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Two new records of the tanaid species Zeuxo holdichi and Apseudopsis tridens are reported for the Venice lagoon. Soft bottom sediment samples were collected as part of a monitoring survey to evaluate the ecological status of the lagoon within the European Directive 2000/60/EC. Specimens of Z. holdichi and A. tridens were found in four and two sampling stations respectively, located in diferent parts of the lagoon. The tanaidomorph species Z. holdichi was previously reported for the Atlantic coasts of France, Spain, Portugal and for southwest England, while the apseudomorph tanaid A. tridens was described only for the Israeli coasts. Therefore, this study represents the frst record of Z. holdichi for the Mediterranean Sea and the frst observation of A. tridens in Italian waters. Despite the low intrinsic dispersal potential of these tanaid species, their native origin or their possible alien status in Italian waters is debated. The dubious native origin of Z. holdichi and the possible underestimation of both species’ presence in Italian Seas due to the lack of taxonomic specialists, attribute to these tanaids a cryptogenic nature. The ability of both species to cope with the diferent environmental parameters characterizing the lagoon may increase the probability of competition with other species that have similar ecological and trophic guilds. published

Large lagoons usually show a salinity gradient due to fresh water tributaries with inner areas characterized by lower mean values and higher fluctuation of salinity than seawater-dominated areas. In the Venice Lagoon, this ecotonal environment, characterized in the past by oligo-mesohaline waters and large intertidal areas vegetated by reedbeds, was greatly reduced by historical human environmental modifications, including the diversion of main rivers outside the Venice Lagoon. The reduction of the fresh water inputs caused a marinization of the lagoon, with an increase in salinity and the loss of the related habitats, biodiversity, and ecosystem services. To counteract this issue, conservation actions, such as the construction of hydraulic infrastructures for the introduction and the regulation of a fresh water flow, can be implemented. The effectiveness of these actions can be preliminarily investigated and then verified through the combined implementation of environmental monitoring and numerical modeling. Through the results of the monitoring activity carried out in Venice Lagoon in the framework of the Life Lagoon Refresh (LIFE16NAT/IT/000663) project, the study of salinity is shown to be a successful and robust combination of different types of monitoring techniques. In particular, the characterization of salinity is obtained by the acquisition of continuous data, field campaigns, and numerical modeling.

The Transitional Water Quality Index (TWQI) is a simple tool for assessing the trophic status in shallow transitional water ecosystems, that can be easily implemented from basic monitoring activities. It integrates six metrics: the main causal factors of eutrophication (N and P concentrations), key biological elements (phytoplankton chlorophyll-a, benthic phanerogams and macroalgal cover) and an indicator of the eutrophication effects (dissolved oxygen saturation). This paper investigates the effectiveness of the TWQI to increase the confidence in trophic status assessment and to reduce the uncertainty due to temporal variability. The temporal variability of TWQI and its six single metrics, individually considered, were investigated in Venice Lagoon using data from 29 stations, sampled in July and October 2010, and 8 stations sampled monthly from April 2014 to March 2015. TWQI resulted less affected by seasonal fluctuations than the individual metrics, generally reducing the mean temporal variability by at least 50%. The influence of monitoring frequency on the uncertainty of the trophic status assessment was investigated as percent error of the TWQI annual mean. Means were firstly obtained from 12-monthly samplings. Lower sampling frequencies were also simulated and the deviation from the annual mean derived by monthly sampling was estimated. Overall, the annual mean values of TWQI was much less affected by the sampling frequency than individual indicators (e.g. Dissolved Inorganic Nitrogen). Based on the performance analysis of this study that demonstrates its reliability and efficiency, the TWQI can be recommended as a routine index to be used in large-scale monitoring of the trophic status in shallow transitional water ecosystems.

Eutrophication represents one of the most impacting threats for the ecological status and related ecosystem services of transitional waters; hence, its assessment plays a key role in the management of these ecosystems. A new multi-index method for eutrophication assessment, based on the ecological index MaQI (Macrophyte Quality Index), the trophic index TWQI (Transitional Water Quality Index), and physicochemical quality elements (sensu Dir. 2000/60/EC), was developed including both driver and impact indicators. The study presents a large-scale implementation of the method, which included more than 100 Italian lagoon sites, covering a wide variability of lagoon typologies and conditions. Overall, 35% of sites resulted in eutrophic status, 45% in mesotrophic, and 25% in oligotrophic status.

