine stations. A multivariate analysis showed salinity gradient and nutrient concentration as the most significant variables in describing lagoon hydrologic heterogeneity. On the basis of those critical parameters, classification analysis of Dzilam Lagoon identified three hydrological affinity zones (HAZ); East and West Zone characterized by higher water residence time and lower salinities during the rainy season; Central Zone with lower residence time and lower inorganic nutrients concentration. Dzilam Lagoon was a NO3− sink and a net source for NO2− and NH4+. Soluble reactive phosphorus was slightly defined and soluble reactive silica was close to conservative condition. [Copyright &y& Elsevier]

Six synoptic sampling events were conducted in the Indian River Lagoon (IRL) between April and June, 1997 to collect TSS (total suspended solids), color (dissolved organic matter), chl a (chlorophyll a), and light (photosynthetically active radiation (PAR)) data. These data were used to develop our understanding of light attenuation dynamics in the IRL and for verification of a numerical light model.Data from our study show that tripton (non-algal particulate matter calculated from TSS and chl a corrected for pheophytin) has a dominant effect on light attenuation in the IRL. For each synoptic event, there exists a positive correlation between the event-averaged downwelling light attenuation coefficient, Kd(PAR), and event-averaged tripton concentration. A negative correlation is found between the event-averaged Kd(PAR) and the event-averaged color, while a positive correlation is found between event-averaged Kd(PAR) and event-averaged chl a concentration. The correlation between event-averaged tripton and event-averaged Kd(PAR) is the only one of the three to show significance at the 0.05 level. Relative contributions of color, chl a, and tripton to light attenuation were found to be 5–25%, 10–26%, and 59–78% of Kd(PAR), respectively. These values depend on the method for partitioning Kd(PAR) and the method for obtaining average value of relative partitioned Kd(PAR) from all the data points. These values show that tripton has a more dominant influence on light attenuation in the IRL than in Tampa Bay and Charlotte Harbor, but comparable to that in Florida Bay. The effect of suspended chlorophyll on light attenuation in the IRL is less than that in Tampa Bay, comparable to Charlotte Harbor, but more than that in Florida Bay.A numerical process-based light attenuation model has been developed to calculate Kd(PAR) based on measured or simulated values of TSS, color, and chl a. The model was found to give reasonable estimates of Kd(PAR) throughout the IRL. [Copyright &y& Elsevier]

We studied the potential of zebra mussel farming for nutrient retention in a eutrophic lake. Duplicate experimental long-line cultivation units were deployed and mussel growth and nutrient retention were quantified after 28 months. Mussels grew well at shallow water depth (<3 m) and our 625 m2 (lake area) experimental units produced 507 and 730 kg dry biomass, respectively, of which 94% were shells. These yields corresponded to an average retention of 92.7 ± 23.1 kg C, 6.1 ± 0.68 kg N, and 0.43 ± 0.04 kg P retention, or 742 kg C, 49 kg N, and 3.5 kg P for a full-size (0.5 ha) mussel farm. We estimate that concentrating the long-lines to a depth of 2.5 m would probably have doubled these yields, based on the differences in mussel growth among depths. We further estimate that a full-size cultivation unit (0.5 ha) thus could compensate for the annual total-P run-off from 23 ha, or the biologically available P from approximately 49 ha of agricultural soils. As traditional measures have proven insufficient, decision-makers need to facilitate novel approaches to mitigate the negative effects of cultural eutrophication. We envision that zebra mussel farming, within their invaded range, provides a promising approach to invert nutrient losses in lakes and coastal lagoons. • Zebra mussel cultivation units produced between 507 and 730 kg dry biomass, of which 94% shells. • 0.5 ha of mussel cultivation can compensate for the bioavailable P from 49 ha of agricultural soils. • Zebra mussel farming is a promising approach to invert nutrient losses to lakes and coastal lagoons. • Zebra mussel can only be applied in the species' invaded range. Zebra mussel cultivation efficiently traps highly bioavailable nutrients, thereby inverting the flux of nutrient from land to water, alleviating cultural eutrophication, and improving water quality. [ABSTRACT FROM AUTHOR]

Intertidal ecosystems, such as marshes, mangroves, and seagrasses, contribute to the global carbon storage, helping to regulate atmospheric CO 2 concentrations. Organic carbon (C org) data from seagrass meadows in the Mexican coastline are still scarce, preventing appropriate evaluations of its contribution to mitigate global climate change. Recent temporal changes (≤100 years) of C org concentrations and burial rates were assessed in 210Pb dated cores from seagrass meadows at Terminos Lagoon, the largest coastal lagoon in the southern Gulf of Mexico. Irrespective of the predominant seagrass species, the cores showed comparable C org concentrations (0.04–3.9%) and burial rates (2.5 – 66.7 g m−2 yr−1). Increasing salinization, likely caused by sea level rise, favoured C org concentrations and burial rates in sediments with Halodule wrightii , while in sediments with Thalassia testudinum only C org burial rates increased, owing to increasing mass accumulation rates, likely promoted by erosion induced by land use changes, and sea level rise. The mean C org stock (1 m depth; 130 ± 29 Mg ha−1) was comparable with the global average C org stock for seagrasses in other tropical areas around the world. Our results suggested that, under the current scenario of land use change and marine transgression, the seagrass meadows in Terminos Lagoon preserve the capacity for C org accumulation and long-term preservation. However, both factors are also known to reduce seagrass resilience caused by water quality deterioration, thus these ecosystems must be monitored and protected from global change impacts, as part of climate change mitigation efforts. Image 1 • C org burial rates and stocks were studied in seagrass meadows from Terminos Lagoon. • 210Pb-dated sediment cores showed C org stocks accumulated during at least 100 years. • Salinity likely enhanced C org sediment storage in a Halodule wrightii seagrass meadow. • C org burial rates were enhanced by increasing sediment accumulation rates. [ABSTRACT FROM AUTHOR]

In the frame of the COZOMED project, concentrations of organic matter (TOC, DOC, POC) were monitored during two seasonal field campaigns (autumn, October 2016 and spring, April 2017) in the Boughrara Lagon, Tunisia. Results indicate strong influence of the seawater exchange and circulation, on the organic matter accumulation inside the lagoon, visible through a significant correlation between TOC and salinity in both seasons. Two times higher concentration of TOC (up to 5.5 mg/l) was recorded in autumn, when high salinity water (46 psμ) was present in the lagoon. POC made a relatively small percentage of TOC in autumn samples when high accumulation of TOC, especially its DOC fraction can be related to remineralization processes and zooplankton-mediated release of DOC. Indeed, PCA analysis identified DOC as the most significant factor influencing the observed variability in autumn samples, and correlated to NH 4 + (p < 0.05) in surface waters, while POC was significantly (p < 0.05) correlated to chlorophyll a. During spring, organic matter in the lagoon was depth-dependent and under the high influence of salinity and temperature, and in the surface correlated to NO 3 -. Satellite data on lagoon water optical properties appear to support changes in measured organic matter concentrations indicating different optical properties of the water inside the lagoon during spring and autumn seasons. The ocean color remote sensing, with properly validated and tested robust algorithms, accommodating optically shallow waters, can provide valuable tools for monitoring and timely detection of possibly detrimental changes inside the lagoon. Image 1 • Accumulation of organic matter in Mediterranean mesotidal lagoon Boughrara, Tunisia. • Organic matter accumulation in Boughrara Lagoon, Tunisia is influenced by seawater exchange. • Remote sensing of surface water properties in Boughrara Lagoon, Tunisia as a proxy for water quality. • Organic matter accumulation in Boughrara Lagoon as a part of eutrophication processes. [ABSTRACT FROM AUTHOR]

Small intermittently open lagoons are the most common type of estuary in NSW but the majority of them have no seagrass despite apparently suitable physical and water quality conditions. This paper describes the consequences of a catastrophic drought on trophic structure of primary producers in two intermittently open coastal lagoons that have negligible anthropogenic stress. It examines the roles of various factors influencing primary producers and hence ecosystems in intermittently open lagoons, in both short and long timeframes. Two estuarine lagoons with undisturbed catchments (Durras Lake and Nadgee Lake) experienced decadal scale shift in production dominance from benthic to pelagic and back to benthic following a catastrophic reduction in water levels during drought conditions. Water quality deteriorated significantly (high turbidity, ammonia and chlorophyll) after loss of macrophytes and then re-established to "normal" conditions within 2–3 years. Despite this, macrophytes did not re-appear for 6–7 years. The high proportion of intermittent estuaries with no seagrass was concluded to be a consequence of recruitment limitation, and estuarine morphology shapes the ecology of these lagoons, rather than an inherent inability for seagrass and macrophytes to live in the estuaries. Recruitment of macrophytes required coincident occurrence of multiple rare stochastic events, making chance an important aspect of re-establishment of biological assemblages in disturbance driven ecosystems. Conceptual models derived for northern hemisphere, riverine, surface-water fed estuaries tend to dominate thinking about estuaries in the literature, but are clearly inappropriate for typical southern-hemisphere low-flow and groundwater-dominated intermittent estuaries. Climate change is likely to increase the frequency of occurrence of the conditions that led to the loss of seagrass and macrophytes and therefore potentially reduce the number of intermittent estuaries in NSW with macrophytes. In the systems described, maintenance of regional seagrass populations is reliant on the stochastic survival of some populations to act as source populations. Climate change is predicted to make what are currently "extreme" events more common. This could, in turn, mean that the likelihood of the sort of loss described in our two cases studies could become more common, increasing the proportion of systems with no seagrass and progressively closing the window of opportunity for external recruitment. Potentially, this could lead to localised extinction of seagrass in intermittent estuaries. Image 1 • In NSW 68% of the 184 estuaries have intermittent entrances and little seagrass. • Drought and low lake levels caused seagrass mortality in two pristine estuaries. • This was followed by eutrophic and then oligotrophic water conditions. • Macrophytes only recruited 6–8 years later due to entrance closure. • Extreme events will increase with Climate Change and threaten macrophyte populations. [ABSTRACT FROM AUTHOR]