Since the 1960s, the Venice Lagoon has suffered a sharp aquatic plant constriction due to eutrophication, pollution, and clam fishing. Those anthropogenic impacts began to decline during the 2010s, and since then the ecological status of the lagoon has improved, but in many choked areas no plant recolonization has been recorded due to the lack of seeds. The project funded by the European Union (LIFE12 NAT/IT/000331-SeResto) allowed to recolonize one of these areas, which is situated in the northern lagoon, by widespread transplantation of small sods and individual rhizomes. In-field activities were supported by fishermen, hunters, and sport associations, the interested surface measured approximately 36.6 km2. In the 35 stations of the chosen area, 24,261 rhizomes were transplanted during the first year, accounting for 693 rhizomes per station. About 37% of them took root in 31 stations forming several patches that joined together to form extensive meadows. Plant rooting was successful where the waters were clear and the trophic status low. But, near the outflows of freshwater rich in nutrients and suspended particulate matter, the action failed. Results demonstrate the effectiveness of small, widespread interventions and the importance of engaging the population in the recovery of the environment, which makes the action economically cheap and replicable in other similar environments.

Coastal salt marshes are among the Earth's most productive ecosystems and provide a number of ecosystem services. Water quality regulation by storing, transforming and releasing nutrients, organic matter and suspended sediment is recognized as one of the most important functions of salt marshes. The self-purification capacity of intertidal ecosystems contributes to mitigating nutrient inputs, acting as a buffer zone between watersheds and coastal waters, especially in relation to climate change and the increasing frequency of impulsive extreme events. Understanding sediment and nutrient fluxes and assessing the mechanisms that control them are valuable for the preservation and future restoration of salt marshes and for enhancing their effectiveness in providing water quality regulation services. To investigate the main driving factors in microtidal environments, changes in suspended sediment and nutrient concentrations were measured during several tidal cycles in a small microtidal reconstructed salt marsh in the Venice Lagoon, which was selected as the experimental site. The tidal amplitude, nutrients and total suspended solid concentrations were measured during 6 tidal cycles between September 2011 and October 2013. The water discharge was derived by forcing the hydrodynamic MIKE-DHI numerical model with the measured tidal levels. Fluxes were assessed by coupling field data with the calculated discharges. The salt marsh filtering function was related to the inflow matter concentrations and tidal amplitude. When high suspended solid and nutrient concentrations enter the salt marsh, accumulation processes prevail on release. In contrast, in the case of low concentrations and high tidal excursion, the salt marsh functions as a nutrient and sediment source. During all campaigns, the nitrogen removal function was more effective within the intertidal vegetated areas. Sediment release was the dominant process in the outermost creek, whereas sedimentation prevailed in the inner area of the salt marsh because of the attenuation of hydrodynamic forcing during tide propagation.

Pristine conditions in transitional water ecosystems are characterized by the dominance of aquatic angiosperms. Aquatic plants consolidate bottoms, prevent erosion, support benthic and fish communities as nursery and food areas, and favour the bird presence. Hence, they may contribute to the achievement of a good ecological status as required by the WFD (2000/60/EC). Their reduction or disappearance is a symptom of environmental deterioration. Over the past few decades, the aquatic angiosperms have shown a significant decrease on a worldwide scale and in some areas of Venice Lagoon (Adriatic Sea), particularly in the central and Northern basins, as a consequence of anthropogenic activities. At present, most of the anthropogenic pressures which caused their decline or disappearance in Venice Lagoon have significantly decreased creating the ecological conditions for a new colonization. In this context, the project SeResto (LIFE12 NAT/IT/000331), funded by the European Commission, aims at restoring the angiosperm meadows in the Northern basin of Venice Lagoon where the natural seed spreading is hampered by the presence of island, tidal marsh barriers and long residence times. The project has two main strengths: i) the widespread transplantations of small angiosperm sods and manual dispersion of rhizomes and seeds and based on a low costs and low impact on donor sites approach, ii) the participation of fishermen and hunters daily living the lagoon for recreational purposes. Thirty-five sites have been selected and in each one 9 sod-bearing plants (diameter: 30 cm), supplied by fish farms where angiosperm meadows are almost natural, have been transplanted. In addition, the plant spreading is enhanced by the dissemination of hundreds of rhizomes, 1500 at minimum in each area during the project period (52 months). In 8 sites, out of the 35, biological and chemico-physical conditions are being monitored monthly during the first and last year and quarterly in the intermediate period. Ecological indices, based on the study of macrophytes, macrobenthic fauna and fish fauna (Biological Quality Elements), as required by the WFD 2000/60/EC, will allow to assess changes in the Ecological Status of the study sites. Preliminary results are encouraging in great part of the selected areas although some difficulties have been recorded in areas with high water turbidity and the presence of thionitrophilous macroalgae, especially Ulvaceae, favoured by the unexpected weather conditions of summer 2014. Information on the restoration effectiveness and the relationship between the angiosperm presence/growth and the environmental conditions can be employed for interventions in other lagoon areas and can be exported in other similar transitional environments.