Understanding the mass exchange patterns between coastal lagoons and ocean plays a key role to explain their impact upon the water quality and biological productivity of these systems. Ria Formosa is a temperate lagoon on the southwestern coast of Iberia, one of the most important coastal system in this region in terms of biological productivity, ecological and economic values. Given its relevance and strong interconnectivity with the adjoining ocean, the quantification of these exchanges is a key issue that had not yet been thoroughly addressed. In this context, this study is focused on understanding the role of Ria Formosa's main inlet in terms of mass budgets dynamics of water, nutrients, suspended solids and chlorophyll a with the Atlantic Ocean and to identify its seasonal variability. In order to attain this purpose, the influence of the forcing mechanisms at different time scales, including tides, oceanographic/meteorological synoptic conditions and seasons, was assessed. To accomplish this, six semidiurnal tidal cycles surveys were conducted at Faro-Olhão inlet, comprising hourly water samples collection and in situ measurements at a selected cross-section of the inlet channel. Results revealed that mass exchanges variability through Faro-Olhão inlet was mainly due to oceanographic processes (upwelling and coastal countercurrent events) and, secondly, to phytoplankton activity within the lagoon. Seasonally, regardless the direction of the residual current through the inlet, Ria Formosa acted as a source of material during Spring and Summer seasons, which contributed to increase the biological productivity of the coastal ocean. Upwelling events that occurred more evidently during the Autumn survey drove an import amount of nutrients into the lagoon, enhancing its biological productivity. Furthermore, the rainfall period that prevailed before the Winter survey contributed to export material and nutrients to the adjacent ocean, confirming that Ria Formosa fertilizes the coastal ocean, even during a period of low productivity. • Driving mechanisms forcing the Ria Formosa-Atlantic Ocean exchanges were assessed. • Net exchanges of the compounds did not follow the tidal rhythm of the water volume. • Oceanographic and biological processes superimposed the tidal influence. • Ria Formosa acted as source of nutrients and chlorophyll a during Spring and Summer. • Ria Formosa acted as sink of nutrients and chlorophyll a during Autumn and Winter. [ABSTRACT FROM AUTHOR]

A correct management of the mobile barriers that have presently been building at the three inlets of the Venice lagoon (Mo.S.E. project) is of paramount importance for the safeguard of the urban settlements located inside the lagoon. In this work, we compare, by means of a 2-D hydrodynamic model, the setup produced by intense winds during the period of closure of the mobile barriers to the pre-Mo.S.E. scenario, when the flow through the three inlets is not regulated. The analysis considers both some recent storm surge events and more systematically all the meteorological (i.e. wind speed, direction and duration) and hydrodynamic conditions (i.e. sea level and tidal amplitude). We demonstrate that the wind setup significantly increases when the gates at the three inlets are closed, up to exceeding four times the pre-Mo.S.E. scenario. This phenomenon will strongly affect the management of the Mo.S.E. barriers and their operating strategy when pursuing the goal of preventing the flooding at all the urban settlements of the lagoon. More precisely, it will impose to close the gates in advance with respect to what expected by considering only the safeguard of the city of Venice, which is not significantly affected by wind setup due to its central position within the lagoon. This would fatally increase the yearly period of closure of the lagoon, enhancing all the issues concerning long and repeated closures, such as, for example, lagoon water quality and port industry. [ABSTRACT FROM AUTHOR]